2. The Importance of Cell Division Section 2.3

3. 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.

5. Purpose of Cell Division 1.Reproduction 2.Growth 3.Repair

6. 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.

8. 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.

9. Growth IN food carbohydrates sugars, proteins amino acids lipids salts, O 2, H 2 O OUT waste ammonia salts CO 2 H2OH2O products 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. IN OUT As organisms grow, the number of cells increases.

10. 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

12. 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

13. How to grow a gummy!

14. 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!

15. 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!

16. Repair

17. Classwork/Homework 1.Read Lab: What is the ideal cell size? 2.Answer pre-lab questions (DUE WEDNESDAY) 3.Answer Q#1-6 on pg. 37