Sexual Reproduction In Animals
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Sexual reproduction in animals involves the production of gametes - eggs from females in ovaries and sperm from males in testes. Eggs are larger and cannot move while sperm are smaller and swim. Fertilization occurs when the sperm nucleus enters the egg nucleus and they join to form a zygote. External fertilization happens outside the body in water animals, while internal fertilization occurs inside the female's body in land animals and some aquatic animals, requiring specialized sex organs. After fertilization, the zygote may be enclosed in a shell and released or remain inside the female's body to develop.
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Sexual Reproduction In Animals
- 1. Sexual Reproduction in Animals Gamete – egg Gonad – ovary Few to many eggs - oogenesis Egg cells are (n) haploid/monoploid Gamete – sperm Gonad – testes Many sperm cells - spermatogenesis Sperm cells are(n) haploid/monoploid Female Male
- 2. Egg *Larger than a body cell *Cannot move on its own *Round shape Sperm *Smaller *Swims through liquid *Head, middle, & tail (flagellum)
- 3. Fertilization Sperm nucleus enters the egg and moves to the egg nucleus. The 2 nuclei join together and then form a zygote .
- 4. External Fertilization *outside the body Animals that breed in the water Many hazards in the environment Sperm and egg may not meet Eggs or offspring may be eaten May die due to environmental conditions Temperature Oxygen level
- 5. Large number of sperm and egg are released to overcome hazards Hormones control behavior to have sperm and egg released at the same time.
- 6. Internal Fertilization *within the female body Land animals Some aquatic animals Shark Octopus
- 7. Requires specialized sex organ to carry sperm to body of female Watery environment needed for sperm to swim to the egg
- 8. After fertilization, zygote is enclosed in a protective shell and released OR remains and develops in female body Zygote Turtle laying eggs
- 9. Internal Fertilization Fewer eggs needed Well protected Increased chance of fertilization Parthenogenesis – development of unfertilized egg into an adult.- Bees & Wasps