Define the term pollination. Differentiate between self pollination and cross pollination. What is the significance of pollination?
Define the term pollination. Differentiate between self pollination and cross pollination. What is the significance of pollination?
Definition of Pollination
Pollination is the process of transfer of pollen grains from the stamen (male reproductive part, specifically the anther) to the sticky terminal part of the pistil called the stigma of a flower.
Difference between Self-Pollination and Cross-Pollination
| Feature | Self-Pollination | Cross-Pollination |
|---|---|---|
| Definition | The transfer of pollen grains occurs from the stamen to the stigma of the same flower (or another flower on the same plant). | The transfer of pollen grains occurs from the stamen of one flower to the stigma of another flower on a different plant of the same species. |
| External Agents | It does not generally require external agents like wind, water, or animals. | It relies on external pollinating agents such as wind, water, or animals to transfer pollen. |
| Genetic Variation | It results in offspring that are genetically identical or highly similar to the parent, leading to minimal variation. | It combines genetic material from two different parent plants, leading to greater genetic variation in the offspring. |
Significance of Pollination
- Enables Fertilisation: Pollination is a prerequisite for fertilisation in flowering plants. It brings the male germ-cell (pollen grain) to the female reproductive organ so that a pollen tube can grow through the style to reach the female gamete (egg cell) in the ovary.
- Seed and Fruit Formation: Successful fertilisation triggered by pollination leads to the development of ovules into seeds and the ovary into a fruit, ensuring the reproduction and survival of the plant species.
- Introduces Variation: Cross-pollination allows the mixing of genetic traits from two different individuals, which introduces variations that help the species adapt to changing environmental conditions.
Marking Scheme
- 1Award 1 mark for the correct definition of pollination.
- 2Award 1 mark for providing at least two clear differences between self-pollination and cross-pollination (preferably in a tabular format).
- 3Award 1 mark for explaining the significance of pollination (enabling fertilisation, seed/fruit formation, or introducing variation).
Hint
Think about how pollen moves from stamen to stigma and why this transfer is necessary for seed formation.
Quick Oral Answer
Pollination is the transfer of pollen from stamen to stigma. It is necessary because the male gamete is non-motile and must reach the female gamete in the ovary for fertilisation.
Analysis & Explanation
Pollination is the physical transfer of pollen, whereas fertilisation is the biochemical fusion of male and female gametes.
- In self-pollination, the pollen lands on the stigma of the same flower or another flower of the same plant. This preserves parental traits but limits genetic diversity.
- In cross-pollination, pollen is carried to a flower on a different plant of the same species. This requires agents of pollination (biotic like insects/birds, or abiotic like wind/water) and promotes genetic recombination, which is the raw material for evolution.
- Once the pollen lands on a compatible stigma, it germinates to form a pollen tube that carries the male gametes down the style to the ovary, where fertilisation occurs.
Common Mistakes
- 1Confusing pollination with fertilisation (pollination is the transfer of pollen, while fertilisation is the actual fusion of gametes).
- 2Not specifying that cross-pollination occurs between different plants of the same species.
Interesting Facts
Some flowers have evolved specific shapes, colors, and scents to attract specific animal pollinators, a process called co-evolution. For example, night-blooming flowers are often white and highly scented to attract nocturnal moths.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2020?
This question carries 3 marks in the CBSE Class 10 Science 2020 examination.
Which chapter does this question come from in Science?
This question is from the chapter "How do Organisms Reproduce?" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Sexual Reproduction in Flowering Plants" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2020 paper?
This is a Short Answer question from Section B in the CBSE Class 10 Science 2020 paper.