CBSE Class 10 Science HOTs How Do Organisms Reproduce Set 02

Modes of Reproduction Used by Single Organisms

Question. Which is the most common method of reproduction in bacteria?
(a) Budding
(b) Spore formation
(c) Binary fission
(d) Multiple fission

Answer: (c) Binary fission

Question. Which of the following is not an artificial method of vegetative propagation?
(a) Cutting
(b) Layering
(c) Budding
(d) Grafting

Answer: (c) Budding

Question. Many unicellular organisms reproduce by the process of
(a) fission
(b) ovulation
(c) regeneration
(d) non-disjunction

Answer: (a) fission

Question. The ability of an organism to develop whole body from a broken piece or fragment is called
(a) binary fission
(b) budding
(c) multiple fission
(d) regeneration

Answer: (d) regeneration

Question. While studying binary fission in Amoeba from a permanent slide under a microscope,
(i) unicellular and uninucleate organisms showing irregular outline is observed under low power.
(ii) unicellular and uninucleate organisms showing irregular outline is observed under high power.
(iii) division of cells of Amoeba are observed under high power.
(iv) division of cells of Amoeba are observed under low power.
(a) (i) and (iii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

Answer: (d) (ii) and (iv)

Very Short Answer Type Questions 

Question. Rajesh observed a patch of greenish black powdery mass on a stale piece of bread.
(a) Name the organism responsible for this and its specific mode of asexual reproduction.
(b) Name its vegetative and reproductive parts. 

Answer: (a) The greenish black powdery mass on a stale piece of bread is due to bread mould Rhizopus, which reproduces by spore formation.
(b) Hyphae or thread like structures are the vegetative part and tiny blob like structures or sporangia are the reproductive parts.

Question. Write two differences between binary fission and multiple fission in a tabular form. 
Answer:
Binary fission:
(i) It is the division of the parent into two nearly equal sized daughter individuals.
(ii) Nucleus of the parent cell divides to form two nuclei.

Multiple fission:
(i) It is the division of the parent into many small daughter individuals.
(ii) Nucleus of the parent cell divides to form a number of nuclei.

Question. How do Plasmodium and Leishmania reproduce? Write one difference in their mode of reproduction. 
Answer: Plasmodium and Leishmania reproduce through fission–an asexual method of reproduction. Leishmania reproduce with the help of binary fission. Plasmodium reproduce by multiple fission dividing itself into many daughter cells inside its cell wall.

Question. Define multiple fission. Give its one example. 
Answer: Multiple fission is a type of cell division in which a single cell divides into many daughter cells simultaneously, inside a protective covering called cyst, e.g. in Plasmodium.

Question. List two advantages of growing grapes or banana plants through vegetative propagation. 
Answer: (i) Traits of the parent plants are preserved.
(ii) Since they do not possess viable seeds, vegetative propagation helps to reproduce.

Question. With the help of a diagram show the different stages of binary fission in Amoeba
Answer: Binary fission is the division of one cell which cuts into two similar or identical cells. [The process involves the elongation of the parent Amoeba, followed by the division of the nucleus, and finally the constriction of the cytoplasm to form two daughter cells.]

Question. List any four reasons for vegetative propagation being practised in the growth of some type of plants. Or List four advantages of vegetative propagation. 
Answer: Advantages of vegetative propagation:
(i) Vegetative propagation is a cheaper, easier and more rapid method of propagation in plants than growing plants from their seeds.
(ii) Better quality of the plants can be maintained by this method.
(iii) It results in propagation of those plants which do not produce viable seeds or produce seeds with prolonged period of dormancy.
(iv) The plants generated from vegetative means require less time to grow and have the advantage of being more uniform and genetically similar to the parent stock.

Question. List two advantages of vegetative reproduction practised in case of an orange plant.
Answer: Two advantages of practising vegetative reproduction in an orange plant are:
(i) the oranges produced are similar in size and shape.
(ii) many oranges do not produce viable seeds and hence, vegetative method is a good alternative.

Question. Explain regeneration.
Answer: Regeneration is the process by which fully differentiated organisms give rise to new individual organisms from their body parts. More complex organisms cannot give rise to new individuals through regeneration.

Question. What is meant by asexual reproduction? List its any two different forms.
Answer: Asexual reproduction: It is the process of producing new organism from a single parent without the involvement of sex cells. Fission and fragmentation are two different forms of asexual reproduction.

Short Answer Type Questions 

Question. Name an organism which reproduces by spore formation. List three conditions favourable for spores to germinate and grow.
Answer: Rhizopus reproduces by spore formation. Conditions favourable for spore formation are: (i) Cool place, (ii) Moist place, (iii) Dark place.

Question. A farmer bought some strawberries and liked the taste. He decided to grow his own strawberries that should have the same taste. (a) Which method of cultivation should the farmer adopt? (b) Why would the farmer choose this method? 
Answer: (a) Asexual reproduction / Vegetative propagation
(b) It is because fruit produced through vegetative propagation would carry conserved parental characteristics.

Question. What could be the TWO most likely reasons for unicellular organisms to reproduce only through asexual reproduction?
Answer: (i) They can produce a large number of offsprings in a small period of time.
(ii) The offsprings are adapted to survive in the same environment.

Question. The process of spore formation takes place in many simple multicellular organisms. Name the (a) organism using this process to reproduce, and (b) reproductive and non-reproductive parts of such organisms. List two benefits to an organism that reproduces through spores.
Answer: (a) The organism that reproduces by spore formation – Rhizopus.
(b) Reproductive parts of Rhizopus – Sporangia; Non-reproductive parts of Rhizopus – Hyphae.
Benefits to an organism that reproduces by spores:
• Spores can be spread through air, water or animals and so it is good for spread of rhizopus to more place.
• Spores can remain dormant till favourable conditions become available.
• Spores help an organism to tide over bad phase. (any two)

Question. What happens when (a) Planaria gets cut into two pieces? (b) A mature Spirogyra filament attains considerable length? (c) On maturation sporangia burst? 
Answer: (a) When Planaria gets cut into two pieces, each piece grows into a complete organism.
(b) A mature Spirogyra on attaining considerable length breaks up into two or more small pieces. Each piece then grows into a new individual.
(c) When sporangia bursts, spores are released, each one of which develops into new individual.

Question. (a) List two advantages of growing grapes or banana plants through vegetative propagation. (b) A potato is cut into a number of small pieces. These pieces are then placed only on wet cotton kept in a tray. After few days some of the potato pieces gave rise to fresh green shoots and roots. Why?
Answer: (a) (i) Traits of the parent plants are preserved. (ii) Since they do not possess viable seeds, vegetative propagation helps to reproduce.
(b) The green shoots and roots were produced only by those potato pieces which have buds on them; pieces of potato without buds were not able to produce green shoots and roots.

Question. What is regeneration? Give one example of an organism that shows this process and one organism that does not. Why does regeneration not occur in the later? 
Answer: Regeneration is defined as the ability of any small part of the body to give rise to a new individual e.g.
(i) Hydra and Planaria shows regeneration.
(ii) Amphibians and human beings do not show regeneration.
Regeneration is carried out by certain specialised cells, which can proliferate to make a large number of cells and different cells undergo development to become various cell types and tissues. Such regenerative cells are not found in amphibians and humans.

Question. (a) Name the following: (i) Thread like non-reproductive structures present in Rhizopus. (ii) ‘Blobs’ that develop at the tips of the non-reproductive threads in Rhizopus. (b) Explain how these structures protect themselves and what is the function of the structures released from the ‘blobs’ in Rhizopus. 
Answer: (a) (i) Hyphae (ii) Sporangium
(b) Spores are enclosed within sporangia which protects the spores. Spores when released from sporangia develop into new Rhizopus.

Question. Explain giving one example of each, the unisexual and the bisexual flowers. When is it used? Name three methods of vegetative propagation.
Answer: Unisexual flowers contain either stamens or carpels but not both. Example: Papaya, watermelon. Bisexual flowers contain both stamens and carpels. Example: Hibiscus, Mustard. The method of developing new plants from the vegetative parts of a plant, such as root, stem or leaf is called vegetative propagation. This method is used when some plants like banana, orange, rose and jasmine have lost the capacity to produce seeds. The three methods of vegetative propagation are cutting, layering and grafting.

Question. What is vegetative propagation? State two advantages and two disadvantages of this method. 
Answer: Vegetative propagation refers to the development of new plants from vegetative parts (roots, stem or leaves) of an existing plant.
Advantages of vegetative propagation:
(i) It is a cheaper, easier and more rapid method of propagation than growing plants from their seeds.
(ii) Better quality of the plants can be maintained by this method.
Disadvantages:
(a) No genetic variation is created.
(b) Continued vegetative propagation can lead to loss of vigour.

Long Answer Type Questions 

Question. (a) What is tissue culture? How it is done? (b) Discuss two advantages of tissue culture.
Answer: (a) Tissue culture is the method of developing plants from plant cells or small pieces of plant tissue in a synthetic/artificial medium. It is done as follows:
(i) The tissue/cells are collected from the shoot tip of a desired plant.
(ii) These cells are then grown in a nutritive artificial medium where they divide and form a mass of identical cells known as callus.
(iii) The callus are then allowed to grow in another medium containing hormones needed for growth and development.
(iv) When small plantlets are developed, they are transplanted into soil or pots where they can grow to form mature plants.
(b) (i) It is a fast technique in which thousands of plantlets can be produced in short span of time. (ii) New plants produced through tissue culture are disease free.

PRACTICE QUESTIONS

Question. The main method of reproduction in yeast is
(a) budding
(b) cutting
(c) sporogenesis
(d) grafting

Answer: (a) budding

Question. The steps of the process of regeneration are given in a random order. Which of the following is the correct sequence of steps?
(i) Regeneration is carried out by specialised cells.
(ii) From the mass of cells, different cells undergo changes to become various cell types and tissues.
(iii) The specialised cells proliferate and make large number of cells.
(iv) The changes take place in an organised sequence referred to as development.
(a) i, ii, iii, iv
(b) i, iii, ii, iv
(c) i, iv, ii, iii
(d) i, iii, iv, ii

Answer: (b) i, iii, ii, iv

Question. Tissue culture technique is used for
(a) rabi crops
(b) cash crops
(c) ornamental plants
(d) fruit trees

Answer: (c) ornamental plants

Question. Vegetative propagation is practiced for growing plants which
(i) produce seeds
(ii) do not produce seed
(iii) produce viable seeds
(iv) produce non-viable seeds
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (ii) and (iv)
(d) (i) and (iv)

Answer: (c) (ii) and (iv)

Question. Leaves of Bryophyllum fallen on the ground produce new plants whereas the leaves of rose do not. Why?
Answer: Bryophyllum leaves possess adventitious buds in the notches along their margins which can develop into new plants. Rose leaves do not possess such buds.

Question. ‘Grafting is a common method of obtaining a superior plant from two different plants’. Explain.
Answer: Grafting involves joining the stem of one plant (scion) with the root system of another plant (stock). This combines the desirable traits of both plants, such as superior fruit quality from the scion and a strong root system from the stock.

Question. How do the ornamental plants propagate? Mention the method of propagation for the following: (i) Jasmine (ii) Rose (iii) Bougainvillea (iv) Hibiscus
Answer: Ornamental plants propagate through various vegetative methods. (i) Jasmine: Layering (ii) Rose: Cutting/Grafting (iii) Bougainvillea: Cutting (iv) Hibiscus: Cutting.

Question. What causes joining up of stock and scion in grafting? Name one positive trait that the plant contributing scion should have and one positive trait that the plant contributing the stock should have.
Answer: The cambium tissues of the stock and scion join together to form a continuous vascular connection. The scion should contribute superior traits like high yield or quality of fruit/flowers, while the stock should provide a strong, disease-resistant root system.

Question. (a) List in tabular form two differences between binary fission and multiple fission. (b) What happens when a mature Spirogyra filament attains considerable length? 
Answer: (a) Binary fission involves the division of a parent cell into two nearly equal daughter cells (e.g., Amoeba), while multiple fission involves the division of a parent cell into many small daughter cells simultaneously (e.g., Plasmodium). In binary fission, the nucleus divides into two, whereas in multiple fission, the nucleus divides into many nuclei. (b) When a mature Spirogyra filament attains considerable length, it undergoes fragmentation, where it breaks into smaller pieces. Each piece then grows into a new individual plant.

Question. What is meant by tissue culture? How this technique is performed? In which area this technique is finding its application? 
Answer: Tissue culture is a technique used to grow new plants from a small piece of plant tissue or cells in an artificial nutritive medium under sterile conditions. The process involves taking cells from the growing tip of a plant and placing them in a medium where they divide to form a mass called a callus. This callus is then transferred to another medium containing hormones for growth and differentiation into plantlets, which are later moved to soil. It is widely used in the production of ornamental plants and for developing disease-free plant varieties.

Question. Describe the different methods of asexual reproduction seen in animals with the help of neat labelled diagrams. 
Answer: Common methods of asexual reproduction in animals include: (i) Fission (Binary fission in Amoeba/Leishmania and Multiple fission in Plasmodium), (ii) Budding (e.g., in Hydra, where an outgrowth develops into a new individual), and (iii) Regeneration (e.g., in Planaria, where body parts can grow into complete organisms). Diagrams typically illustrate the sequential stages of cell division or budding from the parent body until the offspring detaches.

Question. (a) How do Leishmania and Plasmodium reproduce? (b) State one difference in their mode of reproduction. (c) Define the term vegetative propagation (d) List four advantages of vegetative propagation.
Answer: (a) Both Leishmania and Plasmodium reproduce by fission. (b) Leishmania undergoes binary fission in a definite orientation (longitudinal), while Plasmodium undergoes multiple fission to produce many daughter cells at once. (c) Vegetative propagation is a mode of asexual reproduction in plants where new plants are produced from vegetative parts like roots, stems, or leaves. (d) Advantages include: 1. New plants are genetically identical to the parent. 2. It allows propagation of seedless plants like banana and orange. 3. It is a faster method than growing plants from seeds. 4. Superior qualities of a plant can be easily preserved.

DNA Copying and Sexual Reproduction

Question. During the process of copying the DNA, some variations are so drastic that
(a) a new born cell divides to give rise to two cells.
(b) a new born cell will survive and start multiplying.
(c) the new DNA copy will work with the cellular apparatus it inherits.
(d) the new DNA copy will not work with the cellular apparatus it inherits.
Answer: (d) the new DNA copy will not work with the cellular apparatus it inherits.

Question. Pollen grains are produced by
(a) ovary
(b) ovule
(c) anther
(d) corolla [KVS]
Answer: (c) anther

Question. Which of the following is a primary sex organ in a mammal?
(a) Ovary
(b) Vagina
(c) Uterus
(d) Mammary glands
Answer: (a) Ovary