Q25
5 marksLong AnswerSection A

With the help of suitable diagrams, explain the various steps of budding in Hydra. OR What is binary fission in organisms ? With the help of suitable diagrams, describe the mode of reproduction in Amoeba.

How do Organisms Reproduce?
Asexual Reproduction: Budding and Fission
Official Answer

OPTION 1: Budding in Hydra


Budding is an asexual mode of reproduction where a new organism develops from an outgrowth or bud due to repeated cell division at one specific site on the parent body.


#### Steps of Budding in Hydra:

  1. Bud Development: Due to repeated cell division of regenerative cells at a specific site on the parent Hydra body, a small outgrowth called a bud begins to develop.
  2. Growth and Differentiation: The bud grows progressively, developing tiny tentacles and a mouth, mimicking the structure of the parent.
  3. Maturation: The bud matures into a tiny, fully formed individual Hydra.
  4. Detachment: Once fully mature, the young Hydra detaches from the parent body and becomes an independent, self-sustaining individual.


Parent Hydra (Regenerative cells at specific site)Bud Formation (Outgrowth due to cell division)Developing Bud (Tiny individual with tentacles)New Hydra (Detaches to live independently)




OR


OPTION 2: Binary Fission in Amoeba


Binary Fission is a type of asexual reproduction in unicellular organisms where a single parent cell divides into two equal, independent daughter cells.


#### Mode of Reproduction in Amoeba:

  1. No Fixed Plane: In Amoeba, cell division can occur in any plane because it lacks a fixed body shape.
  2. Karyokinesis (Nuclear Division): The process begins with the elongation of the nucleus, which gradually divides into two daughter nuclei.
  3. Cytokinesis (Cytoplasmic Division): Following nuclear division, the cytoplasm starts constricting along the division plane.
  4. Formation of Daughter Cells: The constriction deepens until the parent cell splits completely, producing two identical daughter Amoeba cells.


Parent Amoeba (Single cell with nucleus)Karyokinesis (Nucleus elongates & divides)Cytokinesis (Cytoplasm constricts in any plane)Two Daughter Cells (Identical individuals)
buddingregenerative cellsoutgrowthtentaclesdetachesbinary fissionany planenucleus divisioncytoplasm splitsdaughter cells

Marking Scheme

  • 11.5 marks
  • 22 marks
  • 31.5 marks
  • 41.5 marks
  • 52 marks
  • 61.5 marks

Hint

For Hydra, focus on the role of regenerative cells and the detachment of the mature bud. For Amoeba, focus on nuclear division followed by cytoplasmic division in any plane.

Quick Oral Answer

In budding, a small outgrowth or bud forms on the parent Hydra due to repeated cell division. It grows, develops tentacles, and detaches to become a new individual. In binary fission, a single-celled Amoeba divides its nucleus and cytoplasm to split into two equal daughter cells in any plane.

Analysis & Explanation

Both budding and binary fission are asexual modes of reproduction since they involve only a single parent and do not require the fusion of gametes.

  • In Hydra, reproduction relies on specialized regenerative cells that proliferate rapidly at a localized site to form a multicellular bud.
  • In Amoeba, reproduction is a direct consequence of cell division. Since Amoeba is unicellular and lacks a rigid cell wall or specialized structures (unlike Leishmania, which has a whip-like structure requiring a definite orientation), splitting can occur in any plane.

Common Mistakes

  1. 1Confusing budding with fragmentation; budding involves localized cell division forming an outgrowth, whereas fragmentation is the breaking of a mature multicellular body into pieces.
  2. 2Forgetting to mention that binary fission in Amoeba can take place in 'any plane', unlike in Leishmania which occurs in a definite orientation.

Interesting Facts

Hydra can reproduce both sexually and asexually. Budding occurs when food is plentiful, whereas sexual reproduction is typically triggered by unfavorable environmental conditions.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2011?

This question carries 5 marks in the CBSE Class 10 Science 2011 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 "Asexual Reproduction: Budding and Fission" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2011 paper?

This is a Long Answer question from Section A in the CBSE Class 10 Science 2011 paper.