How Cells Make More Cells: Mitosis
How Cells Make More Cells: Mitosis
At the end of this lesson, you are expected to:
Explain why cell division is important for living organisms.
State that one cell divides into two.
Describe mitosis as a type of cell division for growth and repair.
Warm-Up Activity: Building with Blocks!
Imagine you have a small Lego castle. How do you make it bigger? You add more blocks, right? Our bodies are a lot like that castle! We start small, and as we grow, we need more "building blocks." What do you think these building blocks are?
Think about it for a moment. If you get a small cut on your finger, how does it heal? Do you have to wait for a whole new finger to grow? No! Your body makes new skin cells to fix it.
These tiny building blocks are called cells. And just like you add more Lego blocks to make your castle bigger, your body makes more cells to help you grow and to repair itself when you get hurt. How do you think your body makes more cells? That's what we're going to learn about today!
Lesson Proper: Why Cells Divide
Welcome to the fascinating world of cells! You are made of trillions of these tiny building blocks, and they are constantly working to keep you alive and growing. Today, we're going to explore one of the most important jobs cells do: cell division.
What is Cell Division?
Cell division is like a cell's way of making a copy of itself. Imagine you have a special toy, and you want another one exactly like it. Cell division is how a single cell makes two new cells that are almost identical to the original.
Why Do Cells Need to Divide?
There are two main reasons why cells divide:
Growth: When you were a baby, you were much smaller than you are now. How did you get bigger? Your body made more cells! Cell division is how organisms grow from a single cell (like in the very beginning of life) into complex beings with trillions of cells. Think about a tiny seed growing into a big tree. This happens because the plant's cells are dividing and multiplying.
Real-World Example 1: Growing Taller When you were born, you were tiny! Now, you're much taller. This increase in height is because the cells in your bones, muscles, and skin have been dividing and making more cells. Each new cell adds a little bit to your overall size, helping you grow.
Repair and Replacement: Our bodies are constantly experiencing wear and tear. Even when you don't notice it, cells are dying and need to be replaced. Cell division is crucial for repairing damaged tissues and replacing old or worn-out cells.
Real-World Example 2: Healing a Scraped Knee Remember that scraped knee? When you fall and get a cut, some skin cells are damaged or lost. Your body immediately starts a repair process. Cells near the wound begin to divide rapidly, creating new skin cells to fill in the gap and heal the cut. This is why scabs form and eventually fall off, revealing new, healthy skin underneath!
A Special Type of Cell Division: Mitosis
There are different ways cells can divide, but one of the most common and important ways for growth and repair is called mitosis.
Think of mitosis like a very careful copying process. The original cell has all the instructions (in the form of DNA, which is like a recipe book) for making a new cell. Before the cell divides, it makes a perfect copy of all its DNA. Then, it carefully divides its contents, including the copied DNA, into two new cells.
What happens during Mitosis?
Mitosis is a process that happens in stages, but for now, the most important thing to remember is that one cell divides into two identical daughter cells. These new cells are just like the parent cell.
Parent Cell: The cell that starts the division process.
Daughter Cells: The two new cells that are formed after division.
Imagine a baker who has a special cookie recipe. To make more cookies, the baker first makes an exact copy of the recipe. Then, the baker uses that copied recipe to make two new batches of cookies, each exactly like the original. Mitosis is similar – the cell copies its "recipe" (DNA) and then divides to make two new cells with the same recipe.
Why is Mitosis Important?
Growth: As we discussed, mitosis is how multicellular organisms grow. From a single fertilized egg, mitosis creates all the cells that make up a complex organism like you!
Repair: When you get injured, mitosis helps repair the damage by creating new cells to replace the lost or damaged ones.
Asexual Reproduction: In some simple organisms, like bacteria or some plants, mitosis is also how they reproduce. One cell divides into two, creating a whole new organism that is genetically identical to the parent.
Let's Recap:
Cells are the basic building blocks of all living things.
Cell division is the process where one cell divides into two.
Cells divide for growth (getting bigger) and repair (healing).
Mitosis is a type of cell division that creates two identical daughter cells, crucial for growth and repair.
Isn't it amazing how these tiny cells work so hard to keep us alive and growing?
Enrichment Activities
Guided Practice: "Cell Division Story"
Let's create a simple story together about cell division.
Imagine a tiny cell named "Mitzi." Mitzi is a skin cell on your arm.
Mitzi is happy and healthy, doing her job of protecting your skin.
One day, you get a small scratch on your arm. Some of Mitzi's neighbors are damaged!
Mitzi gets a signal from her body: "We need more skin cells!"
Mitzi's important instructions (her DNA) make a perfect copy of themselves.
Mitzi's cell gets a little bigger, and all her parts, including the copied instructions, are ready to be shared.
Mitzi carefully divides herself right down the middle.
Now, instead of one Mitzi, there are two new cells! Let's call them Mitzi Jr. and Mitzi II.
Mitzi Jr. and Mitzi II are identical to the original Mitzi. They have the same instructions and are ready to start doing their jobs.
These new cells help to cover the scratch and heal your skin.
Can you tell the story of Mitzi in your own words? What was the reason Mitzi had to divide? What happened to Mitzi after she divided?
Interactive Activity: "Growth Chart"
Let's visualize growth.
Get a piece of paper and a ruler.
Measure your height today and write it down at the top of the paper.
Now, imagine you are just starting. Draw a tiny dot at the bottom of the paper. This represents you as a single cell.
Now, imagine that single cell divides. Draw two dots next to each other.
Imagine those two cells divide. Draw four dots. Keep going, doubling the number of dots each time (2, 4, 8, 16, 32...). You can draw them in rows or clusters.
As you draw more and more dots, you'll see how quickly the number grows! This is like how your body grows from one cell to trillions.
You can even try to draw a simple outline of a person next to your dots to show how the cells form a whole body.
Independent Practice: "Why Cells Divide?" Worksheet
Fill in the blanks to show what you've learned:
Cell division is how one cell becomes _____________________________________________________________________________________
Draw a simple diagram showing one cell dividing into two. Label the "Parent Cell" and the "Daughter Cells."
In your own words, explain why cell division is important for a plant.
Real-World Connection: Your Own Growth Story
Think about how much you've changed since you were a baby. You've grown taller, stronger, and learned so many new things. All of this growth happened because your cells have been dividing through mitosis. Every time you heal from a small cut or scrape, it's also thanks to mitosis. Cell division is happening inside you right now, even as you read this, helping to keep your body healthy and functioning!
What I Have Learned
Cell division is the process where one cell makes two new cells.
Cells divide for two main reasons: growth and repair.
Mitosis is a type of cell division that produces two identical daughter cells, which is essential for growing bigger and healing injuries.
When a cell divides by mitosis, it creates two new cells that are exactly like the original cell.
What I Can Do
Observe: Pay attention to how your body grows and heals. Notice how a small cut eventually disappears.
Explain: Tell a family member or friend about why cells divide and what mitosis is. Use the "Mitzi the cell" story if it helps!
Draw: Draw a picture showing a parent cell dividing into two daughter cells, and label them. You can also draw a picture showing how cell division helps heal a scraped knee
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