1. 3-1 Notes - Sexual Reproduction & Meiosis
Chapter 3, Lesson 1

2. Sexual Reproduction
Reproduction in organisms produces new offspring.

3. Sexual Reproduction
Organisms can reproduce their cells in two ways: by sexual reproduction and by asexual reproduction.
Sexual vs. Asexual Reproduction
Sexual Reproduction
Asexual Reproduction
needs two organisms of the same species
only needs one organism
child is different from the parents
child is an exact copy of the parent
special cells called gametes are created
no special cells involved

4. Sexual Reproduction
Sexual reproduction occurs when the DNA from two different cells combine.
46 chromosomes
46 chromosomes
23 chromosomes
23 chromosomes
46 chromosomes

5. Sexual Reproduction Half the DNA is contained in an egg cell.
Half the DNA is contained in a sperm cell.
23 chromosomes
23 chromosomes

6. Sexual Reproduction
In a process called fertilization, the sperm and egg cells fuse together forming something called a zygote.

7. Sexual Reproduction

8. Sexual Reproduction

9. Advantages of Sexual Reproduction
Genetic variation – a variety of genetic traits in a species makes it more likely for the species to survive changes in environmental conditions.

10. Advantages of Sexual Reproduction

11. Advantages of Sexual Reproduction
Selective breeding (the opposite) – when males and females with preferred traits are chosen to breed so they produce offspring with the preferred traits – this reduces genetic variation (offspring are very similar).

12. Advantages of Sexual Reproduction

13. Disadvantages of Sexual Reproduction
Getting egg and sperm together for fertilization can be difficult.

14. Disadvantages of Sexual Reproduction
It takes time for organisms to grow and develop before they are mature enough to reproduce.

15. Importance of Meiosis
Meiosis is a type of cell division that produces sperm or egg cells.

16. Importance of Meiosis
Meiosis ensures that offspring inherit the correct number of chromosomes.
46 chromosomes
46 chromosomes
23 chromosomes
23 chromosomes
46 chromosomes

17. Importance of Meiosis
Without meiosis, the chromosome number would double with each generation.

18. Diploid vs. Haploid Cells
Diploid cells have 2 sets of each homologous chromosome (they are similar, but not identical).
Haploid cells have 1 set from each homologous chromosome pair.

19. Diploid vs. Haploid Cells

20. Diploid vs. Haploid Cells
A diploid human cell has 23 pairs of (or 46 total) homologous chromosomes.

21. Diploid vs. Haploid Cells

22. Meiosis
Meiosis is split into two overall stages: Meiosis I and Meiosis II.

23. Meiosis
Meiosis I
Prophase I – Nuclear membrane breaks apart and pairs of replicated chromosomes condense. (92 human chromosomes)

24. Meiosis
Meiosis I
Metaphase I – Sister chromatids line up along the center of the cell. (92 human chromosomes)

25. Meiosis
Meiosis I
Anaphase I – Sister chromatids move to opposite ends of the cell. (92 human chromosomes)

26. Meiosis
Meiosis I
Telophase I – Nuclear membrane forms around each set of sister chromatids and the cytoplasm divides, forming two daughter cells. (46 human chromosomes)

27. Meiosis
Meiosis II
Prophase II – Chromosomes do not replicate before nuclear membrane breaks apart. (46 human chromosomes)

28. Meiosis
Meiosis II
Metaphase II – Chromosomes line up along the center of the cell. (46 human chromosomes)

29. Meiosis
Meiosis II
Anaphase II – Sister chromatids separate, moving to opposite ends of the cell. (46 human chromosomes)

30. Meiosis
Meiosis II
Telophase II – Nuclear membrane reforms and the cytoplasm divides. (23 human chromosomes)

31. Meiosis
Meiosis results in 4 haploid nuclei from 1 diploid nucleus.

32. Meiosis
Meiosis I produces 2 genetically different cells.

33. Meiosis
Meiosis II produces 2 identical haploid cells from each cell produced in Meiosis I.

36. What is the new cell that forms from fertilization called? A sperm
3.1 Sexual Reproduction and Meiosis
What is the new cell that forms from fertilization called?
A sperm
B egg
C haploid
D zygote

37. 3.1 Sexual Reproduction and Meiosis
How many chromosomes from each homologous pair does a haploid cell contain?
A one
B two
C three
D four

38. How many daughter cells are produced in meiosis? A one B two C three
3.1 Sexual Reproduction and Meiosis
How many daughter cells are produced in meiosis?
A one
B two
C three
D four

39. What is one advantage of sexual reproduction?
A produces many offspring
B offspring are genetically identical
C offspring have more genetic variation
D can produce offspring quickly

40. SCI 2.a
How many times does division of the nucleus and cytokinesis happen in meiosis?
A one
B two
C three
D four