Cell division and Cell processes for SS 1

Class: SS 1
Term: Second Term
Week: 2
Age: 15 years
Duration: 60 minutes
Subject: Biology
Curriculum Theme: Organization of Life and Biochemical
Focal competence: Using a microscope in observing and drawing biological Specimens
Key competencies/values: Critical Thinking; Communication; Collaboration; ICT and Digital Competencies; Digital Competencies
Skills:

• Demonstrating osmosis and diffusion in plant and animal cells
• Drawing cell structure

Previous Lesson: Cell Structure, Organelles, Functions and Plant-Animal Cell Differences
Topic: Cell Structure And Functions: Cell Division
Subject Matter: Cell division, Cell processes

Specific Objectives

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

Cognitive Domain

• Identify and label parts of plant and animal cells.
• Differentiate between plant and animal cells.
• Describe the stages of mitosis.
• Describe the stages of meiosis.
• Explain the concepts of diffusion and osmosis.
• Define plasmolysis and haemolysis.

Psychomotor Domain

• Draw and label the stages of mitosis.
• Draw and label the stages of meiosis.
• Demonstrate the effect of osmosis on cells using simple experiments.

Reference Materials

The following resources were used in planning this lesson:

• 2025 New Revised Senior Secondary Education Curriculum (SSEC)
• Relevant State Unified Scheme of Work
• A suitable Biology textbook for SS 1
• The HeadTeacher Scheme of work For The New Revised Senior Secondary Education Curriculum (SSEC)

Instructional Materials

The teacher will teach this lesson with the aid of:

• Microscope
• Short animations/videos of organelles performing functions
• Diagrams/charts/pictures of both plant and animal cells
• Onion bulbs
• Spatula
• Salt solution
• Freshwater
• Microscope slides and cover slips

Rationale for the Lesson

This lesson is important for understanding how living organisms grow, repair tissues, and reproduce through cell division. It also explains essential processes like diffusion and osmosis that govern the movement of substances in and out of cells, which are fundamental to life functions.

Prerequisite/Previous Knowledge

Students should have prior knowledge of basic cell structure, including the major organelles and their general functions, as well as the concept of living organisms being made of cells.

Lesson Content/Board Summary

Cell Structure And Functions: Cell Division

Differences between Plant and Animal Cells

Although both plant and animal cells are eukaryotic, they have distinct differences:

Cell Division

Cell division is the process by which a parent cell divides into two or more daughter cells. It is essential for growth, repair, and reproduction in living organisms.

Mitosis

Mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

Stages of Mitosis:

1. Prophase: Chromatin condenses into visible chromosomes. The nuclear envelope begins to break down, and the spindle fibres start to form.
2. Metaphase: Chromosomes align along the metaphase plate (equator of the cell). Each chromosome is attached to spindle fibres at its centromere.
3. Anaphase: Sister chromatids separate and are pulled towards opposite poles of the cell by the shortening spindle fibres.
4. Telophase: Chromosomes arrive at the poles and begin to decondense. New nuclear envelopes form around the two sets of chromosomes. Cytokinesis (division of the cytoplasm) usually begins during this stage, resulting in two distinct daughter cells.

(Students should be able to draw and label these stages.)

Meiosis

Meiosis is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell. It occurs in sexually reproducing organisms to produce gametes (sperm and egg cells).

Stages of Meiosis: Meiosis involves two rounds of division, Meiosis I and Meiosis II.

Meiosis I:

1. Prophase I: Chromosomes condense, homologous chromosomes pair up (synapsis) to form bivalents, and crossing over occurs, exchanging genetic material. The nuclear envelope breaks down.
2. Metaphase I: Homologous pairs align at the metaphase plate.
3. Anaphase I: Homologous chromosomes separate and move to opposite poles. Sister chromatids remain attached.
4. Telophase I: Chromosomes arrive at the poles, and the cell divides into two haploid daughter cells, each with replicated chromosomes.

Meiosis II: (Similar to mitosis, but with haploid cells)

1. Prophase II: Chromosomes condense again (if they decondensed in Telophase I).
2. Metaphase II: Chromosomes align at the metaphase plate.
3. Anaphase II: Sister chromatids separate and move to opposite poles.
4. Telophase II: Chromosomes arrive at the poles, and the cells divide, resulting in four haploid daughter cells, each with unreplicated chromosomes.

(Students should be able to draw and label these stages.)

Cell Processes

Diffusion

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. This process occurs in gases and liquids and does not require energy.

Examples:

1. The spread of perfume in a room.
2. The movement of oxygen from the lungs into the bloodstream.
3. The movement of carbon dioxide from the bloodstream into the lungs.

Osmosis

Osmosis is the net movement of water molecules across a selectively permeable membrane from a region of higher water concentration (lower solute concentration) to a region of lower water concentration (higher solute concentration).

Examples:

1. Water absorption by plant roots.
2. The movement of water in and out of red blood cells.
3. The swelling of dried fruits (raisins) when placed in water.

Plasmolysis

Plasmolysis is the process in plant cells where the protoplast (cell membrane and cytoplasm) shrinks and pulls away from the cell wall due to the loss of water by osmosis when the cell is placed in a hypertonic (high solute concentration) solution.

Haemolysis

Haemolysis is the rupture or destruction of red blood cells. This occurs when red blood cells are placed in a hypotonic (low solute concentration) solution, causing water to rush into the cells by osmosis, leading them to swell and burst.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Practical Activity

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Engaging/Questioning

Teacher’s Activity: The teacher greets the students and asks them questions about what they remember about cells and their importance in living organisms. The teacher then introduces the topic of cell division and other cell processes, highlighting their significance.

Pupils’ Activity: Pupils respond to questions and listen attentively to the introduction.

Learning Point: Importance of cell processes

Step 2: Review of Cell Structure and Differentiation

Time: 10 minutes

Teaching Skill: Explanation/Visualisation

Teacher’s Activity: The teacher displays diagrams/charts of plant and animal cells. The teacher guides students to identify and label the key organelles in each cell type and then facilitates a discussion on the differences between them, using the provided table as a guide.

Pupils’ Activity: Pupils observe the diagrams, identify organelles, and participate in the discussion, noting the differences.

Learning Point: Plant and animal cell differences

Step 3: Introduction to Cell Division

Time: 5 minutes

Teaching Skill: Explanation

Teacher’s Activity: The teacher explains the concept of cell division, its necessity for growth, repair, and reproduction. The teacher briefly introduces mitosis and meiosis as the two main types.

Pupils’ Activity: Pupils listen and ask clarifying questions about the purpose of cell division.

Learning Point: Purpose of cell division

Step 4: Mitosis and its Stages

Time: 10 minutes

Teaching Skill: Explanation/Guided Drawing

Teacher’s Activity: The teacher explains the process of mitosis, describing each stage (prophase, metaphase, anaphase, telophase) with the aid of diagrams or video animations. The teacher then guides students to individually draw and label the stages in their notebooks.

Pupils’ Activity: Pupils observe the diagrams/videos, listen to explanations, and draw the stages of mitosis in their notebooks.

Learning Point: Stages of mitosis

Step 5: Meiosis and its Stages

Time: 10 minutes

Teaching Skill: Explanation/Guided Drawing

Teacher’s Activity: The teacher explains the process of meiosis, highlighting its two divisions (Meiosis I and Meiosis II) and describing the key events in each stage. The teacher uses diagrams or animations and guides students to draw and label the stages of meiosis.

Pupils’ Activity: Pupils observe, listen, and draw the stages of meiosis, noting the differences from mitosis.

Learning Point: Stages of meiosis

Step 6: Cell Processes: Diffusion and Osmosis

Time: 10 minutes

Teaching Skill: Demonstration/Practical Activity

Teacher’s Activity: The teacher defines diffusion and osmosis, providing simple examples. The teacher then guides students through a simple experiment to demonstrate osmosis using onion epidermal cells, salt water, and freshwater, observing plasmolysis. The teacher also explains haemolysis.

Pupils’ Activity: Pupils observe the demonstration, participate in discussions, and note down observations and explanations of diffusion, osmosis, plasmolysis, and haemolysis.

Learning Point: Diffusion and osmosis concepts

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. List two differences between plant and animal cells.
2. Describe two stages of mitosis.
3. What is the main difference between mitosis and meiosis?
4. Explain the terms diffusion and osmosis with an example for each.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Understanding cell division/processes

Step 8: Note-Taking

Time: 10 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on cell differences, cell division (mitosis and meiosis), and cell processes (diffusion, osmosis, plasmolysis, haemolysis) into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Recording lesson notes

Step 9: Conclusion

Time: 5 minutes

Teaching Skill: Summarizing

Teacher’s Activity: The teacher briefly recaps the main points of the lesson, emphasizing the importance of cell division for life and the role of diffusion and osmosis in maintaining cell functions. The teacher encourages students to review their notes.

Pupils’ Activity: Pupils listen to the summary and prepare for the next lesson.

Learning Point: Consolidation of cell concepts

Continuous Assessment/Further Study

Type: Homework/Practice Exercise

Instruction: Answer the following questions in your notebook.

1. Draw a well-labelled diagram of a typical plant cell and an animal cell.
2. In your own words, explain why cell division is important for multicellular organisms.
3. Research and write a short paragraph on one real-life application of diffusion or osmosis (e.g., kidney dialysis, food preservation).

Lesson Keywords

• Cell Division – The process by which a parent cell divides into two or more daughter cells.
• Mitosis – Cell division for growth and repair, producing two identical daughter cells.
• Meiosis – Cell division for sexual reproduction, producing four haploid, genetically diverse cells.
• Diffusion – Movement of particles from high to low concentration.
• Osmosis – Movement of water across a selectively permeable membrane from high to low water concentration.
• Plasmolysis – Shrinking of the plant cell protoplast due to water loss in a hypertonic solution.
• Haemolysis – Bursting of red blood cells due to water gain in a hypotonic solution.
• Prophase – First stage of mitosis/meiosis where chromosomes condense.
• Metaphase – Stage where chromosomes align at the cell’s equator.
• Anaphase – Stage where sister chromatids or homologous chromosomes separate.
• Telophase – Final stage where new nuclei form and cytoplasm divides.

Differentiation

Support: Provide simplified diagrams and pre-labelled charts for struggling students. Pair them with more capable peers for drawing activities. Use visual aids like videos repeatedly.

Extension: Challenge advanced students to research and explain the genetic significance of crossing over in Meiosis I or to investigate medical conditions related to abnormal cell division.

Suggested Lesson Videos

For further understanding, search on YouTube for:

• “Mitosis and Meiosis stages for SS1 Biology”
• “Diffusion and Osmosis explained for Senior Secondary Biology”
• “Differences between Plant and Animal Cells Biology SS1”