1. Reproductive Strategies
Differ greatly between groups of species
Many asexual species or species whose sexual reproduction does not involve male/female roles

2. In Humans
The ovaries/testes contain cells called germ cells which undergo meiosis
Produce sperm and egg
Sperm and egg fuse in fertilization forming a zygote

3. Sperm/Egg (aka: the gametes)
You only pass one of your homologous chromosomes on to each sperm or egg cell.
It could be the one you got from your mama or your dad BUT NOT BOTH!
Each gamete randomly receives 1 of the 2 versions of each chromosome

4. A.) Any cell with 2 sets of chromosomes (1 set from mom and 1 from dad) is called a DIPLOID cell. (46 chromosomes)
a.) ALL the cells in your body are diploid EXCEPT the GAMETES (sex cells).
b) Gametes have 1 set of chromosomes (a mix of mom & dad) SO we call them HAPLOID. (at the end 23 chromosomes)
The creation of the gametes is done through a double division of the cells called MEIOSIS 1 & MEIOSIS 2

5. Meiosis 1-division of homologous pairs
-Prophase 1 the homologous pairs hug one arm and cross over (swap some genes = diversity!)
-Metaphase 1 Homologous pairs line up! Totally random side = independent assortment = diversity!
-Anaphase1
then divide.
-telophase 1 the cells are haploid.

6. Crossing Over A.) During Prophase I
1.) each pair of HOMOLOGOUS chromosomes pair up so tightly that they exchange change GENES)

7. Independent Assortment: the different ways chromosomes align; maternal / paternal chromosomes switching sides. Totally random!

8. Which side of the cell the chromosome lines up on = crossing over!!! You can get either 1 of your mother’s pair of chromosomes OR all 23!

9. Meiosis 2
Sister chromatids are gonna split up JUST LIKE IN Mitosis.

12. At the end of meiosis…
1.) Four HAPLOID daughter cells have been formed. None of them have a complete set of chromosomes given to them from their mom/dad, they have a recombination of the chromosomes that they received from mom/dad.
2.) Each daughter cell is GENETICALLY different
3.) These cells are GAMETES (sex cells).

13. Why Sexual Reproduction?
DIVERSITY!
Meiosis produces an incredible amount of diversity
Diversity is good!
B/C diversity increases chances that our species will survive

14. How does diversity happen?
#1 Crossing over
#2 Independent Assortment
#3 Recombining genes of 2 people (aka sexual reproduction

15. Recombination of genes
There are 223 possible chromosome combinations to make a gamete
=8,388,608 possibilities
So you are 1 out of 8,388,6082 possibilities
You are quite literally 1 in a trillion (1 of 70,368,744,200,000 possible combinations of your parents)

16. Mitosis vs. Meiosis Mitosis Meiosis
Identical offspring (same set of chromosomes)
2 daughter cells
Creates all body cells
Offspring have half as many chromosomes
4 daughter cells
Creates sperm/egg