Cell Division Simulation: Bacteria
Activity One
Introduction
All living things are made of cells. Some living things, like plants and animals, are made of millions of cells. But some living things are made of just one cell. One kind of single-celled organism is a bacterium. Bacteria may be very tiny, but they carry out many of the same functions as more complex organisms, like taking in food, getting rid of waste, and
reproducing. (They're also the oldest organisms on earth!) Like all cells, bacteria reproduce by duplicating their DNA. But unlike the cells in more complex organisms, bacteria do not have a nucleus.
Some bacteria are essential to life on earth, like decomposers that break down dead materials into food for other organisms. But some kinds of bacteria, like the E. coli in this simulation, can cause disease.
Directions
Using the cell division simulation, watch and discover how a bacterium divides and multiplies.
Procedure
1. From the Main Screen select the Simulations icon. Then click the Cell Division icon.
2. Read Start Here and close the window. For more information, click Background and close the window. For detailed directions, click Help and read "How to Use this Simulation."
3. Select Bacteria (E. coli) from the pull-down menu. Click Play and watch the video showing the cell cycle.
4. Click Play to review the video. This time, click Pause at the beginning of each step of the cell cycle.
At each step, draw the image in the space below. Then label the parts in each step. In the space beneath your drawing, explain what happens during that step. Click Play to resume the video.
STEP 1 STEP 2 STEP 3 STEP 4 Draw a
picture
Label Cell wall, DNA DNA copies New cell wall Daughter cells Describe
what's happening
5. What must happen before a bacterium can divide into two?
6. What is the division of bacteria called? What does this term mean? How does this term accurately describe the two daughter cells?
7. There are two types of cells: prokaryotes and eukaryotes. Prokaryotes don't have a nucleus, but eukaryotes do. Which type of cell is a bacterium? Where is the DNA in a bacterium located?
Cell Division Simulation: Bacteria
Activity Two
Introduction
Bacteria are single-celled organisms. In Activity 1, you watched a bacteria cell divide and multiply. In this activity, you'll label the parts of a bacterium and see what different kinds of bacteria look like under a microscope.
Directions
Using the cell division simulation, watch the reproduction of bacteria, and then learn about the parts and different types of bacteria cells.
Procedure
1. From the Main Screen select the Simulations icon. Then click the Cell Division icon.
2. Read Start Here and close the window. For more information, click Background and close the window. For detailed directions, click Help and read "How to Use this Simulation."
3. Select Bacteria (E. coli) from the pull-down menu. Click Play and watch the video showing the cell cycle.
4. Bacteria vary in size, shape, and color, but most bacteria have the following parts.
• Cell wall: thick, rigid wall surrounding the bacteria cell; provides structure and protection to the cell.
• Cell membrane: the cell's lining (under the cell wall) that controls what goes in and out of the cell.
• DNA: the genetic material that carries the instructions for how the cell behaves.
• Cytoplasm: the jellylike substance within the cell.
In the diagram below, label these parts on the bacterium shown.
5. Different kinds of bacteria have different ways of moving from one place to the other.
Some simply drift with air or water, or by attaching themselves to other organisms or objects that move. Some bacteria that live in water have special structures called
flagella. They use these long, thin "hairs" to whip through the water. Draw a flagellum on the bacterium above.
6. This image shows bacteria that have multiplied quickly from just one single bacteria cell.
Some types of bacteria can reproduce every 20 minutes in the right conditions. At this rate, how many bacteria would two daughter cells produce in two hours?
7. Bacteria come in different colors, sizes, and shapes. The most common shapes are spheres, rods, and spirals. But they can also come in other strange shapes. Some live alone, while others live in groups. How would you describe the bacteria in the
simulation?
8. Imagine you are a scientist looking at the following specimens of bacteria under a microscope. How would you describe the color, shape, and arrangement of each one?
Do they look like other things you've seen before?
Cell Division Simulation: Cells
Activity One
Introduction
All living things are made of microscopic cells. But cells are different for every organism. That's what makes a banana, a butterfly, and a bacterium different! Every living thing begins as one cell. Then it grows or repairs itself by dividing into more cells. Every cell holds special
instructions that determine how it will divide and whether it will grow into a dog, a tree, or a person. These instructions are held in the genetic material or DNA in every cell.
Directions
Using the cell division simulation, watch how a human skin cell divides and multiplies. As you do, find the different parts of the cell.
Procedure
1. From the Main Screen select the Simulations icon. Then click the Cell Division icon.
2. Read Start Here and close the window. For more information, click Background and close the window. For detailed directions, click Help and read "How to Use this Simulation."
3. Make sure Human (skin cells) is selected from the pull-down menu. Click Play and watch the video showing the cell cycle.
4. Click Play to review the video. This time, click Pause at the beginning of each step of the cell cycle. At each step, draw the image in the space below. Then draw a line from each term to your picture. (There may be more than one image for each term.) Click Play to continue the video.
STEP 1 STEP 2 STEP 3
DNA Nucleus Cell membrane Chromosomes Chromosome halves
STEP 4 STEP 5 CHALLENGE
Spindles are long, thin structures that pull the chromosomes apart.
Nuclear membranes
DNA Nucleus Cell membrane
At what stage do the spindles appear? Label the spindles on your drawing of that stage
5. When does the nucleus disappear? When does it appear again?
6. There are two types of cells: prokaryotes and eukaryotes. Prokaryotes don't have a
nucleus, but eukaryotes do. Which type of cell is a human skin cell? What do you find in the nucleus of a human skin cell?
7. Skin cells are reproducing all the time, as old layers of skin wear away and are replaced by new skin cells. What are some other times that skin cells might reproduce at a faster rate?
Cell Division Simulation: Cells
Activity Two
Introduction
All living things are made of tiny cells. But cells are different for every organism. In Activity 1, you watched how a human skin cell divides. In this activity, you'll compare different types of cells and learn about the steps of cell division.
Directions
Using the cell division simulation, watch how different types of cells divide and identify and compare the cells featured in this simulation. Then identify and describe the different stages of cell division.
Procedure
1. From the Main Screen select the Simulations icon. Then click the Cell Division icon.
2. Read Start Here and close the window. For more information, click Background and close the window. For detailed directions, click Help and read "How to Use this Simulation."
3. Watch how the following cells (or virus) divide: Human (skin cells), Bacteria (E. coli), Fungi (yeast), and Virus. Choose the name in the pull-down menu. Then click Play and watch the video showing the cell cycle. As you watch, take a close look at the genetic material in each cell or virus.
4. After you've watched the videos, complete the chart below.
Name
Kingdom:
Plant, Animal, Fungi, Monerans (Bacteria), Protists, or none
Single-celled or multi- celled
Prokaryote (no nucleus) or Eukaryote (nucleus) Description of cell division. Is there a special term to describe this kind of cell division?
During the cell cycle, a parent cell divides to make two new daughter cells. This is how living things grow and repair themselves. The key to cell division is that the new daughter cells must be identical to the parent cell. This means that the two daughter cells must have the exact same genetic material, or DNA, as the parent cell. If the nucleus of the parent cell simply split in half, the daughter cells would only get half of the DNA - and half the instructions the cell needs. That's why, before any cell divides in two, it must duplicate its DNA. The process of cell division takes place in stages.
The cell cycle is divided into two main stages: interphase, when the cell grows and copies its DNA; and mitosis, when the cell divides into two new daughter cells. Mitosis is divided into four shorter stages: prophase, metaphase, anaphase, and telophase. Then, in a final stage, called cytokinesis, the cell divides into two daughter cells. Review the chart below that describes each stage.
5. Read the descriptions in the table below and complete the last column. Match each image with the step described. Write the letter under each image in the space above.
STAGE DESCRIPTION IMAGE OF STAGE
INTERPHASE Cells spend most of their lives in interphase, when the cell grows. During this stage, the sell makes copies of its genetic material or DNA
MITOSIS
Prophase The DNA forms into visible chromosomes.
The nucleus membrane starts to disappear.
Spindles appear. These long thin fibers stretch between the two ends or "poles" of the cell
Metaphase Chromosomes attach to the spindles and line up along the middle of the cell
Anaphase The chromosomes begin to separate and are pulled apart to opposite ends of the cell
Telophase Two new nuclear membranes begin to form around the chromosomes. The
chromosomes begin to uncoil
CYTOKINESIS The cytoplasm (the substance of the cell) divides into two and forms two new daughter cells
