Solution of How do organisms Reproduce (Page No - 142 - Biology by Lakhmir Singh, Class 10 Class 10 Notes | EduRev

Class 10 Biology Solutions By Lakhmir Singh & Manjit Kaur

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Class 10 : Solution of How do organisms Reproduce (Page No - 142 - Biology by Lakhmir Singh, Class 10 Class 10 Notes | EduRev

The document Solution of How do organisms Reproduce (Page No - 142 - Biology by Lakhmir Singh, Class 10 Class 10 Notes | EduRev is a part of the Class 10 Course Class 10 Biology Solutions By Lakhmir Singh & Manjit Kaur.
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Question 26:
Describe the layering method for the artificial propagation of plants. Illustrate your answer with the help of a labelled diagram. Name any five plants which are propagated by the layering method.
Solution :
Layering – In this method, a branch of the plant is pulled towards the ground and the part of it is covered with moist soil leaving the tip of the branch exposed above the ground. After some time, new roots develop from the part of the branch buried in the soil. The branch is then cut off from the parent plant. The part of the plant which has developed roots grows to become a new plant. The layering method is used for the propagation of plants like Jasmine, Strawberry, Raspberry, Lemon and Guava. 

Solution of How do organisms Reproduce (Page No - 142 - Biology by Lakhmir Singh, Class 10 Class 10 Notes | EduRev

The Propagation of jasmine plant (chameli) by the layering method  


Question 27:
(a) What is meant by the term ‘fission’ as used in biology ?
(b) How does binary fission differ from multiple fission ?
(c) Name one organism which reproduces by binary fission and another which reproduces by multiple fission.
(d) State whether the above named organisms are animals or plants.
Solution :
(a) Fission means the splitting of an organism into two new organisms.(b)
Binary Fission
(i) In binary fission, the parent organism splits to form two new organisms.
(ii) It occurs during normal conditions.
Multiple Fission
(i) In multiple fission, the parent organisms splits to form many new organisms.
(ii)It takes place during unfavorable conditions.
(c) Amoeba reproduces by binary fission and Plasmodium reproduces by multiple fission. (d) Both the above mentioned organisms are animals.

Question 28:
(a) Can you consider cell division as a type of reproduction in unicellular organisms ? Give reason.
(b) What is a clone ? Why do offsprings formed by asexual reproduction exhibit remarkable similarity ?
Solution :
(a) Yes, because it leads to the formation two daughter cells.(b) The new organisms produced by one parent through asexual reproduction (which are genetically identical to the parent) are called clones. The offspring’s formed by asexual reproduction exhibit remarkably similarity because the replication of DNA in the cells is done by certain biochemical reactions which synthesise more of genetic material. When the DNA already present in the nucleus of the parent cell is replicated by making more DNA at the time of asexual reproduction then slight variations come in the two copies formed. Due to this the two DNA molecules formed will be similar but not identical.

Question 29:
(a) The yeast cells fail to multiply in water but they multiply rapidly in sugar solution. Give one reason for
it.
(b) Why does bread mould grow profusely on a moist slice of bread but not on a dry slice of bread ?
Solution :
(a) Water does not provide any energy to the yeast cells. So, yeast cells fail to multiply in water due to inadequate energy in its cells. Sugar provides energy to them to carry out reproduction by multiplying rapidly.
(b) Moisture is necessary for the growth of bread mould. The moist slice of bread provides both moisture and nutrients due to which bread mould grows profusely. On the other hand, the dry slice of bread provides nutrients but no moisture. So, in the absence of moisture, bread mould does not grow on the dry slice of bread.

Question 30:
(a) What is a tuber ? Name one stem tuber and one root tuber.
(b) What is name of the organ of propagation present in a tuber ?
(c) Name one commonly used vegetable which is propagated by using tubers.
Solution :
a) A tuber is the thickened, underground stem (or root) of a plant which is swollen with stored food. Stem tuber: Potato; Root tuber: Sweet potato. (b) Buds. (c) Potatoes.

Question 31:
(a) What is meant by vegetative propagation ?
(b) Vegetative propagation involves the growth and development of ‘something’ present in the old part of the plant to form a new plant. What is this ‘something’ ?
(c) Why do green grass plants spring up in dry fields on their own after the rains ?
Solution :
(a) Vegetative propagation is an asexual method of reproduction in which new plants are obtained from the parts of old plants (like stems, roots and leaves) without the help of any reproductive organs.
(b) Buds.
(c) The fields have dry stems of the old grass plants all over them. These dry stems have buds which are in the inactive state. By getting rainwater, the buds present on the dry grass stems get activated and grow to produce new grass plants.

Question 32:
(a) Explain how, new Bryophyllum plants can be produced from the leaves of the old plant ? Illustrate your
answer with the help of a labelled diagram.
(b) How can you grow money plant bv vegetative propagation ?
Solution :
(a) Bryophyllum can be reproduced by vegetative propagation by using either a piece of its stem or leaves. The leaves of a Bryophyllum plant have special buds in their margins which may get detached from the leaves, fall to the ground and then grow to produce a new plant.

Solution of How do organisms Reproduce (Page No - 142 - Biology by Lakhmir Singh, Class 10 Class 10 Notes | EduRev



(b) Money plant can be grown by vegetative propagation by using a piece of its stem which has at least one leaf on it. One end of the stem is dipped in water and after a few days new roots appear at the point where the leaf was attached. This piece of stem grows gradually into a new money plant.

Question 33:
Match the organisms given in column I with the methods of reproduction/propagation given in column II:

Column I
Column II
(i) Plasmodium
(a) Spore Formation
(ii) Spirogyra
(b) Leaves 
(iii) Jasmine
(c ) Regeneration
(iv) Apple tree
(d) Budding
(v) Bryophyllum
(e) Binary Fission
(vi) Potatoes
(f) Layering
(vii) Rhizopus
(g) Fragmentation
(viii) Hydra
(h) Tubers
(ix) Planaria
 (i) cutting
(x) Leishmania
(j) Multiple fission
(xi) Sugar cane
(k) Grafting
(xii) Rose


Solution :
(i) – (j)
(ii) – (g)
(iii) – (f)
(iv) – (k)
(v) – (b)
(vi) – (h)
(vii) – (a)
(viii) – (d)
(ix) – (c)
(x) – (e)
(xi) – (i)
(xii) – (i)

Question 34:
(a) What is meant by reproduction ?
(b) What are the two general methods of reproduction in organisms ?
(c) How does an Amoeba reproduce ? Describe the process of reproduction in Amoeba with the help of labelled diagrams of different stages in its reproduction process.
(d) What is the name of the process by which Amoeba reproduces ?
(e) Name two organisms which reproduce by the same asexual process as that of Amoeba.
Solution :
(a) Theproduction of new organisms from the existing organisms of the same species is known as reproduction.
(b) The two methods of reproduction in living organisms are asexual reproduction and sexual reproduction.
(c) Amoeba reproduces by binary fission by dividing its body into two parts. When the amoeba cell reaches its maximum size, the nucleus of amoeba lengthens and divides into two parts. After that the cytoplasm of amoeba divides into two parts, one part around each nucleus. In this way one parent amoeba divides to form two smaller amoebae.


Solution of How do organisms Reproduce (Page No - 142 - Biology by Lakhmir Singh, Class 10 Class 10 Notes | EduRev

(d) Binary fission.
(e) Paramecium and Leishmania.

Question 35:
(a) What is the difference between the two asexual methods of reproduction : fission and fragmentation ?
(b) Name one organism which reproduces by fission and another which reproduces by fragmentation.
(c) What is meant by multiple fission ? Name one organism which reproduces by the process of multiple fission.
(d) Describe the process of reproduction in Hydra with the help of labelled diagrams. What is the name of this process of reproduction ?
(e) Name one unicellular organism which reproduces by the same asexual process as Hydra.
Solution :
(a)
Fission
(i) It is a process in which an organism splits to form two or more new organisms.
(ii) Fission occurs in unicellular organisms.
Example : Amoeba.
Fragmentation
(i) It is a process in which the body breaks up into two or more pieces on maturing, each of which subsequently grows to form a complete new organism.
(ii) It takes place in multicellular organisms.
Example : Spirogyra.
(b) Amoeba reproduces by fission and spirogyra reproduces by fragmentation.
(c) Multiple fission is a process in which a parent organism splits to form many new organisms at the same time. Plasmodium reproduces by multiple fission.
(d) Hydra reproduces by budding. In hydra, first a small outgrowth called bud is formed on the side of its body by repeated mitotic divisions of its cells. This bud then grows gradually to form a small hydra by developing a mouth and tentacles. The tiny new hydra detaches itself from the parent body and develops into a separate organism.

(e) Yeast. 

Solution of How do organisms Reproduce (Page No - 142 - Biology by Lakhmir Singh, Class 10 Class 10 Notes | EduRev



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