1. MEIOSIS
HOW SEX CELLS ARE MADE!

2. Make gametes by.....
MEIOSIS!!!!!!!!!
Meiosis forms haploid cells.

3. INTERPHASE OCCURS ONCE
G and S phases help enlarge the cell and replicate the genetic material
Prepares the cell for nuclear division

4. 1. PROPHASE I
Chromosomes become visible.
Nuclear Envelope disappears
Crossing over can occur.

5. 2. METAPHASE I
Chromosomes line up in the middle

6. 3. ANAPHASE I
homologous pairs move to opposite poles

7. 4. TELOPHASE I
Cytokinesis

8. 5. PROPHASE II
no interphase!
New spindles form

9. 6. METAPHASE II
Chromosomes line up again

10. 7. ANAPHASE II
Centromeres divide
Chromatids move apart

11. 8. TELOPHASE II
CYTOKINESIS

12. meiosis contributes to genetic variation.
RESULTS
4 Haploid cells!
meiosis contributes to genetic variation.

13. Gamete formation in male & female animals involves meiosis.
Sperm are formed by spermatogenesis
4 sperm are made by meiosis

14. Ova (eggs) are made by oogenesis.
Only 1 egg results.
The other 3 are called polar-bodies.
The polar bodies die

15. SEXUAL VS. ASEXUAL REPRODUCTION

16. SEXUAL REPRODUCTION...
2 parents form haploid gametes.
The offspring will have traits of both parents.
Advantage: mixes genes Disadvantage: numbers are limited

17. ASEXUAL REPRODUCTION
produces offspring that are clones of parents
advantage: makes many babies in short time
disadvantage: no diversity in unstable environments

18. Examples of asexual reproduction:
binary fission: bacteria
budding: sponges
fragmentation: sea stars