Reproduction in Animals Flashcards
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Why is reproduction important?
Reproduction is important for the continuation of species. It ensures the birth of similar individuals generation after generation. There are 2 types of reproduction - asexual and sexual.
What is sexual reproduction?
The type of reproduction beginning from the fusion of male and female gametes is called sexual reproduction. Both male and female organs produce gametes which fuse to form zygote. Zygote is essentially what grows to become an individual.
Define the male reproductive organs.
The male reproductive organs include a pair of testes, sperm ducts and a penis. The sperm is the male gamete. Millions of sperms are produced by the testes. Even though the sperm is a small cell, it has three different parts - the head (has a thin yellow stringy lining which consists of DNA for fertilisation), the tail (which helps with swimming), and the middle piece (which provides energy). The sperm is a single cell consisting of all the usual cell components.
Define the female reproductive organs.
The female reproductive organs include a pair of ovaries, oviducts, fallopian tubes and a uterus. The ova is the female gamete. In human beings, eggs are released every one month. Uterus is the part where development takes place. The ova is a single cell and consists of all the normal cell components (egg sizes can vary in animals; ostrich eggs).
What is fertilisation?
The first step in the process of reproduction is the fusion of a sperm and an ovum. When sperms come in contact with with the egg, they fuse to form a single cell. Such fusion of the egg and the sperm to form a zygote/fertilised egg is known as fertilisation. The new individual inherits characteristics from both mother and father. The fertilisation which takes place inside the mothers body is known as internal fertilisation. The fertilisation which takes place outside the mothers body is known as external fertilisation.
What is IVF?
In some women, oviducts are blocked. The sperms are unable to reach the egg to fertilise it. In such cases, doctors take freshly released eggs and sperms and keep it in the lab for in vitro fertilisation/IVF. If fertilisation occurs, it is left to develop in the container for a week, before placing it in the mothers uterus where the real development takes place; the baby grows like any other normal baby. These babies are also called test tube babies, but this term is quite misleading as babies don’t grow in test tubes.
How do aquatic animals reproduce?
The type of fertilisation where the fusion of male and female gametes occurs outside the females body is known as external fertilisation. It is very common in aquatic animals like fish, starfish, etc.
How do frogs reproduce?
During the spring or rainy season, frogs and toads move to pond or slow flowing streams. Once the male and female frog meet, the female produces thousands of eggs. These eggs are delicate, and have a thin jelly like covering on them which holds them together and provides protection. The male then produces sperms which swim randomly in the water with the help of their tail. If it comes in contact with the eggs, if gets fertilised and turns into a zygote.
Why do aquatic animals law a large number of eggs at a time?
Though aquatic animals lay hundreds of eggs and release millions of sperms, all of them do not get fertilised. This is because eggs are directly exposed to water movement, powerful winds and rainfall. There are also other animals that might threaten their safety. Laying a large number of eggs ensures the fertilisation of at least some of them.
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