Understanding Cell Growth: Division, Differentiation, and Responses to the Environment Biology SS 1 First Term Lesson Notes Week 8

Subject: Biology

Class: SS1

Term: First Term

Week: 8

Age (years): 15-16

Topic: Some Properties and Functions of the Cell: Growth

Sub-topic: Cell Division and Responses to Environment

Duration: 2 hours

Behavioural Objectives:

By the end of this lesson, students should be able to:

Explain the basis of cell growth, including division (mitosis) and differentiation.
Discuss the regulation of growth by hormones.
Describe how cells react to their environment and the significance of irritability.
Identify the types of responses cells exhibit in various conditions.

Keywords:

Cell Growth, Mitosis, Differentiation, Hormones, Irritability, Cell Responses, Protoplasm

Set Induction:

Begin the lesson by asking students about the growth of plants and animals. Discuss how cells are fundamental to growth and the different ways they can divide and respond to their surroundings.

Entry Behaviour:

Students should have prior knowledge of cell structure and the basics of cellular processes from previous lessons.

Learning Resources and Materials:

Diagrams illustrating the stages of mitosis
Videos demonstrating cell growth and differentiation
Charts on hormone regulation of growth
Interactive simulations of cell responses to stimuli

Building Background / Connection to Prior Knowledge:

Connect this lesson to previous discussions on cell functions and metabolism, emphasizing the importance of growth and response in living organisms.

Embedded Core Skills:

Critical thinking: Analyzing how different factors affect cell growth.
Collaboration: Working in groups to discuss cellular responses to environmental changes.
Research skills: Investigating the role of hormones in growth regulation.

Learning Materials:

Textbook: “Biology for Senior Secondary Schools”
Online resources for interactive learning about mitosis and cell responses
Worksheets summarizing key concepts

Reference Books:

Biology for Senior Secondary Schools by E. B. Olaniyan
Comprehensive Biology by J. A. Akintunde

Instructional Materials:

PowerPoint presentations with graphics illustrating mitosis and cell responses
Models demonstrating different stages of cell division
Handouts outlining hormonal control of growth

Content:

1. Basis of Growth:

Cell Division (Mitosis): Mitosis is the process by which a single cell divides to produce two identical daughter cells. This process is essential for growth, repair, and maintenance of tissues. The stages of mitosis include:
- Prophase: Chromatin condenses into visible chromosomes, and the nuclear envelope breaks down.
- Metaphase: Chromosomes align at the cell’s equatorial plane.
- Anaphase: Sister chromatids are pulled apart to opposite poles of the cell.
- Telophase: The nuclear envelope reforms around each set of chromosomes, and the cell begins to divide (cytokinesis).
Enlargement and Differentiation: After division, cells may grow larger (enlargement) and take on specific functions (differentiation). For instance, stem cells can differentiate into various cell types, such as muscle cells or nerve cells, which have distinct functions and characteristics.
Regulation of Growth by Hormones: Hormones are chemical messengers that regulate growth and development. Key hormones include:
- Growth Hormone (GH): Stimulates overall growth and development.
- Thyroid Hormones: Regulate metabolism and energy production, influencing growth.
- Sex Hormones (Estrogen and Testosterone): Affect growth and differentiation during puberty.

2. Cell Reactions to Its Environment:

Irritability: This refers to the ability of cells (especially protoplasm) to respond to stimuli from their environment. It is a fundamental characteristic of living cells. Cells can sense changes in their environment, such as temperature, light, and chemical signals.
Types of Responses:
- Tropic Responses: These are directional growth responses to environmental stimuli, such as:
  - Phototropism: Growth towards light (e.g., plants bending towards sunlight).
  - Geotropism: Growth in response to gravity (roots grow downward).
- Nastic Responses: These are non-directional responses, such as:
  - Thigmonasty: Response to touch (e.g., closing of the Venus flytrap).
  - Hydronasty: Response to moisture levels (e.g., leaves opening and closing).

Evaluation:

Fill-in-the-Blank Questions (15 Questions):

Mitosis is the process of _____ cell division. a) Asexual
b) Sexual
c) Symbiotic
d) Binary
The stages of mitosis include prophase, _____, anaphase, and telophase. a) Interphase
b) Metaphase
c) Cytokinesis
d) Synthesis
During mitosis, sister chromatids are separated during _____. a) Prophase
b) Metaphase
c) Anaphase
d) Telophase
Growth hormones are produced by the _____ glands. a) Endocrine
b) Exocrine
c) Digestive
d) Nervous
Differentiation is the process by which cells become _____ in structure and function. a) Similar
b) Identical
c) Unique
d) Homogeneous
_____ is the ability of cells to respond to environmental changes. a) Differentiation
b) Irritability
c) Division
d) Metabolism
Phototropism is a growth response to _____. a) Water
b) Gravity
c) Light
d) Temperature
Hormones regulate cell growth and _____. a) Repair
b) Death
c) Excretion
d) Reproduction
_____ cells can differentiate into various specialized cell types. a) Nerve
b) Stem
c) Muscle
d) Epithelial
Geotropism is a growth response to _____. a) Water
b) Light
c) Touch
d) Gravity
The main purpose of mitosis is to produce _____. a) Energy
b) More cells
c) Hormones
d) Nutrients
The growth hormone is primarily responsible for _____ growth. a) Mental
b) Physical
c) Emotional
d) Social
Cells can react to _____ stimuli from their environment. a) External
b) Internal
c) Both a and b
d) None of the above
_____ responses are non-directional movements in response to stimuli. a) Tropic
b) Nastic
c) Phototropic
d) Thigmonastic
The _____ stage of mitosis involves the alignment of chromosomes in the middle of the cell. a) Anaphase
b) Telophase
c) Metaphase
d) Prophase

Class Activity Discussion: FAQs (15 Questions and Answers):

Q: What is mitosis? A: Mitosis is the process of cell division that results in two identical daughter cells, essential for growth and repair.
Q: Why is differentiation important for cells? A: Differentiation allows cells to develop specialized functions necessary for the proper functioning of tissues and organs.
Q: How do hormones regulate cell growth? A: Hormones act as chemical messengers that stimulate or inhibit growth processes in cells, helping coordinate development.
Q: What are the main stages of mitosis? A: The main stages are prophase, metaphase, anaphase, and telophase, followed by cytokinesis.
Q: What is irritability in cells? A: Irritability is the ability of cells to respond to stimuli from their environment, a key characteristic of living organisms.
Q: Can you give examples of tropic responses? A: Examples include phototropism (growth towards light) and geotropism (growth towards gravity).
Q: What are nastic responses? A: Nastic responses are non-directional movements in response to stimuli, such as the closing of a flower when touched.
Q: What happens during the anaphase of mitosis? A: During anaphase, sister chromatids are pulled apart to opposite ends of the cell.
Q: Why do cells need to divide? A: Cells divide for growth, repair, and maintenance of tissues, as well as to replace damaged or dead cells.
Q: How do environmental factors influence cell responses? A: Environmental factors like light, gravity, and moisture can trigger specific growth responses in cells.
Q: What role do stem cells play in growth? A: Stem cells can differentiate into various cell types and contribute to growth and repair in tissues.
Q: How do hormones affect plant growth? A: Plant hormones like auxins promote growth by regulating cell division and elongation in response to environmental signals.
Q: What is the significance of cell differentiation? A: Differentiation allows cells to perform specialized functions, ensuring the proper operation of organs and systems in an organism.
Q: How do cells respond to high temperatures? A: Cells may activate heat-shock proteins to protect themselves from damage due to high temperatures.
Q: What are some examples of excretory products in cells? A: Waste products include carbon dioxide, ammonia, and urea, which are expelled from cells to maintain homeostasis.

Presentation:

Step 1: Review the previous topic on cellular functions, focusing on energy production and metabolism.
Step 2: Introduce the new topic on cell growth and responses by explaining mitosis and differentiation with visual aids.
Step 3: Engage students in discussing real-life applications, such as the growth of plants and the effects of hormones.

Activities:

Teacher’s Activities:

Facilitate discussions on the importance of cell growth in plants and animals.
Use animations or diagrams to illustrate the stages of mitosis and differentiation.
Conduct an experiment to observe cell responses to light or gravity.

Learner’s Activities:

Participate in group discussions about the effects of hormones on growth.
Engage in experiments to observe plant growth in response to different light conditions.
Complete fill-in-the-blank questions and engage in evaluation exercises.

Assessment:

Evaluation Questions (10 Questions):

Define mitosis and explain its significance in cell growth.
Describe the process and stages of mitosis.
What is the role of hormones in regulating growth?
Explain the concept of irritability in cells.
How do cells respond to environmental changes?
What is the difference between tropic and nastic responses?
Discuss the importance of differentiation in multicellular organisms.
What are the waste products of cellular processes?
Explain how growth can be affected by external factors.
How does mitosis contribute to tissue repair?

Conclusion:

The teacher will review students’ answers and assess their understanding of cell growth, division, and responses to environmental stimuli. Students will be encouraged to reflect on how these processes are vital for maintaining life and adapting to changing conditions.