FERTILISATION

 

All living organism ensure their continuance on this earth by reproduction. Reproduction is biological process by which new organism or off springs produce from their parents. Reproduction may occur either asexually ( not involving in sexual activity, feelings, or associations ) or sexually. There is an evident difference between asexual reproduction and sexual reproduction. Asexual mode is easy whereas sexual mode is more complex. Fertilisation is the main difference between two. It is the main stage of sexual reproduction which is little bit absent in asexual mode.

Types of fertilisation

Fertilisation is the process by which male and female gametes are fused together, including the development of a new organism, when the sperm of male meets with egg of female it creates zygote.

There are two types of fertilisation –

External fertilisation

 

In this fertilisation process  male and female members releases egg and sperm in the same area at the same time, and for the fertilisation of these zygote external environment ( water temperature and the length of day light ) support in fertilisation process of Spawning, where one or several females releases their eggs and the male releases sperm in the same area at the same time.

External fertilisation mainly takes place in an aquatic environment and this environment save the zygote and prevent them from drying out.

Sea Urchins, Fish, Frog, Salmon, Coy Coral, Starfish are few example of reproduction through external fertilisation. ( the exceptions are aquatic mammals, sharks and some other special types of fish )

 Internal fertilisation

Internal fertilisation is the union of an egg and sperm cell during sexual reproduction inside the female   body. Internal fertilisation seen using in terrestrial animals, based on internal fertilisation, organism        can be categorised into Oviparous ( Oviparous are female animals that lay their eggs with little or         no other embryonic development within the mother )  and  viviparous ( Viviparous are those in             which fertilisation and embryo development occur inside the individual ), humans are                             viviparous. Mammals     such as cows, elephant, monkeys, etc are viviparous.                                                                                        

FERTILISATION PROCESS

Mainly there are three type of living things on earth as they have the same characteristic features like     breathing, eating, growth, reproduction.                                                                                                        

Plants

Birds and animals

Humans

Fertilisation in plants

Nature gifted to all living creature a very valuable and important thing in the form of plant. Due to this natural gift, life is possible. Plants  provides food, oxygen, shelter, clothing etc. Plants are known as universal producers. Like all other living things, plant also vegetate, germinate, defecate,  respire, grow, develop, excrete and reproduce.  

In plants

 

fertilisation is the process of sexual reproduction, which occurs after pollination (  it is the process of transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seed, it is done often by an birds, animals and by wind ) and germination.       

In the course of fertilisation, male gametes get transferred into the female reproductive organs through pollination and the final product will be the formation of the embryo in a seed.               

In flowers

 

The pollen grain germinates after the pollination of the carpel and grows into the style by creating the pathway for the pollen grain to move down to the ovary.

The pollen tube opens into the ovule through the micropyle and burst into the embryo sac. Here the male nucleus unites with the nucleus of an egg inside the ovule forming a diploid zygote, which later swells up and develops into a fruit.

Double fertilisation in flowering plants is a process of fertilisation characterised by the fusion of a female gametophyte with two male gametes. In this process one sperm cell fuses with the egg-producing zygote and the other fuses with the two polar nuclei to make the endosperm. All angiosperm undergo double fertilisation process.

FERTILISATION IN BIRDS

Normally birds prefer to mate within their own species, exceptionally very few do mating outside of their species. Reproduction in birds may be quite complex and lengthy. Birds reproduce sexually and have separate sexes and internal fertilisation.

Birds actually pair up each mating season, not  lifelong. And the male has to treat his female in better manner. There is actually an elaborate process in which the female chooses  her  mating  partner. Male always try to attract females in so many ways such as singing specific song or putting on some type of visual display like a bird may spread out and display its tail feathers or may do a mating dance.

Once a female bird is receptive to mate,  the actual mating can take place. Unlikely birds don’t have sexual genitals. Means male birds don’t have penis and female birds don’t have vagina. Both male and female have Cloaca, ( reproductive and digestive opening near the tail ).  The position  and  postures birds assume to make can vary, but the most common is for the male bird to balance on top of female, the female would bow to give male easier to balance . Then female would move tail aside and expose her cloaca. During mating male presses his cloaca against his mate’s means female cloaca and passes sperm from his cloaca in her cloaca.

After proper fertilisation eggs pass out the female’s body, exiting through the opening in the cloaca.

 

FERTILISATION IN HUMANS

 

Fertilisation  in human is actually complicated process that has several steps, it starts, when a woman’s egg joins with a man’s sperm. Male sperm are microscopic cells that are made in testicles. Sperm mixes with other fluids to make semen, which comes out of the penis during ejaculation. Only  one sperm cell out of millions to meet with an egg for fertilisation to happen. 

Eggs stay in ovaries, and the hormones that control women’s menstrual cycle cause a few eggs to mature every month. When the egg is mature, it means it is ready to be fertilised by a sperm cell. These hormones also make the lining of the uterus thick and spongy, which gets the women’s body ready for fertilisation.

Fertilisation usually takes place in a fallopian tube and implants in the uterus, an embryo starts growing.

The fertilisation process in animals is almost same.

Well to Conclude –  The result of fertilisation is a cell ( zygote ) capable of undergoing cell division to form a new individual. The fusion of two gametes initiates several reactions in the egg. One of these causes a change in the egg membrane, so that the attachment of and penetration by more than one spermatozoon is not possible.

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