(a) Name the parts of a bisexual flower that are not directly involved in reproduction. (b) Differentiate between self pollination and cross pollination. List any two significance of pollination. (c) What is the fate of ovules and ovary after fertilization in a flower?
(a) Name the parts of a bisexual flower that are not directly involved in reproduction. (b) Differentiate between self pollination and cross pollination. List any two significance of pollination. (c) What is the fate of ovules and ovary after fertilization in a flower?
(a) Non-reproductive parts of a bisexual flower:
The parts of a flower that are not directly involved in reproduction are the sepals and petals.
(b) Difference between Self-Pollination and Cross-Pollination:
| Feature | Self-Pollination | Cross-Pollination |
|---|---|---|
| Definition | The transfer of pollen grains from the anther of a flower to the stigma of the same flower or another flower on the same plant. | The transfer of pollen grains from the anther of one flower to the stigma of another flower on a different plant of the same species. |
| Agents | Does not strictly require external pollinating agents. | Requires external agents like wind, water, insects, or animals. |
| Genetic Variation | Leads to minimal or no genetic variation. | Introduces genetic variations in the offspring. |
Significance of Pollination (Any two):
- It ensures the transfer of male gametes (pollen grains) to the female reproductive organ (stigma), which is a prerequisite for fertilization.
- It stimulates the growth of the pollen tube and subsequent fertilization, leading to the formation of seeds and fruits.
(c) Fate of ovules and ovary after fertilization:
- The ovule develops a tough protective coat and is converted into a seed.
- The ovary grows rapidly and ripens to form a fruit.
Marking Scheme
- 1Part (a): 1 Mark for correctly identifying sepals and petals.
- 2Part (b): 2 Marks (1 Mark for a clear tabular or descriptive difference between self and cross-pollination; 1 Mark for listing two valid significances of pollination).
- 3Part (c): 2 Marks (1 Mark for stating that the ovule becomes the seed; 1 Mark for stating that the ovary becomes the fruit).
Hint
Recall that the petals and sepals are accessory structures. For post-fertilization, think about what we eat (fruit) and what we sow (seed) and map them back to the ovary and ovule.
Quick Oral Answer
In a flower, the non-reproductive parts are the sepals and petals. Self-pollination is the transfer of pollen within the same flower or plant, while cross-pollination is between different plants. After fertilization, the ovule turns into a seed, and the ovary ripens into a fruit.
Analysis & Explanation
This question tests the understanding of sexual reproduction in angiosperms.
- Part (a) highlights the distinction between accessory structures (sepals, petals) and essential reproductive structures (stamens, pistil).
- Part (b) focuses on pollination mechanisms. Self-pollination maintains genetic purity but limits variation, whereas cross-pollination introduces new genetic combinations, enhancing adaptability. Pollination is crucial because male gametes in plants are non-motile and rely entirely on physical transfer to reach the female gamete.
- Part (c) outlines the morphological transformation of the flower into a seed-bearing fruit, which is the ultimate goal of sexual reproduction in plants.
Common Mistakes
- 1Students often confuse self-pollination with cross-pollination when it occurs between two different flowers on the same plant (biologically, this is geitonogamy, a form of self-pollination).
- 2Swapping the post-fertilization fates (e.g., writing that the ovary becomes the seed and the ovule becomes the fruit).
Interesting Facts
Some plants have evolved complex mechanisms to prevent self-pollination entirely, such as having male and female parts mature at different times, to ensure genetic diversity through cross-pollination.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2023?
This question carries 5 marks in the CBSE Class 10 Science 2023 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 2023 paper?
This is a Long Answer question from Section D in the CBSE Class 10 Science 2023 paper.