Sexual Reproduction in Animals

A basic overview of what sexual reproduction involves, what meiosis, fertilisation and development are using a hen as an example.

1. Learning Goals: To be able to explain Sexual Reproduction. To be able to differentiate the different types of fertilisation. To be able to explain different forms of development.

2. Sexual Reproduction Sexual reproduction involves two parents who have sex organs which produce sex cells . The sex cells in sexual reproduction are called gametes and are produced in the gonads . Male gametes are known as sperm , and female gametes are known as eggs.

3. Meiosis A type of cell division that results in half the required DNA for a new organism.

4. Meiosis

5. Fertilisation External fertilization : Eggs and sperm are released into the surrounding water. Occurs in many aquatic invertebrates and most fish. I nternal fertilization : sperm are transferred from the male directly inside the body of the female. This is known as copulation . F ertilization : The fusing of the male and female gametes to form a zygote.

6. Development Development can be external in the water, external on land, or internal. Ovoviparous : live birth from eggs (some sharks and snakes) Oviparous : lay eggs, offspring develops in egg and hatches. ( fish,   amphibians,   reptiles, all  birds, insects, spiders) Viviparous : live placental birth

7. Development

8. Hermaphroditism : individual has both male and female reproductive systems. Earthworm Hermaphrodites

9. Animal Location of Fertilisation Location of Development Number of Eggs Fertilised Amount of Parental Care Advantages of reproduction method Disadvantages of reproduction method