CBSE Class 10 Biology How do Organisms Reproduce Worksheet

Question. Asexual reproduction takes place through budding in
(a) amoeba.
(b) yeast.
(c) plasmodium.
(d) leishmania.
Answer : B

Question. The anther contains
(a) sepals
(b) ovules
(c) carpel
(d) pollen grains
Answer : D

Question. Growing foetus derive nutrition from mother’s blood through
(a) uterus
(b) fallopian tube
(c) placenta
(d) cervix
Answer : C

Question. Where does fertilisation occur in human females?
(a) Uterus
(b) Cervix
(c) Oviduct
(d) None of these
Answer : D

Question. What is the surgical method of contraception used in human males?
(a) Vasectomy
(b) Condoms
(c) Contraceptive pills
(d) Tubectomy
Answer : A

Question. Which one of the options is incorrect?
Vegetative propagation is practised because
(a) Plants which produce non viable seeds can be grown.
(b) It is a easier method than sowing seeds.
(c) Such plants produce seeds and fruits much earlier than other methods
(d) For obtaining better species of plants.
Answer : C

Question. What is the surgical method of contraception in female and male respectively?
(a) Tubectomy and Vasectomy
(b) Vasectomy and Copper-T
(c) Tubectomy and Copper-T
(d) None of these
Answer : A

Question. Which of the following is not a sexually transmitted disease?
(a) Warts
(b) Kala azar
(c) Syphilis
(d) Gonorrhoea
Answer : B

Question. In which of the following plant bud in notches of leaves help in its propagation?
(a) Radish
(b) Bryophyllum
(c) Bougainvillea
(d) Jasmine
Answer : B

Question. What is the puberty age in human males?
(a) 8-10
(b) 10-12
(c) 12-14
(d) 14-16
Answer : C

Question. The simple animals like Planaria can be cut into a number of pieces and each piece grows into a complex organism. What is the process known as?
(a) Budding
(b) Fragmentation
(c) Spore formation
(d) Regeneration
Answer : D

Question. Fruit is formed from
(a) Stamen
(b) Stigma
(c) Ovary
(d) Ovule
Answer : C

Question. The female reproductive part of the flower consists of
(a) Stigma, Anther, Filament
(b) Style, Ovary, Thalamus
(c) Stigma, Ovary, Style
(d) Anther, Corolla, Filament
Answer : C

Question. ___________ is the portion on which grafting is done and it provides the roots?
(a) Stock
(b) Scion
(c) Both (a) and (b)
(d) None of these
Answer : A

Question. The process of the transfer of pollen grains from the flower of one plant to the stigma of the flower of another plant of the same species is known as
(a) Cross pollination
(b) Fertilisation
(c) Self pollination
(d) None of the above
Answer : A

Question. The two oviducts in a human female unite into an elastic bag like structure known as
(a) Vagina
(b) Uterus
(c) Fallopian tube
(d) Cervix
Answer : B

Question. Which of the following is not a part of the female reproductive system in human beings?
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube
Answer : C

Question. Which of these is not the function of the seminal vesicles present in human males?
(a) To covert the sperms in a fluid medium.
(b) To provide nutrition.
(c) To make their transport easier.
(d) To make them sticky.
Answer : D

Question. Why are the testes located outside the abdominal cavity in scrotum?
(a) Because sperm formation requires more spaces.
(b) Because sperm formation requires a lower temperature.
(c) Because sperm formation requires a higher temperature.
(d) None of the above.
Answer : B

Question. Unicellular organisms reproduce by
(a) Mitotic cell division
(b) Meiotic cell division
(c) Both (a) and (b)
(d) None of the above
Answer : A

Question. Which of the following disease is transmitted sexually?
(a) Kala azar
(b) Jaundice
(c) Elephantiasis
(d) Syphilis
Answer : D

Question. Reproduction is essential for living organisms in order to ……………………
(a) Keep the individual organism alive
(b) Fulfill their energy requirement
(c) Maintain growth
(d) Continue the species generation after generation
Answer : D

Question. Identify the organism that can divide in only one plane
(a) Plasmodium
(b) Leishmania
(c) Amoeba
(d) Spirogyra
Answer : B

Question. Cloning is a mode of :
(a) Sexual reproduction
(b) Asexual reproduction
(c) Both a and b
(d) none
Answer : B

Question. When a animal is cut into pieces and each piece grows into a complex organism. What is the process?
(a) Budding
(b) Fragmentation
(c) Spore formation
(d) Regeneration
Answer : D

Question. Vegetative propagation refers to formation of new plants from ———-.
(a) stem,roots,flowers
(b) stem,roots,leaves
(c) stem,flowers,fruit
(d) stem,leaves,flowers
Answer : B

Question. The ability of a cell to divide into several cells during reproduction in Plasmodium is called
(a) budding
(b) reduction division
(c) binary fission
(d) multiple fission
Answer : D

Question. How do spores develop into Rhizopus?
(a) spores divide and grow into new individual
(b) spores combine with other spores and grow
(c) spores enlarge in size for the growth of new individual
(d) spores land on other organisms and increase with their growth in size
Answer : A

Question. Bryophyllum can be propagated vegetatively by the
(a) stem
(b) leaf
(c) root
(d) flower
Answer : B

Question. The number of chromosomes in parents and offspring of a particular species remains constant due to
(a) Doubling of chromosomes after zygote formation
(b) Halved chromosomes during gamete formation
(c) Doubling of chromosomes after gamete formation
(d) Halving of chromosomes after gamete formation
Answer : B

Short Answer

Question. (a) What is the basic difference between asexual reproduction and sexual reproduction ?
(b) Which of the following organisms reproduce by sexual method and which by asexual method ?
Amoeba, Cats, Humans, Hydra, Birds
Answer : (b) Sexual method : Cats, Humans, Birds ; Asexual method : Amoeba, Hydra

Question. (a) What is meant by regeneration ? Name two animals which can regenerate fully from their cut body parts.
(b) Explain why, more complex multicellular organisms cannot give rise to new organisms through regeneration.
Answer : (a) Planaria and Hydra

Question. Explain vegetative propagation with the help of two examples. List two advantages of vegetative propagation.
Answer : The process in which new plants are grown from the old parts of another plant like roots, shoots and leaves, without involving any reproductive organ, is termed as vegetative propagation. For example, guava trees can be propagated using their roots, and Bryophyllum can be propagated by using its leaves.
The advantages of vegetative propagation are as follows:
The plants cultivated are genetically identical to their parents.
Plants can be cultivated faster as compared to growing them from seeds.

Question. (a) What is meant by the term ‘artificial propagation of plants’ ?
(b) Name three common methods which are used for the artificial propagation of plants.
(c) Name two plants which are usually propagated by artificial propagation methods. Name the method of artificial propagation used in each case.
Answer : (a) Artificial propagation of plants is the man-made technique in which a large number of new plants are cultivated from the mother plant by giving them a suitable environment.
(b) The three common methods of artificial propagation of plants are cutting, layering and grafting.
(c) Rose plant is cultivated through the method known as cutting; while Jasmine plant is cultivated by layering.

Question. 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.
Answer : In the layering method, one of the branches of a plant is pulled down into the ground and covered with moist soil in such a way that the tip of the branch remains above the surface. After a few days, new roots start growing from the part buried in the soil. This part of the branch is then separated from the parent plant to let it develop into a new plant.

Question. (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.
Answer : (c) Binary fission : Amoeba ; Multiple fission : Plasmodium (d) Microscopic animals

Question. (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 ?
Answer : (a) Yes, because it leads to the formation of two daughter cells

Question. (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 ?
Answer : (a) Water does not provide any energy to yeast cells. So, yeast cells fail to multiply in water due to inadequate energy in its cells. Sugar provides energy to yeast cells 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. (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.
Answer : (a) Stem tuber : Potato ; Root tuber : Sweet potato (b) Buds (or Eyes) (c) Potatoes

Question. (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 ?
Answer : (b) Buds

Question. (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 by vegetative propagation ?
Answer : (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.

Question. 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) Cuttings
(x) Leishmania (j) Multiple fission
(xi) Sugar cane (k) Grafting
(xii) Rose
Answer : (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 : Differentiate between the processes of binary fission and budding. 

Answer :

 

 

Question :  Define menstruation. Precocious puberty and Menopause. 

Answer :  a. Menstruation: It is a process in which the blood, mucus and uterine tissue eliminated in female mammals.

b. Precocious puberty: Normally a woman's fertile life starts from the age of puberty (about 13 years), but under some abnormal conditions like high level of sex hormones (LH and FSH), menstruation starts at an early age than the normal, it is called precocious puberty.

c. Menopause: The natural physiological stoppage of menstruation is called menopause or the arrest of reproductive capacity at the age of 45-50 is called menopause. Woman is unable to bear the children.

 

Question : What is the importance of reproduction?  

Answer :  Importance of reproductiona.

Maintenance of the existence- Organisms are maintaining their existence on the earth since their origin, million year ago, only because of reproduction.

b. Preservation of species- Species (a group of similar organisms) are preserved because of reproduction. It is possible because reproducing organisms produce new individuals which are very similar to themselves.

c. Role in evolution- some variations is produced in the new organisms during reproduction which play an important role in evolution.

 

 

Question : Draw a labeled diagram of the longitudinal section of a flower. 

Answer :

 

 

 

Long Answer

Question :  Briefly explain vegetative propagation by stems. 

Answer :   Vegetative propagation by stems : All underground stems even some aerial stems help in vegetative propagation. Some of these are aerial and creeping e.g. runners (Cynodon dactylon, lawn grass), stolons (Fragaria vesica, strawberry), and offsets (Eichhornia); other are underground e.g. rhizomes (Zingiber officinale), corms (colocasia), bulbs (Allium cepa) and tubers (Solanum tuberosum) Aerial stems of sugarcane, ipomoea, grape vine and cacti are also used for vegetative propagation.

In sugarcane, portions of the stem bearing one or more nodes and buds are cut and planted in the soil. Adventitious roots develop from the nodes and the buds grow into aerial shoots.

 

 

 

Question : Describe the menstrual cycle. 

Answer :  Mensurational cycle is the monthly cycle of changes in ovaries and lining of uterus i.e. endometrium. It occur in 3 phase follicular phase, ovulation, and luteal phase.

i. In case fertilisation occurs, the inner wall of uterus thickens to receive the developing zygote.

ii. In case fertilisation does not occurs, the hormonal level drop which breaks and sheds, the thickened wall along with the blood vessels, which moves out of the vagina in the form of discharge called menstrual flow, which lasts for 2-8 days.

iii. The cycle of events takes place in the ovaries and uterus in every twenty eight days and marked by menstrual flow is called menstrual cycle.

Question. (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.
Answer : (d) Binary fission (e) Paramecium and Leishmania

Question. (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.
Answer : (b) By fission : Amoeba ; By fragmentation : Spirogyra (c) Plasmodium (d) Budding (e) Yeast

Question. (a) Name the method by which bread mould (Rhizopus fungus) reproduces. Is this method sexual or asexual ?
(b) What is yeast ? Describe the process of reproduction in yeast with the help of labelled diagrams.
(c) Name a tiny fresh-water animal which reproduces by the same method as that of yeast ? What is this method known as ?
(d) Name two marine organisms which also reproduce by the same method as yeast but form colonies.
Answer : (a) Spore formation ; Asexual method (c) Hydra ; Budding (d) Sponges and Corals

Question. (a) What is meant by ‘grafting’ as a means of propagation in plants ?
(b) Define ‘stock’ and ‘scion’.
(c) Describe the grafting method for the artificial propagation of plants with the help of labelled diagrams.
(d) Name two fruit trees which are usually propagated by grafting method.
(e) State two advantages of grafting method of artificial propagation of plants.
(f) What is the difference between the cuttings method and grafting method for the artificial propagation of plants ?
Answer : (a) Grafting is a method of artificial propagation in which the stem of two plants are cut, one with and the other without roots. Then the stems are then joined together to form a single plant.
(b) The lower portion of the graft, which is the stem and with roots is termed as a stock. The upper portion of the graft, (stem) without roots is termed as a scion.
(c) In this the cut stem of two different plants (One with root and other without root) are joined together in such a way that the two stems join and grow as a single plant.
(d) Peach and Pear trees are propagated by the method of grafting.
(e) The advantage of this method of propagation is:
● Plants with desired characteristics are obtained
● Young stems can be made to flower and bear fruits quickly
(f) Cutting: In this method, only one plant is required and the new plant forms are identical to its parent. Example: Banana and Sugar cane

Question. (a) What is tissue culture ?
(b) Name any four types of ornamental plants which are being produced by tissue culture technique.
(c) What is the importance of DNA copying in reproduction ? Explain with an example.
(d) How does reproduction help in providing stability to populations of species ?
(e) Why is variation during reproduction beneficial to the species but not necessarily for the individual ?
Answer : (a) Tissue culture is the process of propagating new plants from a small piece of a plant's tissue that is obtained from the growing tip of that plant in a suitable growth medium.
(b) Orchids, Dahlia, carnation and Chrysanthemum are propagated by the method of tissue culture.
(c) DNA copying refers to the replication of DNA at the time of cell division. It plays a very important role in giving rise to slight variations in offsprings in comparison to the parents particularly in asexual reproduction where an only single parent is involved.
Example: When a cell divides, the DNA of the cell gets replicated first so that the daughter cells get an equal amount of DNA from the parent. DNA replication occurs through a biochemical process which is not accurate. Hence, variations are introduced in the DNA during replication. When the cell divides, the daughter cells acquire a slightly different DNA to that of the parent. Therefore, the DNA of the daughter cell is similar to that of the parent but not identical.
(d) Reproduction ensures that new offsprings are produced continuously to replace the dying individuals of the population. Thus, it ensures continuity of life and provides stability to the population.
(e) Variation during reproduction ensures that a species can survive and flourish even in adverse conditions. Thus, it is beneficial to the species but not necessary for the individual.

Question. (a) What is a ‘cutting’ in respect of plants for propagation purposes ?
(b) What care should be taken while making a cutting from a plant ?
(c) Describe the cuttings method for the artificial propagation of plants. Illustrate your answer with the help of labelled diagrams.
(d) Name any two plants which are usually propagated by the cuttings method.
Answer : (a) Cutting is a method of vegetative propagation of plants. It is a means of asexual reproduction.
(b) Proper care should be taken while cutting a stem, for this purpose, so as to ensure that the stem has a few buds on it.
(c) In the cutting method, a part of the stem comprising buds on it is cut from the plant using a sharp knife. This stem is then buried in a suitable medium. After some days, the stem develops roots and starts growing into a new plant.
(d) Rose and sugarcane are propagated by the cutting method.

Questions Based on High Order Thinking Skills (HOTS)

Question. There are four tiny organisms A, B, C and D. The organism A is a parasitic protozoan which causes a disease known as kala-azar. The organism B is a microscopic single-celled animal which causes malaria disease in human beings. The organism C is a unicellular animal which can change its body shape according to need, it has no fixed shape. The organism D is also a unicellular animal which is slipper-shaped having a large number of tiny hair all around its body.
(a) Name the organisms A, B, C and D
(b) Name one characteristic body feature of organism A.
(c) Name the insect which carries organism B and transmits it from one person to another.
(d) What name is given to the asexual method of reproduction of (i) organism A, and (ii) organism B ?
(e) Where do organisms C and D live ?
Answer : (a) A is Leishmania, B is Plasmodium, C is Amoeba and D is Paramecium (b) Organism A (Leishmania) has a whip-like structure called flagellum at its one end (c) Female Anopheles mosquito (d) (i) Binary fission (ii) Multiple fission (e) In pond water

Question. Two very small organisms X and Y both reproduce by the method of budding. Organism X is industrially very important because it is used in making alcohol from sugar. It is also used in making bread. Organism Y lives in freshwater. If organism Y gets cut into a number of parts accidently, each cut part can grow to form complete organism.
(a) What are organisms X and Y ?
(b) What is the name of the process in which X converts sugar into alcohol ?
(c) To which class of organisms does X belong ?
(d) Name an important body feature of organism Y.
(e) Which organism is multicellular and which one is unicellular ?
Answer : (a) X is yeast and Y is Hydra (b) Fermentation (c) Fungi (d) Y has tentacles (e) Y is multicellular whereas X is unicellular

Question. When a moist slice of bread was kept aside for a few days then some organism grew on it to form a white cottony mass which later turned black. When this slice of bread was observed through a magnifying glass, then fine thread-like projections and thin stems having bulb-like structures at the top were seen.
(a) What is the common name and scientific name of the organism which grew on the moist slice of bread ?
(b) How did this organism grow on the moist slice of bread automatically ?
(c) What are the fine, thread-like projections on the surface of slice of bread known as ?
(d) What name is given to the knob-like structures and what do they contain ?
(e) What is the name of this method of reproduction ?
(f) Name one unicellular organism which reproduces by this method.
(g) Name two non-flowering plants which reproduce by this method.
Answer : (a) Bread mould ; Rhizopus (b) Spores of bread mould plant are always present around us. One such spore landed on moist slice of bread and finding the conditions favourable (presence of moisture, nutrients and warmth, etc.) grew into bread mould (c) Hyphae (d) Sporangia ; Spores (e) Spore formation (f) Bacteria (g) Ferns and Mosses

Question. A scientist removed some cells from the growing point of a plant and placed it in a suitable medium leading to the formation of a shapeless lump of mass X. X is then transferred to another medium which stimulates it to develop roots. When X with developed roots is placed in a yet another medium, then it develops shoots to form tiny plantlets. These plantlets can then be transplanted in pots or soil where they can grow to form mature plants.
(a) What is the shapeless lump of mass X known as ?
(b) What name is given to this method of producing new plants ?
(c) The growth medium used in this method contains plant nutrients in the form of a ‘jelly’. Name this jelly.
(d) What is the general name of chemicals used to stimulate the growth of plant cells and development of roots and shoots ?
(e) Name any two plants which are produced by this method.
(f) State any two advantages of this method of producing plants.
(g) What is the other name of this method [other than that given in (b) above] ?
Answer : (a) Callus (b) Tissue culture (c) Agar (d) Plant hormones (e) Dahlia and Carnation (f) See page 139 (g) Micropropagation

Question. The stem of a fruit tree X fixed in soil is cut in a slanting way. The upper part of stem of another fruit tree Y of different variety of same species is also cut in a slanting way. The cut stem of tree Y, without roots but having some leaves, is placed over the rooted cut stem of tree X in such a way that their cut surfaces fit together properly. While joining the two cut stems, care is taken to make sure that the layer Z of one cut stem is in contact with layer Z of the other cut stem. The joint of cut stem is bound tightly with a piece of cloth and covered properly with polythene. Soon the cut heals and the two stems grow together and become one fruit tree producing leaves, flowers and fruits.
(a) What is the name of this method of producing plants or trees ?
(b) What name is given to the cut stem of tree X having roots ?
(c) What name is given to the cut stem of tree Y which has no roots but has some leaves ?
(d) Name the layer Z.
(e) Why should the layer Z of one cut stem be in contact with the layer Z of the other cut stem ?
(f) Name any four fruit trees which are usually bred by this technique.
(g) State any one advantage of producing fruit trees by this technique.
Answer : (a) Grafting (b) Stock (c) Scion (d) Cambium layer (e) Because the layer Z (called cambium layer) in the stem is responsible for growth (f) Apple, peach, apricot and pear trees (g) It enables us to combine the most desirable characteristics of the two plants in fruits.

Question. A small part of the shoot of a plant is removed with a sharp knife. When the lower end of this small part of the shoot is buried in moist soil, it gradually develops roots and shoots and grows to become a new plant.
(a) What is the name of this method of propagating plants ?
(b) What care should be taken while removing a small part of the shoot from the parent plant with a knife ?
(c) Name any two plants which provide us with food directly or indirectly and are grown by this method.
(d) Give one advantage of this method of producing new plants.
(e) State whether it is a sexual method of reproduction or an asexual method. Why ?
(f) What special name can be given to the genetically identical new plants produced by this technique ?
Answer : (a) Cuttings method (b) The cutting should have one (or more) bud on it (c) Sugar cane and Banana plants (d) By using the cuttings method, we can produce many new plants from just one plant quickly, without waiting for flowers and seeds (e) Asexual method of reproduction ; Because new plants are produced from a single parent plant without the involvement of sex cells (or gametes) of the plant (f) clones

Question. When the branches of a plant growing in the field are pulled towards the ground and a part of them is covered with moist soil (leaving the tips of the branches exposed above the ground), then after some time new roots develop from the parts of branches buried in the soil. On cutting these branches from the parent plant, new plants are produced from the cut parts of branches which had developed roots.
(a) What is this method of propagation of plants known as ?
(b) What type of branches should a plant have to be able to be propagated by this method ?
(c) Name any two plants which are grown for their flowers and propagated by this method.
(d) Name any two plants which are grown for their fruits and propagated by this method
(e) Name one plant which gets propagated by this method naturally by forming runners (soft horizontal stems running above the ground).
Answer : (a) Layering (b) Slender branches (Thin branches) (c) Jasmine and China rose (d) Lemon and Guava (e) Strawberry

Question. A worm X found in freshwater and slow-moving streams has been accidently cut into three pieces. It was observed that in due course of time, each cut piece of the worm develops to become a complete worm by growing all the missing parts.
(a) Name the worm X which can exhibit this phenomenon of making complete worm from its cut body parts.
(b) Name another organism Y which possesses the same characteristic of growing fully from its cut body parts.
(c) What is the name of this process in which a complete organism is formed from its cut body part.
(d) State whether X and Y are unicellular and/or multicellular organisms.
(e) Can a dog be produced completely from its cut body part (say, a cut tail) just like organisms X and Y ?Why ?
Answer : (a) Planaria (Flatworm) (b) Hydra (c) Regeneration (d) Simple multicellular organisms (e) No ; Because dog is a complex multicellular organism

Question. A thickened underground stem X of a plant which is swollen with stored food has a number of points Y on its surface. When the old stem X is planted in the soil of a field in the next growing season, then each point
Y present on its surface grows into a new plant.
(a) What is the general name of the underground stems like X ?
(b) Give one example of X.
(c) What are points Y present on X known as ?
(d) Is it necessary to plant the whole of stem X in the ground to obtain its new plants ? Explain your answer.
(e) What is the name of this method of reproduction of plants ?
(f) What is the advantage of growing new plants from the underground stems like X ?
Answer : (a) Stem tubers (b) Potato tuber (c) Eyes or Buds (d) No ; Even cut pieces of X can be planted in the soil to obtain new plants provided each cut piece has an eye or bud on it (e) Vegetative propagation by tubers (f) The vegetative propagation method of growing new plants from tubers like X is much faster than the production of new plants from their seeds.

Question. A filamentous alga X is found in ponds, lakes and slow-moving streams. The filament of this alga simply breaks into two (or more) pieces on maturing and each piece then grows to become a complete new alga.
(a) Name an alga which X is likely to be.
(b) What is the colour of X ?
(c) What is the method of forming new algae by the breaking of parent alga known as ?
(d) An Amoeba also breaks up to form two daughter Amoebae. What is the difference in the splitting of Amoeba and splitting of this alga as a method of reproduction ?
(e) Name one marine animal which reproduces in the same way as alga X.
Answer : (a) Spirogyra (b) Green (c) Fragmentation (d) The binary fission in Amoeba is a reproduction process which takes place in unicellular organisms ; Fragmentation in alga is a reproduction process which takes place in simple multicellular organisms (e) Sea anemone

Question. When a broken piece of the stem of a plant X is planted in the soil, a new plant grows from it in a week’s time. The leaves of plant X also have many small entities Y in their margins which can fall to the ground alone or alongwith leaves and grow into new plants.
(a) Name a plant which X could be.
(b) What are the entities Y present on the leaves of X known as ?
(c) Name a plant other than X which can be reproduced from its leaves.
(d) Name a common plant grown in many homes which can be propagated from its broken stems like plant X.
(e) Name a kind of dormant organs present in dry stems of old grass plants lying in the fields which get activated and produce green grass plants after the rains.

Answer : (a) Bryophyllum (b) Buds (c) Begonia (d) Money plant (e) Buds.

Question. What is the importance of DNA copying in reproduction ?
Answer : (i) The chromosomes in the nucleus of a cell contain information for the inheritance of features from the parents to next generation in the form of DNA (Deoxyribo Nucleic Acid) molecules. So, the first importance of DNA copying is that the characteristics of the parent organism are transmitted to its offsprings. (ii) When the DNA already present in the nucleus of a parent cell is copied by making more of DNA by certain biochemical reactions, then slight variations come in the two copies formed. These slight variations in the copying of DNA molecules lead to slight variations in the offspring produced. Thus, another importance of DNA copying is that some variations are produced in the offsprings during reproduction which form the basis for evolution.

Question. Why is variation beneficial to the species but not necessarily for the individual ?
Answer : Variation is useful for the survival of a species even in adverse environmental conditions. This happens as follows : There may be some drastic changes like excessive heat or cold or shortage of water (drought), etc., in the habitat of a species of organisms. Now, if all the organisms of a population living in that habitat are exactly identical, then there is danger that all of them may die and no one would survive under those conditions. This will eliminate the species from that habitat completely. However, if some variations are present in some individual organisms to tolerate excessive heat or cold or survive on meagre water supply, then there is a chance for them to survive and flourish even in adverse environment. For example, if there is a population of certain bacteria living in temperate water (which is neither very hot nor very cold) and the temperature of water increases too much due to global warming, then most of these bacteria will not be able to tolerate excessive heat and hence die. But some bacteria which had variations to resist heat would survive and grow further.

Question. How does binary fission differ from multiple fission ?
Answer : In binary fission, the parent organism splits (or divides) to form two new organisms. On the other hand, in multiple fission the parent organism splits (or divides) to form many new organisms simultaneously. Amoeba reproduces by the process of binary fission whereas the malarial parasite Plasmodium reproduces by the process of multiple fission.

Question. How will an organism be benefitted if it reproduces through spores ?
Answer : The reproduction by spores takes place in plants. Spores are covered by hard protective coat which enables them to survive under unfavourable conditions like lack of food, lack of water and extreme temperatures. But when the conditions become favourable (food and water are available, and temperature is suitable), then the spores can grow to produce new plants. Thus, the reproduction by spores benefits the plants because by surviving under adverse conditions, the spores make these plants live for ever.

Question. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration ?
Answer : In complex multicellular organisms, specialised cells make up tissues; tissues make up organs; organs make up organ systems; and finally organ systems make up organisms. Since complex multicellular organisms have a very high degree of organisation in their body, they cannot be reproduced from their cut body parts by the process of regeneration. For example, a dog is a complex multicellular organism which cannot be regenerated from its cut body part say, a cut tail. This is because the cells present in the cut tail of a dog cannot produce dog’s organs like heart, brain, lungs, stomach, intestines and limbs, etc., needed for the making of a complete dog. The complex multicellular organisms need more complex ways of reproduction like sexual reproduction.

Question. Why is vegetative propagation practised for growing some types of plants ?
Answer : Vegetative propagation is practised for growing some type of plants because it has the following advantages : (i) All the plants produced by vegetative propagation are genetically similar enough to the parent plant to have all its characteristics. (ii) The fruit trees grown from seeds may take many years before they start to bear fruits. But the fruit trees grown by vegetative propagation methods like cuttings or by grafting start to bear fruits much earlier (only after a few growing seasons). (iii) The plants grown by vegetative propagation usually need less attention in their early years than the plants grown from seeds. (iv) Many plants can be grown from just one parent plant by artificial propagation. (v) Vegetative propagation makes possible the propagation of plants such as banana, rose, jasmine and orange that have lost the capacity to produce viable seeds.

Question. Why is DNA copying an essential part of the process of reproduction ?
Answer : DNA contains information for the inheritance of characteristics from the parents to the next generation. DNA copying is an essential part of the process of reproduction because it makes possible the transmission of characteristics of the parents to its offsprings in the next generation.

Question. How is the process of pollination different from fertilisation ?
Answer : Pollination is the transfer of pollen grains from the anther of stamen of a flower to the stigma of a carpel in the same flower or another flower of the same species. On the other hand, fertilisation occurs when the male gamete present in the pollen grain joins with the female gamete (or egg) present in ovule to form a zygote.

Question. What is the role of seminal vesicles and prostrate gland ?
Answer : Seminal vesicles and prostrate gland occur in male reproductive system. The seminal vesicles and prostrate gland add their secretions to the vas deferens which carries sperms from the testes. The secretions of seminal vesicles and prostrate gland provide nutrition to the sperms and also make their further transport easier.

Question. What are the changes seen in girls at the time of puberty ?
Answer : The various changes which occur in girls at puberty are : Hair grow under armpits and pubic region. Mammary glands (or breasts) develop and enlarge. The hips broaden. Extra fat is deposited in various parts of the body like hips and thighs. Fallopian tubes, uterus and vagina enlarge. Ovaries start to release eggs. Menstruation (monthly periods) starts. Feelings and sexual drives associated with adulthood begin to develop.

Question. How does the embryo get nourishment inside the mother's body ?
Answer : The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. Placenta is a disc-shaped tissue which is embedded in the uterus wall (uterine wall). It has villi on the embryo side of the tissue. On the mother’s side are blood spaces which surround the villi. Placenta provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The developing embryo also produces waste substances which can be removed by transferring them into the mother’s blood through the placenta.

Question. If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases ?
Answer : No, the use of copper-T for contraception will not protect a woman from sexually transmitted diseases.

Question. Asexual reproduction takes place through budding in :
(a) amoeba
(b) yeast
(c) plasmodium
(d) leishmania
Answer : (b) yeast

Question. Which of the following is not a part of the female reproductive system in human beings ?
(a) ovary
(b) uterus
(c) vas deferens
(d) fallopian tube
Answer : (c) vas deferens

Question. The anther contains :
(a) sepals
(b) ovules
(c) carpel
(d) pollen grains
Answer : (d) pollen grains

Question. What are the advantages of sexual reproduction over asexual reproduction ?
Answer : (i) Sexual reproduction combines DNA from two individuals (male and female) due to which the offspring has a lot of variations. On the other hand, in asexual reproduction, only the DNA of one individual is copied due to which the variations in the offspring are extremely small. (ii) Due to lot of variations sexual reproduction allows species to change to more advanced forms from one generation to the next and speed up evolution. On the other hand, asexual reproduction does not allow a species to change much from one generation to the next and hence evolution becomes very, very slow.

Question. What are the functions performed by testes in human beings ?
Answer : The function of testes is to make male sex cells (or male gametes) called sperms and also to make the male sex hormone called testosterone. The testosterone hormone brings about changes seen in the appearance of boys at the time of puberty such as deeper voice, beard, moustache, and more body hair (than girls).

Question. Why does menstruation occur ?
Answer : Since the ovary of a woman releases one egg (or ovum) every month, therefore, the uterus also prepares itself every month to receive a fertilised egg (if formed). In this process, the inner lining of the uterus becomes thick and soft with lots of blood capillaries (blood vessels) in it. This preparation in uterus is necessary because in case the egg is fertilised by a sperm, then the uterus has to keep this fertilised egg and nourish it to develop it into a baby. If, however, the egg released by the ovary is not fertilised, then the thick lining of the uterus is not needed. So, the uterus lining breaks down and comes out through the vagina in the form of blood and mucous. This is called menstruation.

Question. What are the different methods of contraception ?
Answer : The various methods of contraception (preventing pregnancy in woman) are : Barrier methods, Chemical methods, use of Loop or Copper–T, and Surgical methods. (i) In the barrier methods of preventing pregnancy, the physical devices such as condoms and diaphragm (or cap) are used. Condoms are used by males (by putting them as a covering on the penis). Diaphragm (or cap) is used by females (by putting it in the vagina to cover the cervix). Condom as well as diaphragm prevent the sperms from meeting the ovum (or egg) by acting as a barrier between them. (ii) In the chemical methods of preventing pregnancy, the females use oral pills. The oral pills contain hormones which stop the ovaries from releasing ovum (or eggs) into the oviduct. (iii) The loop or copper–T are also very effective in preventing pregnancy. A loop or copper–T is placed inside the uterus by a doctor or a trained nurse. The loop or copper–T prevents the implantation of fertilised egg in the uterus. Loop and copper–T are called intra-uterine contraceptive devices (IUCD). (iv) Surgical methods of birth control are available for males as well as females. In males, a small portion of the sperm duct (or vas deferens) is removed by surgical operation and both the cut ends are ligated (or tied) properly. This prevents the sperms from coming out. The surgical procedure carried out in males is called ‘vasectomy’. In females, a small portion of the oviducts is removed by surgical operation and the cut ends are ligated (or tied). This prevents the ovum (or egg) from entering into the oviducts. The surgical procedure carried out in females is called tubectomy.

Question. How are the modes of reproduction different in unicellular and multicellular organisms ?
Answer : (a) Most of the unicellular organisms (such as protozoa and bacteria) reproduce by the asexual process of ‘fission’. In this process, mere cell division leads to the creation of new individuals. (b) In simple multicellular organisms, reproduction occurs by asexual methods such as budding, spore formation, fragmentation and regeneration, etc. But in complex multicellular organisms, reproduction takes place by sexual methods involving gametes (sex cells) from two parents — a male and a female.

Question. How does reproduction help in providing stability to populations of species ?
Answer : The process of reproduction introduces some variations in the individual organisms of a species. The variations introduced in some individual organisms may enable them to survive even in adverse environmental conditions such as excessive heat or cold or shortage of water, etc. (when most other members of the species will die). In this way, the introduction of variations during reproduction provides stability to the populations of various species by preventing some of their individuals from getting wiped out during adverse environmental conditions.

Question. What could be the reasons for adopting contraceptive methods ?
Answer : (i) The use of contraceptive methods helps in family planning (birth control). By adopting contraceptive methods, a couple can avoid unwanted pregnancy. They can choose how many children to have and when to have them. A couple can also space the birth of children properly by using contraceptive methods. (ii) Some of the contraceptive methods (like the use of condom) also provide protection to a person from sexually transmitted diseases.

Please click on below link to download CBSE Class 10 Biology How do Organisms Reproduce Worksheet