(i) Name and explain the two modes of asexual reproduction observed in hydra.
(ii) What is vegetative propagation ? List two advantages of using this technique.
(i) Name and explain the two modes of asexual reproduction observed in hydra.
(ii) What is vegetative propagation ? List two advantages of using this technique.
(i) Two modes of asexual reproduction observed in Hydra:
- Budding:
In Hydra*, a bud develops as an outgrowth due to repeated cell division at one specific site on the parent body.
- These buds gradually develop into tiny individuals. When they are fully mature, they detach from the parent body and become new independent individuals.
- Regeneration:
If a Hydra* is somehow cut or broken into many pieces, each piece has the ability to grow into a complete, fully functional organism.
- This process is carried out by specialised cells that proliferate rapidly to make a large mass of cells. From this mass, different cells undergo changes in an organised sequence (development) to form various cell types and tissues.
(ii) Vegetative Propagation:
- Definition: It is an asexual mode of reproduction in plants where vegetative parts like the root, stem, and leaves develop into new plants under appropriate environmental conditions.
Advantages of Vegetative Propagation (any two):
- Earlier Flowering and Fruiting: Plants raised by vegetative propagation can bear flowers and fruits much earlier than those produced from seeds.
- Propagation of Seedless Plants: It makes possible the propagation of plants such as banana, orange, rose, and jasmine that have lost the capacity to produce seeds.
- Genetic Uniformity: All plants produced are genetically similar enough to the parent plant to retain all of its desirable characteristics.
Marking Scheme
- 1Naming the two modes in Hydra (Budding and Regeneration) (1 mark)
- 2Explanation of Budding in Hydra with key details (outgrowth, cell division, detachment) (1 mark)
- 3Explanation of Regeneration in Hydra (specialised cells, proliferation, development) (1 mark)
- 4Definition of Vegetative Propagation (reproduction via roots, stems, leaves) (1 mark)
- 5Listing any two valid advantages of vegetative propagation (0.5 marks each) (1 mark)
Hint
For Hydra, think about an outgrowth that detaches, and what happens if the organism is cut into pieces. For plants, think about growing new plants without using seeds.
Quick Oral Answer
In *Hydra*, budding involves a small outgrowth forming due to repeated cell division at one site, which matures and detaches. Regeneration is the growth of a complete organism from a cut piece using specialised cells. Vegetative propagation is growing new plants from vegetative parts like roots, stems, or leaves, which helps in propagating seedless plants and ensures genetic uniformity.
Analysis & Explanation
This question tests the student's understanding of asexual reproduction in both simple animals (Hydra) and plants.
Part (i): Hydra* is unique because it can reproduce asexually using two distinct pathways depending on the situation. Budding is its regular, active asexual reproductive method. Regeneration, on the other hand, is an inherent capability of its specialised regenerative cells to rebuild the entire body if injured or fragmented, though it is not its primary voluntary reproductive method.
- Part (ii): Vegetative propagation is highly valued in agriculture and horticulture. Since it bypasses the seed-formation stage, it saves time and energy, allowing faster crop yields. It also ensures that high-quality traits of a parent plant (like sweet fruit or disease resistance) are perfectly preserved in the offspring clones.
Common Mistakes
- 1Confusing regeneration with a normal, voluntary method of reproduction (NCERT notes that most organisms do not normally depend on being cut up to reproduce).
- 2Forgetting to mention that regeneration is carried out by 'specialised cells' that proliferate.
- 3Writing general advantages of asexual reproduction instead of specific advantages of vegetative propagation (like seedless plant propagation).
Interesting Facts
The leaves of the Bryophyllum plant have notches along their margins containing buds. If a leaf falls on moist soil, these buds can grow directly into tiny new plantlets!
Regeneration in Planaria and Hydra is so powerful that a tiny piece, even 1/279th of the original animal, can regenerate into a complete individual.
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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 "Modes of Reproduction" 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.