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

Sexual Reproduction Reproduction in organisms produces new offspring.

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

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

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

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

Sexual Reproduction

Sexual Reproduction

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.

Advantages of Sexual Reproduction

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).

Advantages of Sexual Reproduction

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

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

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

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

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

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.

Diploid vs. Haploid Cells

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

Diploid vs. Haploid Cells

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

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

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

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

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)

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

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

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

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

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

Meiosis Meiosis I produces 2 genetically different cells.

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

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

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

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

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

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