1. Meiosis Review and Differentiation

2. Meiosis is the process that forms gametes.
Review:
Meiosis is the process that forms gametes.
Gametes are sex cells (sperm for males and egg for females)
Gametes contain half the number of chromosomes than a body cell. There are no homologous pairs in gametes. (23 chromosomes in humans)
Egg meets Sperm

3. Fertilization- when the sperm and egg come together
Chromosome pairs return at fertilization
Sperm + Egg  Fertilized Egg
(23) (23) (46)
Only one sperm can fertilize an egg
2 nuclei in a
Fertilized Egg

4. Immediately after fertilization:
A hard shell covering forms over the zygote

5. Zygote- name for a fertilized egg
The zygote or fertilized egg will begin to divide into many cells.
What process is happening in the zygote and why?

6. Mitosis begins and the zygote begins to grow into a ball of cells.
The cells will all have the total number of chromosomes (46 in humans)
Day 3
Day 4

7. Drawing of Fertilized Egg

8. Cleavage is the splitting of the zygote into many identical cells.
Zygote 2 cell cell cell cell

9. Migration The movement of cells The solid ball becomes almost empty
Forms a hollow ball of cells

10. The blastocyst
Hollow ball of cells containing the inner cell mass

11. The inner cell mass will become the baby
The outer cells will help the baby attach to the inside of its mother.
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12. Human hatching
The embryo will “crawl” out of the shell

13. Review

14. Implantation
The outer cells of the blastocyst will form “roots” and attach to the inside of the mother’s uterus