Text Book Back Questions and Answers - Chapter 1 Reproduction in Organisms 12th Biology Zoology Guide Samacheer Kalvi Solutions - SaraNextGen [2024-2025]

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On April 24, 2024, 11:35 AM

Reproduction in Organisms
Text Book Back Questions and Answers
Question 1.
In which type of parthenogenesis are only males produced?
(a) Arrhenotoky
(b) Thelytoky
(c) Amphitoky
(d) Both $a$ and $b$
Answer:
(a) Arrhenotoky
Question 2.
Animals giving birth to young ones:
(a) Oviparous
(b) Ovoviviparous
(c) Viviparous
(d) Both $a$ and $b$
Answer:
(c) Viviparous
Question 3.
The mode of reproduction in bacteria is by
(a) Formation of gametes
(b) Endospore formation
(c) Conjugation
(d) Zoospore formation
Answer:
(c) Conjugation
Question 4.
In which mode of reproduction variations are seen?
(a) Asexual
(b) Parthenogenesis
(c) Sexual
(d) Both $a$ and $b$
Answer:
(c) Sexual

Question 5.
Assertion and reasoning questions:
In each of the following questions there are two statements. One is assertion (A) and other is reasoning (R). Mark the correct answer as
(a) If both $A$ and $R$ are true and $R$ is correct explanation for $A$
(b) If both $A$ and $\mathrm{R}$ are true but $\mathrm{R}$ is not the correct explanation for $\mathrm{A}$
(c) If $A$ is true but $R$ is false
(d) If both $A$ and $R$ are false
I. Assertion: In bee society, all the members are diploid except drones.
Reason: Drones are produced by parthenogenesis.
II. Assertion: Off springs produced by asexual reproduction are genetically identical to the parent.
Reason: Asexual reproduction involves only mitosis and no meiosis.
III. Assertion: Viviparous animals give better protection to their off springs.
Reason: They lay their eggs in the safe places of the environment.
Answer:
(I) A (II) A (III) C
Question 6.
Name an organism where cell division is itself a mode of reproduction.
Answer:
Amoeba
Question 7.
Name the phenomenon where the female gamete directly develops into a new organism with an avian example.
Answer:
Parthenogenesis is the phenomenon where the unfertilized female gamete (egg) develops into a new individual, e.g. Turkey
Question 8.
What is parthenogenesis? Give two examples from animals.
Answer:
Development of an egg into a complete individual without fertilization is known as parthenogenesis. It was first discovered by Charles Bonnet in 1745.
E.g. Honey bees, Aphis.

Question 9.
Which type of reproduction is effective - Asexual or sexual and why?
Answer:
Sexual reproduction is highly effective than asexual reproduction since the off springs produced are genetically different from parents causing variations. Variation leads to evolution.
Question 10.
The unicellular organisms which reproduce by binary fission are considered immortal. Justify.

Answer:
In unicellular organisms during binary fission, the entire cell (organism) divides completely to form two daughter cells which later on develop into adult and the process goes on repeatedly during each division leading to immortality of cell (organism). Hence unicellular organisms like amoeba are 'biologically immortal'.
Question 11.
Why is the offspring formed by asexual reproduction referred as a clone?
Answer:
Off springs developed by asexual reproduction are referred as clones since they are genetically \& morphologically similar to this parent.
Question 12.
Why are the off springs of oviparous animal at a greater risk as compared to off springs of viviparous organisms?
Answer:
Oviparous animals are egg-layers. The eggs containing embryo are laid out of their body and are highly susceptible to environmental factors (temperature, moisture etc.) and predators.
Whereas, in viviparous animals, the embryo develops inside the body of female and comes out
as young ones. Hence off springs of oviparous animals are at risk compared to viviparous animal.
Question 13.
Give reasons for the following:
1. Some organisms like honey bees are called parthenogenetic animals
2. A male honey bee has 16 chromosomes whereas its female has 32 chromosomes
Answer:

1. Among honey bees, the queen bee and worker bees develop from fertilized eggs whereas the drones develop from unfertilized eggs. Hence the honey bees are parthenogenetic animals showing incomplete parthenogenesis.
2. Female honey bees (Queen or worker bees) are diploid having 32 chromosomes since they develop from the fertilized egg. On the other hand, the male honey bees (drones) develop from unfertilized egg possessing only 16 chromosomes (i.e., Haploid)
Question 14.
Differentiate between the following:
(a) Binary fission in amoeba and multiple fission in Plasmodium
(b) Budding in yeast and budding in Hydra
(c) Regeneration in lizard and Planaria
Answer:
(a) Binary fission in amoeba and multiple fission in Plasmodium
1. Binary fission in amoeba: In binary fission of amoeba, the plane of division is hard to observe. The nucleoli disintegrates. The nucleus divides mitotically forming two nucleus. The cell constricts in middle, so the cytoplasm divides forming two daughter cells.
2. Multiple fission: In Multiple fission of plasmodium, the oocyte or schizont divides into many similar daughter cells simultaneously. Nucleus undergoes repeated mitosis producing many nuclei without the division of cytoplasm. Later the cytoplasm divides \& encircles each nucleus forming many daughter cells oocyte undergoes sporogony forming sporozoites. Schizont undergoes schizogony forming merozoites.
(b) Budding in yeast and budding in Hydra:
1. Budding in Yeast: Yeast is $\mathrm{xxxx}$ cellular organism in which the bud develops as a small protuberance following the nuclear division and finally detached to new individual.
2. Budding in Hydra: Hydra is a multicellular organism where the bud xxxxxx from the parents body, grows gradually and finally gets detached.
(c) Regeneration in lizard and Planaria:
1. Regeneration of Lizard: If the tail of the lizard is cut and removed, a new tail will regenerate in damaged part. In lizard only the new tail is regenerated.
2. Regeneration of Planaria: If a planarian worm get cut then each half regenerates the lost part resulting in two worms. In planaria, the cut removed part developed into an entire worm.
Question 15.
How is juvenile phase different from reproductive phase?
Answer:

1. Juvenile phase: Juvenile phase is the period of growth between the brith of an organism and before its reproductive maturity.
2. Reproduction phase: Reproductive phase is the period of growth after juvenile phase when an individual attain reproductive maturity and reproduces.
Question 16.
What is the difference between syngamy and fertilization?
Answer:
Syngamy \& fertilization both are more similar terms with a difference that syngamy refers to the process of fusion of two gametes forming zygote while fertilization refers to the process of being fertile.