Class :


Term :

First Term

Week :

Week 2

Educational Teaching Materials :

  • Footage of Digestive system of animal
  • Pattern alimentary canal of animal



  • Scheme of Work
  • On-line Info
  • Textbooks
  • Workbooks

Earlier Tutorials 

The pupils have earlier information on

The Human Digestive System and The Alimentary Canal

that was previously taught as a topic before this particular lesson


Behavioural Goals :  On the finish of the lesson, the learners will be capable to

  1. Clarify animals based on their feeding patterns
  2. define Herbivores ,Carnivores and Omnivore animals


Content material :


  1. Herbivores
  2. Carnivores and
  3. Omnivores



These refer to all the animals that are plant-eating. Examples include grasshoppers, goat, cow, Grass cutter etc. They all feed on low vegetation such as grass. Giraffes and elephants feed on taller plants or shrubs. Herbivores such as rabbits and guinea pigs use very sharp incisors to cut shoots or browse, feed on roots and bark. Other animals like antelopes, cows and goats pull up grass using the lower front teeth and pad on the front of the upper jaw. The pad is called Diastema. Some herbivores such as elephant use a specialised organ (the trunk) to pull leaves, bark and branches off trees.


These are animals that feed majorly on flesh or bones and other animals. They are referred to as the primary consumers. Some examples are fishes which eat aquatic insects and other fishes, toads and reptiles (Snakes, lizards, wall gecko), cats, dogs, and lions. Mammalian carnivores are characterized by well developed dentition, large canines and a pair of carnassials teeth. These are adapted to stabbing their prey, cutting and crushing meet and bones.


Omnivorous animals are animals that feed on both plants and animals, cooked and uncooked food. Some of the examples include, man, wild boar, bush and domestic pig, and the domestic fowl.


Scavengers are animals that feed on the remains of dead animals are called scavengers e.g. Vultures.

Feeding Habits

There are various modification among the alimentary systems of some animals so far considered, suggest that the parts are modified according to the type of food they eat. It has also been discovered that there is a close relationship between feeding mechanism and the diet of each organism.

Based on the modification on the feeding habits of organisms, we have the following;

  1. Filter feeding, and
  2. Fluid feeding adaptations in animals
  3. Saprophytic
  4. Parasitic feeding in animals and plants.

1. Filter Feeders

Some aquatic organism feed on some tiny microscopic organisms (planktons) in their habitat. A great number of them are gathered, filtered and consumed at the same time, from the surface of the water. Typical examples of filter feeders include; water fleas, (Daphnia), mosquito larvae, fish such as herring, and molluscs such as oyster, and mussels. Water containing suspended plankton enters the mouth of the animal e.g. herring. Water passes between the gill rakers to the gills. Oysters and clams draw water into their shells and trap food particles on the muscles covering their gills.

2. Fluid Feeders

Fluid feeders are organisms that can only feed on soluble or fluid food materials from the body fluid of other animals or plants, or convert solid food into a liquid form before ingesting it. Examples of fluid feeders are bees, wasps, aphids, housefly, mosquito, tsetse fly, and butter fly. The house fly has a proboscis which is flattened its anterior end. This consists of numerous food channels called pseudo- tracheae. Whenever the fly is prepared to feed, it extends its proboscis and saliva is passed down salivary duct via the pseudo tracheae on to the food.

The adult female anopheles mosquito feeds on blood. It has mouth parts which are modified into a tube like a hypodermic needle. It pierces the skin of a blood capillary; saliva containing an anti- coagulant is passed down the hypopharynx into the capillary. This prevents the blood from coagulating when it is sucked up by the tubular labrum.

Many other insects bite and/or chew their food. Examples are the ants, beetles, cockroach, locust, caterpillar, termites, and weevils. Most of these are crop pests as were taught in your Basic classes.

Orchid Bees

The orchid bee is one of the most brilliantly coloured insects, and may appear metallic green, blue, purple, gold, or red. A close relative of the bumblebee, it has a long tongue that allows it to reach nectar deep inside tropical flowers. It is found in tropical and subtropical regions of the western hemisphere.

3. Saprophytic Feeders

These are organisms which obtain their food materials from dead or decaying food materials or dead organic matters. They non-green plants and therefore cannot carry out photosynthesis.  Typical examples include: many fungi, e.g. mushroom, mucor or rhizopus, penicillum and yeast as well as some bacteria. The rhizoids penetrate into the dead organic matter or substrate, and excrete enzymes into it, and digestion occurs extracellulary. The digested food; a soluble end products diffuse into the rhizoids and from there to the other parts of the plants.

Structure of a Fungus

Fungi are made of filamentous tubes called hyphae. In many species, perforated walls, or septa, divide the hyphae into cells containing one or two nuclei. Protoplasm flows through the opening in the septa to provide the cells with nutrients, which are stored in the hyphal walls as glycogen. Hyphae elongate from the tip. The entire mass of hyphae is collectively called the mycelium.

4. Parasitic Feeders

In parasitic feeding, parasites are plants or animals which live and feed on or in other organisms and harm the hosts at the end. Parasites which live outside the body or the surface of their hosts are called ectoparasites e.g. tick, mites, lice and flaes. These live the skin, or hairs of mammals. Those parasites which feed and live inside their hosts are called endoparasites e.g. tapeworm, roundworm etc[mediator_tech]

Feeding in Protozoa

Amoeba proteus is an example of a protozoan. It feeds on minute microscopic organisms. These are mainly phytoplankton, desmids and diatoms, flagellates, bacteria, and decayed parts of plants in water. The presence of the food stimulates the formation of pseudopodia towards the object. Soon, the pseudopodia encircle the food material. This is taken into the body with a drop of water and a food vacuole is formed. The cytoplasm secretes digestive enzymes on to the food and digestion occurs. Later, the digested food materials diffuse into the plasmasol. The indigestible parts are left behind or allowed to pass out through the plasmagel.  Ingestion and egestion can occur at any time through the body surface.

Feeding in Hydra

Hydra is at tissue and considered as multicellular, aquatic organism (animal). It feeds mainly on tiny crustaceans e.g. water fleas. The food is usually caught by the tentacles with the aid of nematocysts which immobilize the prey. The tentacles draw the prey into the mouth and then into the enteron (digestive cavity). The digestive enzymes in the enteron digest the food extracellularly. The absorptive cells ingest the partially digested food materials food material and complete digestion intracellularly. The soluble materials diffuse to various part of the animal. The waste products are egested through the mouth.

Feeding Mechanisms

There are four modifications and mechanisms of feeding associated with some organisms. They include

  1. Absorbing mechanism
  2. Biting (cutting) chewing
  3. Piercing and sucking
  4. Trapping and absorbing

1. Absorbing mechanism

Organisms that use this mechanisms has no mouth and alimentary canal, hence food is digested food is absorbed through its entire body surface from the intestine of its host. E.g tape worm, it attaches its self to its host through hooks and suckers.

2. Biting (cutting) chewing

Organisms with this mechanism have four different mouth parts adapted for biting and chewing. These mouth parts include:

  • Labrum or upper lip
  • Labium or lower lip
  • Mandibles
  • Maxillae[mediator_tech]

Examples of such organisms are cockroach and grasshopper.

3. Piercing and sucking

Organisms that posses this mouth parts have different modifications which enables them to adapt to feeding on food through mechanism of sucking. E.g mosquito and butterfly posses proboscis for piercing and sucking. For mosquito, the mouth parts altogether forms a strong Stylet. Housefly posses labella for sucking. It has the ability to convert solid food to liquid by secretion of saliva on the solid food.

4. Trapping and absorbing

This is common among plants that feed on insects. They are called insectivorous or carnivorous plants. E.g bladderwort, sundew, Venus flytrap, pitcher plant.

The Pitcher Plant

Pitcher plants, found throughout the tropical and temperate regions of the world, are insectivorous plants, using specially modified leaves to capture and consume insects. Pitcher plants usually grow in poor soils and rely on the captured insects for added nutrition.

Venus’s Fly Trap

The two lobes of a Venus’s-flytrap leaf form a deceptively safe and attractive landing place for insects and other animals. Less than a second after the frog trips the trigger, bristles on the inside surface of the leaf, the lobes close enough to trap the intruder below interlocking spines. If sensory organs determine that the prisoner contains protein, the leaf closes further, and the plant’s digestive enzymes start to flow.

Feeding in Mammals

Mammals feed on different types of food materials. They are often classified according to the food they eat. Thus, we have herbivores- plant eaters; carnivores-flesh eaters and omnivores- plant and animal eaters.

Each group of mammals has a peculiar type of dentition related to its diet even though mammals generally have heterodont dentition. They have incisors, canines, premolars and molars. Each tooth has a different shape and function. In human, there are two sets of teeth, namely: temporary or milk teeth and permanent teeth. The formal are used at childhood (6months to 6-8years) while they replaced by permanent teeth at old age

The Mammalian Teeth

The type of teeth possessed by a mammal is related to the type of food it eats. The number, arrangement and conformation of teeth in an organism are referred to as its dentition. When all the teeth are the same shape and size as in fishes, amphibians and reptiles it is called homodont dentition. When they differ in shape as in dogs, man and rabbits it is heterodont dentition.

Mammals usually have four different types of teeth namely the incisors, canines, premolars and molars. Man has two sets of teeth during his lifetime; the milk teeth when young and the permanent teeth when mature. There are 20 milk teeth and 32 permanent teeth.

Types of Teeth

  1. Incisors – These are flattened, chisel-like with a sharp edge for cutting and holding onto the food/prey. They are located in the front of the jaw.
  2. Canines – These have sharp, pointed tips and are used for tearing flesh. They are next to the incisors.
  3. Premolars – These have broad ridged surfaces called cusps. They are used for grinding and chewing food. They are located towards the back of the jaw.
  4. Molars – These also have broad, ridged surfaces and are used for chewing and grinding food. They are found at the extreme back of the jaws.

Section of Adult Teeth

Dental Formula

This refers to the number, type and arrangement of teeth in one half of each jaw.

Example in;

  • Man; I 2/2 ; C 1/1 ; PM 2/2 ; M 3/3
  • Dog; I 3/3 ; C I/I ; PM 4/4 ; M 2/3
  • Rabbit; I 2/1 ; C 0/0 ; PM 3/2 ; M 3/3

Structure of a Tooth

A typical tooth has three parts; the crown, the neck and the root. The crown is the part above the gum. The root is embedded in the jaw and the neck is the part on the same level with the gum, it is the narrow junction between the crown and root.

The incisors and canines have one root each while the premolars and molars have two or three roots each.

A Typical Tooth

In the centre of the tooth is a pulp cavity which contains blood vessels and nerves that make extremely sensitive to heat, cold and pain. The dentine, a hard bone-like material, encloses the pulp. The enamel, a white, hard material covers the dentine, protecting it and the pulp within. At the root region a thin layer of cement covers the dentine. The cement is surrounded by the periodontal membrane, a fibrous tissue that fixes the tooth into the jaw bone.

The tooth is not rigidly fixed but can move slightly while biting and chewing. A hole at the tip of each root allows blood vessels and nerves of the pulp to be connected to those of bones and gums. This ensures a continuous flow of of blood supply to the tooth and keeps the tooth alive. However, the supply of blood is not sufficient for the tooth to grow. This type of teeth is known as closed teeth.

Dental Care

Tooth decay caused by bacteria and fermentation of carbohydrates that get stuck in the teeth can be prevented by;

  1. Practicing regular oral hygiene
  2. Eating balanced diet containing enough vitamin, phosphorus and calcium.
  3. Eating hard, fibrous fruits after each meal.
  4. Avoiding sweet food, very hot and very cold.
  5. Visiting a dentist regularly.





The subject is offered step-by-step


Step 1:

The category trainer revises the earlier matters


Step 2.

He introduces the brand new subject


Step 3:

The category trainer permits the pupils to present their very own examples and he corrects them when the wants come up



Conclusion :


The category trainer wraps up or conclude the lesson by giving out brief observe to summarize the subject that she or he has simply taught.

The category trainer additionally goes spherical to guarantee that the notes are properly copied or properly written by the pupils.

She or he does the required corrections when and the place  the wants come up.




    1. Explain the meaning of herbivores, carnivores and omnivores.
    2. Explain feeding in protozoa and hydra.