1. Importance of Cell Division

2. Importance of Cell Division
You began life as a single cell: a fertilized egg
Now your body is made up of trillions of cells
How??
Cells divide to for 3 main reasons 2

3. 1. Reproduction
Involves the transfer of genetic information from parents to offspring
Single cell organisms
Asexual reproduction = 1 parent, offspring are exact genetic copies 3

4. 1. Reproduction Multicellular Organisms
Sexual Reproduction = cell from each parent containing 1/2 DNA (gametes) combine
Offspring inherits traits from both parents 4

5. 2. Repair
When part of an organism is damaged the remaining cells divide to repair injury 6

6. 2. Repair Every day your body sheds millions of dead skin cells
Blood cells are replaced every 120 days
Bones break and are healed
Cells fill in gaps caused by cuts
Lysosomes = search and destroy
Ability to repair self keeps organism alive 5

7. Which organism has larger cells?7

8. 3. Growth
As multicellular organisms grow, the number of cells increases
Cells divide rather than grow beyond a certain size
Why? 8

9. 3. Growth Why? All cells need nutrients, water, energy & gases
Large cell = increased volume
Diffusion of these materials into and out of the cell would not happen fast enough
Therefore cell would not function properly 9

10. What Limits Cell Size? Lab
Monday
Read over lab on page 38-39
Testable question: How does the size of a cell affect the distribution of chemicals throughout a cell?
Come up with hypothesis/prediction - Ticket into Lab 10

11. Homework Questions
Page 37 # 2-6
HAVE A GREAT WEEKEND! 11