1. Cell Division!
3.1: Cell division occurs in all organisms

2. Do Now!!  What happens when you get cut?
Explain in your own words what happens when you are cut and the healing process.

3. Objectives To identify various reasons for cell division
To define chromosomes and identify their importance
To relate surface area : volume ratio to reasons for cell division

4. Cellular Division Cell division occurs in all organisms:
Performs different functions
Unicellular organisms (ex: bacteria):
Binary fission: division into 2 identical cells (clone)
Multicellular organisms (ex: US!):
Mitosis
Binary fission
Mitosis

5. Cellular division videos
Binary fission:
Mitosis:

6. Cell division is involved in growth, development and repair
All organisms start as a single cell:
Growth: limited by surface area (needs high ratio of surface area to volume)
Cells are limited in size:
Nutrients in and wastes out through membrane
If cell grows too big, not enough material can cross membrane fast enough
So the cell divides!

8. Worksheet!!

9. Do Now!! 
What is the surface area to volume ratio of a cube with a 3 cm length?
Would this be ideal for the cell? Explain why or why not.

10. Objectives
To discuss how cell division is involved with development and repair.
To identify the steps of mitosis.

11. Cell division is involved in growth, development and repair (cont.)
c) Development:
Makes specialized cells- cells modified for particular functions
Ex: blood cell, nerve cells,
muscle cells

12. Cell division is involved in growth, development and repair (cont.)
Heals cuts and any wounds
Cells divide and fill up space to close the wound
As cells age and die, they need to be replaced.

13. DNA – DeoxyriboNucleic Acid
A chemical that contains information for an organism’s growth and functions:
Has directions for how to make proteins!
Double helix like a twisted ladder
Eukaryotes: located in nucleus

14. Chromosome Structure
DNA coils around histones (proteins) to form nucleosomes
This coils to form chromatin fibers
The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis.

15. We have 46 total chromosomes= 23 pairs

16. Question
Even when you are done growing and development appears to stop, is cell division still occurring?