Courtship

Courtship behaviour is displayed by many mammals, birds and some fish

Occurs before mating and helps males and females recognise each other

Courtship prevents immature animals from breeding

It also allows the females animal to make a choice as to which males she wishes to breed with.

-secretion of chemicals (pheromones) to attract a mating partner-change in appearance of males to attract the females e.g. peacock displaying his feathers to attract a peahen - making sounds: male frogs make a loud croaking sound to attract female frogs

Courtship behaviour is of survival values it is only the strong, fittest males that mate with the females and in so doing, passes on their genes to the next generation.

Occurs when a sperm fuses with an egg to form a zygote Fertilization may take place outside a female (external) or it may take place inside a female’s body (internal)

External fertilisation Internal fertilisation

Fertilisation occurs outside the body, usually in water

The female lays her eggs in the eggs in the water and the male releases sperm over the eggs

Aquatic animals they rely on external fertilization produce large numbers of gametes to increase the chances of successful fertilisation

Sperm are realised into the females body and the sperm swim towards the egg where fertilization occurs

Internal fertilization allowsterrestrial animals to reproduce since the eggs and the sperm cannot survive the terrestrial environment

Animals that rely on fertilisation are some fish species, birds and all mammals

THERE ARE THREE WAYS AN EMBRYOS MAY DEVELOP

Ovipary refers to the development of a fertilized egg that has been laid. The development of this egg occurs outside the body and the young hatchling from the egg e.g. Birds and reptiles

Refers to the development of fertilised egg that is retained in the mother’s body. The developing young obtain nutrients from the yolk of the egg. The young hatch within the mother’s body and are then born.-occurs in some insects, some fish and some reptiles.

Refers to the development of an embryo within the females body. Nutrients and oxygen are obtained from the others blood via the placenta. Most mammals are viviparous and the young are born alive.

The amniotic egg allows the embryos of vertebrates to develop in a liquid. The egg is protected by a shell and has four membrane, namely, the amnion, yolk sac, allantoisand chorion

Birds produce chicks that display precocial development or altricial development

Precocial development Altricial development

This type of chick development is mainly found in birds that make their nest on the ground. The eggs have a lot of energy. The hatchlings are easy pray for roving predators. The young chicks are able to move immediately after hatching and leave the nest two days later

This is typical of birds that build nests high up on the trees. The eggs have little energy. The young chicks are poorly developed when they hatch, and their eyes are closed; they are helpless and totally dependent on their parents for food and protection