Grade: 10th grade biology

Time Frame: 3-4 days

Goal: Students have learned about the organelles and the functions of those organelles. Students have also learned why cells are small. Cells must divide to be able to function properly. The goal of this lesson is for students to have applicable understanding as to why a cell divides. Students will also be able to describe to their classmates each process that occurs in each step of cell division.

Overview: After a brief explanation of the purpose and overview of mitosis students will examine the process of mitosis on a laser disc, and they will examine mitosis in the onion utilizing the microscope. Students will be broken up into groups of five, and each group will be required to explain the process of mitosis to the class through drawings on a poster board. Finally, students will walk through mitosis utilizing string. This will lead into the next concept being meiosis.

Materials: poster board, colored pencils, microscope, slides, onion, string lab and directions, computers, and laser disc player

Invitation:

Students will hopefully understand that a cell must divide to function efficiently and properly. Students will access the internet on the following web sites to get an introduction to the phases of mitosis:

http://darwin.ceh.uvic.ca/people/koop/bio225?ch24.htm

www.botany.utexas.edu/facstaff/facpages/ksata/ecpf96/9/index.htm

Students will also watch the laser disc player showing the phases of mitosis in motion.

Exploration:

Students will examine mitosis in an onion using a microscope. This will enable students to actually see the process of mitosis occurring. Using the mentioned internet sight will reinforce what students see under the microscope.

Students will also take a quiz over the internet:

www.und.nodak.edu/dept/jcarmich/102lab/102lab.html Take the quiz!!!  

Explanation:

Students will be broken up into groups of five. Each person in the group will be assigned a specific phase of mitosis, and they will explain each phase to their other members of their group. The groups will be required to draw the phases on the poster board provided, and the groups will present their drawings to the class.

Take Action:

Students will walk through the phases of mitosis through a string lab. This activity will aid students in understanding the difference between chromatin, chromatids, and chromosomes. The purpose of this activity will also introduce the difference between mitosis and meiosis. This activity will lead into meiosis.

PURPOSE: The purpose of this lab is to help students gain an understanding of the changes that occur in the nuclear area of a cell during cell division ( mitosis ).

MATERIALS: 4 long pieces of green yarn

6 pieces of pipe cleaner ( different lengths in sets of 2 )

2 pieces each of red, white, and blue yarn ( each other &emdash; different lengths )

 

PROCEDURE: Go through the steps of mitosis with the students, and then have them follow you through the steps with their yarn and pipe cleaners.

For example: 

1. Have the students place one piece of red, white, and blue yarn on their desk or work area, and put all other pieces of the lab to the side or in their laps. Have them pick the pieces of yarn up and drop them on the desk so that they are curled up and overlapping. Tell the students that the cell has gotten too big and it needs to divide. All the information that the cell needs to stay alive is held in the yarn on their desk. How can the cell be sure that both of the new cells get all of the information needed to stay alive.

    

2. The cell duplicates its genetic material ( during the S of the cell cycle ). Tell the students to take the other piece of red, white, and blue yarn and drop them on top of the yarn already on their desk. Now there is enough genetic information for both cells, but it needs to be separated. How is this going to happen?

    

3. First the cell gets its genetic material into a more manageable state. Tell the students to take their yarn and wrap each piece around a pipe cleaner. Wrap the shortest color of yarn around the shortest pipe cleaner, and so on. The pipe cleaners represent the protein core of the chromatid. Now what?

    

4. The nuclear membrane disappears and the cell lays down spindle fibers. Tell the students to lay the four long pieces of green yarn across their desk horizontally and then pull the ends on either side together ( it will end up looking somewhat like a football ). This is the cell's "guide" for making sure each new cell has the correct amount of genetic material. How does the cell use this guide?

    

5. Have the students take their chromatids and match up the ones that are similar ( in length and color ). Twist the two pipe cleaners somewhere along their length so that the two pieces stay together ( represents the centromere ). Then have the students lay each pair of sister chromatids ( now called chromosomes ) on its spindle fiber. The chromosomes are now attached, but still scattered throughout the cell. How does the cell get them where they need to go?

    

6. Tell the students to move all of the chromosome to the center of the cell along the spindle fibers, until they all line up. This is called the metaphase plate. Now how does the cell separate the sister chromatids?

    

7. Have the students untwist the pairs of chromatids, but leave them in the middle of the cell. When they are all untwisted, have them start to move one of each color yarn to the opposite sides of the cell. The genetic material is not usable when it is in chromsome form ( it is "unreadable" by the cell ). The cell needs the information stored in the cells. What happens next?

    

8. Have the students unravel the chromatids and remove the pipe cleaners. Then have them take away the green yarn spindle fibers. When the yarn is unraveled and clumped together, a new nuclear membrane forms around each set of genetic material. This part of cell division is now complete. ( The division of cellular constituents takes place separately in a process called cytokinesis ).

Cells have an outer covering called the cell membrane. The cell membrane controls what moves into and out of cells. Food and oxygen move into cells through the cell membrane. They move by diffusion. The movement of a substance from where it is in large amounts to where it is in small amounts is called diffusion.

Osmosis is a special kind of diffusion. Water will move across a membrane from where it is in large amounts to where it is in small amounts. The diffusion of water is called osmosis.

GOAL: In this exercise, you will observe osmosis across the membrane of an egg.

MATERIALS: plastic cup, raw egg in shell, vinegar, corn syrup, water, plastic wrap, rubber band, paper clip, paper towels

PROCEDURE: 

1. Place an egg in a plastic cup. Fill the cup with vinegar until it covers _ of the egg.

    

2. Cover the egg with plastic wrap and secure it with a rubber band.

    

3. Leave the egg for 48 hours.

    

4. Remove the plastic wrap. Pour out the vinegar. BE CAREFUL NOT TO BUST THE EGG!!!!!!

    

5. Get a new cup and put in the egg. Fill the cup with corn syrup until it covers _ of the egg.

    

6. Cover the egg with plastic wrap and secure it with a rubber band.

    

7. Let the egg sit for 24 to 48 hours.

    

8. Remove the plastic wrap. Pour out the corn syrup.

    

9. Get a new cup and put in the egg. Fill the cup with water until it covers _ of the egg.

    

10. Cover the egg with plastic wrap and secure it with a rubber band.

     

11. Let the egg sit for 24 hours.

     

12. Remove the egg. Pour out the water. Pop the egg with a paper clip over the trash can.

QUESTIONS: 

1. Vinegar is made of acetic acid and water. When the egg was placed in vinegar, which way did the water molecules move?

    

2. How do you know?

    

3. How can you explain the amount of liquid remaining when the egg was removed from the syrup?

    

4. When the egg was placed in water after being removed from the syrup, which way did the water move?

    

5. How do you know?

    

6. Why are fresh fruits and vegetables sprinkled with water at a market?

    

7. If a lawn is fertilized and it does not rain, the grass often dies. Why?

    

8. Roads are sometimes salted to melt ice. What does this salting do to the plants along the roadside? Why?

    

9. Why do dried fruits and dried beans swell when they are cooked?

    

10. The movement of a substance from where it is in large amounts to where it is in small amounts is called __________?

     

11. Water diffuses across a membrane by a process called ______?

     

12. The outer covering of a cell that controls what enters and leaves is called the _____?