12th Zoology / Bio Zoology Chapter 1 Important 2, 3, 5 Mark Questions 2026

Reproduction in Organisms

Most Repeated Questions

Number next to question tells how many times the question has been repeated in the past few years

TWO MARKS

1.What is Parthenogenesis? What are its types?(3)

  • Development of an egg into a complete individual without fertilization is known as parthenogenesis.
  • Types :
    • Natural Parthenogenesis : Ex: Honey bees, Gall Fly
    • Artificial Parthenogenesis : Ex. Anelid ,  Seaurchin

2.What is apolysis?(2)

  • Apolysis is the process in Taenia solium where gravid (ripe) proglottids are detached from the posterior end of the body (strobila).
  • This helps in releasing embryos and transferring them from the primary host (man) to the secondary host (pig).

3.Differentiate External fertilization, Internal fertilization(3)

External fertilizationInternal fertilization
the fusion of male and female gametes takes place outside the body of female organisms in the water medium.the fusion of male and female gametes takes place within the body of female organisms
e.g. sponges, fishes and amphibianse.g. reptiles, aves and mammals.

4.What is Plasmotomy? Give example.(2)

Plasmotomy is the division of multinucleated parent into many multinucleate daughter individuals with the division of nuclei.Plasmotomy occurs in Opalina and Pelomyxa (Giant Amoeba).

THREE MARKS

1.What do you mean by Regeneration? What are its types? (3)

Definition

  • Regeneration is the regrowth of lost or injured body parts.
  • First studied in Hydra by Abraham Trembley (1740).

Types of Regeneration

1. Morphallaxis

  • Whole body develops from a small fragment
  • Involves reorganization of existing cells
  • Body parts retain original polarity (oral & aboral ends)
  • Examples: Hydra, Planaria

2. Epimorphosis

  • Replacement of lost body parts by growth of new cells

Types:

  • Reparative regeneration
    • Only damaged tissues are repaired
    • Example: Humans
  • Restorative regeneration
    • Complete body parts are regenerated
    • Examples: Starfish, tail of wall lizard

FIVE MARKS

1.Explain the different kinds of syngamy in living organisms.(3)

Definition

  • Syngamy is the fusion of male and female gametes to form a zygote.

Types of Syngamy

  1. Autogamy
    • Fusion of gametes from the same organism
    • Example: Actinosphaerium, Paramecium
  2. Exogamy
    • Fusion of gametes from different individuals
    • Biparental
    • Example: Human beings
  3. Hologamy
    • Whole organism acts as gamete and fuses
    • No distinct gametes formed
    • Example: Trichonympha
  4. Paedogamy
    • Fusion of young individuals formed after division
    • Example: Actinophrys
  5. Merogamy
    • Fusion of small, unequal and different gametes (merogametes)
    • Example: Protozoa
  6. Isogamy
    • Fusion of morphologically identical gametes
    • Example: Monocystis
  7. Anisogamy
    • Fusion of dissimilar gametes
    • Common in higher organisms
    • Example: Vertebrates

2.What is Parthenogenesis? Explain the types of Parthenogenesis.(2)

Definition

  • Parthenogenesis is the development of an unfertilized egg into a new individual.
  • First discovered by Charles Bonnet (1745).

Types of Parthenogenesis

1. Natural Parthenogenesis

  • Occurs naturally in life cycle

a) Complete Parthenogenesis

  • Only mode of reproduction
  • No males present (only females)

b) Incomplete Parthenogenesis

  • Both sexual reproduction and parthenogenesis occur
  • Example: Honeybee
    • Fertilized eggs → Queen & workers (female)
    • Unfertilized eggs → Drones (male)

c) Paedogenetic Parthenogenesis (Paedogenesis)

  • Larvae produce new individuals by parthenogenesis
  • Examples: Liver fluke (sporocyst, redia), Gall fly

2. Artificial Parthenogenesis

  • Unfertilized egg is induced to develop by physical or chemical stimuli
  • Examples: Annelids, Sea urchins
error: Content is protected !!
Scroll to Top
🔗
Link copied!