chpater 43 - Animal Reproduction 43 Asexual Reproduction...

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43 Animal Reproduction
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43 Animal Reproduction Asexual Reproduction Sexual Reproduction The Human Reproductive System Human Sexual Behavior
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43 Sexual Reproduction Gametogenesis Sperm Eggs Uniting the Gametes External fertilization Internal fertilization Fertilization Specificity Blocks to polyspermy
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43 Gametogenesis Despite the time, energy, and risk required, sexual reproduction confers an overwhelming evolutionary advantage: the production of genetic diversity. Sexual reproduction requires the joining of two haploid cells into one, which becomes a diploid individual. These haploid cells, or gametes, are produced by gametogenesis , involving meiotic cell divisions. Two events in meiosis contribute to genetic diversity: crossing over of homologous chromosomes and independent assortment of the chromosomes.
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43 Gametogenesis The gonads ( testes and ovaries ) are the sites of gametogenesis. Male gametes ( sperm ) move by beating flagella; female gametes ( eggs or ova ) are nonmotile. The gametes are formed by germ cells which originate very early in the developing embryo.
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43 Gametogenesis
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Figure 43.9 Seminiferous Tubules Are the Site of Spermatogenesis (Part 1)
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Figure 43.9 Seminiferous Tubules Are the Site of Spermatogenesis (Part 2)
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Gametogenesis Oogenesis produces eggs through two meiotic divisions. The primary oocyte enters prophase of the first meiotic division, and then its development is arrested (for days, months, or for as long as 50 years). During this phase, the primary oocyte grows and adds to its energy, ribosome, and organelle store. This permits the later embryo to have
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This note was uploaded on 04/30/2008 for the course BIO 201 taught by Professor Masters during the Spring '08 term at Johns Hopkins.

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chpater 43 - Animal Reproduction 43 Asexual Reproduction...

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