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© August 2015 Moshe Brody

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Reproduction: Approved by Harav Yisroel Belsky shilit”a. 3

Regents Review.. 9

Evolution. 13

Regents Review.. 20

Reproduction: Approved by Harav Yisroel Belsky shilit”a

1) There are two types of reproduction: Asexual and Sexual reproduction.

  1. Asexual reproduction: The organism reproduces itself and the offspring has the same genes as the parents.
  2. Sexual reproduction: Both parents join together and produce offspring with some characteristics from each parent.

2) In organisms that reproduce through the second process, the mixing of genes comes from specialized cells, which are called Gametes or sex cells.

  1. Gametes: Both the female and male have these cells. The female produces them in the form of eggs in her ovaries and the male in the form of sperm (seed material) in the testes. These sperm are small egg-shaped cells with tails attached to them that are deposited in the female and meet up with the eggs. These cells are different than regular cells since they have only one set of genes as opposed to two in regular cells. The reason for having only half of the DNA is so that the two parents’ genes can meet up and produce a new being with parts of the father’s and mother’s genes mixed together.
  2. Meiosis: The process that produces sex cells. The process starts with a cell that has four sets of chromosomes. The cell then splits into two different cells, each with its own pair of double-stranded DNA. The two cells that were created in step one then break into four cells, each cell containing only one chromosome or double strand of DNA. This process creates a sperm cell (in the male) onto which a little tail is attached which helps it move. In an egg cell (female), the cell breaks up into four cells but with one large egg cell taking all the cytoplasm (food and nutrients) with it, and leaving three small non-functioning cells.