Fertilization
Fertilization
Fertilization: Fertilization is a process which involves fusion of haploid gametes to give rise to a zygote. Fertilization can be of two types , External fertilization which occurs outside the body and internal fertilization which occurs with in the body.
Fertilization in plants :
In plants sexes may or may not be seperated. Accordingly, a flower is either unisexual(bearing either male or female gamete or ova) or bisexual (bearing both gametes). The pollen grain represent the male gametophyte and embryo sac represents the female gametophyte which encloses the egg. The transfer of pollen grain from anther to the stigma of other flower is called as cross pollination and if the pollen get transfered to the stigma of same flower it is called as self pollination.
After reaching the stigma pollen grains germinate on the stigma. The inner wall of the pollen grain grows into a pollen tube, which grows down through the style and finally reaches the ovule. Inside the ovule, a male gamete fuses with the female gamete and a zygote is formed. This is known as fertilization.
he zygote divides repeatedly to form the embryo (future plant) in the ovule. The embryo possesses a tiny future root (radicle), a tiny future shoot (plumule) and cotyledons to store food. The ovary grows rapidly to form the fruit. The ovary wall ripens and forms the fruit wall. The sepals, petals, stamens, style and stigma of the flower degenerate and usually fall off. Sometimes the sepals may persist in the fruit. The ovule develops into a seed. The wall of the ovule thickens to form the protective seed coat. The seed loses water and becomes hard and dry. Seeds can withstand drought and other adverse conditions in this state. This is an advantage for seed-producing plants. The embryo lies dormant in the seed, but under favourable environmental conditions it becomes active and germinates to form a small seedling. The radicle forms the root while the plumule forms the shoot. The growing root and shoot utilize the food stored in the cotyledons.
Fertilization in Humans :
The fertilization is internal in humans . The transfer of the male gamete occur by insertion of penis in to the vagina of the female. The sperms are deposited in the vagina of the female during a process called as copulation or sexual intercourse. The release of sperms is called as ejaculation. Of large number of sperms only few make the journey from the vaginal canal to the oviduct. This may ake 4 -8 hours. In the fallopian tube many sperms surrounds the egg but only one is able to fuse with it. The enzymes of acrosome digest different layers of tissue to reach the egg. Once the sperm is inside the female and male nucleus become lighter and are called as pro - nuclei. The two pro nuclei fuse to form zygote. Once a sperm enters an egg, the thickening of the outer walls of the egg blocks the entry of other sperms.
Animals laying eggs are known as ____________________ | |||
| Right Option : A | |||
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Fertilizartion takes place in _______________ part of human body | |||
| Right Option : A | |||
| View Explanation | |||
Internal fertilization occurs: | |||
| Right Option : A | |||
| View Explanation | |||
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