1. The Importance of Cell Division
Section 2.3

2. We all started out as a single cell
a fertilized egg called a zygote
As adults, we have bodies consisting of trillions of cells through the process of cell division.

4. Purpose of Cell Division
Growth
Reproduction
Repair

5. Reproduction
All cells, including single-celled organisms use cell division to reproduce
There are 2 basic kinds of reproduction:
Sexual and asexual
Asexual Reproduction:
Involves only 1 parent dividing into two cells
Offspring are genetically identical to parent cell.

7. Sexual Reproduction:
Process of producing offspring by the fusion of two gametes (egg and sperm cells)
Gamete (sex cells)
“half-cell” contains only have of the DNA usually found in a cell.
Offspring have genetic information from both parents, and therefore are NOT genetically identical to their parents.

8. Growth As organisms grow, the number of cells increases. OUT IN OUT IN
waste
ammonia
salts
CO2
H2O
products IN
food
carbohydrates
sugars, proteins
amino acids
lipids
salts, O2, H2O
OUT IN
FOOD must be able to move into and throughout the cell quickly enough for the proper function of the cell. WASTES also must be transported quickly out of the cell.

9. How does material move in and out of the cell?
Diffusion
Materials move from an area of higher concentration to and area of lower concentration
Concentration
the amount of a substance (solute) in a given volume of water

11. Osmosis is just diffusion of water
Water is very important to life, so we talk about water separately
Osmosis
Diffusion of water from HIGH concentration of water to LOW concentration of water
across a semi-permeable membrane

12. How to grow a gummy!

13. Cells do not substantially increase in size. Why?
Food and nutrients have less distance to travel to organelles
Food and nutrients take too long to reach organelles
Cells need to be efficient at getting food in and wastes out!

14. Repair
All organisms must repair themselves to stay alive by the division of the remaining cells
Skin cells: millions replaced every day
Red blood cells: each red blood cell is replaced every 120 days
Broken bones, cuts and blisters: new cells needed to fill in gaps
Nerve cells: cannot regenerate!

15. Repair

16. Classwork/Homework
Answer Q#1-6 on pg. 37
LAB Handout.????