The Importance of Cell Division

Section 2.1Pages 36-38

BC Science Probe 9

The Importance of Cell Division

• What would you look like if every cut or scratch that you ever had remained?

The Importance of Cell Division

• Imagine what you would look like if your skin cells didn’t die and get replaced by new ones.

• Throughout your life, your body will use cell division to replace damaged or dead cells.– It will slow as you get older, but it won’t stop

completely until you die!

Functions of Cell Division

• Growth– All living things are made up of one or more cells.– All living things begin life as one single cell.– Why don’t cells just increase in size to grow?

Functions of Cell Division

• Growth– Well, as a cell grows, the volume of the cytoplasm

gets too big compared to the surface of the cell membrane for the cell to work properly.

– Once a cell gets big enough, it has to divide into two smaller cells that will do the same things.

Functions of Cell Division

• Growth– So to increase in size

or grow, a multicellular organism has to use cell division.

– Once a body has enough cells, they can start to specialize to form tissues and organs.

Functions of Cell Division

• Repair– Multicellular organisms also use cell division to

repair damaged cells.– You don’t actually go through life will all the same

cells that you were born with.

Functions of Cell Division

• Repair– Every second, old and dead cells are replaced in

your body and in the bodies of other multicellular organisms.

Functions of Cell Division

• Reproduction– Unicellular organisms, like a paramecium, are each

only made up of one cell.– They need to use cell division to reproduce.

Functions of Cell Division

• Reproduction– The new cells will contain the same structures and

carry out the same functions as the parent cell.– There are actually even some multicellular

organisms that can reproduce by cell division too, like mushrooms.

Functions of Cell Division

• Reproduction– There are still lots of questions about how and

why cell division works as it does.• Why do some cells reproduce at different rates at

different times?• Why can some cells divide while

others can’t?• Why do cancer cells divide out of

control?

Try This!

• From One Cell to Trillions (page 37)– The human body contains trillions of cells. They all

came from a single cell. In this activity, you will investigate the number of cells divisions needed to form a human body.

Try This!

• Calculate the number of cells after each division on handout 2.1.

Try This!

• How does the number of cells that are produced relate to the number of cell divisions that occur?

• How many cells would there be after 25 divisions?

• How many cell divisions are needed to produce more that a trillion cells?

Assignment

• CYU page 38– #1, 3, 4, 5, 7, 10, 12, 14