15 extra multiple-choice questions for Reproduction in Organisms (12th Standard Zoology, Samacheer Kalvi), beyond the ones printed in the textbook — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
What is another term used to describe blastogenic reproduction in organisms?
- A. Sexual reproduction
- B. Asexual reproductionCorrect
- C. Parthenogenesis
- D. Conjugation
Explanation. Blastogenic or somatogenic reproduction is also known as asexual reproduction because it involves amitotic or mitotic division of somatic body cells without gamete fusion.
Q2
Which of the following organisms exhibits longitudinal binary fission as a mode of asexual reproduction?
- A. Amoeba
- B. EuglenaCorrect
- C. Hydra
- D. Aurelia
Explanation. Euglena reproduces asexually by dividing along its longitudinal axis, which is a type of binary fission where karyokinesis is followed by cytokinesis along the length of the cell.
Q3
The process of apolysis in Taenia solium is highly significant because it helps to:
- A. Regenerate lost posterior body segments
- B. Transfer developed embryos to a secondary hostCorrect
- C. Initiate the formation of new male gametes
- D. Trigger binary fission under unfavorable conditions
Explanation. Apolysis involves regularly cutting off gravid proglottids containing developed embryos from the tail end of Taenia solium. This enables the transfer of embryos from the human host to the pig host.
Q4
Regeneration was first studied in Hydra in the year 1740 by which of the following scientists?
- A. Charles Bonnet
- B. Abraham TrembleyCorrect
- C. Robert Holley
- D. Ian Wilmut
Explanation. Abraham Trembley discovered the power of regeneration in 1740 while studying Hydra, demonstrating how cut pieces can grow back into complete individuals.
Q5
The replacement of severed body parts, such as the tail of a wall lizard or the arm of a starfish, is classified as:
- A. Morphallaxis regeneration
- B. Reparative epimorphosis
- C. Restorative epimorphosisCorrect
- D. Blastogenic regeneration
Explanation. Restorative regeneration is a type of epimorphosis where entirely lost or severed body parts can be regrown, whereas reparative regeneration only repairs damaged tissues.
Q6
Which of the following describes hologamy as seen in lower organisms like Trichonympha?
- A. Union of young individuals immediately after mitosis
- B. Fusion of morphological and physiologically identical gametes
- C. Fusion of small-sized and morphologically different gametes
- D. Entire mature organisms behaving as gametes and fusingCorrect
Explanation. In hologamy, mature individuals do not produce distinct gametes; instead, the entire adult organisms function as gametes and fuse together to form a zygote.
Q7
The sexual union of young individuals produced immediately after mitotic division of the adult parent cell is called:
- A. PaedogamyCorrect
- B. Hologamy
- C. Merogamy
- D. Autogamy
Explanation. Paedogamy is the sexual fusion of young, immature individuals that are formed right after the mitosis of the mature adult cell, typically seen in Actinophrys.
Q8
Which of the following organisms is a classic example of isogamy, where morphologically and physiologically identical gametes fuse?
- A. Trichonympha
- B. MonocystisCorrect
- C. Actinophrys
- D. Planaria
Explanation. Isogamy refers to the fusion of gametes that are identical in both structure and function. This type of sexual reproduction is found in Monocystis.
Q9
Which of the following animals is classified as a continuous breeder, continuing to breed throughout their period of sexual maturity?
- A. Frog
- B. Lizard
- C. RabbitCorrect
- D. Deer
Explanation. Rabbits are continuous breeders because they can reproduce throughout their active reproductive life, unlike seasonal breeders such as frogs and lizards that only breed during specific times.
Q10
In which type of natural parthenogenesis are only females produced from unfertilized eggs?
- A. Arrhenotoky
- B. ThelytokyCorrect
- C. Amphitoky
- D. Paedogenesis
Explanation. Thelytoky is a specific type of natural parthenogenesis where unfertilized eggs develop exclusively into female offspring, as observed in insects like Solenobia.
Q11
In Aphis gossypii, unfertilized eggs can develop into individuals of either sex. This phenomenon is known as:
- A. Thelytoky
- B. Arrhenotoky
- C. AmphitokyCorrect
- D. Paedogenesis
Explanation. Amphitoky is a parthenogenetic pattern where unfertilized eggs have the potential to develop into either male or female individuals, as seen in Aphis gossypii.
Q12
In complete parthenogenesis, which of the following statements is true regarding the population?
- A. The population consists of diploid males and haploid females.
- B. There are no male organisms, and the species is represented by females only.Correct
- C. Both sexual reproduction and parthenogenesis occur alternately.
- D. Unfertilized eggs are artificially induced to develop by chemical stimuli.
Explanation. Complete parthenogenesis means asexual development is the sole reproductive pathway. Since there is no biparental mating, male organisms are absent, and the population consists entirely of females.
Q13
Paedogenetic parthenogenesis is a unique reproductive phenomenon where larvae produce a new generation of larvae. This occurs in which of the following?
- A. Honeybees
- B. Annelids
- C. Solenobia
- D. Redia larvae of liver flukeCorrect
Explanation. Paedogenetic parthenogenesis occurs when the larval stage of an animal reproduces asexually to produce more larvae, which is famously observed in the redia and sporocyst stages of liver flukes.
Q14
Which of the following organisms' unfertilized eggs can be induced to undergo development via physical or chemical stimuli in artificial parthenogenesis?
- A. Honeybees
- B. Sea urchinsCorrect
- C. Aphis gossypii
- D. Solenobia
Explanation. In artificial parthenogenesis, environmental, physical, or chemical triggers stimulate unfertilized ova to develop, which can be demonstrated using the eggs of annelids and sea urchins.
Q15
During endogenous budding in sponges, internal buds are formed within the parent body. These specialized structures are called:
- A. Ephyrae
- B. GemmulesCorrect
- C. Gravid proglottids
- D. Pseudopodiospores
Explanation. Gemmules are internal asexual reproductive units formed in sponges during endogenous budding. They consist of protective layers enclosing active cells called archaeocytes that can hatch into new sponges.
