Chapter-1
Reproduction in
Organisms
Evaluation
1. In which type of parthenogenesis are only males produced?
(a) Arrhenotoky (b) Thelytoky
(c) Amphitoky (d) Both a and b
[Ans. (a) Arrhenotoky]
2. Animals giving birth to young ones:
(a) Oviparous (b) Oviviviparous
(c) Viviparous (d) Both a and b
[Ans. (c) Viviparous]
3. The mode of asexual reproduction in bacteria is by
(a) Formation of gametes
(b) Endospore formation
(c) Conjugation
(d) Zoospore formation
[Ans. (b) Endospore formation]
4. In which mode of reproduction variations are seen
(a) Asexual (b) Parthenogenesis
(c) Sexual (d) Both a and b
[Ans. (c) Sexual]
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 R are true but R is not the correct explanation for 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.
A B C D
[Ans. (A) Both A and R are true and R is correct explanation for A]
II. Assertion: Offsprings produced by asexual reproduction are genetically identical to the parent.
Reason: Asexual reproduction involves only mitosis and no meiosis.
A B C D
[Ans. (C) If A is true but R is false]
III. Assertion: Viviparous animals give better protection to their offsprings.
Reason: They lay their eggs in the safe places of the environment.
A B C D
[Ans. (C) A is true but R is false]
6. Name an organism where cell division is itself a mode of reproduction.
[Ans. Bacteria, Amoeba]
7. Name the phenomenon where the female gamete directly develops into a new organism with an avian example.
Phenomenon – Parthenogenesis
Eg: Turkey.
8. What is parthenogenesis? Give two examples from animals.
(i) Development of an egg into a complete individual without fertilization is known as parthenogenesis.
(ii) Parthenogenesis is of two main types namely, Natural Parthenogenesis and Artificial Parthenogenesis.
(iii) Ex: Honey bees, Gall fly.
9. Which type of reproduction is effective Asexual or sexual and why?
(i) Reproduction is a biological process by which organisms produce their young ones. Reproduction results in continuation of species and introduces variations in organisms which are essential for adaptation and evolution of their own kind.
(ii) Sexual Reproduction can only bring about variation in the organism since it involves fusion of gametes from two different individuals, (parents). A sexual reproduction involves uniparental inheritance and cannot bring about variation.
(iii) Thus, sexual & asexual reproduction can help to create the next generation but only sexual reproduction is said to be more effective than asexual reproduction.
10. The unicellular organisms which reproduce by binary fission are considered immortal. Justify.
(i) In binary fission (asexual reproduction), the parental organism divides into two halves and each half forms a daughter individual. This is seen in unicellular organism like bacteria, Amoeba etc.
(ii) At maturity the single parent cell divides, to form the daughter cells. The parent cell does not die but it becomes a part of the daughter cells formed.
(iii) Thus the unicellular organisms which reproduce by binary fission are considered immortal.
(iv) In other cases of asexual reproduction, the parent produces special structures like buds, spores etc for reproduction but the parent organism continues to live and grow. It dies a natural death.
11. Why is the offspring formed by asexual
reproduction referred as a clone?
Clones refers to the group of genetically identical cells or organisms asexually produced from a single progenitor cell or organism. Asexual reproduction involves a single parent. Offsprings produced by asexual reproduction are morphologically and genetically similar to their parents and are hence called clones.
12. Why are the offsprings of oviparous animal at a greater risk as compared to offsprings of viviparous organisms?
Oviparous animals lay eggs outside their body. These eggs are exposed to various environmental conditions and may be eaten by predators also. They face lot of risks until the young ones hatch. But the offsprings of viviparous animals are more safe and protected in the maternal womb until they are born.
13. Give reasons for the following:
(a) Some organisms like honey bees are called parthenogenetic animals
(b) A male honey bee has 16 chromosomes where as its female has 32 chromosomes.
(a) Development of an egg into a complete individual without fertilization is known as parthenogenesis It is of two types. Natural parthenogenesis occurs in Nature in many animals such as honey bees. Artificially it can be induced in animals by physical or chemical stimuli which is called artificial parthenogenesis.
(b) In honey bees both sexual reproduction and parthenogenesis occurs, and it is described as incomplete parthenogenesis. It is a kind of natural parthenogenesis. During sexual reproduction, the fertilized eggs (zygotes) develop into queen bee and workers (females). The unfertilized eggs develop into drones (males). This honey bees are called parthenogenesis animals. In honey bees the normal chromosomal number in a cell is 2n = 32. Gametes (sperms & egg) will have only n = 16 chromosomes since they are haploid. The female bees are formed by fertilization of gametes.
sperm (n) + egg (n) = 2n
Therefore they have 32 chromosomes. Since the drones (males) are formed from unfertilized eggs(n) they have only 16 chromosomes. Honey bees show incomplete parthenogenesis.
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
Binary Fission in Amoeba |
Multiple Fission in Plasmodium |
The nucleus divides mitotically only once. |
The nucleus divides repeatedly. |
The cell constricts in the middle after nuclear to form the daughter cells. |
The cytoplasm divides into as many parts as that of nuclei and each part encircles a daughter nucleus. |
Two daughter cells are formed. |
Many daughter cells are formed. |
b)
Budding in Yeast |
Budding in Hydra |
Yeast is a unicellular organism. The single cell produces an outgrowth to form a bud. Nucleus of the parent cell divides and a daughter nuclei enters the bud which is unicellular. |
The Bud is developed by mitotic divisions of its cells and is multicellular. |
A Chain of buds may be formed in the parent cell at times |
Chain of buds are not formed. |
In both cases, the buds separate and lead an independent life.
(c) Regeneration is regrowth in the injured region.
Regeneration in Planaria |
Regeneration in Lizard |
It shows the morphallaxis type of regeneration in which the whole body grows from a small fragment. |
Lizard shows the epimorphosis type of regeneration in which replacement of lost body parts occur. |
The whole body can be got by regeneration. |
It shows the restorative type of regeneration in which several body parts can only develop but the whole body cannot develop. |
15. How is juvenile phase different from
reproductive phase?
Organisms have three phases – Juvenile phase, reproductive phase and senescent phase.
(i) Juvenile phase/ vegetative phase is the period of growth between the birth of the individual upto reproductive maturity.
(ii) During reproductive phase/ maturity phase the organisms reproduce and their offsprings reach maturity period.
(iii) Senescent phase begins at the end of reproductive phase when degeneration sets in the structure and functioning of the body.
16. What is the difference between syngamy and fertilization?
The entire process involved in fusion of male and female gamete in sexual reproduction is called fertilization. It includes the entry of sperm into the egg followed by fusion of nuclei to form a zygote. Syngamy refers to the process of fusion of the male & female gametes. (fusion of cytoplasm and nuclei).
Also Unit test question papers and extra questions are available.
Prepared by,
S.Dharshini
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