1. Section 6.1 Sexual Reproduction
Text Pages

2. Key Terms Sexual Reproduction Gamete Fertilization Zygote Embryo
Diploid
Haploid
Meiosis
Homologous Chromosomes
Interkinesis

3. Section 6.1 Learning Objectives
Define sexual reproduction
Define gamete, fertilization, zygote, and embryo
Define diploid and haploid
Describe the role of meiosis in sexual reproduction
State and briefly describe the eight phases of meiosis

4. Sexual Reproduction: Genetic variety
Sexual Reproduction: reproduction that combines the genetic information from two different parents to produce offspring that are genetically unique.

5. Sexual Reproduction: Genetic variety
Brothers may look similar, and look something like their parents, but neither one is exactly the same as anyone else in their family. (Unless they are identical twins!! This is a special case)

6. Sexual Reproduction: Genetic variety
Since sexual reproduction creates unique individuals, it increases the genetic variety in a species. It is like shuffling DNA around without ever knowing exactly what the combination will be.

7. Sexual Reproduction: Genetic variety
This can give some individuals a better chance of surviving! Unfortunately, sometimes it makes others less likely to survive!
Overall this can help the species to survive in changing environments.

8. Sexual Reproduction: The Role of Gametes
You have 46 chromosomes in each of your body cells:
They are found in 23 pairs of similar chromosomes.
In each pair, one chromosome came from your father and one came from your mother.

9. Sexual Reproduction: The Role of Gametes
In Section 5.1, you learned that Mitosis is the process of cell division that creates genetically identical cells. Body cells formed by mitosis are known as Diploid cells. Diploid cells: same # of chromosomes as the parent cell (46 in humans)

10. If humans reproduced through mitosis like Bacteria or Fungi, we would all have exactly the same 46 chromosomes (with the occasional mutation).
So what makes us unique?

11. Sexual Reproduction: The Role of Gametes
Sexual reproduction involves combining cells called gametes.

12. Sexual Reproduction: The Role of Gametes
Gametes: cells that combine during sexual reproduction. Sperm in males and eggs in females. They are haploid cells.

13. Haploid Cells: half the number of chromosomes as normal body cells (23 in human gametes)

14. Diploid Haploid Formed by mitosis
Same # of chromosomes as parent cells
Humans = 46 chromosomes
Body cells
Formed by meiosis
Half the # of chromosomes as parent cells
Humans = 23 chromosomes
Sperm and eggs (gametes)

15. Fertilization: a sperm cell penetrates an egg cell and the 23 chromosomes in each combine to create a new diploid cell called a zygote

17. Zygote: The diploid cell formed as a result of fertilization.

18. Embryo: A zygote that is growing larger
Embryo: A zygote that is growing larger. It creates more cells through mitosis.

19. Salmon Reproduction
In Nature
Aquaculture

20. Meiosis: How Gametes are Formed

21. Meiosis: How Gametes are Formed
Meiosis: the process through which gametes are created from diploid cells. It involves two cell divisions (Meiosis I and Meiosis II)
Meiosis occurs in the sex organs: - testicles in males (sperm)
- ovaries in females (eggs)

22. Meiosis must create haploid cells
Meiosis must create haploid cells. If sperm and eggs were diploid they would combine to create a zygote with twice the number of chromosomes as the parents (92 instead of 46)!

23. Meiosis occurs in two distinct stages: Meiosis I and Meiosis II
Meiosis I Interkinesis Meiosis II
i) Prophase I - cell grows and i) Prophase II
ii) Metaphase I makes various ii) Metaphase II
iii) Anaphase I proteins iii) Anaphase II
iv) Telophase I iv) Telophase II

24. Meiosis: How Gametes are Formed
Meiosis Video

27. Comparing Mitosis and Meiosis
Homologous Chromosomes
Homologous Chromosomes

28. Mitosis
Meiosis
Type of Cells
In body cells
In sex organs to produce sex cells (gametes)
Number of Daughter Cells Produced
Two daughter cells
Four daughter cells
Genetic Material in each Cell
Same # of chromosomes as in parent cell
Genetically identical cells
Half the # of chromosomes as in the parent cell
Genetically different cells.
Function
Grow new body cells or replace dead/damaged cells.
Creating haploid cells for sexual reproduction.