Date post: | 18-Jul-2015 |
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Science |
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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