Gametogenesis Aim: How do male and female sex cells form? How does fertilization occur?

Gametogenesis A. Process which gametes develop in gonads. B. Production of sex cells. C. Develop in specialized organs called gonads. 1. Ovaries - females. 2. Testes - males. D. Gametes - haploid (n) sex cells. 1. Egg (ovum) - female. 2. Sperm - male.

Gametogenesis E. Sexes 1. Separate male & female in higher forms of animals. Example: chordates. 2. Individual has both testes & ovaries (hermaphrodites). Usually found among some lower organisms. Example: earthworms.

Oogenesis A. Egg production in females. B. Produced in ovary during meiosis. Produces one ovum & 3 polar bodies. Polar bodies are not viable cells D. Ovum larger than polar bodies. 1. Unequal division of cytoplasm. E. Number of human eggs are limited.

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Spermatogenesis A. Sperm production in males. B. Produced in testes during meiosis. C. Produces 4 spermatids which develop into 4 mature sperm. D. Contain flagellum.

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Comparison of Egg vs. Sperm Round shape Head with long tail Non-motile Motile .05 mm in diameter .10 mm in diameter Contains nucleus Contains nucleus Human/mammal eggs contain no yolk because they get nourishment from mother.

Fertilization A. Fusion of haploid egg nucleus & haploid sperm nucleus. B. Forms a diploid fertilized egg (zygote). C. Two types of fertilization: 1. Internal 2. External Internal External

External Fertilization A. Gametes fuse outside the body of the female. Examples: fish & amphibians. B. Must take place in animals that breed in water. C. Produce many eggs because survival rate is low. D. For improvement with union of gametes, their release is hormonally controlled.

Internal Fertilization A. Gametes unite inside the body of the female. Examples: most terrestrial (land) animals; reptiles, birds, mammals. B. Fewer eggs needed because well protected by mother. C. Greater chance of egg & sperm uniting with internal environment.