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All the reproductive methods… (Class 10 Science 2023, Q38)

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ScienceCBSE Class 10 · Board exam 2023, set 31/2/1 · 4 marks · Case-based

CBSE Class 10 Science 2023: question 38

Set in the CBSE Class 10 board exam of 2023, paper 31/2/1, section E, question 38, for 4 marks. Try it first; the hints and our step-by-step solution are below.

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

All the reproductive methods of living organisms are broadly categorized into two types : 1. Asexual reproduction, and 2. Sexual reproduction.
Asexual reproduction involves the participation of a single parent without the formation of gametes, fertilisation and transfer of genetic material. This method is a common means of rapidly increasing offsprings under favourable conditions.

  1. (a)

    Name the type of fission that occurs in Leishmania and Plasmodium.

    1 mark
  2. (b)

    Write one advantage of sexual mode of reproduction over asexual reproduction.

    1 mark
  3. (c)

    Give reasons why: (i) Colonies of yeast fail to multiply in water but multiply in sugar solution. (ii) Rhizopus individuals do not grow on a dry slice of bread.

    2 marks

  4. OR

    (c)

    Name the filamentous structures a student could identify when he collected water from a pond that appeared dark green. How do these organisms multiply ? Explain.

    2 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/2/1.

Hints

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

Hint 1

Leishmania divides into two cells, while Plasmodium divides into many cells at once.

Hint 2

Think about what living cells need besides water to grow, and what fungi need from their surroundings.

Hint 3

Green pond scum is a filamentous alga that reproduces by breaking into pieces.

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) Leishmania reproduces by binary fission (along a definite plane). Plasmodium reproduces by multiple fission.

    1 mark

  2. (b) Sexual reproduction combines DNA from two parents, so it produces more variations. These variations help a species survive changing environmental conditions.

    1 mark

  3. (c)(i) Water contains no food. Sugar solution gives yeast the nutrients and energy it needs to grow and to multiply by budding, so yeast colonies multiply only in sugar solution.

    1 mark

  4. (c)(ii) Rhizopus needs moisture to germinate its spores and grow hyphae. A dry slice of bread has no moisture, so Rhizopus cannot grow on it.

    1 mark

  5. (c) OR – The dark green filamentous structures are Spirogyra (a filamentous green alga).

    ½ mark

  6. (c) OR – Spirogyra multiplies by fragmentation.

    ½ mark

  7. (c) OR – On maturing, a Spirogyra filament simply breaks up into two or more small pieces (fragments). Each fragment grows into a new filament.

    1 mark

Answer: (a) Leishmania – binary fission; Plasmodium – multiple fission. (b) Produces more variations, which aid survival of the species. (c)(i) Sugar provides nutrition; plain water does not. (ii) Rhizopus needs moisture. OR: Spirogyra; multiplies by fragmentation.

Where the marks are

  • Binary fission for Leishmania and multiple fission for Plasmodium (½ + ½ mark)
  • More variations aiding survival of the species (1 mark)
  • Sugar solution supplies nutrients for growth and budding (1 mark)
  • Moisture is needed for Rhizopus growth (1 mark)
  • OR: names Spirogyra (½ mark); fragmentation (½ mark); explains breaking into pieces, each growing into a new individual (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 paper2023 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.