Lesson Plan: The Cell's Two Dances - Mitosis & Meiosis
Subject: Science (Biology)
Grade Level: 9 (Bilingual Program)
Topic: Mitosis vs. Meiosis
Time Allotment: ~60 minutes
Big Idea: Our bodies use two different types of cell division: one for growth and repair (making identical copies) and another for creating unique reproductiv cells.
Learning Goals: By the end of this lesson, you will be able to:
Explain the purpose of mitosis and meiosis.
Compare the outcomes of both processes (number of cells, chromosome count).
Model the basic steps of mitosis and meiosis.
Materials:
Whiteboard or large paper & markers
Sets of colored beads or pipe cleaners (at least 4 colors)
Student notebooks
Diagrams of mitosis and meiosis
1. Engage: The Story of a Cut and a Seed (10 mins)
Goal: To get you thinking about why cells divide. ð§
Teacher's Steps:
Present this story:
"Think about two things:
You get a small cut on your hand, and over a few days, new skin grows and heals it.
A mango seed is planted, grows into a big tree, and eventually makes its own mangoes with seeds inside.
Both stories involve cells dividing. But is the purpose of the division the same?"
In small groups, ask students to quickly discuss:
For the cut skin, what is the goal of the new cells? (To be exactly the same as the old skin cells).
For the mango tree making new seeds, what is the goal of the cells in the seed? (To create a new, unique tree).
Briefly share ideas as a class. Transition by saying, "You've noticed there are different reasons for cells to divide. Today, we'll learn about the two processes that make this happen: mitosis and meiosis."
2. Explore: Modeling Cell Division (20 mins)
Goal: To discover the key differences between mitosis and meiosis yourselves. ✋
Teacher's Steps:
Divide students into groups of 3-4. Give each group a set of colored pipe cleaners (or beads). Explain that these are the chromosomes.
Challenge 1: Model MITOSIS (for Growth & Repair)
Start with one "parent cell" that has 4 chromosomes (e.g., 2 long red, 2 long blue).
First, duplicate each chromosome. (You should now have 4 'X' shapes).
Now, divide this cell into TWO new "daughter cells."
Key Question: Look at your new cells. How do they compare to the original parent cell? (They should be identical!).
Challenge 2: Model MEIOSIS (for Reproductive Cells)
Start with the same parent cell (4 chromosomes).
First, duplicate the chromosomes.
Now, divide the cell TWICE. You should end up with FOUR new "daughter cells."
Key Question: Look at your four new cells. How do they compare to the original parent cell? (They should have half the number of chromosomes and be genetically different!).
Circulate and guide students. If they model meiosis with only one division, ask: "Reproductive cells (like sperm and egg) need to have half the DNA. How can your model show that?"
Differentiation (Advanced): Challenge them to show crossing over in their meiosis model by swapping small pieces of the pipe cleaners between matching pairs.
3. Explain: Putting It All Together (15 mins)
Goal: To connect your models to the scientific vocabulary and concepts. ð
Teacher's Steps:
Ask groups to share what they found. What was the biggest difference between their two models?
Use their discoveries to introduce key terms. Draw this simple comparison table on the board and fill it in with the students.
Show clear diagrams of the actual stages, pointing out how they match the students' models.
Address Misconceptions Directly:
"Look at our table. Are the final cells identical in both processes? No! This shows they have very different jobs."
"Where did the chromosome number change? Only in meiosis, where it was cut in half. This is essential for sexual reproduction."
4. Elaborate: The Apple Tree Mystery (10 mins)
Goal: To apply your knowledge to a new problem. ð
Teacher's Steps:
Present this problem:"A farmer has a delicious apple tree. But when she plants the seeds from its apples, the new trees grow apples that taste different—some are sweet, some are sour. Why aren't the new trees exact copies of the parent? Use the word meiosis in your explanation."
Have students discuss in pairs and then write a short answer.
Share answers. Guide them to the conclusion that meiosis creates genetically unique seeds, which is why the new trees have variation. Ask: "What if the tree could reproduce using mitosis? What would the new trees be like?" (They would be identical clones).
Differentiation (Advanced): Ask them to research and explain what happens if an error occurs during meiosis (e.g., Trisomy 21).
5. Evaluate: Exit Ticket (5 mins)
Goal: To check your individual understanding. ✅
Teacher's Steps:
Ask students to answer this question in their notebooks on their own:In your own words, what are the two main differences between mitosis and meiosis?
Exemplar Answer: A good answer should mention:
Purpose: Mitosis is for growth/repair, while meiosis is for creating sex cells.
Outcome: Mitosis makes 2 identical cells with a full set of DNA (diploid). Meiosis makes 4 unique cells with half the DNA (haploid).
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