Lesson Notes By Weeks and Term - Senior Secondary 1

TERM – 1^ST TERM

WEEK EIGHT

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Biology

Topic: GROWTH

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

1. Define growth and identify major aspects of growth
2. Identify basis of growth.

iii. describe irritability

1. Define movement and identify reasons for movement

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

NOTE

GROWTH

Growth is the irreversible increase in size, mass, or number of cells in an organism. It is a fundamental characteristic of living organisms and is essential for the development and maintenance of their structure and function. Growth involves various processes, including cell division, enlargement, and differentiation.

Basis of Growth

1. Cell Division: The primary basis of growth is cell division, where existing cells divide to produce new cells. Mitosis and, in some cases, meiosis contribute to cell division in organisms.
2. Cell Enlargement: Cells can also grow by increasing their size through the accumulation of additional cellular material.
3. Cell Differentiation: As cells divide and grow, they may undergo differentiation, where they become specialized for specific functions. This is crucial for the development of tissues and organs.

Aspects of Growth

1. Apical Growth: Occurs at the tips of roots and shoots in plants.

   - Process: Apical meristems, found at the growing tips, continuously divide, leading to elongation of the plant. This contributes to the lengthening of roots and shoots.

2. Auxiliary (Lateral) Growth: Occurs at the sides or lateral meristems of stems and roots in plants.

   - Process: Lateral meristems, such as the vascular cambium and cork cambium, add layers of cells to the diameter of the stem or root, resulting in an increase in girth or thickness.

Regulation of growth by hormones

Hormones play a crucial role in the regulation of growth in organisms. Different types of hormones, produced by various glands or tissues, influence cell division, elongation, and differentiation. Below are some key hormones involved in the regulation of growth:

1. Auxins: Auxins are plant hormones that promote cell elongation and are essential for the growth of stems and roots.

   - Mechanism: They stimulate the proton pump in the cell membrane, leading to increased acidity and cell wall loosening, facilitating cell expansion.

2. Gibberellins: Gibberellins are plant hormones that promote stem elongation, germination, and flowering.

   - Mechanism: They stimulate cell division and elongation, influencing internode elongation in stems.

3. Cytokinins: Cytokinins are plant hormones that promote cell division and delay aging in plants.

   - Mechanism: They stimulate cell division in the presence of auxins, contributing to the formation of new tissues.

4. Abscisic Acid (ABA): ABA is involved in inhibiting growth and inducing dormancy in plants, particularly under stressful conditions.

   - Mechanism: ABA regulates stomatal closure, slows down metabolic processes, and influences bud dormancy.

5. Thyroid Hormones: Thyroid hormones (T3 and T4) influence growth and development in animals.

   - Mechanism: They regulate metabolic processes, including energy expenditure and protein synthesis.

6. Insulin: In animals, insulin regulates nutrient uptake and storage, influencing overall growth.

   - Mechanism: Insulin promotes the uptake of glucose by cells, facilitating energy storage and cell growth.

Irritability/Cell reaction to it environment

Irritability, also known as responsiveness or excitability, is a characteristic of living cells to respond to changes in their environment. This responsiveness allows cells to adapt and interact with their surroundings. The following are key aspects of cell reaction to environmental stimuli:

1. Sensitivity to Stimuli: Cells can detect and respond to various stimuli, including physical, chemical, and environmental cues. These stimuli can trigger a cellular response.
2. Receptor Proteins: Cells often possess specialized receptor proteins on their surfaces that recognize specific molecules or signals. These receptors transmit information from the external environment to the inside of the cell.
3. Signal Transduction: Once a cell receives a signal, it undergoes signal transduction, a series of molecular events that convert the external signal into a cellular response. This may involve changes in protein conformation, activation of enzymes, or alterations in gene expression.
4. Cellular Responses: Cells can exhibit various responses to environmental stimuli, such as changes in shape, movement, secretion of substances, or alterations in metabolic activities. For example, muscle cells contract in response to a nerve signal.
5. Homeostasis: Cells strive to maintain internal stability or homeostasis. Irritability allows cells to respond to changes in the environment and make adjustments to preserve internal balance

Movement

Movement in biology refers to the ability of living organisms to change their position, either internally or externally. It is a fundamental characteristic of life and occurs at various levels, from cellular processes to complex behaviors in multicellular organisms.

Reasons for Movement

1. Survival: Movement allows organisms to respond to environmental changes, escape from predators, or find food and shelter.
2. Reproduction: Organisms often need to move to locate mates for reproduction, facilitating genetic diversity.
3. Feeding: Movement is crucial for finding and capturing food. This can involve both simple movements at the cellular level and complex behaviors in higher organisms.
4. Response to Stimuli: Movement is a way for organisms to react to stimuli, whether it's light, temperature, chemicals, or other environmental factors.
5. Development: Movement is involved in various stages of development, from the movement of cells during embryogenesis to the growth and shaping of tissues and organs.

EVALUATION: 1. What is movement, what are the reasons behind movement

2. Mention 4 hormones that regulates growth
3. Define growth, give three bas es for growth.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively