Fertilization in Humans
Fertilization is the fusion of the male gamete (sperm) and the female gamete (ovum) to form a zygote.
- During copulation, the sperms are released into the vagina near the cervix of the uterus.
- These sperms actively pass through the passage of the cervix into the uterine cavity.
- Of the millions of sperms released into the vagina, very few are able to reach the upper parts of the
- Oviducts. The rest die on the way and are absorbed.
- It is located in the head region of the sperm.
- The enzyme present in the acrosome facilitates the entry of the sperm into the ovum by dissolving its wall.
The nucleus of sperms contains
genetic material (22 + X/22 + Y chromosomes).
- The mitochondria are contained in the middle piece.
- It provides energy (ATP) for the swimming activity of the sperm.
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The tail part helps the sperm in its forward movement while crossing the
passage of the cervix.
Fertilization in Plants
Fertilization is the fusion of the male gamete present in the pollen with the female gamete or the egg present in the ovule.
Events in Fertilization
- The pollen grains germinate after falling on the stigma of the same plant species
- The pollen tube grows out of the pollen grain.
- The generative nucleus divides into two nuclei.
- The pollen tube grows through the stigma and style and reaches the ovary.
- It pushes through the micropyle and reaches the embryo sac.
- The tube nucleus eventually disintegrates.
- The pollen tube enters one of the synergids and releases two sperm nuclei.
- One sperm nucleus enters the egg cell and fuses with its nucleus.
- The other sperm nucleus moves towards the two polar nuclei and fuses with them.
Fate of Floral Parts After Fertilization:
|Sepals||Usually wither away, but |
in some cases these
remain attached to the fruit.
Examples: Brinjal, tomato
|Placenta||Stalk of the seed|
|Outer integument||Testa (seed coat)|
|Inner integument||Tegmen (seed coat)|
|Egg cell and synergids||Embryo|
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