1. Review

2. Meiosis
Sexual Reproduction

3. What is meiosis? Animals Process that makes the sperm and egg Plants
Process that makes the pollen and ovule

5. Sexual Reproduction Fertilization Example:
The combination of two haploid Cells to create a diploid cell
Example:
Haploid (n) Sperm or egg
Diploid (2n)– Zygote (fertilized egg)
Sperm(n) + egg(n) = zygote(2n)
N= 23 Chromosomes
For Humans only

6. Fertilization vs Pollination
Fertilization (animals)
Gamete + Gamete -->Zygote
Sperm Egg > Zygote
n n > 2n
Haploid Haploid --> Diploid
Pollination (Plants)
Pollen Ovule --> Seed
n n > 2n

7. Meiosis

8. Phases of Meiosis Meiosis I Interphase Prophase I Metaphase I
Basically Mitosis, twice….
Meiosis I
Interphase
Prophase I
Metaphase I
Anaphase I
Telophase I
Meiosis II
ProphaseII
Metaphase II
Anaphase II
Telophase II

9. Meiosis

10. Meiosis 2 gametes combine to form one zygote Meiosis I
The cell (2n) splits into 2 cells
Each cell is haploid (n) has 23
replicated chromosomes
Meiosis II
Those 2 cells then split into 4 cells
Separating the sister chromatids
The 4 resulting cells become egg and sperm [each is haploid (n)]
Oogenesis creates eggs
Spermatogeneis creates the sperm

11. Sperm and Egg Creation Spermatogenesis creates 4 sperm
Oogenesis creates 1 egg

12. Genetic Variation
Meiosis is IMPORTANT to genetic variation (different types)
Crossing- over: Exchange of genetic material between chromosomes, creates new combinations (Prophase I)
Independent Assortment : Whichever copy goes into the gamete (egg or sperm) is random
(Metaphase I)

13. Comparison of Mitosis and Meiosis
Purpose
Growth and Repair
Reproduction
(genetic variation)
# of Divisions 1 2
Parent Cell
2n (diploid)
Daughter Cells
2n and Identical to parent 4
n and not identical
Type of Cells Produced
Somatic Cells
Gametes

14. Review
Mitosis or Meiosis? A B
Mitosis
Meiosis

15. Ribbit…..ribbit
Thanks for listening!!

16. Meiosis Video Clip http://www.ebaumsworld.com/video/watch/82148080/