How do Organisms Reproduce?- Lakhmir Singh Manjit Kaur Solutions Pg No. 145 Class 10 Biology

Solutions of How do Organisms Reproduce? Lakhmir Singh Manjit Kaur HOTS and SAQ Pg No. 145 Class 10 Biology

Solutions of How do Organisms Reproduce? Lakhmir Singh Manjit Kaur HOTS and SAQ Pg No. 145 Class 10 Biology

Questions Based on High Order Thinking Skills (HOTS)-Pg-145

80. 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 slippet-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 Band 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) Leishmania (A) has a whip-like structure called flagellum at its one end.
(c) Female Anopheles mosquitocarries plasmodium (B) and transmits it from person to person.
(d) (i) Leishmania (A) reproduces by binary fission. (ii) Plasmodium (B) reproduces by multiple fission.

(e) Amoeba (C) and Paramecium (D) live in pond water.

81. 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) The process by which sugar converts into alcohol is fermentation.
(c) Yeast (X) belongs to class fungi.
(d) Hydra (Y) has tentacles that wave in the water.
(e) Yeast (X) is unicellular and Hydra (Y) is multicellular.

82. 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) Common name-Bread mould; Scientific name-Rhizopus fungus
(b) Spores of rhizopus fungus (bread mould) are always present in air. These air-borne spores landed on moist slice of bread, under favorable conditions like presence of moisture, nutrients and warmth, they grew and produced new individuals.
(c) The fine, thread-like projections on the surface of slice of bread are known as hyphae.
(d) The knob-like structures are called sporangia and they contain spores.
(e) It is type of asexual reproduction method called spore formation.
(f) Bacteria (unicellular organism) reproduces by this method.
(g) Ferns and Mosses are two non-flowering plants which reproduce by spore formation.

83. 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) The shapeless lump of mass (X) is known as callus.
(b) This method is known as tissue culture.’
(c) The growth medium used in this method contains plant nutrients in the form of a 'jelly'. This jelly is known as agar.
(d) The general name of chemicals used to stimulate the growth of plant cells and development of roots and shoots is known as plant hormones.
(e) Dahlia and Carnation
(f) Advantages: (i) The new plants produced by tissue culture are disease free.
(ii) Tissue culture can grow plants round the year, irrespective of weather or season.
(g) The other name of tissue culture is micropropagation.

84. 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 y four fruit trees which are usually bred by this technique.
(g) State any one advantage of producing fruit trees by this technique.

Answer

→ (a) The method of producing plants or trees is known as grafting.
(b) The cut stem of a plant having roots and fixed in soil is called stock.
(c) The cut stem of plant which has no roots but has some leaves is called scion.
(d) Z is cambium layer.
(e) The layer Z called cambium layer of one stem be in contact with the layer of the other cut stem because cambium layer in the stem is responsible for growth.
(f) Peach, apple, apricot and pear trees are usually bred by the grafting method.
(g) Advantage: It enables us to combine the most desirable characteristics of the two plants in its flowers and fruits.

85. 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) It is cutting method for propagation of plants.
(b) While cutting, care should be taken to see that there are some buds on it.
(c) Sugarcane and banana are two plants which provide us with food directly or indirectly and are grown by cutting method.
(d) By using the cuttings method, we can produce many new plants from just one plant quickly, without waiting for flowers and seeds.
(e) Cutting method is an asexual method because only single parent involved in it without forming gametes.
(f) Clones.

86. 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) This method of propagation of plants is known as layering.
(b) Slender branches (Thin branches)
(c) Jasmine and China rose plants are grown for their flowers and propagated by layering method.
(d) Lemon and guava plants are grown for their fruits and propagated by layering method.
(e) Strawberry plant reproduces naturally by layering method by forming runners (soft horizontal stems running above the ground).

87. 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) Worm (X) is planaria.
(b) Organism (Y) is hydra.
(c) Regeneration is the process in which a complete organism is formed from its cut body part.
(d) X and Y are simple multicellular organisms.
(e) No, dog cannot be produced completely from its cut body part because dog is a complex multicellular organism.

88. 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 (X)
(b) Potato tuber
(c) Eyes or Buds
(d) No, it is not necessary, even cut pieces of stem tuber (X) can be planted in the soil to produce new plants provided each cut piece has an eye or bud on it
(e) Vegetative propagation by tubers
(f) The method of vegetative propagation is much faster than the production of new plants from their seeds.

89. 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 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 (X)
(b) The colour of spirogyra (X) is green.
(c) Fragmentation is the method of forming new algae by the breaking of parent alga.
(d) Amoeba is a unicellular organism which reproduces by the asexual method called binary fission whereas alga is a multicellular organism which reproduces by the asexual method called fragmentation.
(e) Sea anemone

90. 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' 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 activated and produce green grass plants after the rains.

Answer

→ (a) The plant (X) could be bryophyllum.
(b) Buds (Y) are present on the leaves of bryophyllum (X).
(c) Begonia is also reproduced from its leaves.
(d) Money plant
(e) Buds are dormant organs which present in dry stem of old grass lying in the fields and activated and produce green grass plants after the rains.

Very Short Answer Type Questions-Pg-168

1. Where are a plant's sex organs located?

Answer

→ The plant’s sex organs are located in flowers.

2. What is the function of a flower ?

Answer

→ The main function of flower is reproduction. The reproductive parts of a flower produce male and female gametes that take part in reproduction.

3. What are the reproductive organs in a flower ?

Answer

→ The reproductive organs in a flower are stamen and carpel.

4. What is the name of :
(a) male part of a flower?
(b) female part of a flower ?

Answer

→ (a) Stamen is a male part of a flower.
(b) Carpel is a female part of a flower.

5. What is the name of female organ of a flower (other than carpel)?

Answer

→ The female organ of a flower is called the carpel or pistil.

6. What is the other name of sex cells?

Answer

→ Sex cells are also known as gametes.

7. What is the name of sex cells (other than gametes)?

Answer

→ The sex cells are also known as germ cells.

8. Name the male and female gametes in animals.

Answer

→ In animal, the male gamete is sperm and female gamete is ovum (egg).

9. Where is the male gamete formed :
(i) in humans ?
(ii) in flowering plants ?

Answer

→ (i) In humans, the male gamete is formed in testes.
Tagging ||| Biology||How Do Organisms Reproduce||Male and Female Reproductive System
(ii) In flowering plants, the male gamete is formed in anther.

10. Where is the female gamete formed :
(i) in humans ?
(ii) in flowering plants?

Answer

→ In humans, the female gamete is formed in ovary.
Tagging ||| Biology||How Do Organisms Reproduce||Male and Female Reproductive System
(ii) In flowering plants, the female gamete is formed in ovary.

11. Name two animals which undergo external fertilisation and two animals which undergo internal fertilisation?

Answer

→ External fertilization: Frog and fish
Internal fertilization: Human and cow

12. Define sexual reproduction.

Answer

→ Sexual reproduction is a form of reproduction in which fusion of two special reproductive cells called 'sex cells' takes place.

13. Do all organisms give birth to individuals like humans?

Answer

→ No. All organisms do not give birth to individuals like humans.

14. Write the full forms of the following as they occur in biology:
(i) STD (ii) AIDS (iii) HIV

Answer

→ (i) STD - Sexually Transmitted Diseases.
(ii) AIDS - Acquired Immune Deficiency Syndrome.
(iii) HIV - Human Immunodeficiency virus.

15. What is the causative organism for the following diseases ?
(i) Gonorrhoea
(ii) Syphilis
(iii) AIDS

Answer

→ (i) Gonorrhoea---- Bacteria
(ii) Syphilis----- Bacteria
(iii) AIDS---- Virus

16. What are the organs in humans which produce the gametes ?

Answer

→ In humans, the reproductive organs are testes (in male) and ovaries (in female).

17A. What are the male sex cells in humans called?

Answer

→ The male sex cells in humans are called sperms.

17B. Name the organ which produces male sex cells.

Answer

→ Testes produce male sex cells (sperms).

18A. What are the female sex cells in humans called?

Answer

→ The female sex cells in humans are called eggs.

18B. Name the organ which produces female sex cells.

Answer

→ Ovary produces female sex cells called eggs.

19. Which part of the human body :
(a) produces sperms ?
(b) produces ova ?
(c) passes sperms from a map to a woman?

Answer

→ (a) In human body, testes produce sperms.
(b) In human body, ovaries produce eggs.
(c) Penis is a part of male reproductive system which transfer sperms into a woman.

20A. What do the testes in a man produce ?

Answer

→ Testes in a man produce male gametes called sperms.

20B. What do the ovaries in a woman produce ?

Answer

→ Ovaries in a woman produce female gametes called eggs.

21A. Where in the human body does an ovum get fertilised?

Answer

→ In the human body, fertilization takes place in the fallopian tube (oviduct).

21B. Where does a fertilised ovum develop into a baby in the human body?

Answer

→ In the human body, the development of a fertilized ovum into a baby occurs in the uterus.

22. Name the liquid that contains sperms.

Answer

→ The liquid containing sperm is known as semen.

23. What is the name of the process in which thickened uterus lining along with blood vessels is removed from the body of a human female through vaginal bleeding?

Answer

→ Menstruation is a process in which blood and mucous flows out every month through the vagina.

24A. For how much time does menstruation last in human females (or women)?

Answer

→ Menstruation usually lasts for 3 to 5 days in human females.

24B. What is the frequency of menstrual cycle in human females (or women)?

Answer

→ The frequency of menstrual cycle in human females is once in a month if egg is not fertilised.

25. Fill in the following blanks with suitable words :
(a) Pollen grains contain ................ gametes of a plant.
(b) Ovules contain ................ gametes of a plant.
(c) The ovary of a flower becomes ................ after fertilisation.
(d) The ovule becomes a .......... after fertilisation.
(e) Flowering plants reproduce by.................method of reproduction.
(f) The female organ of reproduction in the flower is the ...................
(g) The male organ of reproduction in the flower is the .................... .
(h) The name of the structure in the flower in which the male gamete is formed is ............
(i) The ................ at the base of the carpel contains egg cells.
(j) The term used to refer to the transfer of pollen from the stamen of one flower to the carpel of another flower of the same species is ................
(k) The cells involved in sexual reproduction are called ................
(l) Fusion of gametes gives rise to a single cell called ................
(m) The process of fusion of gametes is called ................
(n) A multicellular animal starts its life from a ................ through sexual reproduction.
(o) The union of a sperm nucleus with an egg nucleus is known as .................... and results in a ..................egg.
(p) The menstrual cycle is controlled by.....

Answer

→ (a) male (b) female (c) fruit (d) seed (e) sexual (f) carpel (g) stamen (h) anther (i) ovary (j) cross-pollination (k) gametes (l) zygote (m) fertilisation (n) single cell (zygote) (o) fertilisation ; fertilised (p) hormones

Short Answer Type Questions-Pg-169

26A. What are gametes?

Answer

→ Gametes are reproductive cells which take part in reproduction.

26B. In which sort of reproduction are gametes involved ?

Answer

→ Gametes are involved in sexual reproduction.

26C. What is formed when two gametes fuse?

Answer

→ Zygote is formed by the fusion of two gametes.

26D. What is this act of fusion called ?

Answer

→ Fusion of male and female gametes is called fertilisation.

27A. Write the names of (a) male sex hormone, and (b) female sex hormones.

Answer

→ Testosterone is a male sex hormone.

27B. What name is given to the fusion of sperm and ovum?

Answer

→ Oestrogen and Progesterone are female sex hormones.

27C. Name the tissue through which the foetus gets all the requirements from the mother's body.

Answer

→ The fusion of sperm and ovum is known as fertilisation.
Placenta is a special tissue between developing foetus and uterine wall through which the foetus gets all the requirements from the mother's body.

28A. Draw a neat sketch of the stamen of a flower. Mark in it filament and anther.

Answer



28B. Draw a neat sketch of the carpel of a flower. Mark in it stigma, style and ovary.

Answer



28C. What is made in (i) anther, and (ii) ovary, of a flower?

Answer

→ (i) Male gametes inside the anther and (ii) female gametes inside the ovary.

29A. Explain the terms 'self pollination' and 'cross-pollination' ?

Answer

→ Self-pollination: when pollen grains of a flower are transferred to the stigma of the same flower (or another flower on the same plant) is known as self-pollination.
Cross-pollination: When pollen grains of one flower are transferred to the stigma of another plant is known as cross-pollination.

29B. How do the insects help in cross-pollination?

Answer

→ Insects moves from flower to flower to suck nectar. When an insect sits on the flower of a plant, pollen grains from the anther of this flower get attached to its body. And When this insect sits on another flower of similar plant (or another plant), these pollen grains are transferred to the stigma of the other flower. Thus, insects help in cross-pollination.

29C. How is the process of pollination different from fertilization?

Answer

→ Pollination is the process of transfer of pollen grains from anther to the stigma. It occurs with the help of certain pollinator such as wind, water, insects, etc. Fertilisation, in other hand, is the fusion of male and female gametes. It occurs inside the ovule and leads to the formation of zygote.

30A. Explain the term 'fertilisation'.

Answer

→ The fusion of male and female gametes to form zygote is known as fertilisation.

30B. Give some examples of different modes of fertilisation in nature ?

Answer

→ The modes of fertilisation in nature are internal fertilisation and external fertilisation.

30C. What type of fertilisation takes place in (i) fish, and (ii) bird?

Answer

→ (i) External fertilisation takes place in fish.
(ii) Internal fertilisation takes place in birds.

31A. What are the male and female gonads in human beings? Mention their functions.

Answer

→ Testes are male gonads in human beings.
Functions of testes: (i) To produce sex cells called sperms.
(ii) To produce sex hormone called testosterone.
Ovaries are female gonads in human beings.
Functions of Ovaries - (i) To produce sex cells called ova or egg.
(ii) To produce female sex hormones called oestrogen and progesterone.

31B. State the advantages of sexual reproduction over asexual reproduction.

Answer

→ Advantages of sexual reproduction:
(i) In sexual reproduction, offspring has lot of variation because DNA of both individuals (male and female) get combine whereas in asexual reproduction, DNA of one individual is copied so, offspring has small variations.
(ii) In sexual reproduction, produced offspring has characteristics of both the parents.
(iii) 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 whereas asexual reproduction does not allow a species to change much from one generation to the next and hence, evolution becomes very slow

32. Describe the various steps involved in the sexual reproduction in animals. Draw labelled diagrams to show the fertilisation of an ovum (or egg) by a sperm to form a zygote.

Answer

→ Following steps are involved in the process of sexual reproduction in animal:
(i) In animal, male parent produce male gametes called sperms. Millions of sperms are produced by testes (male gonad). The sperm is very small in size and has a head, a middle piece and a tail.
(ii) The female parent produces female gamete called ova (eggs) which is much bigger cell than the sperm, having a lot of cytoplasm. Like a sperm, an egg is also a single cell.
(iii) The next step is fertilisation. In this step, sperm enters the ovum and fuses with it to form a new cell called zygote. The zygote is the beginning of a new individual.(iv) In this step, zygote begins to develop into an embryo. The zygote divides repeatedly to form a large number of cells and ultimately the zygote grows and develops to form a baby.


33. Why does menstruation occur? Describe the menstrual cycle in human females (or women).

Answer

→ In female, ovary produces one egg every month. The uterus also prepares itself to receive a fertilised egg. So, the wall of uterus becomes thick and soft containing lots of blood capillaries. If egg gets fertilised with sperm, then fertilised egg gets attached with uterus wall and gets nourishment from it. In case, egg is not fertilised, then the inner lining of uterus breaks down and comes out in the form of blood and mucus through the vagina. This cycle occurs every month and is called menstruation.
Menstrual Cycle:
(i) Menstrual cycle begins when a girl reaches the age of puberty. At this age, ovaries release sex hormones in the blood which cause maturation of ova in ovaries.
(ii) One mature egg is released from the ovary into fallopian tube. This is termed as ovulation.
(iii) Before ovulation, uterus prepares itself to receive the fertilised egg. The inner linning of the uterus becomes thick and soft with lots of blood capillaries in it.
(iv) If the ovum does not get fertilised, then the inner lining of uterus is not required and hence it breaks down and comes out through the vagina in the form of blooding called menstruation.
(v) Menstruation usually lasts for 3 to 5 days.
(vi) After menstruation is over, the inner lining of the uterus starts building up again so that it becomes ready to receive the next ovum in case it gets fertilised.
(vii) If the ovum does not get fertilised even now, then the menstruation takes place again and this cycle goes on repeating.

34A. Write the various steps involved in the sexual reproduction in plants.

Answer

→ Following steps are involved in the process of sexual reproduction in plant:
(i) The male reproductive part of a flower is called stamen which consists a filament and an anther. Anther contains pollen grains.
(ii) The female reproductive part of a flower called carpel makes the female gametes. These gametes are present in the ovules and are called ova or egg.
(iii) The male gamete in the pollen grain fuses with the female gamete in the ovule to form a zygote (fertilised egg cell). This process of fusion is known as fertilisation.
(iv) The zygote grows within ovule and becomes seed.
(v) The seed produces new plant on germination.

34B. Name two plants which reproduce by sexual reproduction method and two plants which reproduce by asexual reproduction methods.

Answer

→ Sexual reproduction: Sunflower plant and wheat plant
Asexual reproduction: Ferns and mosses.

35A. What type of plants reproduce by sexual reproduction method?

Answer

→ Flowering plants reproduce by sexual reproduction.

35B. What is a seed? What are the parts of a seed? Explain with the help of a labelled diagram.

Answer

→ Seed is reproductive unit of a plant which is capable to grow another such plant.
A seed is the reproductive unit of a plant (which can be used to grow a new plant). The parts of a seed are plumule, radical and cotyledon.


36A. What is puberty ? Who attains puberty at an earlier age in human beings : male or female (boy or girl) ?

Answer

→ (a) The age at which boy and girl become sexually mature and able to reproduce is called puberty. Females attain puberty at an age of 10-12 years.
(b) Functions of testes: (i) To produce sex cells called sperms.
(ii) To produce sex hormone called testosterone.

36B. Mention two functions each of (i) human testes, and (ii) human ovaries.

Answer

→ Functions of Ovaries-(i) To produce sex cells called ova or egg.
(ii) To produce female sex hormones called oestrogen and progesterone.

37A. What is gestation period ? How much is the gestation period in humans?

Answer

→ Gestation is the time period from the fertilisation up to the birth of a baby. The average gestation period in humans is about 9 months (about 38 weeks).

37B. Name one method of contraception which also protects against sexually transmitted diseases.

Answer

→ Sexually transmitted diseases are prevented to some extent by using condoms.

37C. Name one sexually transmitted disease for which no definite cure has been found so far. What is the causative organism of this disease ?

Answer

→ AIDS is a sexually transmitted disease for which no definite cure has been found so far. HIV is the causative organism for AIDS.

38. What are the three types of methods used for birth control (or regulating child birth)? Give one example of each type.

Answer

→ There are three methods used for birth control:
(a) Barrier method – Diaphragm (or Cap).
(b) Chemical method - Oral pills.
(c) Surgical method - Tubectomy.

39A. What is the name of surgical method of birth control in human males in which the sperm ducts are cut and ligated (tied) at both ends?

Answer

→ Vasectomy is the surgical method of birth control in human males in which the sperm ducts are cut and ligated (tied) at both ends.

39B. What is the name of surgical method of birth control in human females in which the oviducts are cut and ligated (tied) at both ends?

Answer

→ Tubectomy is the surgical method of birth control in human females in which the oviducts are cut and ligated (tied) at both ends.

39C. Name the contraceptive device used by the human males which acts as a sheath over the male organ and traps the sperms in it.

Answer

→ Condom is a contraceptive device used by the males which acts as a sheath over the male organ and traps the sperms in it.

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