Biology Ss 1 1st Term Scheme of work E Notes

NTRODUCTION TO BIOLOGY

CONTENT

  1. Meaning of (a) Science and (b) Biology
  2. The Scientific Method
  3. Experimental Pattern
  4. Living And Non-living Things
  5. Differences between Plants and Animals
  6. Levels of Organization
  7. Complexity in Multicellular Organisms

 

Meaning of Science and Biology

Science can be defined as a systematic process of making inquiry about the living and non-living things in our environment. Science is both an organized body of knowledge and a process of finding out knowledge.

Biology is the branch of science that studies living things. The word ‘biology’ is derived from two Greek words: ‘bios’ which means life, and ‘logos’ which means study. Biology therefore means the study of life or of living things.


Biology has several branches, these include

  1. Botany (study of plants)
  2. Zoology (study of animals)
  3. Morphology (study of the external features of living things)
  4. Anatomy (study of internal structure of living things)
  5. Physiology (Study of how living things function)
  6. Ecology (study of the relationships between living things and their environment),
  7. Genetics (Study of how living things inherit characters from their parents) etc.

The prime purpose of science is research, i.e. finding out about things, so biology involves finding out or making inquiry about living things, their interaction with themselves and with nature.

EVALUATION

  1. Define the terms (a) Science (b) Biology
  2. State five branches of biology.
  3. Of what use is (a) science (b) biology to man?

[mediator_tech]

Methods of Science (The Scientific Method)

The method of science involves systematically making inquiries about something under study. It begins with observation (that is, looking at something carefully with a view to finding an answer to a question). This involves using all the senses i.e. sight, hearing, touch, feeling, pressure, taste, etc. and instruments (e.g. ruler, microscope, magnifying lens, weighing balance, telescopes, barometer, etc.) where necessary.

Observation is followed by a hypothesis i.e. a sensible, reasonable guess which is capable of being tested or verified.

The hypothesis is tested by an experiment. Experiments usually involve measurements/counting, as such they have to be carried out as accurately as possible. Scientific experiments have a control. The control experiment is identical with the experiment proper, but the factor to be tested is omitted. This gives the investigator a higher degree of confidence in his result and conclusion.

Results from an experiment are put together and a conclusion (inference/generalization) is made.

Other scientists may repeat the same experiment and if similar results are obtained then the generalization is accepted as a theory.

When a theory has been tested extensively, worldwide and found to be consistently true, it becomes a law e.g. the law of gravity

 

Experimental Pattern

Experiments are designed to eliminate all forms of bias so as to avoid making false conclusions. To achieve this, only the factor being tested is varied, all other factors that may affect the result are kept constant. These experiments are known as controlled experiments.

While experimenting, a biologist uses processes of science such as counting, measuring, classifying, organizing data, communicating, recording and interpreting data.

In recording an experiment/giving the account of a scientific investigation, the following pattern is used:

  1. Date of experiment
  2. Aim/purpose of experiment
  3. Apparatus/materials required
  4. Procedure/method used (including control and precautions)
  5. Observations
  6. Inference (deduction from what is already known)

In biology, experiments are carried out on living things. It may not be possible to get a sample of test population with identical organisms. This problem can be reduced by using large test samples and also repeating the experiment many times.

EVALUATION

  1. State and explain the processes involved in making inquiries in science?
  2. In your own words, what are the proper attitudes which should characterize a scientist?
  3. Enumerate the steps specified in giving account of a scientific investigation.
  4. How is bias taken care of in a biological investigation?

 

SUGGESTED PRACTICAL

Setting up and using of a light microscope.

Objectives of the Practical Exercise

Students should be able to;

  1. Identify the parts and functions of each part of the microscope
  2. Calculate the magnification of a diagram
  3. Draw and label a light microscope (10 – 12cm long)
  4. Observe a chosen specimen using the microscope (cells of an onion bulb)

Note: Quality and details to be graded in any required diagram

  1. Title (TL)
  2. Size (Sz)
  3. Clarity of lines (CL) – not broken, not wooly
  4. Neatness of Label (NL) – ruled guide lines, horizontal labels          `
  5. Details (DL) – depending on the diagram of the specimen

 

Living and Non-living Things

Everything in the world can be classified as either a living thing or non-living thing. Living things include plants and animals (things that have life) e.g. Man, Monkey, Earthworm, Flies, Mango, Fresh okra plant, Hibiscus etc. Non-living things do not have life e.g. stone, water, air, table, etc.

Characteristics of Living Things

Some features have been found in every living thing ever studied by Biologists, these are;

Living things consist mainly of water and compounds carbon.

They are made up of one or more units called cells

They carry out seven basic life processes namely;

(i) Movement: This is defined as the ability of an organism to change its position. It may be a total change in position of the body as in the case of animals that move their whole body from one place to another or a limited change in position as in the case of plants which can only move parts of their body (e.g. in bending). Living things move in order to look for food, shelter, mates (reproduction) and to escape from danger. Generally, most animals can walk, swim, or fly from one place to another but plants can only move parts of themselves in response to external stimuli. Movement from place to place is also referred to as Locomotion.

(ii) Nutrition: This is the ability of an organism to feed. The reason for feeding is to enable living things to live and carry out life processes like growth, respiration and reproduction. Plants manufacture their own food through the process of photosynthesis (autotrophic nutrition). Animals cannot manufacture their own food but depend directly or indirectly on plants for food (heterotrophic nutrition).

(iii) Respiration: This involves the taking in of oxygen in order to burn down (oxidize) food substances to release energy which is used to carry out all life processes. Carbondioxide is given off in the process.

(iv) Excretion: This is the removal of metabolic waste products from the body. Many chemical activities go on in an organism and produce waste. These waste products are substances which the organism does not need and which may poison it if allowed to build up in the body. The waste products of metabolism include carbondioxide, water, urea, etc.

(v) Irritability or Sensitivity: This is the ability of an organism to perceive and respond to stimuli (changes in the surrounding). Living things exhibits sensitivity in order to survive in their environment. The response is often by some form of movement. Stimuli include heat, light, pain, sounds, chemical substances, etc.

(vi) Growth: This is defined as permanent increase in size and mass of an organism especially while young. Organisms also replace and repair worn or damaged parts of the body throughout life. The food eaten provides the basis of growth.

(vii) Reproduction: This is the ability of a living organism to produce young ones or offsprings. This ensures continuity of life. Reproduction occurs in two forms.

Asexual reproduction – This involves only one organism producing offsprings from itself.

Sexual reproduction – This involves two organisms coming together to produce offspring(s).

Apart from these seven basic life processes another characteristic of living things is that they all die. All living things have a definite and limited period of existence, and they pass through five basic stages of existence;

Birth  →   Growth  →   Maturity  →  Decline (old age)  →  Death.

 

EVALUATION

  1. Make a list of five living things and five non-living things.
  2. Briefly discuss the characteristics of living things.

 

Differences between Plants and Animals

PLANTS ANIMALS
Green plants carry out photosynthesis Animals cannot carry out photosynthesis;
they depend on plants for their food.
Plants do not move from one place to
another and do not have organs of movement.
Animals move from one place to another
and have organs of movement. They exhibit
locomotion.
Growth is indefinite (continues throughout life)
and apical.
Growth is definite and occurs uniformly in
every part of the body. It stops when they
become adults.
Plants do not have specialized organs for
excretion, respiration and coordination.
Animals have specific organs for excretion,
respiration and coordination.
Plants are slow in response to stimuli Animals are fast in their response to stimuli
Excess carbohydrates are stored as starch Excess carbohydrates are stored in form of
glycogen
They have many branches They do not have any branches

Some organisms exist which posses characteristics of both plants and animals an example is Euglena viridis. Euglena viridis is a microscopic unicellular organism, which lives in water.

The characteristics of Euglena which make it an animal are;

  1. Possession of flagellum used for movement.
  2. Possession of gullet for passage of food and which acts as a reservoir.
  3. Presence of eye spot which enables it respond to light.
  4. Possession of contractile vacuole used for excretion.
  5. Possession of pellicle which makes its body flexible.
  6. It can feed on other organisms (holozoic nutrition) in the absence of sunlight.

The plant characteristics of Euglena are;

  1. Possession of chloroplast which enables it to carry out photosynthesis.
  2. Possession of pyrenoid where starch is stored
  3. It can produce its own food (holophytic or autotrophic nutrition)

EVALUATION

  1. State five differences between plants and animals
  2. Mention two characteristics of Euglena that makes it (a) a plant (b) an animal

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Levels of Organisation of Life

The bodies of living things are highly organized. This organization occurs in levels, with the simplest structure occurring at the lowest levels (single cells) which interact to build up more complex structures (multicellular organisms).

The basic levels of organization of life in organisms are; cells, tissues, organs and systems.

(i) Cell: This is the smallest unit of living organism. It is the first and simplest level of organization of life. Plants and animals are made up of cells. One celled organisms are called unicellular organisms. They include Amoeba, Plasmodium, Euglena, Paramecium, etc. Organisms made up of many cells are called multicellular organisms e.g man, mango, trees etc. The single celled organism can carry out all life processes on its own.

(ii) Tissues: This is a group of similar cells which come together to perform a particular function. A tissue consist of two or more different types of cells aggregating together to perform a specific function e.g. the mesophyl layer in leaves, xylem tissue in stems, muscles, blood (a liquid tissue) etc. Organisms which exist at the tissue level include the hydra, jelly fish, sponge etc.

(iii) Organ: Is a group of similar tissues which come together to perform a specific function. Examples in plants are flowers, roots, leaves, seeds, a rhizome, a corm, an onion bulb, a tuber, etc. Examples in animals are the skin, stomach, heart, brain, liver, eyes, ears, kidney, etc.

(iv) System: This is a group of functionally related organs which work together to perform specific functions. Examples in plants include the shoot system and root system. Examples in animals include the digestive, nervous, excretory and circulatory systems. Examples in plants are the transport system, shoot and root system.

 

Complex Multicellular Organisms

The climax of organization in higher living things is the aggregation of systems to form an organism. Complex multicellular organisms are composed of several organ systems which work harmoniously for the benefit of the organism. All animals from Platyhelminthes to Mammals, and all vascular plants are organized on this level.

Complexity of Organization In Higher Animals

As organisms acquire more layers of cells, they become complex in structure, thus there is an increase in complexity from unicellular to multicellular organism.

Advantages of Complexity

  1. It leads to cellular differentiation, thus groups of similar cells are differentiated to form tissues which carry out similar functions
  2. It leads to internal structural specialization in which the tissues become specialized to carry out specific functions.
  3. There is mutual interdependence between component cells i.e division of labour among the cells.
  4. Complexity makes higher organisms to be more efficient in carrying out life processes.
  5. Complexity leads to increase in size of organisms.
  6. It makes it possible for organisms to become more resistant to adverse condition within the environment.

 

Disadvantages of Complexity

  1. The cells lose their independence and become increasingly dependent on one another’s activities.
  2. Difficulties in acquisition of materials (such as oxygen and food materials) and removal of waste products by the millions of cells making up a multicellular organism
  3. Slower rate of diffusion of oxygen or respiratory gas to individual cells.
  4. Slower rate of expulsion of waste products from cells.
  5. Decrease in ability to regenerate
  6. Difficulties in reproduction.

 

EVALUATION

  1. Mention and explain the levels of organization of life.
  2. State three advantages and disadvantages each, of complexity.
  3. Is a virus a living thing or a non-living thing? Give reasons for your answers.
  4. Describe one organism at the tissue level of organization (e.g. Hydra).

CLASSIFICATION (TAXONOMY) OF LIVING THINGS

CONTENT

  1. Classification/Taxonomy of Living Things
  2. Binomial System of Nomenclature
  3. Classification and Evolution

Definition of Classification

To classify means to arrange or organize things into groups. Classification of living things involves placing living things that have certain important features in common into specific groups which distinguish them from other groups.

The largest group of organisms is the kingdom. The kingdom has the largest variety of organisms.

The kingdoms are further split into a large number of smaller groups called ‘phyla’ (singular phylum) for animals and ‘division’ for plants. All members of a phylum or division have certain features in common. Each phylum or division is broken down into classes. Classes are split into orders. Orders are split into families. Families are split into genera (singular genus) and genera into species.

The seven groups used in classification of living things in order of hierarchy are;

Kingdom

Phylum (Animal) or

Division (Plant)

Class

Order

Family

Genus

Species

The species is the basic (i.e. smallest) unit in biological classification. A species is a group of individuals which can interbreed to produce fertile offspring. Example, all human beings belong to one species and all monkeys belong to a different species, thus human beings and monkeys cannot interbreed.

Classification Human Dog Lion
Kingdom Animalia Animalia Animalia
Phylum Chordata Chordata Chordata
Class Mammalia Mammalia Mammalia
Order Primate Carnivora Carnivora
Family Hominidae Canidae Felidae
Genus Homo Canis Panthera
Species sapiens familiaris leo

EVALUATION

  1. What is taxonomy?
  2. Make a list of the hierarchy of groups used in classification of living things.

 

Binomial System of Nomenclature

A Swiss scientist, Carl Von Linne (1707 – 1778) (Latin – Carolus Linnaeus) introduced the present system of classification of living things. He also introduced the binomial system of nomenclature in which an organism is given two names. The first name is the generic name and always begins with a capital letter while the second name is the specific name (species) and begins with a small letter. The generic name is common to all the species in a genus e.g. Equus cabellus (horse), Equus asinus (the donkey), Equus burchelli (common Zebra) are different species of the same genus.

Examples of Scientific names of some organisms

(i) Man – Homo sapiens

(ii) Housefly – Musca domestica

(iii) Maize – Zea mays

(iv) Orange – Citrus sinensis

(v) Pawpaw – Carica papaya

 

EVALUATION

  1. Who introduced the binomial system of nomenclature?
  2. Write the scientific names of the following: (a) Rice plant (b) Domestic cat  (c) Monkey

[mediator_tech]

Classification and Evolution

As a result of advances in the field of science a five-kingdom system introduced by R.H Whittaker (1969) has been adopted by some biologists. Most biologist however, prefer to divide living things into prokaryotids (bacteria and blue-green algae) and eukaryotids (all other organisms) based on the complexity of cell structure and cell chemistry.

Prokaryotids – Monera: bacteria, blue-green algae

Eukaryotids – Protista: protozoa, unicellular algae

Fungi: yeasts inclusive

Plantae: multicellular plants and multicellular algae

Animalia: multicellular animals

The five kingdom classification is as follows;

  1. Kingdom Monera,
  2. Kingdom Protista (Protoctista),
  3. Kingdom Fungi,
  4. Kingdom Plantae and
  5. Kingdom animalia.

Viruses

These are not cells. They are particles made up of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) surrounded by a protein coat. The genetic material is composed of a few genes that code for the proteins that form the coat and other proteins that help it reproduce.

They are very harmful parasites that enter the cells of another organism (host) in order to multiply.

They do not respond to antibiotics and are constantly changing into new strains.

A. Kingdom Monera

  1. They are unicellular
  2. The cells are prokaryotic with no organized nucleus and no nuclear membrane, just a loop of DNA within the cytoplasm.
  3. They do not have complex chromosomes
  4. Cells have no mitochondria, endoplasmic reticulum and no chloroplasts.
  5. Cell wall does not contain cellulose but polysaccharides and amino acids
  6. No sexual reproduction.
  7. They may be autotrophic or heterotrophic

Examples include bacteria and blue-green algae.

  https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-Helicobacter-pylori.jpghttps://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-anatomy-of-a-simple-bacterium.jpg

B. Kingdom Protista

(i) The organisms are eukaryotic and unicellular.

(ii) Some are heterotrophic, some are autotrophic and some are both

(iii) Reproduction is usually asexual by mitosis but some have sexual reproduction by fusion of gametes.

(iv) Movement may be by cilia, flagella or may be amoeboid

(v) The kingdom is divided into the following phyla;

(a). Phylum protozoa: Examples are Amoeba, Paramecium, Zooflagellates, Plasmodium, Trypanosoma

(b). Phylum Euglenophyta: Example Euglena

(c). Phylum Chrysophyta: Example diatoms

(d). Phylum Pyrrophyta: Example dinoflagellates

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-paramecium.jpg https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-amoeba-engulfing-a-paramecium.jpg

C. Kingdom Fungi

(i) Some are unicelleluar e.g yeast, many are multicellular e.g rhizopus, mushroom and toadstools .

(ii) The body of a fungi is composed of threads/filaments each called a hypha.

(iii) All the hyphae of a single organism are collectively called a mycelium.

(iv) There are many nuclei in a cell.

(v) All fungi are heterotrophic – They lack chlorophyll. Some are saprophytic, some are parasitic and some are symbiotic.

(vi) Fungi together with bacteria are the principal decomposers in the biosphere

(vii) Fungi reproduce by asexual or sexual methods.

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-fly-agaric-mushroom.jpg

The brightly colored fly agaric mushroom is a deadly poisonous mushroom. Containing ibotenic acid and a number of other organic poisons, the fly agaric can cause severe damage to the central nervous system, blood vessels, kidneys, liver, and muscles. Symptoms, which may not become apparent for 8 to 12 hours or longer, include nausea, vomiting, and severe diarrhea and can lead to coma and death.

EVALUATION 

  1. List the five kingdoms of classification of living things.
  2. Give two characteristics each of organisms in each group mentioned above.
  3. State two differences between prokaryotic and eukaryotic cells.

SUGGESTED PRACTICALS

Make a large well labeled diagram of a mushroom, 8 – 10 cm.

KINGDOM PLANTAE; KINGDOM ANIMALIA

CONTENT

  1. Kingdom Plantae
  2. Kingdom Animalia

 

Kingdom Plantae

(i) They are mainly non-motile

(ii) They are all autotrophic

 

1. Division Thallophyta (Algae):

E.g. pondweeds, seaweeds, diatoms

(a) They are nearly all aquatic

(b) Some are unicellular e.g. Chlamydomonas and diatoms some are filamentous e.g. spirogyra while some have flat body called a thallus e.g. seaweeds.

(c) The body is simple in structure. They have no true roots, stems, leaves or specialized conducting systems.

(d) All have chlorophyll and they photosynthesis. However, some have other pigments which mask the green colour of chlorophyll e.g. seaweeds may be brown, red, and green in colour.

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-euglena.jpg https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-spirogyra.jpg

2. Divisions of Embryophyta

(i) Bryophyta

E.g. mosses and liverworts.

(a) The cells are differentiated into tissues.

(b) They lack true roots stems and leaves, but have structures resembling them e.g. a typical moss has a stalk, small leaves which are one or two cells thick and thread-like rhizoids.

(c) There are no specialized conducting tissues.

(d) They are terrestrial and most live in deep and shady places.

(e) They need moisture for fertilization.

(f) They exhibit asexual reproduction by spores in which there is alteration of generation.

 

(ii) Tracheophyta (Vascular plants)

(a) Pteridophyta: E.g. ferns

(i) They re more complex in structure than Bryophytes.

(ii) They have proper roots, stems and leaves and a well-developed conducting system (i.e they are vascular green plants).

(iii) They are non-flowering and non-seed producing plants.

(iv) A large number of spores develop on the under surface of the leaves (or ponds) which are dispersed by wind.

(v) They need moisture for fertilization.

(vi) Nearly all ferns are terrestrial, growing in damp and shady places. Many tropical ferns grow as epiphytes on palms and other trees.

(vii) Most are herbs but a few are small trees.

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-fern.jpg[mediator_tech]

(b) Spermatophyta: E.g. all seed-bearing plants.

(i) They are multicellular, seed producing plants.

(ii) They have true roots, stems and leaves.

(iii) They have well developed vascular tissues.

(iv) They reproduce sexually and do not need water for fertilization.

(v) They are mainly terrestrial plants.

 

There are two main sub-divisions namely:

(a) Sub-division Gymnospermae: All cone-bearing plants e.g. cycads, conifers and pines.

(i) They produce seeds in cones (naked seeds).

(ii) They do not form flowers and fruits.

(iii) All are woody plants and most are trees.

(b) Sub-division Angiospermae: All flowering plants.

(i) The seeds are produced in special structures called flowers.

(ii) Fertilized seeds are enclosed in fruits

(iii) They are nearly all terrestrial.

Angiosperms can be further divided into two classes according to the number of seed leaves (cotyledons). These are:

Dicotyledonous plants (Seed having two seed leaves) e.g. Cowpea, groundnut, etc.

Monocotyledonous plants (Seeds having one seed leaf) e.g. maize, millet, wheat, etc. https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-angiosperms-conifer.jpg https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-angiosperms-pine.jpg

Kingdom Animalia

Classification of Animals

Types of Invertebrates

P – Porifera (sponges)

C – Coelenterata(Cnidaria)

P – Plathyhelminthes (flat worms)

N – Nemathoda (round worms)

A – Annelida (segmented worms)

M – Mollusca

A – Arthropoda

E – Echinodermata

 

1. P – Porifera (Sponges)
Features
  1. They are simple aquatic invertebrates that are motile.
  2. They are attached to rocks, shell or corals
  3. They reproduce both sexually and asexually
  4. They live in colonies
  5. Most are hermaphrodites (i.e possess male and female sex organs)
  6. They are primitive multicellular animals with asymmetrical bodies
Examples

Demosponge, calcareous sponge, hexactinellid, siliceous sponge, Purple and Yellow Tube Sponge

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-porifera-sponges.jpg

Purple and Yellow Tube Sponge

The purple and yellow tube sponge displays one of the many different body forms typical of sponges. Sponges, considered to be the most primitive of the multicellular animals, are represented in the fossil record back to the Cambrian Period, at least 600 million years ago. The interior body cavities of sponges provide shelter for a variety of small crabs, sea stars, and other marine invertebrates.

 

2. Coelenterata
Features
  1. They are multicellular aquatic organisms
  2. Have radially symmetrical bodies
  3. They reproduce asexually
  4. Have two body layers (diploblastic)
  5. They have tentacles with stinging cells for capturing prey
Examples

Hydra, sea anemone, jelly fish.

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-coelenterata-red-sea-anemone.jpg

Red Sea Anemone

Sometimes mistaken for plants, sea anemones are true animals that kill prey with their poisonous tentacles. When a fish contacts them, the tentacles eject dozens of microscopic poisonous darts, paralyzing the victim. The tentacles then pull the prey into the mouth of the baglike body, which is basically one large stomach. The red sea anemone, Actinia equina, is a common species, inhabiting the intertidal zone along the Atlantic and Mediterranean coasts of Europe and Africa. It has 192 tentacles arranged around its mouth in six rings. Marine biologists believe some sea anemones can live 100 years or longer.

 

3. Plathyhelminthes (flat worms)

They consist of three classes

Class i: turbelleria e.g planaria

Class ii: Trematoda e.g liver fluke

Class iii: Cestoda e.g tape worm.

General Features
  1. Free living aquatic animals
  2. They are parasitic
  3. They are hermaphrodites and reproduce asexually
  4. They have sac-like flat bodies
  5. Bilaterally symmetrical bodies with definite head and a tail.

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-plathyhelminthes-flatworms.jpg

Tapeworm

Tapeworms are parasitic worms that infest the intestinal lining and other organs of vertebrates. Tapeworms, having no mouth or digestive tract, are able to absorb partially digested material through their body surface.

 

4. Nematoda (round worms)
Features
  1. They have round bilaterally symmetrical bodies, with makes it advanced over flat worms.
  2. Have gut that is a straight tube with mouth and anus at opposite end.
  3. Some are parasites (e.g filarial worm causes elephantiasis also called filariasis) in animals while some are free-living
  4. Some are hermaphrodites while some reproduce sexually
  5. They have three body layers (triploblastic)
Examples

Hook worm, filarial worm, thread worm

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-nematoda-elephantiasis.jpg

Elephantiasis

The upper legs of this patient with elephantiasis show the typical sign of the disease, a hardening and thickening of the skin. Elephantiasis results from a blockage in the lymphatic system generally caused by a parasitic worm.

 

5. Anellida (segmented worms)

They consist of three classes

Class i: polychaete e.g sea worm

Class ii: Oligochaete e.g earthworm

Class iii: hirudinean e.g leech

General Features
  1. They posses long cylindrical bodies
  2. Most are marine forms and others in fresh water or damp soil.
  3. Have internal and external segmented bodies which enable the animals to grow bigger.
  4. Their body is partitioned by means of a septa
  5. Alimentary canal has two opening, mouth and anus.
  6. Have a well developed nervous and circulatory system, have nephrida for gaseous exchange through moist skin.

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-anelida-earthworm.jpg

Earthworm

Earthworms have a segmented, compartmentalized, cylindrical body and range in length from several centimeters (a few inches) to nearly 3.3 m (11 ft). They have no eyes, ears, or lungs. Earthworms breathe when air that is present between soil particles diffuses through their thin skins, and they are forced to the surface if these air pockets fill with rainwater. When a worm moves, it uses its longitudinal muscles to extend the front of its body into the soil ahead of it, pulling the back part up behind it. Setae, tiny projections from each segment of the worm, stick into the surrounding soil to keep the worm from slipping. The digging action of earthworms helps to aerate and mix the soil. Earthworms actually consume some of the soil as they dig, and their fecal deposits, called castings, also help enrich the soil.

6. Mollusca

They consist of three classes

Class i: Gastropoda e.g snail

Class ii: Pelecypoda e.g mussel

Class iii: Cephalopoda e.g Octopus

General Features
  1. About half are marine organisms, others live in fresh water and on land
  2. They posses soft unsegmented bodies
  3. Some posses calcareous  shells (secreted by the mantle) for protection against physical damage, predators and drying out period
  4. They posses muscular foot adapted for crawling, burrowing  and swimming
  5. They posses tentacles
  6. The anus open into mantle cavity

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-mollusca-octopus.jpg

Octopus

The octopus is an invertebrate animal that lives in the sea. Octopuses have eight tentacles (arms). Two rows of suckers line each tentacle. Octopuses use their tentacles to catch crabs and other small animals to eat.

https://classhall.com/wp-content/uploads/2017/04/classification-of-living-things-mollusca-giant-African-snail.jpg

Giant African Snail

The giant African snail, Achatina fulica, is the largest land mollusk. Individuals may grow up to 23 centimeters (up to 9 inches) in length and weigh up to 0.5 kilograms (up to 1.1 pounds). This snail is native to tropical West Africa, and humans have accidentally spread it to many lands. It has a ravenous appetite and a taste for many crops and wild plants, making it a notorious worldwide pest. Control programs have met with little success and often harm native species. Studies have shown that processed giant African snails are nutritious as human food and can be cultivated as a protein source.

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7. Insecta

They consist of four classes

Class i: Crustacea e.g crabs, lobster, prawns

Class ii: Insecta e.g grasshopper, praying mantis, cockroach

Class iii: Arachnida e.g spider, scorpion, mites, ticks

Class iv: Myriapodia e.g millipede and centepedes

General Features
  1. They have segemented bodies
  2. They three body layers (triploblastic)
  3. They have various means of respiration eg gills, trachea, lung-book and body surface
  4. They have jointed appendages
  5. They exhibit moulting (shedding of exoskeleton at intervals to permit growth)

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Hermit Crab

Hermit crabs are distinguished from other crabs by the lack of a shell on the abdomen. As a result, hermit crabs must find empty snail shells to temporarily inhabit. While walking or feeding, hermit crabs extend their antennae, claws, and two pairs of walking legs out of the shell opening. When threatened by predators, hermit crabs quickly withdraw their bodies back into the protection of the shell. The large claw, the last part of the body to be withdrawn, often acts as a door, closing off the interior of the shell from predators. As hermit crabs grow, they must continually find new, larger shells in which to live.

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Imperial Shrimp

The brilliant-red coloring of the imperial shrimp matches the coloring of the Spanish-dancer sea slug, on which it lives. The shrimp feeds on plankton and detritus that get caught in the mucous covering of the host’s skin.

 

 8. Echinodermata
  1. They have radially symmetrical body
  2. They are slow – moving marine animals living on the sea shore and sea beds
  3. It has no head and brain
  4. They are not segmented.
  5. They are spiny – skinned animals.
  6. They have tube feet used for movement
Examples

Sea urchins, sea cucumber, starfish.

 

EVALUATION 

  1. List the groups in the division embryophyta.
  2. Give two characteristics each, of organisms in each group mentioned above.
  3. State the two groups of the animal kingdom and their respective phyla.
  4. Enumerate the general characteristics of vertebrates and list the classes.
  5. Make a well labeled diagram of the ventral view of an earthworm.

 

Phylum Chordata – Vertebrates

Vertebrata is a subphylum of the phylum chordate. The chordates have a notochord, a flexible rod of tightly packed cells, a tubular nerve chord (dorsal) and gill slit at some stage in their life history. The back bone or vertebral column replaces the notochord in vertebrates.

General Features of Vertebrates

Vertebrates are animals with back bone.

  1. All vertebrates have the following features
  2. A well developed central nervous system
  3. Two pairs of limbs
  4. Kidney for eliminating body waste
  5. Well developed sense organs
  6. An internal or external skeleton
  7. A bilaterally symmetrical body divided into head trunk and tail
Classes of Vertebrates

There are five classes of vertebrates

  1. Pisces
  2. Amphibians
  3. Reptiles
  4. Aves
  5. Mammals.

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Tilapia Fish

Fishes of the genus Tilapia are popular as both aquarium and food fishes. Some species of tilapia are mouth brooders, protecting unhatched eggs and newly hatched young by carrying the eggs and young in their mouths. Usually the female carries the offspring, but in a few species the male also participates in mouth brooding.

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Although both amphibians, frogs and toads have several basic anatomical differences between them. The smooth, moist skin characteristic of frogs covers long legs specialized for jumping and swimming. (It is these musclebound limbs that give the Edible frog, left, its name.) The skin of toads like the Green toad, right, is dry and covered by knobby glandular projections often referred to as “warts.” With relatively short legs, toads lack the jumping ability and range of frogs.

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Indian Gavial

The Indian gavial, found only in the Brahmaputra, Ganges, and Mahamadi rivers of India and the Koladon River of southeastern Asia, is differentiated from all other species of crocodilians by its long, narrow snout and weak legs. Growing to a size of 7 m (23 ft), the gavial feeds primarily on fish.

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Gouldian Finches

Gouldian finches are one of about 153 species of finches found worldwide. The bills of finches are structurally adapted for shelling seeds, their primary food. A seed wedged in a small groove on the side of the palate is crushed when the lower portion of the bill is raised up against it. The tongue then removes and discards the husk, after which the seed is swallowed.

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Clouded Leopard Climbing

The clouded leopard (Neofelis nebulosa) inhabits rain forests of Asia and can be found in Nepal, Thailand, Indonesia, and Borneo. This beautifully patterned wild cat hunts for birds and mammals usually in the early morning and late afternoon. Amazing climbers, clouded leopards spend much of their time in trees, sometimes hanging upside down from branches.

 

ASSIGNMENT

State five characteristics each of the five classes of vertebrates and an example each class.

SUGGESTED PRACTICALS

  1. Identify each specimen
  2. State which phylum each specimen belong
  3. highlight TWO general features of each specimen

Required specimen (a) lizard (b) house fly/grasshopper (c) earthworm (d) rat (e) bird (f) fish (g) snail (h) toad

THE CELL

CONTENT

  1. The Cell as a Living Unit of an Organism
  2. Forms in Which Cells Exist
  3. The Structure and Functions of the Cell
  4. Cell Theory
  5. Differences and Similarities between Plant and Animal Cells

 

The Cell as a Living Unit of an Organism

The cell is defined as the simplest, the smallest and basic unit of life. It is the structural and functional unit of a living organism. The cell can carry out all life activities such as feeding, respiration, movement etc.

Classification of Living Things Based on The Number of Cells

All living things are classified into two major groups depending on the number of cells they possess. These groups are:

  1. Unicellular or Acellular organism: Organisms which consist of only one cell e.g. Amoeba, Paramecium, Chlamydomonas and Euglena.
  2. Multicellular Organisms: Organisms which consist of two or more cells, e.g. Hydra, Flowering plants, Fish, Bird, Man etc.

Forms in Which Cells Exist

Living cells exist basically in four forms;

1. As single and free living organisms

These are organisms which possess only one cell and are able to live freely on their own. The single cell carries out all life processes such as feeding. Euglena, etc. Parts of the cell may be specialized to carry out a particular process, for example Paramecium.

Paramecium is a fresh-water protozoan. It lives in ponds and puddles and feeds mainly on bacteria. It is often described as having a slipper shape and is about 0.25mm long. It has a stiff outer-covering called the pellicle which gives it a fixed shape. Its cytoplasm is divided into a clear outer layer called the ectoplasm and a granular inner layer called the endoplasm. The endoplasm contains several food vacuoles, two contractile vacuoles and two nuclei. The larger one called the meganucleus and the smaller one the micronucleus. It moves (swims) in the water by means of cilia. The cilia are tiny projections of the ectoplasm through the pellicle.  The oral groove and gullet are specialized for feeding, while the contractile vacuole is specialized for water regulation.

2. As a colony

A colony consists of many similar cells which are joined together. E.g. Volvox, Pandorina, etc. Diagram of volvox

3. As a filament

This consists of many similar or identical cells joined end to end to form unbranched filaments. e.g. spirogyra, zygnema, oscillatoria and oedogonium.

Each cell in a colony or filament behaves as an individual. Each carries out life processes independently of its neighbours.

4. As a part of a living multicellular organism

In multicellular organism cells which perform the same function are grouped together to form a tissue, e.g. tissues of the ileum wall, the retina, and the blood (a tissues which perform a specific function form an organ and a group of organism working together to perform a specific task form a system.

The Structure and Functions of the Cell

From the general point of view, cell is considered as an idea. The dictionary explains the meaning as ‘a small room in a prison for one or more persons’ or as ‘a small number of people.’ When one commits a crime, such a person is put in a police cell while investigation is going on.

However, in Biology the term cell is a vital subject matter and has a special definition. It is defined as the smallest, structural and functional unit of life having a nucleus at the centre and bounded by a cell membrane.

They are two types of cells: Plant and Animal cells. See diagram below

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Plant Cell

Plant cells contain a variety of membrane-bound structures called organelles. These include a nucleus that carries genetic material; mitochondria that generate energy; ribosomes and rough endoplasmic reticulum that manufacture proteins; smooth endoplasmic reticulum that manufactures lipids used for making membranes and storing energy; and a thin lipid membrane that surrounds the cell. Plant cells also contain chloroplasts that capture energy from sunlight and a single fluid-filled vacuole that stores compounds and helps in plant growth. Plant cells are surrounded by a rigid cell wall that protects the cell and maintains its shape.

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Animal Cell

An animal cell typically contains several types of membrane-bound organs, or organelles. The nucleus directs activities of the cell and carries genetic information from generation to generation. The mitochondria generate energy for the cell. Proteins are manufactured by ribosomes, which are bound to the rough endoplasmic reticulum or float free in the cytoplasm. The Golgi apparatus modifies, packages, and distributes proteins while lysosomes store enzymes for digesting food. The entire cell is wrapped in a lipid membrane that selectively permits materials to pass in and out of the cytoplasm.

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EVALUATION:

  1. Define the term cell.
  2. Mention the two groups in which organisms can be placed based on the number of cells.
  3. State the forms in which living cells exist
  4. Sketch a well labelled diagram of plant and animal cells

The Cell Theory

The man who first discovered and described cell in living things is called Robert Hooke in 1665, he also invented the microscope, but the cell theory was proposed by another man called Mathias Schleiden, a German Botanist 1838, and Theodor Schwann, a German Zoologist, these two men postulated the theory known as cell theory in 1839. In 1855, another German Biologist, Rudolf Virchow stated that all cells comes originated from cells.

The cell theory states that:

  1. All living things are composed of one or more cells
  2. Cell is the structural and functional unit of all living things;
  3. Cell originates from a pre-existing cell; and
  4. Cell contains hereditary materials.

Another name for cell components are cell organelles e.g of an organelle is the nucleus of a cell as shown below.

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Mitochondria

Mitochondria, minute sausage-shaped structures found in the hyaloplasm (clear cytoplasm) of the cell, are responsible for energy production. Mitochondria contain enzymes that help convert food material into adenosine triphosphate (ATP), which can be used directly by the cell as an energy source. Mitochondria tend to be concentrated near cellular structures that require large inputs of energy, such as the flagellum, which is responsible for movement in sperm cells and single-celled plants and animals.

Description and Functions of Cell Components

1. Cell wall          

Description: Non-living, made of cellulose, permeable to water and substance

Functions: Provides rigidity to the cell and gives it a definite shape.

2. Cell membrane

Description: Living and differentially permeable to water and substance.

Function: Allows selective movement of materials in and out of the cell.

3. Cytoplasm

Description: Semi-fluid mass enclosed within the cell membrane and contain many organelles.

Functions: The largest and liquid part of the cell in which metabolic reactions occur.

4. Nucleus

Description: Enclosed by a nuclear membrane, and contains chromatin and nucleolus.

Functions: It stores and carries hereditary information from generation to generation. It also translates genetic information into the kind of protein characteristic of the cell. It controls the cell’s life processes

5. Vacuoles

Description: This is the fluid filled spaces in the cytoplasm.

Functions:  Help in maintaining turgidity in the plant cell.

6. Mitochondria

Description: It is a double membrane system, found in all cells. It contains the enzymes for cellular respiration.

Functions: it carries out metabolism for all life processes. Kreb’s cycle and electron transfer system take place in the mitochondria.

 

EVALUATION

  1. State the cell theory.
  2. Who is the first founder of the cell?
  3. List four men who contributed to the discovery of the cell
  4. Describe the nucleus and its functions.
  5. What was the contribution of Felix Dujardin to the cell theory?
  6. State Five (5) differences between plant and animal cell.
  7. Outline four similarities between plant and animal cell.
  8. Describe and state the functions of the following cell components or organelles: (a) Endoplasmic reticulum (b) Ribosome (c) Centrioles, and (d) Chloroplasts

         [mediator_tech]      

SUGGESTED PRACTICAL

ObserveTHE CELL AND ITS ENVIRONMENT

CONTENT

  1. Introduction
  2. Diffusion
  3. Osmosis
  4. Plant Nutrition
  5. Micro and Macro Elements

Introduction

The topic ‘Cell and its Environment’ refers to the activities of the cell in a given environment or the functions of the cell given a particular condition. Some conditions can be harmful to the cell while others are helpful for proper functioning of the cell. This is why we discuss the cell and its environment.

Diffusion

Diffusion can take place in liquid and gases, but diffusion is faster in gases than in liquid, because air and gases as a medium has more spaces to be filled.

Diffusion can be defined as the process by which molecules of substances, such as liquid and gases move randomly from a region of higher concentration to a region of lower concentration until they are evenly distributed.

It is also a process by which fine particles (molecules) flow in and out of cells of living things, and it can occur in non-living things or membrane.

SUGGESTED PRACTICALS

Stand at the corner of the classroom, and spray a perfume, after a while the scent of the perfume will circulate the whole class and every student will attest to the perception. This is diffusion in gas.

You can also demonstrate diffusion of solid material in liquid medium using potassium tetraoxomanganate (vii) crystals. i.e. KMnO4

Materials: Distilled water, Beakers, Spatula, and KMnO4.  

The Rate of Diffusion

The rate of diffusion is the time taken by molecules of a diffusing substance to be uniformly distributed in any given area of the diffusing medium.

Some factors may affect (inhibit or facilitate) the rate of diffusion:

  1. State of matter of diffusing molecules
  2. Size of diffusing molecules
  3. Differences in concentration of diffusing molecules and the medium (conc. gradient).
  4. Temperature of diffusing medium.

The Importance of Diffusion

In a biological systems, diffusion is essential in the following ways:

  1. Gaseous exchange in lungs during external respiration.
  2. The movement of carbon iv oxide and Oxygen during photosynthesis and respiration in plants.
  3. Movement of digestive food from the intestine into the blood circulatory system.
  4. Movement of nutrients, and other metabolic products from the mother through the placenta to the foetus.
  5. The upward movement of mineral salts and nutrients from the soil through the roots to other parts of the plant.

 

EVALUATION

  1. Define the term diffusion.
  2. What is rate of diffusion?
  3. State three importance of diffusion.

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Diffusion

Diffusion is the natural tendency of molecules to flow from higher concentrations to lower concentrations. When the barrier between two substances is removed (as shown here), the molecules will diffuse throughout the entire container. While the number of molecules in the container is the same as it was before the barrier was removed, the substances are now at lower concentrations. The rate of diffusion depends on the weight of the molecules—heavy molecules diffuse more slowly than light molecules.

Osmosis

Osmosis is the movement of water molecules from a dilute solution into a more concentrated solution through a semi-permeable membrane. Living organisms has the cell as the semi-permeable membrane. Since the water molecules are small, the cell is somewhat limited in the amount of direct control it can impose on their passage across the membrane. In osmosis, the stronger solution is called hypertonic solution, while the weaker solution is called hypotonic solution. In osmosis, water molecule move from hypotonic to hypertonic solution, but when the concentrations are equal, the solution is said to be isotonic.

Application of Osmosis in Animals

The application of osmosis in animals include the following:

  1. Reabsorption of water in kidney tubules,
  2. Entry of water into the cytoplasm of unicellular animals, e.g. Amoeba and Paramecium,
  3. Movement of water in and out of living animal cells,
  4. Absorption of water in the large intestine.

The Application of Osmosis in Plants

The application of osmosis in plants include the following:

  1. Absorption of water from the soil by the root hairs,
  2. The movement of water in and out of living plant cell,
  3. The movement of water from the root hairs to the cells of the cortex, and
  4. Opening and closing of the stomata by the guard cells in the leaf.

Demonstration of Osmosis

  1. Using a living membrane or tissue such as yam, pawpaw etc.
  2. By Osmometer; Osmometer can be constructed using a thistle funnel covered with cellophane.
  3. The cellophane is semi-permeable. The thistle funnel is filled with a strong sugar solution to a certain level.
  4. It is then lowered into the beaker containing water. After about 30 minutes, it could be seen that the level of the solution in the thistle funnel has increased due to passage of water through the cellophane membrane.
  5. This indicates that cellophane membrane is a semi-permeable membrane allowing only molecules of water to pass through, but preventing the passage of sugar molecules.
  6. This is the demonstration of osmosis using a non-living membrane.

Osmotic Pressure

This is the minimum pressure that needs to be applied to a solution to prevent the inward flow of water across a semi-permeable membrane. It is the measure of the tendency of a solution to take in water by osmosis.  It is simply the pressure needed to stop osmosis. The osmotic pressure that a solution is capable of developing depends on the number or concentration of its solute molecules. The stronger the solution, the greater the osmotic pressure.

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Osmosis

The experiment shown above demonstrates the process of osmosis. Water flows through a semipermeable membrane into a sugar solution, diluting the solution. The sugar molecules cannot pass through the membrane, so the water outside remains pure.

The Importance of Osmosis

  1. Osmosis regulates the concentrations of salt and water of the blood and other body fluid in animals.
  2. It maintains the cell shape through turgidity and plasmolysis if need be.
  3. It enables the absorption of water molecules from the soil solution to the plants through the root hair.
  4. Movement of water molecules within the plant from the root to the leaves.

EVALUATION

  1. Define the term osmosis.
  2. Write two application of osmosis each in plant and animals.
  3. What is osmotic pressure?
  4. Enumerate three importance of osmosis.

 

Nutrition

Nutrition can be defined as the totality of the processes by which a living thing obtains, and uses food. We have two types of nutrition; plant and animal nutrition.

Plant Nutrition

In plant nutrition, we have photosynthesis and chemosynthesis. The later is a process through which non-green plants use either parasitic or saprophytic modes of nutrition to obtain their food. It can occur in colourless autotrophic bacteria.

Photosynthesis is the process by which green plants make use of raw materials such as carbon (iv) oxide and water to produce sugar and Oxygen in presence of sun light or solar energy and chlorophyll.

Equation for Photosynthesis

6CO2     +     6H2O     →     C6H12O6        +    6O2

Light Reaction

(i) Light energy is captured by chlorophyll

(ii) The energy splits water into hydrogen (H+) and hydroxyl (OH) ions. The process is called photolysis of water and it is the first step in photosynthesis.

4H2O    →     4H+ +   4(OH)   + ATP

(a) The hydroxyl part is reconverted to water and Oxygen is given off as a by-product.

4(OH)   →     2H2O + O

(b) The compound (NADH) coenzyme is reduced by hydrogen ion and ATP is formed.[mediator_tech]

With the energy provided by ATP, the reduced compound (NADH) brings about the assimilation of carbon (iv) oxide through series of small steps , each controlled by a specific enzyme to form sugar or starch.

CO2 + 2H2    →     CH2O + H2O

The overall reaction is below:

CO2 + 2H2O      →       CH2O + H2O + O

The Significance of Photosynthesis

  1. All living things are supported by the by-products of photosynthesis. For example all animals and non-green plants obtain their energy from green plants.
  2. It brings about the purification of the atmosphere by removing excess carbon (iv) oxide (carbon iv oxide)

Materials Necessary for Photosynthesis

These materials are divided into two basic parts: (1) External conditions and (2) Internal conditions.

External conditions:

  1. Water
  2. Light
  3. Carbon (iv) oxide.

Internal conditions:

  1. Mineral salts
  2. Chlorophyll
  3. Enzymes

Some Factors Affecting Photosynthesis:

They include;

  1. Temperature,
  2. Light intensity,
  3. Carbon (iv) oxide,
  4. Amount of soil water/moisture

EVALUATION

  1. What is nutrition?
  2. Define photosynthesis.
  3. Explain what happens in light and dark reaction stages of photosynthesis using equations.
  4. List materials necessary for photosynthesis in the order of external and internal conditions.
  5. Outline some factors that affects photosynthesis.

 

Micro and Macro Elements

Micro Elements

Micro elements are also known as minor or trace elements or micronutrients. These are elements required by plants in very tiny or very little amounts. Although they are needed in trace amounts, it leads to some deficiency when not available at all.

Some micronutrients include; Boron (B), Cobalt (Co), Copper (Cu), Manganese (Mn), Silicon (Si), Zinc (Zn), Chlorine (Cl).

On other hand, macro or major or macronutrients refer to elements that are required by plants in large amounts. Examples are the seven major elements which include Nitrogen (N), Potassium (K), Calcium (Ca), Magnesium (Mg), Iron (Fe), Phosphorus (P), Sulphur (S).

Micro Nutrients

Elements Uses/Importance to Plants Effects of Deficiency
Boron (B) Transport of Calcium and sugar Shoot goes brown
Cobalt (Co) For action of some enzymes Poor growth
Copper (Cu) For respiratory enzymes Poor growth
Manganese(Mn) Activation of some enzymes Shoots die back
Silicon (Si) Cell wall formation, particularly in grasses May affect growth
Zinc (Zn) Activation of some enzymes Poor leaf formation
Chlorine (Cl) For Oxygen release during photosynthesis and for growth and development Plant wilts and chlorophyll necrosis and reduce growth.

Macro Nutrients

Elements Uses/Importance to Plants Effects of Deficiency
Nitrogen (N) Formation of amino acids, protein and nucleic acids. Hormone synthesis. Poor growth, underdeveloped
Potassium (K) Formation of amino acids, protein and cell membranes, crop maturation. Death of plant, yellow leaf at edges.
Calcium (Ca) Development of the cell wall at the growing points. Activate some enzymes Poor growth, particularly of the root.
Magnesium (Mg) Part of the chlorophyll molecule Leaves go yellow.
Iron (Fe) Needed for the synthesis of chlorophyll molecule Leaves go yellow.
Phosphorus (P) Formation of energy storage compound Poor growth leaves go dark green.
Sulphur (S) Needed for protein formation Leaves go yellow, stunted growth.

 

EVALUATION

  1. Define the terms micro and macronutrients
  2. List Four (4) each of micro and micro nutrients[mediator_tech]
  3. Write two (2) importance each of macro and micro nutrients
  4. Outline two (2) each of the effects of deficiency of micro and macro nutrients.

SUGGESTED PRACTICALS

Carry out an experiment to demonstrate osmosis using a living membrane.

a spirogyra filament and draw a well labeled diagram of 10 – 12c

THE PROPERTIES AND FUNCTIONS OF THE CELL

CONTENT

  1. Animal Nutrition
  2. Balanced Diet
  3. Heterotrophic Nutrition
  4. Enzymes
  5. Practical Guide on Food Tests

 

Animal Nutrition

All living things feed in order to obtain energy for their daily activities and also to carry out their metabolic processes. Plants can manufacture their own food (i.e. make complex chemical compounds) from simple raw materials (CO2 and H2O) through the process of photosynthesis. Plants need minerals to make some of the complex compounds and these are obtained from the soil as mineral ions. Animals however cannot manufacture their own food, they depend directly or indirectly on plants. Nutrients that animals require are present in their diet.

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Hamburger and Fries

One of the meals most associated with the United States is a hamburger and French fries. This burger and fries, a daily special, is accompanied by baked beans and coleslaw.

Food Substances

All food taken in by animals can be divided into six groups of food nutrients namely Carbohydrates, Protein, Fats, Vitamins, Minerals, and Water. Fibre/roughage is also an important component of a diet but it is not a nutrient. All these are needed for a balanced diet, for humans.

Carbohydrates, Protein, Fat & oil, and Water are primary food substances and are necessary for the maintenance of life. Minerals salts and Vitamins are welfare food substances and are essential for the well being of an individual.

Types of Food Substances

A. Carbohydrates

These contain the elements carbon (C), hydrogen (H) and Oxygen (O). The ratio of hydrogen to oxygen is 2:1. Carbohydrates are represented by the formula Cx (H2O)y. The major sources of carbohydrate are Sugar (e.g. glucose, maltose) and starches (e.g. yam, maize, rice).

Types of Carbohydrates
  1. Monosaccharides/Simple sugars: These are made up of only one unit of simple sugar e.g.

(a) Hexose sugars: These consist of six carbon atoms arranged into a ring e.g. glucose, fructose and galactose. They make up the most important energy storage molecules in an organism. Their chemical formula is C6H12O6

(b) Pentose sugars: These consist of five carbon atoms e.g. ribose and de-oxyribose. They are used in the formation of nucleic acids.

2. Disaccharides/Complex sugars: These are formed by the condensation (i.e. chemical bonding of two molecules) of two simple sugar molecules. They are represented by the formula C12H22O11 .

Examples are:

(a) Maltose (glucose + glucose – H2O) found in malted cereals and spouting grains.

(b) Lactose (glucose + galactose – H2O) found in milk.

(c) Sucrose (glucose + fructose – H2O) found in sugar cane stems, ripe sweet fruits, sugar – beet and carrot.

NB: All sugars are sweet and soluble and provide energy in a ready-to-use form.

3. Polysaccharides: These are formed by the condensation of hundreds of simple sugar molecules. They are represented by the general formula (C6 H10O5) n where n represents a large number. Examples include starch, cellulose, glycogen (animal starch). Starch and glycogen are insoluble and do not taste sweet.

NB: Condensation is a reaction in which two or more molecules join to form a large molecules with the removal of a molecule of water (H2O) or some other simple molecule.

Importance of Carbohydrates

(i) They provide us with energy.

(ii) It provides heat during its oxidation which is used in maintaining body temperature.

(iii) It is used in building the exoskeleton of arthropods.

 

B. Proteins

Proteins are complex molecules made up of carbon, hydrogen, oxygen and nitrogen (N) many also have sulfur (S). They are long – chain molecules made up of smaller molecules called amino–acid. There are 25 types of amino acids and these occur in different numbers and order in different types of protein. Thus one protein is different from the other. Each individual amino acid joins the chain by means of a peptide bond.

During digestion the breakdown of protein occur in the following sequence;

Protein   →    Proteoses  →   Peptones  →   Polypeptides   →   Amino Acids.

Examples of Proteins

Examples of proteins include:

(a) Soluble proteins e.g. haemoglobin (in blood), enzymes (in water/cytoplasm), antibodies, and some hormones (e.g. insulin).

(b) Insoluble proteins e.g. keratin (a fibrous protein found in skin and hair), collagen (found in bones and cartilage), myosin and actin (found in muscle cell). Sources of protein include (a) animal sources such as fish, meat, milk, egg and cheese. (b) Plant sources such as beans, groundnut and soya beans etc.

Uses/Importance of Proteins
  1. Protein is used for making body building substances which are necessary for building new cells and replacing old ones.
  2. Essential for the repair of cells and worn- out tissues.
  3. Essential for formation of enzymes
  4. Essential for formation of hormones
  5. Essential for formation of antibodies
  6. Essential for formation of heamoglobin etc.
  7. Essential components of cell membranes
  8. It may be required to provide energy.

 

C. Fats and Oils

These are also called lipids and are composed of carbon, hydrogen and oxygen. Each fat molecule is made up of one molecule of glycerol attached to 3 fatty acids. There are different types of fatty acids and these form different fats with different properties. At room temperature fats are solid while oils are liquid. Lipids are macromolecules and have to be broken down into fatty acids and glycerol before they can be absorbed into the body. Sources of fats include margarine, butter, cheese, fatty meat, melon, groundnuts, palm fruits, castor oil seeds, lard etc.

Importance of Fats and Oils
  1. Fats and oil are used for energy storage in the body. They provide more energy to the body than carbohydrate when metabolized.
  2. They are solvents for fat soluble vitamins and also for hormones.
  3. They are important components of cell membranes.
  4. They help in maintaining the body temperature / for thermal insulation in the body. In cold countries, the fat layers under the skins of mammals act as insulators and prevent loss of heat from their bodies.
  5. Fats give buoyancy to marine animals e.g. whales have a thick layer of blubber.

 

D. Mineral Salts

These regulate the metabolic activities within the body. They are also important components of enzymes, pigments and structural parts.

The major source of mineral salts is the diet. Examples of minerals include sodium, potassium, calcium, chlorine, phosphorus, magnesium, iron, copper, cobalt, fluorine and manganese.

Sodium calcium and phosphorus are needed in large quantities in the body while some others like iron and iodine are only needed in small quantities.

A lack of minerals in the diet results to ill health and development of symptoms of deficiency diseases.

Sources, Functions and Deficiency Symptoms of Some Minerals
Mineral Function Deficiency symptom Sources / Daily need
Iron Formation of haemoglobin in red blood cells;
myoglobin in muscle cells and enzymes
involved in cell respiration.
Tiredness, lack of
energy (Anaemia)
Liver, meat, cocoa, eggs,
green vegetables (10mg)
Calcium Strengthens bones and teeth;
needed for blood clotting, proper functioning
of heart and nervous system, and normal
contraction of muscles.
Weak, brittle bones
and teeth (Rickets)
Calcium
Muscle
weakness
and cramps.
Milk, fish, green vegetables (1g) Muscle weakness
and cramps.
Milk, fish, green
vegetables (1g)
Sodium Important component of blood plasma;
maintains correct osmotic pressure of
body fluids;
needed in transmission of impulses in nerves,
sensory cells and muscles and for normal
cell membrane permeability.
Dehydration muscle
cramps, kidney failure.
Salt, natural foods especially
meat, milk and eggs (5-8g)
Phosphorus Involved in transfer of energy, required for
most chemical reactions in the body ;
essential component of DNA and RNA;
major component of bones & teeth.
Rickets Fish, shell-fish, eggs,
milk and cheese. (1.5g)

 

E. Vitamins

These are organic compounds required by man and other animals in only small quantities for normal growth and healthy development. They are biocatalysts (they promote chemical reactions in the body).

Examples include vitamins A, D, E and K which are water soluble. The main sources are fruits, eggs, milk, palm oil, vegetables and animal organs. Inadequacy or lack of these vitamins leads to nutritional deficiency diseases and ill health.

Sources, Functions and Deficiency Symptoms of Some Vitamins
Vitamin Function Deficiency Symptom Sources
Vitamin A
(Retinol)
(i) For normal growth of
body cells and skin
(ii) For proper vision of
the eye in dim light.
(i) Skin becomes flaky.
(ii) Night blindness
(iii) Xerophthalmia
Fish – liver, oil, egg yolk,
green and yellow vegetables,
fruits.
Vitamin D
(Calciferol)
(i) For strong bone and teeth
formation and development.
(ii) It increases the absorption
of calcium and phosphorus
in the intestine.
(i) ricket in children
(ii) Softening of bones in
adults (osteomalacia).
Fish, milk, egg, liver, butter,
synthesized in the skin
when exposed to sunlight.
Vitamin E
(tocopherol)
(i) Promotion of fertility in
animals
(ii) Protects fatty acids and
cell membrane from oxidation.
(i) Sterility and premature
abortion.
Leafy green vegetables,
seeds, egg, milk, liver.
Vitamin k
(phylloquinone)
(i) Aids blood clotting. Slow clotting of blood
leading to severe bleeding
from cuts (Haemorrhages).
Liver fresh green vegetables,
made by intestinal bacteria.
B1
(thiamine)
(i) Needed for formation of
co-enzymes involved in cellular
respiration.
(ii) For normal growth.
(iii) Proper functioning of
heart and nervous system.
(i) Reduced growth.
(ii) Beriberi (a disease of
the nervous system).
Yeast, rice bran, beans,
groundnut, liver.
B2
(Riboflavin)
(i) For formation of co-enzymes
involved in cellular respiration
(ii) For growth, healthy skin and
proper functioning of the eye.
(i) Slow growth.
(ii) Sores in skin (dermatitis)
and around the mouth.
Eggs, liver, kidney, yeast,
leafy vegetables.
B5
(pantothenic acid
or Folic acid)
(i) For formation of co-enzymes
in cellular respiration.
(ii) For formation of red blood
cells.
Disorder of nervous system
and gut. Anaemia
Yeast, eggs, rice bran.
Leafy vegetables, liver.
Vitamin C
(Ascorbic acid)
(i) For maintenance of connective
tissues, bones and dentine
(ii) Helps to resist inflection
(i) Scurvy
(ii) Wounds heal slowly.
Fresh citrus fruits, pawpaw,
guava, green vegetables.

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Apples

The apple tree is widely cultivated throughout temperate regions of the world for its juicy, edible fruit. The many varieties of apples have been popular for centuries and growers have selectively bred certain superior wild varieties for domestication and mass production.

 

F. Water

This is composed of hydrogen and oxygen and makes up two-thirds (70%) of the body mass of a human being.

Water is taken in when we eat or drink. Sources include metabolic water from food, water from rivers, rain, ponds, springs, etc.

Importance of Water
  1. It is required for metabolic activities in the body. It makes up a large part of the protoplasm, thus it is the medium in which chemicals reaction take place in the body.
  2. It transfers digested food substances, excretory products (urine & sweat) and hormones.
  3. It plays an important role in the regulation of body temperature (sweat cools us down)
  4. It helps to maintain the osmotic content of the body tissues.
  5. It is an important solvent for food substances during digestion.
  6. It constitutes a greater part of the blood.[mediator_tech]
  7. It is the main component of plants and animals.

Daily intake of water must equal the loss in urine, faeces, sweat and breath to keep healthy.

 

G. Roughages/Fibre

This is indigestible fibrous materials derived mainly from vegetables, fruits and seed coats (of carbohydrates and proteinous seed).

Fibre adds bulk to food thus stimulating the movement of the bowel. It passes down the entire gut from mouth to anus and does not provide any energy.

Sources include bran cereals, cabbage, sweet corn, celery, etc.

https://classhall.com/wp-content/uploads/2017/04/the-cell-and-its-environment-animal-nutrition-papaya-fruit.jpg

Papaya Fruit

A view of the interior of the papaya fruit shows the pulp and seeds. This edible fruit, capable of growing as large as 9 kg (20 lb), is widely cultivated in the tropics. The latex of the fruit contains a substance called papain, which can be extracted and used to tenderize meat.

Importance of Roughages/Fibre
  1. Fibre helps the movement of food in the alimentary canal by peristalsis so preventing constipation.
  2. Fibre absorbs poisonous waste from bacteria in the gut.
  3. Many doctors believe a high fibre diet lowers the concentration of cholesterol in the blood.
  4. Fibre reduces the risk of heart diseases and bowel cancer.

 

The Balanced Diet

The intake of a variety of food in the right quantity and proportion that provides the body with all the nutrients and energy needed to sustain the body and ensure good health and growth is referred to as a balanced diet.

A balanced diet must contain the seven food substances i.e Carbohydrates (60%), Proteins (15%), Fats (15%), Vitamins (10%), Minerals, Water and Fibre.

Energy Requirements

Even at rest energy is required for basic functions such as heart beats, working of the lungs and keeping body temperature constant. Also chemical reactions in the body such as those involved in growth & repair are occurring and these need energy. The energy required for these body functions is called the basal metallic rate.

https://classhall.com/wp-content/uploads/2017/04/the-cell-and-its-environment-animal-nutrition-balanced-diet.jpg

USDA Food Pyramid

The United States Department of Agriculture Food Pyramid provides a practical visual guide to healthful eating, indicating the recommended daily portions of the basic food groups.

(BMR). BMR varies from person to person; an adult needs 7000kg per day, even at rest this energy is still required.

The Importance of a Balanced Diet

  1. It is required for normal healthy living.
  2. It gives us resistance to diseases.
  3. It provides energy required for normal activities.
  4. It prevents malnutrition/deficiency diseases e.g. a lack of protein in the diet can cause kwashiorkor and marasmus in children.

 

EVALUATION

  1. Name the constituent element, four food sources and three functions of each of the following

(i) Carbohydrates (ii) Protein (iii) Lipid

  1. List the sources and functions of four vitamins and minerals.
  2. State one deficiency disease/condition associated with each type of nutrient mentioned in 1 and 2 above
  3. Define the terms: (a) balanced diet (b) BMR
  4. Mention three importance of taking a balanced diet

 

Heterotrophic Nutrition

This is the type of nutrition in which the organism feeds on complex organic molecules. There are different forms of heterotrophic nutrition.

Types of Heterotrophic Nutrition

1. Holozoic Nutrition:

In this type of nutrition an organism feeds on complex organic materials, usually in solid form. These materials require ingestion, digestion and absorption before assimilation into the body.

Animals that practice holozoic nutrition include herbivores, carnivores and omnivores.

2. Parasitic Nutrition:

In this form of nutrition, one organism (the parasite) lives in or on another organism (the host) causing harm/death to the host. Parasites may be plants or animals.

Parasitic plants attach themselves to the host by means of suckers and send special absorbing organs called haustoria into the tissues of the host’s stem where they absorb water, mineral salts and food substances. Examples are the dodder plant, cassytha and mistletoe (a partial parasite).

https://classhall.com/wp-content/uploads/2017/04/the-cell-heterotrophic-nutrition.jpg

Parasitic animals which live outside the host (ectoparasites) have mouth parts that are modified for piercing or boring into the skin of animals or epidermal layer of plants and suck the body fluid of the host. Examples are ticks, aphids, lice, etc. parasitic animals which live within the host (endoparasites) possess attachment organs such as suckers with which they fasten themselves onto the walls of the host’s gut and suck already digested food. Examples are tapeworm, liverfluke, plasmodium and hookworm.

https://classhall.com/wp-content/uploads/2017/04/the-cell-heterotrophic-nutrition-ectoparasites-tsetsefly-and-chigger-.jpg

https://classhall.com/wp-content/uploads/2017/04/the-cell-heterotrophic-nutrition-endoparasites-plasmodium-and-tapeworm.jpg

 

3. Saprophytic Nutrition

This is a form of nutrition in which an organism feeds on dead and decaying organic matter. Examples are Rhizopus, mushroom, mucor, toadstool and bacteria. These organisms have rhizoids through which they secrete enzymes into the substrate extracellularly. The digested portion is then absorbed into the body of the saprophyte.

Feeding Mechanisms In Holozoic Organisms

All animals obtain their food directly from plants or by feeding on other animals. Their nutritional requirements are obtained from ingested food. Various organisms obtain and ingest their food in different ways; this is referred to as their feeding mechanism. The feeding mechanism of an organism depends on the organism’s mode of nutrition and the type of food on which it feeds.

The ingested food is broken down into simple, soluble and diffusible substances through the process of digestion. The digested food is then absorbed into the fluids of the organism and transported to the body cells where it is assimilated (i.e. used). Undigested food is egested from the body.

Feeding mechanism in holozoic organisms include the following;

  1. Use of pseudopodia to engulf food e.g. in Amoeba
  2. Beating movement of cilia to move food into the oral groove e.g. Paramecium.
  3. Sweeping movement of flagella to move food into the mouth e.g. in Euglena.
  4. Use of tentacles e.g. Hydra.
  5. Filter feeding e.g. Mosquito larvae, whales, oysters, etc.
  6. Fluid feeding e.g. Insects, hummingbirds, etc.
  7. Saprophytic feeding e.g. mushroom, rhizopus, etc.
  8. Parasitic feeding e.g. Dodder plant, Mistletoe, liver fluke, lice, guinea worm, tapeworm, etc.

 

EVALUATION

  1. What are heterotrophs?
  2. Give and explain two forms of heterotrophic nutrition
  3. Mention two forms of feeding mechanism in holozoic organisms
  4. Briefly describe the modification of the mouth parts of a grasshopper to its mode of feeding.

 

Enzymes

An enzyme is an organic catalyst. A catalyst is a substance which brings about or greatly speeds up a chemical reaction and it is not used up or changed during the reaction. Enzymes speed up metabolic reactions in living cells without changing their composition in the process. Enzymes are protein molecules and are manufactured by an organisms own cells.

https://classhall.com/wp-content/uploads/2017/04/the-cell-and-its-environment-animal-nutrition-enzymes.jpg

Structure and function of an enzyme

 

Types of Enzymes

Enzymes are classified based on the nature of chemical changes brought about on a substrate. Examples include:

1. Hydrolases: These bring about the decomposition of a substrate by the addition of water molecules to it. This process is called hydrolysis. However, they can also bring about a reverse reaction in which complex substance are synthesized from simple substances by the removal of water (condensation). Most digestive enzymes are hydrolysis enzymes.

Hydrolysis
E.g. starch https://classhall.com/wp-content/uploads/2018/03/arrows.jpg Glucose
Condensation

2. Oxido-reductase: These bring about oxidation of a substrate by the addition of oxygen or removal of hydrogen. This reaction is usually accompanied by the reduction of another substance. Most respiratory enzymes such as dehydrogenases, oxidases and catalases belong to this group.

3. Transferases: These catalyse reversible reactions

4. Isomerases: These usually change the spatial configuration of a molecule in a living cell. They work on isomers.

5. Lyases: These catalyse the breaking up of bonds by elimination or addition reactions.

6. Ligases: These catalyse the joining of two molecules with accompanying hydrolysis of a high energy bond.

Characteristics of Enzymes

  1. They are proteins in nature.
  2. They are soluble
  3. Some enzymes require the presence of non-proteinous molecules called co-enzymes to activate them.
  4. Enzymes are specific in action e.g. amylases will only act on starch.
  5. Enzymes are organic catalysts i.e. they speed up chemical reactions in the body but are unchanged at the end of the reaction.[mediator_tech]
  6. They are affected by the acidity or alkalinity of their surrounding and will only work in specific pH medium.
  7. They have a specific temperature range above or below which they become denatured/ inactive. They work best between 35 to 40ºc.
  8. Enzymes can be inactivated by inhibitors like cyanide and mercury.
  9. They are usually involved in reversible reactions.
  10. Enzymes act in small quantities and catalyses large amount of substrate.
  11. They can function outside organisms producing them.

 

EVALUATION

  1. What is an enzyme?
  2. What are the functions of enzymes?
  3. Enumerate five characteristics of enzymes.

SUGGESTED PRACTICALS

Practical Guide on Food Tests

The materials/nutrients present in food can be identified using various types of tests. These are:

1. Test for carbohydrates

(a) To test for simple sugar e.g. glucose and fructose.

Put a small quantity of glucose solution in a test tube.

Add an equal amount of benedict solution.

Boil the mixture for 4 – 6 minutes. A bricks-red or orange precipitate indicates the presence glucose.

(b) To test for complex sugar e.g. sucrose, maltose or lactose

Put a small quantity of the sucrose solution in a test-tube

Add a few drops of dilute hydrochloric acid to the solution, (This hydrolyses the complex sugar to simple sugar)

Place the test-tube in a boiling water bath for a few minutes.

Add a few drops of dilute caustic soda (to neutralize the excess acid).

Add an equal amount of feeling’s solution and place the test-tube in a boiling bath. An orange-red precipitate/yellow precipitate indicate the presence of sucrose.

(c) To test for starch

  1. Boil a sample of the starch material (e.g. yam/rice)
  2. Add a few drops of dilute iodine solution to it. A blue-black colouration indicates the presence of starch.

2. To test for proteins

(a) Biuret test

  1. Take a small quantity of fresh milk, egg white solution or malt extract in a test-tube.
  2. Add a few drops of water and 1cm³ of dilute sodium hydroxide.
  3. Carefully add 1% of copper II sulphate solution in drops. Shake the mixture thoroughly after each drop.
  4. A violet, purple, violet colour indicates the presence of protein
  5. A pink colour indicates the presence of peptones.

(b) Millon’s test

  1. Put 3cm³ of egg white/colloidal solution of a protein into a test-tube
  2. Add 3cm³ of millon’s reagent and warm the mixture in a water bath for a few minutes.
  3. A deep red colour or precipitate shows the presence of protein.

(c) Xanthoproteic test

  1. Put 2cm³ of egg white or milk solution in a test-tube.
  2. Carefully add about 1cm³ concentrated trioxonitrate (v) acids. A white precipitate forms which turns yellow on heating.
  3. Cool the contents and add about 3cm³ of ammonium hydroxide solution. Heat the solution and allow it to cool. The colour of the precipitate deepens to orange indicating the presence of protein.

3. To test for fats and oils

(a) Translucent mark test

  1. Drop oil on a spot, on a piece of paper or rub the surface of a fatty food against the surface of a piece of white paper. A translucent mark shows the presence of fat.

(b) Sudan III test

  1. Add a few drops of sudan (iii) solution to some oil in a test-tube. A red colouration is obtained
  2. Boil the solution. A black precipitate is formed.

 

ESSAY QUESTIONS

  1. Distinguish between autotrophic and heterotrophic modes of nutrition
  2. Describe the symbiotic mode of nutrition
  3. Mention three insectivorous plants and discuss one.

THE PROPERTIES AND FUNCTIONS OF THE CELL

CONTENT

  1. Cellular Respiration
  2. Excretion
  3. Growth

 

Cellular Respiration

Respiration is the enzymatic breakdown of organic food substances, like glucose, through a series of chemical reactions in the cell to release energy and produce carbon (iv) oxide and water as by-products. Respiration occurs in all living cells.

Now, the energy released during respiration is used by the organism for such activities as synthesis of proteins, lipids and protoplasm; germination; cell division and enlargement leading to growth; movement; transmission of nerve impulses; active transport and maintenance of body temperature. There is variation in the amount of energy used by different organisms depending on their activities. A very active organism like Tiger uses much more energy than a sluggish one, like Chameleon.

The reactions that occur in cellular or tissue respiration are usually represented by the following equation:

C6H12O6 + 6O2 https://classhall.com/wp-content/uploads/2018/03/single-arrow.jpg 6CO2 + 6H2O + Energy
https://classhall.com/wp-content/uploads/2018/03/pointer.jpg https://classhall.com/wp-content/uploads/2018/03/pointer.jpg https://classhall.com/wp-content/uploads/2018/03/pointer.jpg https://classhall.com/wp-content/uploads/2018/03/pointer.jpg
Glucose Oxygen Carbon
iv oxide
Water

The equation represents only a summary of the raw materials and the end products of tissue respiration. The complex pathway of cellular respiration is shown below:

Tissue respiration is divided into two main parts. The first is the glycolysis, the stepwise series of reactions which leads to the breakdown of glucose to pyruvic acid. The process occurs in the cytoplasm in the cells. It consists of step- wise reactions, each brought about by specific enzymes. Glycolysis is common to, and occurs in the same general manner in all organisms.

Types of Respiration

You already know that we have external and internal respiration, while external deals with breathing in and out i.e. inhalation and exhalation, the internal which takes place in the cell hence, cellular respiration is divided into two basic parts:

  1. Anaerobic Respiration and
  2. Aerobic Respiration

Anaerobic respiration is that type which involve the use of very little or no Oxygen, while Aerobic Respiration is that type which involves the use of large amount of Oxygen.

Anaerobic Respiration

In anaerobic respiration, pyruvic acid is converted alcohol in plants and lactic acid in animals

Equation for lactic acid formation:

C6H12O6 https://classhall.com/wp-content/uploads/2018/03/single-arrow.jpg 2C3H6O3 + Energy

In plant cell, the products of anaerobic respiration are ethanol and carbon iv oxide. Formation of alcohol is represented by the equation:

C6H12O6 https://classhall.com/wp-content/uploads/2018/03/single-arrow.jpg 2C2H5OH + 2CO2 + Energy

This series of reaction convert glycogen in animal and starch in plant to glucose. The glucose is then converted by ten steps to pyruvic acid as below:

https://classhall.com/wp-content/uploads/2017/04/the-cell-anaerobic-respiration-converting-food-to-usable-energy.jpg

Converting Food to Usable Energy

Cellular respiration is a complex series of chemical reactions that harvests the energy trapped in the bonds of glucose sugar molecules and converts it into a chemical form that can be stored for later use. Humans and other animals obtain glucose sugar molecules from food, such as the fruits and grains shown here, while plants create glucose sugars in the process of photosynthesis. Essential to the survival of most organisms on Earth, cellular respiration yields the energy that makes our bodies function properly.

Aerobic Respiration

Aerobic respiration is a breaking down process known as catabolism, an aspect of metabolism. It is represented by the Kreb’s Cycle.  Diagram required.   In Kreb’s Cycle, for one molecule of pyruvic acid 15 molecules of ATP are produced. Since a molecule of glucose produce 2 molecules of pyruvic acid, therefore 30 molecules of ATP are produced from the the 2 molecules of pyruvic acid. Hence, a molecule of glucose produceds a total of 38 molecules of ATP during a complete aerobic respiratory process. The oxidation of glucose can thus be summarised with the following equation:

C6H12O6 + 6O2 https://classhall.com/wp-content/uploads/2018/03/single-arrow.jpg 6CO2 + 6H2O + Energy
https://classhall.com/wp-content/uploads/2018/03/pointer.jpg https://classhall.com/wp-content/uploads/2018/03/pointer.jpg https://classhall.com/wp-content/uploads/2018/03/pointer.jpg https://classhall.com/wp-content/uploads/2018/03/pointer.jpg
Glucose Oxygen Carbon
iv oxide
Water

Another aspect of metabolism is Anabolism which is a building up process. An example is an aspect of plant nutrition commonly known as photosynthesis.

EVALUATION

  1. Explain the terms; Aerobic and anaerobic respiration.
  2. Discuss with a diagram the glycolytic pathway and Kreb’s cycle.
  3. State the following equations: respiration, lactic acid, and fermentation.

[mediator_tech]

Excretion

Definition of Excretion

Excretion is defined as the process by which living things eliminate waste products or toxic substances from their body through their excretory organs.

Excretory System of Some Organisms

ORGANISM EXCRETORY SYSTEM
Some unicellular organism Contractile Vacuole
Flatworms Flame cells
Annelids (e.g. earthworm) Nephridia
Insects Malpighian tubules
Vertebrates Kidneys, lungs, skin, and liver.
Plants Stomata and Linticels

 

Excretory Organs and Substances they Excrete in Vertebrates

In Animals

Lungs: Carbon (iv) oxide, and water vapour.

Skin: Sweats, salts and nitrogenous waste.

Kidney: Urea, excess water, excess salts, ammonium compounds, and acids.

Liver: Bile pigments.

In Plants

Stomata: Oxygen, Carbon (iv) oxide and water vapour.

Bark: Tannins, resins and latex.

Leaves: Crystals of calcium oxalate, calcium carbonate and anthocyanin pigments which give red, blue, and violet colours to many flowers.

Lenticels: Oxygen, Carbon (IV) oxide and vapour.

EVALUATION

  1. Define the term excretion
  2. List some organs of excretion and the organism concerned.
  3. Outline some waste products in animals and plants and organs responsible.

ASSIGNMENT

  1. Sketch an annotated diagram of photosynthetic leaf structure.
  2. Sketch the glycolytic pathway and the kreb’s cycle in your note book (Well labelled)

 

Growth

The Meaning of Growth

Growth is defined as an irreversible increase in size and mass due to formation of new protoplasm in the cell. Whenever the anabolic processes proceed at a faster rate than the catabolic process, there will be a supply of new substances to cause growth.

The three distinct processes that contribute to growth are cell division, cell enlargement and cell differentiation. In cell division, the nucleus and then the cytoplasm of the parent cell divide to form two daughter cells, then into four and so on bringing about an increase in the number of cells.

The daughter cells then increase in mass and size (i.e. enlarge) and eventually develop into a special type of cell (i.e. differentiate) by changing its shape and structure to carry out a particular function. The kind of cell it becomes depends on its position in the body of the organism. It may develop into a nerve cell in the brain, a muscle cell in the heart or a ciliated lining cell in the trachea.

Diagram of Root Tip Showing Apical Meristem

https://classhall.com/wp-content/uploads/2017/04/the-cell-excretion-root-tip-showing-apical-meristem.jpg

Root Tip Showing Apical Meristem

This lengthwise section of the tip of a plant root shows the apical meristem, which, with its rapidly dividing cells, is responsible for primary growth. Apical meristem can also be found at the tips of stems.

Basis of Growth

Cell division (mitosis) is the basis for growth in all multicelluar organisms. Mitosis is the cell division which occurs in the body cell (somatic cells) during which a parent cell divides to produce two daughter cells having the same number of chromosomes as itself.

Mitosis does not occur in all the cells of growing region of the organisms e.g. the root tips or shoot apices and cambium that undergo mitosis. These growing regions are described as meristems.

Cell division by mitosis occurs in four successive phases of continuous sequence namely prophase, metaphase, anaphase and telophase. Between the end of one mitosis and the commencement of a new mitotic division is a period described as interphase or pre-mitotic phase.

Interphase is not a resting time, but a period during which the young daughter cells accumulate and synthesize new body materials, thus preparing itself for the next division.

Diagram Showing the Growth of an Embryo

https://classhall.com/wp-content/uploads/2017/04/the-cell-growth-diagram-showing-the-growth-of-an-embryo.jpg

Spemann’s Experiments

The experiments of Hans Spemann in the early 1900s demonstrated the role of certain cytoplasmic signalling substances in the amphibian embryo. (Left): By cleaving the fertilized egg unnaturally, Spemann showed that an area called the gray crescent is essential to embryonic development. (Right): By the two-cell-layer (blastula) stage, the cells in the embryo have already been “mapped” to the structures they will form in the complete embryo. Spemann showed that if the embryo were cleaved at this point, only the section containing the dorsal lip of the blastopore (once the gray crescent area) would continue to develop.

The daughter cells synthesize new structures from the raw materials that they absorb from their surroundings. This process is called assimilation and results into cell enlargement. Cell differentiation also occurs as the cell develops into specialized cells.

An organism may be said to achieve growth when there is an increase in its dry weight, size or number of cells.

Factors Affecting Growth

These factors may be divided into external and internal factors. The external factors include the following:

  1. Nutrient availability: Body substances are synthesized from available nutrient materials and energy.
  2. Accumulation of toxic byproducts of metabolism may inhibit growth.
  3. Temperature: All biological processes including growth are accelerated as temperature rises from a minimum value at which no growth occur to a certain point beyond which retardation occurs.
  4. Light is essential for the growth of photosynthetic plants because it supplies the energy by which all new tissues are synthesised.
  5. PH: the Ph of the fluid in contact with a cell has a profound effect on all its activities. Some species grow best in a given PH range.
  6. The main internal factors controlling growth are hormones and enzymes.

https://classhall.com/wp-content/uploads/2017/04/the-cell-growth-rodents.jpg

Rodents

Rodents represent nearly 40 percent of all mammal species. Over 1700 species of rodents, including (top from left) porcupines, beavers, chinchillas, pacas, (bottom from left) flying squirrels, mice, muskrats, and capybaras, can be found in nearly every terrestrial and arboreal habitat. The success of this group is due in part to its adaptability to new food sources and habitats and its relatively brief reproductive cycle.

Regulation of Growth by Hormones

The auxins in plants influence cell division (e.g. cytokinins), cell elongation (e.g. gibberellins), regeneration of tissues at cut surfaces, growth of ovaries into fruits, development of buds and roots, and the growth of abscission layer in leaves. The thyroid glands of vertebrates produce thyroxin at a concentration that promotes normal growth. In the absence of thyroxin growth does not occur. Other hormones that exert influence on growth are produced by the pituitary gland and sex hormones.

 

EVALUATION

  1. Define growth
  2. List three processes that contribute to growth
  3. Define mitosis and list the four main phases of mitosis
  4. Name five external factors and two internal factors that affect growth
  5. Name two plant hormones and state their influence on plant growth

SUGGESTED PRACTICAL

Activity

  1. Identification of fastest growth regions in plant.
  2. Experiment to find out the effect of light on the growth of seedlings.

THE PROPERTIES AND FUNCTIONS OF THE CELL

CONTENT

  1. The Cell’s Reactions to its Environment
  2. Movement
  3. Reproduction

 

The Cell’s Reactions to its Environment

The protoplasm of plant and animal cells is irritable. It can detect and respond to the changes in their environment. Any change in conditions which is enough to produce a change in the activities of an organism or its part is called a stimulus.

Types of Responses

The three responses of the cell to its environment are tactic, nastic and tropic responses.

A. Tactic Responses (Taxism)

It is a response made by a whole organism or its freely locomotive parts in response to an external stimulus. Types of tactic responses are:

(i) Phototactic (Phototaxis): response to variation and intensity of light e.g. in free swimming Euglena, Chlamydomonas etc.

(ii) Chemotactic (Chemotaxis): response to the presence of chemical substances e.g. chemotactic movement of Amoeba away from an acidic environment.

(iii) Aerotactic (Aerotaxis): response to the source of oxygen

(iv) Osmotactic (Osmotaxis): response to variation in osmotic concentration

B. Nastic Responses (Nastism)

This is a response made by a fixed plant in response to a non-directional or diffuse stimulus. Various types of nastic responses include the following:

(i) Nyctinastic (Nyctinastism): response to changing day and night conditions as exhibited by some flowers and leaves due to changing conditions of temperature and light intensity. Nyctinastic movement is a combination of two factors- temperature and light i.e. thermonastic and photonastic respectively e.g. leaflets of leguminous plants such as acacia, groundnut and clover.

(ii) Haptonastic (Haptonastism): response due to contact e.g. movement of leaves of insectivorous plants such as venus flytrap.

(iii) Hydronastic (Hydronastism): response to humidity changes

(iv) Chemonastic: response to presence of specific chemical substances.

C. Tropic Responses (Tropism)

This is a response made by a fixed plant part to a stimulus. The direction of movement is determined by the direction from which the stimulus originates. Various types of tropic responses include the following:

(i) Phototropism: growth movement in response to the stimulus of light e.g. growth of plant stems. Shoot is positively phototropic while the root is negatively phototropic.[mediator_tech]

(ii) Geotropism: a growth response to the stimulus of gravity e.g. geotropic response of root and shoot. Root is positively geotropic while shoot is negatively geotropic.

(iii) Hydrotropism: a growth response to the stimulus of water e.g. root of plants grow towards a water source.

(iv) Chemotropism: response to concentration of chemical substances.

(v) Haptotropism (Thigmotropism): a response to the stimulus of touch e.g. tendrils of climbing plants.

 

EVALUATION

  1. Give three examples of tactic responses.
  2. State the differences between nastic and tropic responses
  3. List three forms of tropic response with relevant example of each

 

Movement

Living cells are metabolically very active and their contents are constantly moving because:

  1. Materials constantly enter or leave the cell or move from one part of the cell to the other.
  2. Genetical information flows from the nucleus to the cytoplasm and
  3. Protein and other substances which are manufactured or broken down are transported within or out of the cell. These can be seen as protoplasmic streaming or cyclosis.

1. Cyclosis: This is the circulation of protoplasm in the cell where the protoplasm flows around the cell constantly in one direction.

2. Amoeboid Movement: This is characteristics of the naked non-cellular masses of protoplasm of many of the protozoan’s, the sliming fungi, some plants and animal gametes and certain wandering cells in higher animal bodies e.g. leucocytes in man.

Amoeba moves in a slow streaming way by pulling out lobe-shaped extensions of the cell called pseudopodia.

When a pseudopodia form, a thin plasmosol flows into it and is changed into the semi-solid plasma gel. As a pseudopodium streams forward at one end of the cell another is withdrawn. By this means amoeba moves about. Human white blood corpuscles use amoeboid movement to pursue and capture bacteria in the blood plasma.

3. Organelles for Movement: These include pseudopodia, cilia and flagella. Pseudopodium is an organelle of locomotion in Amoeba. In some protozoans and tiny aquatic animals, movement is brought about by cilia and flagella. They are similar in structure composed mainly of microtubules powered by ATP.

Cilia are short hair-like structures. They are usually numerous and packed closely together. They move in a co-ordinate way to bring about movement. In the paramecium, the action of the cilia moves the whole organism at the same time it also directs a current of water containing food into the paramecium gullet. In the cells lining the human wind pipe, the beating of the cilia causes mucus to more up towards the throat.

Flagella are at least ten times longer than cilia and are fewer in number. It is a whip-like structure which can send waves of movement along its length. Flagella help to move the organisms like Euglena and Chlomydomonas and motile parts of organisms like human sperms.

Growth Movement Regulated by Auxins

Auxins are produced at the apices of shoots and roots but move to the region of sell elongation to bring about their effect. Auxin functions as hormones or chemical messengers.

1. Phototropism: When a shoot receives light from all sides, the auxins produced at the shoot apex pass down and exert a stimulating effect on the region of cell elongation, causing the shoot to grow evenly and vertically. When a shoot receives light from one side only, it bends and grows towards the light. If the shoot tip is covered, the shoot continues to grow vertically. This shows that somehow, one sided lighting causes less auxins to gather on the shaded side. This makes the cells on the shaded side grow and enlarge faster, causing the shoot to bend toward the light.

Diagram Showing the Growth-regulator Hormone

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Pituitary Gland

Called the master gland, the pituitary secretes hormones that control the activity of other endocrine glands and regulate various biological processes. Its secretions include growth hormone (which stimulates cellular activity in bone, cartilage, and other structural tissue); thyroid stimulating hormone (which causes the thyroid to release metabolism-regulating hormones); antidiuretic hormone (which causes the kidney to excrete less water in the urine); and prolactin (which stimulates milk production and breast development in females). The pituitary gland is influenced both neurally and hormonally by the hypothalamus.

Geotropism

If a young plant is placed horizontally more auxins seem to collect on the lower sides of the shoot and root. In the shoot the high auxin concentration in the lower side stimulates growth and tends to make the side grow rapidly, so that the shoot bends and grow vertically upwards.

In the root, the high auxin concentration on the lower side inhibits growth and tends to make this side grow slowly so that the root bends and grows vertically downwards.

EVALUATION

  1. Define cyclosis
  2. Describe amoeboid movement
  3. State two differences between flagella and cilia
  4. State two uses of cilia to paramecium
  5. Name two growth movements that are controlled by auxins in plant.

 

Reproduction

Reproduction is the ability of living organisms to produce offspring’s i.e. new individuals of their type. It is the only way in which each kind of organism can continue to live on forever although the individual must eventually die. The two forms of reproduction are sexual reproduction and asexual reproduction

Asexual Reproduction

In asexual reproduction, an individual produces an offspring by itself i.e. only one parent is present. There is no fusion of nuclei and the cells that give rise to the offspring usually divide by means of mitosis. As a result, asexual reproduction often produces clones-offspring which are identical to the parent. In rare cases the offspring may not be identical due to mutation.

Asexual reproduction is common among simple organisms and flowering plants. Forms of asexual reproduction include the following:

  1. Fission: It is commonly found in bacteria and protists. The parent organism simply divides into two or more parts, each of which can exist by itself. e.g. binary fission in bacteria.
  2. Budding: In budding the offspring develops as an outgrowth of the parent. The bud may form on an internal or external surface of the parents. Internal buds are formed in some sponges and released when the parent dies. External buds occur in Hydra and Coral polyps. The buds break off from the parent without causing any injury and lead an independent life.

Diagram Showing Cell Division During Growth

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Comparative Embryology

Some anatomists study embryonic development to compare different organisms and help determine the evolutionary relationships between them. Sea urchins, frogs, humans, and many other animals are remarkably similar in their early development. All begin with a single cell that divides into two cells, the first step is the process of cleavage (1a, 2a, 3a). During cleavage, cell divisions occur so rapidly that the cells do not have time to grow between divisions, and the result is smaller and smaller cells. Cleavage produces a solid ball of cells called a morula (1b, 2b, 3b). Within the morula, a fluid-filled cavity called the blastocoel develops, converting a morula into a blastula (1c, 2c, 3c). In a process called gastrulation, certain cells of the blastula migrate to different regions of the blastula to create the gastrula, a structure with three cell layers (1d, 2d, 3d). The outer cell layer of the gastrula, called the ectoderm (shown in blue), forms the outer covering of all animals, and in the frog, human, and other higher animals, it also forms the nervous system. The inner layer of the gastrula, known as the endoderm (shown in yellow), gives rise to the gut in all animals, and in higher animals, other organs including the stomach, pancreas, liver, and lungs. The mesoderm, which forms between the ectoderm and endoderm, produces the simple excretory system of the sea urchin and frogs and the kidneys of humans. In higher animals, the mesoderm also gives rise to blood, bone, muscle, and other structures. Cell specialization is followed by the development of primitive organs, which marks the larval form of sea urchins and frogs, and the embryo stage of human development (1e, 2e, 3e). Size and time of development vary widely among species. The sea urchin larva, for example, forms in 12 to 76 hours and measures 0.1 to 0.3 mm (0.004 to 0.01 in), while the human embryo takes eight weeks to fully form, and measures about 30 mm (about 1.2 in) from crown to rump.

  1. Spore Formation: Spore are small unicellular bodies which are produced in large numbers. They are small, light and easily dispersed by air. Under favourable conditions each spore can develop into an independent organism. Spores are commonly produced by Bacteria, Fungi, Protists, Algea, Mosses and Ferns.
  2. Fragmentation: In this process a part of an organism breaks up or fragments from the parent organism and give rise to a new individual. It is a form of regeneration that occurs in simple organisms like algae, coelenterates and sponges.
  3. Vegetative propagation: It occurs mainly in higher plants where a new plant grows from any portion of an old one other than the seeds. This is the formation of new individuals or plants by vegetative portion of the plant such as roots, stems and leaves. They are tubers, corns, bulbs, rhizomes, suckers and runners.
  4. Root tubers are modified roots which grow under-ground and act as food storage organs. New plants may develop from buds which arise near the point of origin with the stem e.g. cassava, sweet potato and carrots.
  5. Corns: These are modified underground stem which grow vertically. They produce lateral shoots which are capable of growing into new plants when detached e.g. cocoyam
  6. Bulbs: There are modified underground leaves adapted for food storage. New bulbs in the axils of the scale leaves. Examples of bulbs are onions and lilies.
  7. Parthenogenesis: This is the development of an egg without fertilization. It occurs in honey bee drones and aphids.[mediator_tech]

Sexual Reproduction

Sexual reproduction involves two parents of different sexes (Male and female). Each parent produces gamete male and female gametes respectively. There is meiosis during which the chromosomes number is halved i.e. from diploid to haploid in the formation of gametes. The egg cell (female gamete is large and non-motile). The sperm (male gamete) is motile and small. During fertilization, the two haploid gametes (male and female) fuse to form a diploid zygote. The zygote undergoes repeated cell division and forms an embryo. The embryo undergoes repeated cell division and differentiation and develops into a young organism similar to the parents.

In lower animals and plants such as protozoa, fungi and algae, there is no formation of specialized reproductive organs. In this case, whole individuals from different strains become differentiated into male and female organisms. They join together and exchange nuclear materials.

In paramecium, after the exchange of nuclear materials they separate and each cell divides to form four daughter animals.

Conjugation in Spirogyra

In spirogyra, two filaments lie close to each other and outgrowths appear on the walls of the cell lying opposite one another. The cells meet and their walls break and a conjugation tube is formed. One of the gametes passes through the conjugation tube and merges with the gamete in the other cells and their nuclei unite. This results into formation of a zygospore.

The zygospore can withstand dry conditions and can germinate into a new individual when moisture is available. This process of reproduction is called conjugation. It also occurs in mucor.

Meiosis

Meiosis is the cell division that gives rise to gametes and haploid spores. In flowering plants and animals, it occurs only in the reproductive organs. When a diploid cell undergoes meiosis, the chromosomes replicate once and the nucleus and cell duplicate (divide equally) twice. This results in the diploid parent cell giving rise to four haploid cells.

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Gigantism

Gigantism results from the overproduction of growth hormone during childhood or adolescence. The arms and legs grow especially long, and height can surpass 2.4 m (8 ft). The disorder is caused by a pituitary tumor that, if untreated, usually kills the patient by early adulthood. If the tumor develops after growth of the long bones is complete, the result is a condition called acromegaly, characterized by a long face, jutting jaw, and large feet and hands.

At the start of meiosis, each member of a homologous pair of chromosomes moves to lie side by side so that all parts of the two chromosomes match exactly. Each chromosome is also made up of two chromatids while they are thus paired; genetic material is exchanged between the chromatids. This is known as crossing over and leads to greater variation in the offspring.

When the nucleus divides for the first time the chromosomes in a given pair (not chromatids) separate and move to opposite ends of the cell. This results in only half the number of the chromosomes going to each daughter cell.

During the second nuclear division, the chromatids separate and move to opposite ends of each daughter cell. This gives rise to four gamete cells, each with a haploid number of chromosomes.

Differences between Mitosis and Meiosis
Mitosis Meiosis
1. Occurs during the growth of
somatic cells and asexual
reproduction.
Occurs during gamete
production.
2. Two daughter cells (offspring)
are formed.
Four daughters cells (offspring)
are formed.
3. Chromosome number of parent
and daughter cells is the same.
Chromosome number of daughter
cells is half the number in the parent cell.
4. The chromosome and their genes
in each daughter cell is identical.
The chromosomes and their
genes in the four daughter cell are not identical.
5. No crossing over occurs Crossing over occurs.
6. Offspring produced by mitosis
are exact replicates or clones
of the parent organism.
Offspring produced by meiosis
in sexual reproduction will show
variations among themselves
and their parents.

Structure and Functions of the Male Gonad

A typical male gonad consists of a pair of testes, which are enclosed in a fold of skin known as scrotum (scrotal sac). The scrotum hangs behind the spongy, muscular and erectile structure called penis. The scrotum, testes and penis are situated externally in the pubic region. Each testis consists of numerous tubules called seminiferous tubules.

The cells of these tubules divide repeatedly to form sperm cells in a process called spermatogenesis. A set of profusely coiled tubule known as epididymis connects each testis to the vas deferens, which conveys the sperm cells to the seminal vesicle for storage until there is the need for ejaculation. Seminal fluid secreted by the prostate gland provides a medium for sperm cells to swim and be nourished. On ejaculation, the sperms are discharged to the outside through the urethra.

The testes produce the sperm-the male gametes. It also secretes the hormones testosterone, which is responsible for producing secondary sex characteristics in males as well as stimulating sperm production. 

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Internal View of Male Reproductive System

The reproductive anatomy of the male human is largely external. Beginning at puberty, sperm are produced within seminiferous tubules of the testicles, a pair of glands that reside in a pouch called the scrotum. The external location of the scrotum keeps the temperature of sperm slightly below body temperature, which is necessary for their healthy development and survival. From each testicle, sperm migrate to a long, coiled tube known as the epididymis, where they are stored for one to three weeks until they mature. Also located outside the body is the penis, the erectile organ responsible for the excretion of urine and the transfer of sperm to the vagina of the female. Just before ejaculation during sexual arousal, mature sperm travel from the epididymis, a coiled tube behind each testicle, through a long duct called the vas deferens. Sperm leave the body in semen, a fluid produced by the seminal vesicles.

Structure and Functions of the Female Gonad

The female mammalian gonad consists of a pair of ovaries suspended by connective tissues at the lower dorsal portion of the abdominal cavity. Ovaries produce the ova (singular-ovum), the female gamete. When the ovary releases an ovum, it is captured by an oviduct (also called fallopian tube). The oviduct conveys the ovum to the muscular uterus. Each oviduct has a funnel-shaped end, which opens close to the ovary in the abdominal of ova.

The uterus is connected to the outside of the organism through the vagina (or birth canal). Externally, the vagina opens at the vulva.

The ovary plays the following important roles, namely the production of female sex hormones oestrogen and progesterone. Oestrogen stimulates and maintains the development of the female secondary sex characteristics, whereas progesterone stimulates and promotes the growth of the uterine lining in readiness for implantation of an embryo.

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EVALUATION

  1. Define reproduction
  2. State two differences between sexual and asexual reproduction
  3. State three differences between mitosis and meiosis
  4. List three forms of asexual reproduction
  5. State three functions of male gonad
  6. Name two hormones produced by the female gonad and state their functions
  7. Compare sexual and asexual reproduction
  8. State five differences between mitosis and meiosis
  9. List the four major phases of cell division in mitosis
  10. Define reproduction
  11. State three functions of (i) mammalian testes (ii) mammalian ovary.

TISSUES AND SUPPORTING SYSTEMS – SKELETONS AND SUPPORTING SYSTEMS IN ANIMALS

CONTENT

  1. Biological Significance of the Skeleton (Importance of the Skeleton)
  2. Forms of Skeletons
  3. Types of Skeletons
  4. Bones of the Vertebral Column
  5. Joints
  6. Functions of Skeleton in Animals

 

Skeletons and Supporting Systems in Animals

What would animals including you look like as well as incapable of doing without the support of bones and cartilage? Sitting, standing, crawling, walking, swimming, flying, and more, would be impossible.

Multicellular organisms have some form of rigid support system that give them shape that enable them to exhibit movement of various degrees as well as withstand forces of wind and water. The framework and the tissues that support it is known as tissue and supporting system.

Skeleton is the framework which gives support and shape to an animal. This supporting framework can be on the inside of the organism: in higher animals such as reptiles, birds and mammals, the organisms have a skeleton  which  form the central core of the body. It is covered by muscles, blood vessels, nerves and skin.

In man the various structures such as tendons, ligaments, interstitial tissues and bones make  up the skeletal and supporting system in animals.

Biological Significance of the Skeleton

Most living organisms whether they are plants or animals, posses a form of rigid frame work called skeleton. Skeleton consists of various tissue and supporting systems in both plants and animals. Skeleton is biologically significant in the life of living organisms. Without skeleton, soft tissues will not have adequate support, protection and shape. Their bodies will collapse and animals may not be able to move parts or all of their bodies. Body movement in a complex animal is brought about by muscles which work by pulling on some kind of support. This support is the rigid framework – skeleton- in animals to affect work and movement. Aquatic multicellular animals need a supporting system to succeed in their hunt for food. As a result, most complex animals have evolved supporting structures or skeletons which provide support against gravity, but the skeletons are flexible enough to allow movement.

[mediator_tech]

EVALUATION

  1. What is Skeleton?
  2. State three biological significance of skeleton in the life of living organisms.

Forms of Skeletons

There are three basic forms of animal skeleton: chitin, cartilage and bone. These are the main types of materials found in the skeleton of animals.

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Exoskeleton of a Goliath Beetle

Instead of an internal skeleton, the goliath beetle, like other insects and crustaceans, has an exoskeleton covering the outside of the body. This exoskeleton provides support for the body much as an internal skeleton does in higher animals. It also provides protection from predators. The exoskeleton is composed of a hard, waterproof, proteinaceous material called chitin. The one main drawback to this type of skeleton is that it does not grow along with the rest of the animal and must periodically be shed in a process called molting.

Chitin

Chitin is a tough light and flexible material that is a major component of the skeletons of arthropods. It is a non-living substance and incapable of growth. It consists of cellulose-like carbohydrate and some deposits of proteins and minerals. Animals with chitinous skeleton can only grow by moulting because the exoskeleton restricts the growth and size of the   organism.  The skeleton of insects is composed of chitin and a thin, waterproof layer of wax.

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Arthroscopic Knee Surgery

Cartilage disks, or menisci, in the knee act as cushions between the bones of the upper and lower leg. Under normal circumstances the menisci stretch and give, but under heavy stress, such as strenuous and repetitive activity, the cartilage can be torn. This painful condition causes the knee to lock in position or buckle unexpectedly. Physicians use a tool called an arthroscope to view the inside of joints and evaluate cartilage damage. An arthroscope is a thin fiber-optic viewing instrument that is inserted into the joint through a small incision in the knee. Arthroscopes may also be equipped with surgical tools, enabling the correction of many knee problems without invasive surgery.

Cartilage

This tissue is found in the skeletons of complex vertebrates. It consists of living cells (chondroblasts) and carbohydrate and protein fibres. It is a tough and flexible tissue that has great tensile strength. It acts as a shock absorber, cushioning the effect of bones moving against bones when we move.

Cartilage does not have its own blood supply but depends on the oxygen and nutrients that diffuse across it from nearby tissues. It is usually found inside animals and can be replaced by bones as in young embryos. It is the skeletal material found as endoskeleton of cartilaginous fish such as rays  and sharks,  in human babies and in several part of adults (but in very small  portions) e.g. Pinna, tip of  the nose and end of long bones.

Cartilage occurs in three forms: elastic, fibro and hyaline cartilage.

  1. Elastic cartilage is present in the external ear and epiglottis. It also supports the Eustachian tube and the external ear canal.
  2. Fibro cartilage is tougher than hyaline cartilage and is found in the discs between the small bones (vertebra) of the vertebral column.
  3. Hyaline cartilage makes up the rings which support the trachea and bronchi and keep them open. It covers the surfaces of movable joints and also supports the protruding part of the nose.

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Joint Damage Caused by Arthritis

The term arthritis refers to more than 100 different diseases causing pain, stiffness, and inflammation in the joints. Healthy joints are composed of cartilage and lubricating fluid, called synovial fluid, encased in a joint capsule, or synovial membrane. In osteoarthritis, the most common form of arthritis, joint cartilage is destroyed and, in some cases, bony outgrowths known as bone spurs develop. In rheumatoid arthritis, white blood cells in the synovial membrane divide, grow, and multiply, producing inflammation, pain, and stiffness in the joint, which may eventually lead to cartilage destruction.

Bone

Bone is the main skeletal structure found in vertebrates. It consists of living bone cells (osteocytes), protein fibres (collagen) and minerals, mainly calcium phosphate and calcium carbonate. The minerals, are mainly calcium phosphate and calcium carbonate.  Minerals  are non-living matter and make up two-thirds of the mass of a bone.  As a result, bone is a stronger and more rigid tissue than cartilage. Bones have their own blood supply to nourish them.

In a young vertebrate embryo, the skeleton is made up of cartilage. As the embryo grows, bone cells replace cartilage cells. This causes the cartilage tissue to harden into bone through the addition of minerals. This process is known as ossification.

The long bones such as humerus, femur, and tibia, consist of a hard outer layer called shaft and a spongy and hallow cavity filled with bone marrow. The middle part, in the hollow is occupied by the yellow marrow and it consists of fat cells. Red marrow fills the spongy spaces in the two ends. A layer of hyaline cartilage covers their articulating surfaces. The numerous tiny openings in the bones allow circulation of blood and sensitivity.

Differences between a Bone and a Cartilage

Bone Cartilage
1. Made up of living cells surrounded
by non-living cells
made up mainly of living cells.
2. Made up mainly of minerals Not made up of minerals.
3. Made up of a hard substance Made up of soft substances
4. Inflexible particularly in adults Very flexibe or elastic
5. Never replaced by cartilage Can be replaced by bone

Types of Skeleton

Skeletal tissue differs as observed in invertebrates and vertebrates. The types are as follows:

1. Hydrostatic Skeleton: This is the simplest type of skeleton. It depends on turgor pressure of its body fluid.[mediator_tech]

A typical example of an organism with this type of skeleton is Earthworm. The muscle in the body wall works against its fluid. The walls of each of the body segment have two sets of muscles. One set is longitudinal, while the other is circular. By contracting and relaxing antagonistically, movement is affected in the organism and a form of shape is affected.

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Earthworm

Earthworms have a segmented, compartmentalized, cylindrical body and range in length from several centimeters (a few inches) to nearly 3.3 m (11 ft). They have no eyes, ears, or lungs. Earthworms breathe when air that is present between soil particles diffuses through their thin skins, and they are forced to the surface if these air pockets fill with rainwater. When a worm moves, it uses its longitudinal muscles to extend the front of its body into the soil ahead of it, pulling the back part up behind it. Setae, tiny projections from each segment of the worm, stick into the surrounding soil to keep the worm from slipping. The digging action of earthworms helps to aerate and mix the soil. Earthworms actually consume some of the soil as they dig, and their faecal deposits, called castings, also help enrich the soil.

2. Exoskeleton: anthropods like these, spiders, insects, have hard cuticle of chitin and some hardening m. ineral salt like phosphates and carbonates of calcium. The outermost layer is of this cuticle is usually covered with a thin layer of wax that keeps the organism waterproof. This outer head covering is the skeleton is outside the visceral of the organism, it is known as an exoskeleton. Shells of molluses of snail are also Exoskeletons.

3. Endoskeleton: this term describes the skeleton of higher animals i.e. vertebrates such as Man, birds etc. This skeleton is inside the body of the animal and it is covered by tissues and muscles. This type of skeleton is made up of bones and cartilage. The muscles are attached to the skeleton by tendons.

EVALUATION

What are vertebrates? Differentiate between endoskeleton and exoskeleton

Vertebrate Skeletons

The skeletons of vertebrates are made up of bones and cartilage. They are Endoskeleton. All the bones are joined together to allow movement. Vertebrate skeleton has a central spinal column. This column is a flexible stack of bones called vertebrae. All vertebrates’ skeletons are built on the same plan. The vertebrate skeleton is divisible into two parts.

  1. Axial skeleton: It consists of the skull, spinal column (vertebrae) and Ribs.
  2. Appendicular skeleton: This consists of the limbs (fore-limbs-hands and hind limbs-legs) in man, shoulders (Pectoral girdles), hip bone (Pelvic girdle).

 

SUGGESTED PRACTICALS

  1. Illustrate skeletal support using clay and plasticine.
  2. Practical examination of samples of: Arthropods such as  spider, cockroach, millipede.
  3. Examine an intact mammalian skeleton. Identify and name the main parts of the skeleton.
  4. Students to draw and label the fore-limb.

Axial Skeleton

The Human Skull

The human Head consists of several flat bones which form the skull. The skull is hollow and houses and protect the soft tissues of the brain. The upper and lower jaws are also part of the human skull. The jaws contain the teeth. The skull also have socket and cavities which contains and protect the delicate sense organs the like the eyes and ears.

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Human Skull, Side View

This bony profile elaborates the many functions served by the human skull. The cheekbones so exaggerated in some people are actually formed by the fusion of two bones, the zygomatic arch and a section of the temporal bone. The zygomatic anchors one of the two main chewing muscles, the other of which attaches to the flattened side of the cranium. The thoroughness with which we can chew our food is attributable to the wide range of movement (upwards and downwards, side to side, grinding) possible where the lower jaw joins the rest of the skull. The hole just behind the jaw is the ear canal.

The skull is the topmost part of the body. It pivots on the top of the backbone on the first two vertebrae called  atlas and axis respectively.

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Human Skull, Front View

Inside the familiar features of the skull lie some of the most important and vulnerable parts of the body. The bones of the cranial region enclose the center of all intellectual, emotional, and vital activity—about 1500 cc of brain tissue, the consistency and sturdiness of which resembles jelly. Bony orbits protect our delicate eyeballs, and the fragile organs and bones of the inner ear lie deep within the skull. The sense of smell, less well protected than hearing and sight, relies on nasal passages that protrude on a cartilaginous frame from the center of the face.

Starnum and Ribs

The sternum and twelve pairs of ribs form the rib cage. The ribs articulate with thoracic vertebrae at the back, curve to the front and get attached to the sternum by the means of elastic cartilage.  First ten pairs of ribs are  attached to the sternum. The other two pairs are not attached and are referred to as floating ribs. The rib cage houses and protects vital organs such as the heart, lungs and other contents of the thorax as well as help in breathing.

Vertebral Column (Back Bone)

The vertebral column is made up of 33 bones. These bones of the column are built on the same plan. All 33 small irregular bones are joined to form a strong fairly flexible S – shaped rod in the middle of the body. Each vertebra has a hole through which the spinal cord pass from the skull to the coccyx  hence it is called Vertebral Column .

Atlas: The first vertebrae of the column is called atlas

Diagram of the Atlas Vertebrae

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Atlas and Axis

The top two vertebrae in the spinal column are specialized to allow the head a greater range of movement than would be possible with normal vertebrae. A stable ball-and-socket joint accommodates both side-to-side and up-and-down motion.

The second vertebra of the column is called Axis. Axis has a projection called Ondotoid process. It projects upward into a space in the Axis. This peg-like projection allows pivoting and rotation movements of the skull.

The 33 bones are divisible into five sections:

Cervical vertebrae    7          –       neck

Thoracic vertebrae   12        –       chest

Lumbar vertebrae    5          –       waist area

Sacral vertebrae        4          –      fused bones

Cervical vertebrae are 7 in number. They are the bones of the neck region, the first two of which are the Atlas and Axis which are structurally different from the remaining 5.

Lumber vertebra: these are 7 in number. They are lower back and carry most of the weight of the body. They have a large centrum.

Sacra vertebra: these are 5 bones fused together. Together, they are called sacrum. They connect the pelvic girdle to the backbone.

Coccyx: they are the bones of the tail. They are 4 small fused bones which ends the vertebral column.

Functions of the Vertebral Column
  1. It supplies the thorax and the abdomen.
  2. It houses and protects the spinal cord.
  3. The vertebra all have holes through which spinal nerves pass to all parts of the body.
  4. Intervertebral discs located between vertebrae permits smooth movement between the vertebrae well as absorb shocks of landing as the animal moves.

Joints

A joint is a place where two separate bones meet in order to effect different movements which is one of the functions of the skeletal system. Joints are held in place by tough ligaments.

Parts of a Joint

A typical joint has two separate bones. Each ends with a “cap-like” layer of cartilage and synovial fluid encased in a capsule. The cartilage and fluid keeps the friction-free.

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Movable Joints

The elbow shown in this X ray is an example of a movable joint, a joint with full mobility. The bones of movable joints are covered with cartilage and are lubricated by a thick fluid known as synovial fluid. There are several types of movable joints including ball-and-socket, hinge, gliding, and pivot joints. The elbow is a hinge joint.[mediator_tech]

Types of Joints

There are two main types of joints

  1. Immovable: fixed joint as in the cranium.
  2. Movable: they do not permit movement of bones in the /skull cranium. On the basis of the function of the joint or degree of movement possible, movable joints include:
  3. Hinged joints: found at the knees, elbows and fingers. This type of joint allows movement in one plane.
  4. Gliding Joints: found at the wrist and ankles. The bones glide over each other, permitting movements in several planes. This movement permits fine dexterity movements such as writing, knitting, moulding etc.
  5. Ball and socket Joint: this is located at the shoulder and hip. Movement at this joint is in many places.

Functions of the Skeleton in Animals

  1. It gives the animal shape.
  2. It supports and protects soft tissues and organs e.g. brain, heart; the weight of the body e.g. lumbar vertebrae.
  3. It brings about movement. It provides surfaces for attachment of muscles which pull on the bones by contracting and relaxing to effect mouth.
  4. Red blood cells are produced in the marrow of long bones of the skeleton.
  5. It also stores mineral salts.

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Pelvis

The human pelvis consists of the hipbone on the sides and front, and the sacrum and coccyx behind. The pelvis supports the spinal column and rests on the lower limbs.

The Pectoral and Pelvic Girdles

The Pectoral Girdle

In humans the pectoral girdle holds the upper limbs or arms to the axial skeleton. It consists mainly of four separate bones: two large flat triangular shoulder blades or scapulae are attached to the vertebral co.umn by muscles. Each scapula has a depression called glenoid cavity into which the head of the upper arm bone or humerus fits to form the shoulder joint. The clavicles are attached to a scapula at one end and to the sternum at the other end. The pectoral girdle is not rigid. It enables the arm and shoulders to fairly freely.

The Pelvic Girdle

In humans, the pelvic girdle or hips consists of two bones, the right and left pelvis. These are joined to the sacrum at the back and held together by a fibro cartilage at the back and held together by fibro cartilage at the facets in front, to form a complete, rigid girdle. On the outer edge of the pelvis is a deep cavity, the acetabulum, into which the head of the thigh bone or femur fits to form the hip joint. The pelvic girdle is designed to receive the weight of the upper body and persists on to the legs (if you are standing), or to the surface on which you are sitting. The rigid structure of the girdle restricts the movements of the hips and legs.

Diagram of Pectoral Girdle and Pelvic Girdle on page 261 of Modern Biology for SSS, figure 12.5

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Bones of the Leg

The human leg includes all the bones between the hipbone and the foot. The large bone at the top of the leg is the femur (thighbone), which is the strongest bone of the body. The femur has a rounded head that fits into a socket in the hipbone to form a ball-and-socket joint. This joint enables the leg to move freely in almost any direction. At the knee the femur connects to the tibia (shinbone) to form a hinged joint, which permits back-and-forth movement. The joint is protected in front by a small triangular bone, called the patella (kneecap). The tibia is the supporting bone of the lower leg. It is attached via ligaments to a smaller bone called the fibula. The fibula provides an attachment site for leg muscles and does not provide supportive strength for the leg.

The Fore and Hind Limbs

The fore and hind limbs of all terrestrial vertebrates are built on a basic penladactly plan. It consists of a long bone, followed by a pair of long bone placed side by side, a set of nine small bones in three rows, five thin long bones and finally five digits.

The forelimb consists of the following:

  1. Humerus which has a rounded head for articulation with the glenoid cavity of the scapula;
  2. Radius and ulna lie side by side as the long bones of the forearm, they articulate with the deeply grooved lower end of the humerus.
  3. Carpals are the nine small irregular bones of the wrist that are arranged in three rows.
  4. Metacarpals are the fire finger bones and
  5. Digits are the five long tiny bones that are made up of small bones called phalanges.

The hind limb consists of the following:

  1. Femur has a round head which fits into the acebulum of the pelvic girdle. It is the longest bone in the body.
  2. Tibia and fibula, the latter is smaller than the former.
  3. Fibula, a small bone which is joined to the tibia at its distal end;
  4. Patella or kneel cap is a small round bone in front of the knee joint.
  5. Tarsals are the ankle bones.
  6. Metatarsals are the foot bones.
  7. Digits are the toes.

 

EVALUATION

  1. Name two bones of the pectoral girdle.
  2. Name three bones each of the (a) fore-limb (b) hind limb.
  3. Define a joint. Give two examples each of (a) hinge joint (b) ball and socket joint.[mediator_tech]a

ASSIGNMENT

Draw and label the human skeleton.

 

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