Examkin

Question

Difficulty: MediumKingdom Protista: Protozoa and Unicellular Algae

During binary fission in Paramecium caudatum, the cell undergoes nuclear division prior to transverse cytoplasmic division. Which statement accurately describes the division process of its nuclei?

  1. The macronucleus divides amitotically by constriction, while the micronucleus divides mitotically.Answer
  2. B
    Both the macronucleus and micronucleus divide by standard mitotic division.
  3. C
    The micronucleus disintegrates while the macronucleus undergoes meiotic division.
  4. D
    The macronucleus undergoes meiosis to produce haploid pronuclei for daughter cells.

Answer

The macronucleus divides amitotically by constriction, while the micronucleus divides mitotically.
Paramecium displays nuclear dualism. During asexual binary fission, the small diploid micronucleus undergoes mitosis to distribute genetic material equally, whereas the large polyploid macronucleus elongates and divides amitotically by simple constriction.

Step-by-Step Solution

1
Identify the nuclear structure of Paramecium.
Paramecium exhibits nuclear dualism, possessing a small diploid micronucleus (germline/reproductive function) and a large polyploid macronucleus (somatic/metabolic function).
The different ploidy levels and roles determine their division mechanisms during asexual reproduction.
2
Determine the mode of division for each nucleus during binary fission.
The micronucleus duplicates its chromosomes and undergoes mitosis. The macronucleus elongates and splits amitotically by constriction without chromosome condensation or spindle assembly.
Mitotic distribution ensures equal genetic division of the micronucleus, while the somatic macronucleus divides its mass amitotically.

Key Concept

Nuclear Dualism and Binary Fission in Paramecium
Rate this question

Topics

Kingdom Protista: Protozoa and Unicellular Algae

More questions from this topic