Ch. 4 Reproduction of Organisms

Sexual reproduction and meiosis Sexual reproduction: requires two sex cells to combine during fertilization. Egg: female sex cell Sperm: male sex cell Fertilization: the joining of egg and sperm Zygote: a fertilized egg

Diploid Cells Diploid cells are body cells and are produced by mitosis.

Diploid Cells Diploid cells have pairs (2N) of chromosomes. One chromosome comes from each sex cell. Each pair of chromosomes contain genes for the same traits. Each pair is called homologous chromosomes.

Haploid Cells Only have one chromosome from each pair (1N) Are sex cells (sperm or egg) Are formed by the process of meiosis In meiosis, one diploid cell divides and forms 4 haploid sex cells.

Meiosis Is necessary to reduce the chromosome number otherwise each generation would have twice as many chromosomes as their parents!!! Only occurs in forming gametes/sex cells used in sexual reproduction. Fertilization restores the species chromosome number. 1N + 1N = 2N

Sexual Reproduction Advantages: Disadvantages: Genetic variation. Selective breeding. Takes time and energy Finding a mate

Asexual Reproduction Lesson 2

Asexual Reproduction One parent organism produces offspring without meiosis and fertilization. The offspring are genetically identical to each other and their parent.

Types Of Asexual Reproduction Fission: cell division in prokaryotes that forms two identical cells.

Types of Asexual Reproduction Mitotic Cell Division: occurs in many unicellular eukaryotes.

Types of Asexual Reproduction Budding: the new offspring grows by mitosis and cell division on the body of its parent. This occurs in hydra (shown above) and in yeast.

Types of Asexual Reproduction Regeneration: occurs when an offspring grows from a piece of its parent. This occurs in starfish. And planaria.

Types of Asexual Reproduction Vegetative Reproduction: occurs when offspring grow from a part of parent plant. This usually involves structures such as roots, stems, and leaves. Again, each new plant is genetically identical to its parent.

Types of Asexual Reproduction Cloning: a type of asexual reproduction performed in a laboratory that produces identical individuals from a cell or from a cluster of cells taken from a multicellular organism. This can be done with plants, using a tissue culture. Or with animals, using chromosomes from only one parent.

Advantages of Asexual Reproduction No need for a mate. Can produce a large number of offspring quickly.

Disadvantages of Asexual Reproduction Because all of the offspring are genetically identical to the parent, an entire population is at risk if the environment changes suddenly. Mutations! Weed Killer