Animal Survival Reproduction

Comparison of Eggs and Sperm Produced by Females Produced by Males Smaller number produced Larger number produced Much larger than sperm Much smaller than eggs Are not ‘self propelled’ Have ‘tails’, so can swim Contains food reserves Have very limited food reserves

Fertilisation FERTILISATION. New vocabulary = gamete = sex cell Sperm = male gamete Egg = Female gamete When a sperm and an egg fuse together, the nuclei fuse and their genetic information mix together. This is called FERTILISATION.

External Fertilisation Takes place outside the female’s body. This is inefficient and wasteful. Must occur in water environment.

Internal Fertilisation Takes place inside the female’s body. Female keeps the egg in her body, male deposits sperm directly into females body (in mammals, penis deposits sperm into female vagina) More efficient and less wasteful (fewer gametes are lost and less gametes are produced) Some animals then lay eggs for development outside body. In others, the egg (new life) develops insode the female.

Development in Fish G6: State that in fish, eggs are protected by flexible coverings and that embryos obtain food from the enclosed yolk sac. Tough but flexible membrane protects the egg and developing embryo after fertilisation Nucleus Cytoplasm contains yolk to feed the developing embryo

Development in Fish G7: State that in a fish, such as trout, the young emerge from the eggs able to maintain themselves. Yolk sac remains attached providing nourishment until the young fish is able to feed itself

Development in Mammals G8: Describe how the fertilised egg passes down the oviduct and becomes attached to the wall of the uterus, develops in fluid of the amniotic sac and obtains food from the maternal circulation.

Development in Mammals

C1: Explain the importance of internal fertilisation to land-living animals Internal fertilisation allows animals to live on land. Eggs are kept within the female body and sperm are deposited directly into the female

C2: Explain the relationship between the no C2: Explain the relationship between the no. of eggs/young produced and the amount of protection given during fertilisation and development in fish and mammals No. of eggs Chances of fertilisation Protection of eggs Parental protection of young Chances of successful development Fish Mammals Large number None (or limited) None (or limited) Poor Low Protected inside mother’s body Young are dependant on parents for food and protection Few High High G9: State that at birth, the young of mammals are dependant on the adult for care and protection

C3: Describe the structure and function of the placenta Animal Survival Booklet Pages 35 - 42