Fertilisation in Reproduction in organisms NEET Biology Class 12
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Fertilisation in Reproduction in organisms NEET Biology Class 12


Welcome to NEETLab. This is an online self learning platform to
improve your intelligence and to clear NEET examination. In this video we are going to understand the
Fertilisation. Fertilisation is the most vital event of sexual
reproduction. Fertilisation is perhaps the fusion of male
and female gametes. This process is known as syngamy. Which results in the formation of a diploid
zygote. The term fertilisation is also often used
for this process. The terms syngamy and fertilisation are frequently
used to denote the union of male and female gametes. Now the question is What would happen if syngamy
does not occur at all? As we know fertilisation is the union of male
and female gametes. But in some organisms like rotifers, honeybees
and even in some lizards and birds (turkey), the female gamete undergoes development to
form new organisms without fertilisation. A good example is honey bee colony. you would have observe the worker bees in
honey bee colony. The worker bees in a honey bee colony are
result of the female gamete undergoes development to form new organisms without fertilisation. They are sterile and will not participate
in reproduction. This phenomenon is called parthenogenesis. Remember , parthenogenesis is the development
of an embryo from an unfertilised egg cell. Whereas in plants the term parthenogenesis
is a component process of apomixes. Apomixis is the development of an embryo without
the occurrence of fertilisation in plants. ok
Now let us discuss where does syngamy or fertilisation occur? In most aquatic organisms, such as a majority
of algae and fishes as well as amphibians, syngamy or fertilisation occurs in the external
medium like water, that is the fusion of male and female gametes takes place in outside
the body of the organism. This type of gametic fusion is called external
fertilisation. Organisms exhibiting external fertilisation
show great synchrony between the sexes maturity and release a large number of gametes into
the surrounding medium mostly water in order to enhance the chances of syngamy or fertilisation. This happens in the bony fishes and frogs
where a large number of offspring are produced.In this type of fertilisation A major disadvantage
is that the offspring are extremely vulnerable to predators threatening their survival up
to adulthood. In many terrestrial organisms, belonging to
fungi, higher animals such as reptiles, birds, mammals and in a majority of plants including
bryophytes, pteridophytes, gymnosperms and angiosperms, syngamy or fertilisation occurs
inside the body of the organism, hence this kind of syngamy or fertilisation process is
called internal fertilisation. In all these organisms, egg is formed inside
the female body of organisms.where the egg fuse with the male gamete. In organisms exhibiting internal fertilisation,
the male gamete is motile and has to reach the egg in order to fuse with it. In these organisms even though the number
of sperms produced is very large, there is a significant reduction in the number of eggs
produced. In the case of seed plants, the non-motile
male gametes are carried to female gamete by pollen tubes. Thus fertilisation or syngamy is the process
by which male and female gametes are fused to develop a new organism. This is about the fertilisation process in
organisms. Lets discuss the post-fertilisation events
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