Fertilisation in Reproduction Organisms

Fertilisation in Reproduction

Fertilisation is the process in which the male and female gametes fuse to form a zygote. This marks the beginning of a new organism in sexual reproduction. The fertilisation process ensures that the offspring has genetic material from both parents, contributing to genetic diversity.

Key Phases of Fertilisation:

1. Gamete Fusion: The male and female gametes meet and fuse to form a zygote.
2. Zygote Formation: The resulting zygote is the first cell of the new organism.
3. Post-Fertilisation Development: The zygote undergoes cell division and develops into an embryo.

Fertilisation can occur either externally (outside the body, as in many aquatic organisms) or internally (inside the body, as in mammals and flowering plants).

Example: Fertilisation in Flowering Plants

In flowering plants, fertilisation occurs after pollination and involves the following steps:

1. Pollination: Pollen from the male anther is transferred to the female stigma.
2. Pollen Tube Growth: Once on the stigma, the pollen grain germinates and forms a pollen tube. The tube grows down the style towards the ovule in the ovary.
3. Fusion of Gametes: The male gamete travels through the pollen tube and fuses with the female gamete (ovule) in the ovary.
4. Zygote Formation: The fertilised ovule develops into a zygote, which eventually becomes a seed.

How to Draw Fertilisation in Flowering Plants

1. Flower Structure: Draw a simple flower with the following parts:
   • Anther: A small oval shape at the tip of the stamen (male reproductive part).
   • Stigma: A small round shape at the top of the pistil (female reproductive part).
   • Style: A thin tube connecting the stigma to the ovary.
   • Ovary: A rounded structure at the base of the pistil, containing ovules (small circles).
2. Pollination:
   • Show pollen grains being transferred from the anther to the stigma. You can draw small dots representing pollen grains.
3. Pollen Tube Growth:
   • From the pollen on the stigma, draw a thin tube (pollen tube) growing down the style toward the ovary.
4. Fertilisation:
   • Show the pollen tube reaching the ovule, with the male gamete (a tiny dot) traveling through the pollen tube.
   • Inside the ovary, depict the fusion of the male gamete and female ovule, forming a zygote.
5. Final Touches:
   • Label the parts: anther, stigma, style, ovary, ovule, pollen tube, zygote.

See in Fig.

Index NCERT 12th Class Biology