1. Cell Division When do cells divide? How do cells divide? What is Meiosis? How do Chromosomes combine and form new chromosomes?

2. Cell Size The size of the animal does not affect the size of the cell Mouse cell size = elephant cell size

4. Eukaryotic Cell Size 10 -100 micrometers Cell membrane determines cell size Why? Allows nutrients to enter or exit Larger cells require a larger cell membrane

5. Is there a limit to a cell’s size? You must look at surface area and volume Surface area = the sum of all the areas of all the shapes that cover the surface of the object. Volume: The amount of space occupied by a three-dimensional object or region of space, expressed in cubic units.

6. Surface Area and Volume : Cube Surface Area = 6 sides x H x W Volume = L x W x H

7. Ratio Ratio = The comparison between 2 numbers How do you write a ratio of 4 to 8? 4:8 4/8 Surface Area : Volume

8. Smaller cells are better!

9. Bigger is Not Better Cells need to remain small to survive Larger cells have a small SA : V ratio Makes it difficult to transport materials into or out of the cell Nucleus controls the cells size

11. Cell Division Cells divide when they reach their maximum size Cell division = one cell split and becomes 2 cells

12. Why do cells divide? Essential for Three Life Processes Growth Repair Reproduction

13. Growth Cells divide to increase the size of the organism Differentiation: cells develop specialized shapes and functions Ex. Nerve cells, heart cells, intestine cells, intestine cell Each cell has a unique function

14. Repair Repairs tissue Mending of skin, blood vessels, and bone Regeneration of old skin cells Regeneration: ability to replace a missing body part, like a starfish or worm

15. Reproduction Asexual reproduction: one parent produces an offspring Offspring is genetically IDENTICAL to parent Sexual Reproduction: 2 parents produce an offspring Offspring has a combination of genetic material

16. Asexual Reproduction Fission Spores Budding Bacteria, fungi, plants, ocean animals

17. Sexual Reproduction Gamete = reproductive cell; sperm or egg Two gametes fuse to form a zygote Zygote will divide and become an individual Humans, some plants, animals

18. Technology Human Growth Hormone (HGR) controls the rate of cell division HGR is produced in the pituitary gland Makes most HGR during puberty

19. Pituitary Gland Malfunction Does not make enough HGR Dwarfism: person never reaches adult height or weight 1985 – Genetic engineers discovered a way to obtain HGR to