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Asexual reproduction… (Class 10 Science 2024, Q38a)

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ScienceCBSE Class 10 · Board exam 2024, set 31/2/1 · 4 marks · Case-based

CBSE Class 10 Science 2024: question 38(a)

Set in the CBSE Class 10 board exam of 2024, paper 31/2/1, section E, question 38(a), for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q38(a) · 4 marks · Case-basedCompetency-basedHow do Organisms Reproduce?

Asexual reproduction involves a single parent to produce offsprings without the formation of gametes. It occurs by the following ways : Fission, Budding, Fragmentation, Spore formation and Regeneration. In one of the methods like regeneration, Planaria A is cut horizontally into three pieces – L, M and N and Planaria B is cut vertically into two equal halves – O and P.

  1. (a)

    Which of the cut pieces of the two Planaria could regenerate to form a complete organism ?

    1 mark
  2. (b)

    Give an example of another organism which follows the same mode of reproduction as Planaria.

    1 mark
  3. (c)

    What is the meaning of 'development' in regeneration ?

    2 marks
  4. (c)

    Differentiate between regeneration and fragmentation.

    2 marks

Figure in the paper: Planaria A (left) is shown being cut horizontally into three pieces labelled L (head end), M (middle) and N (tail end). Planaria B (right) is shown with a vertical line through its length, separated into two equal halves labelled O (one half with head) and P (other half with head), with arrows pointing from B to O and P. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/2/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Planaria can rebuild its entire body from small pieces.

Hint 2

Name another simple animal, also used as an example of budding, that can regrow from pieces.

Hint 3

Development has two stages: cells first multiply, then change into different kinds of tissues in order.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) Planaria has a very high power of regeneration. Its body contains specialised cells that can form all the missing parts. So all the cut pieces can grow into complete planarians: L, M and N of Planaria A, and O and P of Planaria B.

    1 mark

  2. (b) Another organism that reproduces by regeneration (like Planaria): Hydra.

    1 mark

  3. (c)(a) In regeneration, specialised cells in the cut piece first proliferate, that is, divide repeatedly to make a large mass of cells.

    1 mark

  4. (c)(a) This mass of cells then changes (differentiates) into different cell types and tissues, which form the missing organs. These changes happen in an organised sequence. That organised sequence is called development.

    1 mark

  5. (c)(b) [OR] Regeneration: specialised cells of a body part proliferate and differentiate to form the lost parts. The whole new individual arises from any cut piece through this organised development. Example: Planaria, Hydra.

    1 mark

  6. (c)(b) Fragmentation: the body simply breaks into pieces on maturing. Each fragment grows by ordinary cell division into a new organism, without needing specialised cells. Example: Spirogyra.

    1 mark

Answer: (a) All pieces L, M, N, O and P; (b) Hydra; (c)(a) proliferation of specialised cells, then their organised change into different cell types and tissues; (c)(b) regeneration uses specialised cells to rebuild lost parts, while in fragmentation each broken piece grows by simple cell division

Where the marks are

  • States that all the cut pieces (L, M, N, O, P) regenerate (1 mark)
  • Names Hydra (1 mark)
  • Proliferation of specialised cells into a cell mass (1 mark)
  • Organised change of the cell mass into different cell types and tissues, called development (1 mark)
  • OR: correct features of regeneration (1 mark) and of fragmentation (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from How do Organisms Reproduce?, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 31/2/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.