NCERT MOST IMPORTANT QUESTIONS CLASS – 12 | BIOLOGY IMPORTANT QUESTIONS | CHAPTER -1 | REPRODUCTION IN ORGANISM | EDUGROWN |

In This Post we are  providing Chapter-1 REPRODUCTION IN ORGANISM NCERT MOST IMPORTANT QUESTIONS for Class 112BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTIONS ON REPRODUCTION IN ORGANISM

Question 1.
Define:
(i) juvenile phase,

Answer:
Juvenile phase. The period of growth in the life of organisms before they start reproducing sexually and attain a level of maturity is called juvenile phase. It is followed by the reproductive phase.

(ii) reproductive phase
Answer:
Reproductive phase. The period of active reproductive behaviour, when the organisms show marked morphological and physiological changes is called reproductive phase. It is followed by senescence phase.

(iii) senescence phase.
Answer:
Senescence phase. The period when the reproductive phase ends and concomitant changes occur in the body such as slowing of metabolism is called senescence phase. It is followed by death.

Question 2.
Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?

Answer:
1. Differences between asexual reproduction and sexual reproduction.

Asexual Reproduction	Sexual Reproduction
1. The process involves only one cell or one parent.	1. This process involves two cells or gametes belonging to either the same or different parents.
2. The whole body of the parent may act as a reproductive unit or it can be a single cell or a bud.	2. The reproductive unit is called gamete which is unicellular and haploid.
3. The offspring are genetically similar to the parent.	3. The offspring differ from the parents.
4. Only mitotic division takes place.	4. Meiosis and mitosis both take place.
5. No formation of sex organs.	5. Formation of sex organs is essential.
6. No evolutionary significance.	6. It introduces variation; hence it is of evolutionary significance.

2. Vegetative reproduction is also considered a type of asexual reproduction because it does not involve meiotic division and there is no formation and fusion of gametes.

Question 3.
How does an encysted Amoeba reproduce on the return of favourable conditions?

Answer:
Multiple fission in encysted Amoeba:

• Amoeba withdraws pseudopodia and secretes a cyst wall around itself. This phenomenon is called encystation.
• Amoeba divides by multiple fission.
• It produces a large number of pseudo- conidiospores.
• The cyst wall breakdown.
• The spores are liberated and settle down on suitable substrates and grow as amoebae. This process is also called sporulation.

Question 4.
Discuss the advantages and disadvantages of asexual reproduction.

Answer:
Advantages of asexual reproduction:

1. It involves simple mitotic division in single-parent and it may produce a large number of young ones.
2. Young ones produced by asexual methods are genetically similar to the parent.
3. It helps in the dispersal of offspring to far off places.

Disadvantages of asexual reproduction.

1. The young ones thus produced do not possess much capacity to adapt rapidly to the environmental changes taking place in quick succession.
2. No genetic recombination occurs; thus no variation occurs.

Question 5.
Discuss the advantages and disadvantages of sexual reproduction.

Answer:
Advantages of sexual reproduction:

1. Genetic recombination, interaction, etc. take place which causes variations in the offspring, thus also form raw materials for evolution.
2. The offspring adapt more comfortably and quickly to the change in environmental conditions and have better chances of survival.

Disadvantages of sexual reproduction. Usually, two parents of opposite sexes are required (except in hermaphrodite).

Question 6.
List various methods of natural vegetative propagation. Give examples:

Answer:

1. Vegetative propagation by stems, e.g.Grasses, Turmeric, Onion, Colocasia, Potato, Gladiolus and Crocus.
2. Vegetative propagation by roots, e.g. Murraya sp., Albizzia Lebbac, Dalbergia sissoo, Tuberous roots of sweet potato, Asparagus, Tapioca, Dahlia and Yams (Dioscorea).
3. Vegetative propagation from reproductive organs. Flower buds of century plant (Agave sp.) develop into bulbils.

Question 7.
Define external fertilisation. Mention its disadvantages:

Answer:
The fertilisation in which the fusion of gametes occurs outside the body of the female in an external medium, i.e. water, is called external fertilisation.

Examples. Bony fishes, amphibians, etc. Organisms that exhibit external fertilisation show great synchrony between the sexes in order to liberate the gametes at the same time.

Disadvantages of external fertilisation:

1. A large number of gametes are produced to ensure fertilisation, thus there is wastage.
2. The offspring formed are extremely vulnerable to predators, thus threatening their survival up to adulthood.

Question 8.
Explain the process of budding in yeast.

Answer:
Budding in yeast. It is a common type of vegetative reproduction. In a medium which is abundantly supplied with sugar, yeast cytoplasm forms a bud-like outgrowth. The growth soon enlarges and a part of the nucleus protrudes into the bud and breaks off. The bud then begins to grow and then separates from the mother cell. Often it will itself form a bud before it breaks away, and straight or branched chains are produced.

Thus, as a result, branched or unbranched chains of cells called pseudo my cilium are produced. The cells are loosely held together. Sooner or later they become independent.

Question 9.
Describe the importance of vegetative propagation.

Answer:
Merits of vegetative propagation:

1. Plants produced by vegetative propagation are genetically similar and constitute a uniform population called a clone.
2. Plants with reduced power of sexual reproduction, long dormant period of seed, poor viability, etc. are multiplied by vegetative methods.
3. Some fruit trees like banana and pineapple do not produce viable seeds. So these are propagated by only vegetative methods.
4. It is a more rapid and easier method of propagation.
5. Good characters are preserved by vegetative propagation.
6. Some plants such as doob grass (Cynodon dactylon) which produce only a small quantity of seed are mostly propagated by vegetative propagation.
7. Grafting helps in getting an economically important plant having useful characteristics of two different individuals in a short time.

Question 10.
Write a note on sexuality in plants.
Or
Coconut palm is monoecious while date palm is dioecious. Why are they called so?

Answer:
Sexuality in organisms: Sexual reproduction in organisms generally involves the coming together of gametes from two different individuals. But this is not always true.

Sexuality in Plants: Plants may have both male and female reproductive structures in the same plant (bisexual) or on different plants (unisexual). In several fungi and plants, terms such as homothallic and monoecious are used to denote the bisexual condition, and heterothallic and dioecious are used to describe the unisexual condition.

In flowering plants, the unisexual male flower is staminate, i.e. bearing stamens, while the female is pistillate or bearing pistils. In some flowering plants, both male and female flowers may be present on the same individual (monoecious) or on separate individuals (dioecious). Some examples of monoecious plants are cucurbits and coconuts and dioecious plants are papaya and date palm.

Very Important Figures: