NCERT Exemplar Solution Class 10 Science Chapter 8

NCERT Exemplar Solution Class 10 Science Chapter 8

NCERT Exemplar Solution Class 10 Science Chapter 8 How do Organisms Reproduce all Questions Answer Solution. NCERT Exemplar Class 10 Science Chapter 8 Solution PDF.

NCERT Exemplar Solution Class 10 Science Chapter 8: Overview

NCERT Exemplar Solution Class 10 Science Chapter 8

Board

NCERT
Topic

Exemplar Problem Solution

Class

10
Subject

Science

Chapter

8
Chapter Name

How do Organisms Reproduce

NCERT Exemplar Solution Class 10 Science Chapter 8 How do Organisms Reproduce

Multiple Choice Questions

1.) In the list of organisms given below, those that reproduce by the

asexual method are

(i) banana

(ii) dog

(iii) yeast

(iv) Amoeba

(a) (ii) and (iv) (b) (i), (iii) and (iv)

(c) (i) and (iv) (d) (ii), (iii) and (iv)

Answer: Answer is B. The except dog all reproduces via asexual mode of reproduction, in case of dog involvement of 2 parents.

2.) In a flower, the parts that produce male and female gametes (germ cells) are

(a) stamen and anther

(b) filament and stigma

(c) anther and ovary

(d) stamen and style

Answer: Answer is C. The filament produces male gametes whereas stigma responsible for female gametes.

3.) Which of the following is the correct sequence of events of sexualreproduction in a flower?

(a) pollination, fertilisation, seedling, embryo

(b) seedling, embryo, fertilisation, pollination

(c) pollination, fertilisation, embryo, seedling

(d) embryo, seedling, pollination, fertilization

Answer: Answer is C. pollination, fertilisation, embryo, seedling, because when pollen grain reaches to stigma pollination occurs, due to which male and female gametes fused and fertilization occur, it leads to formation of embryo and seedling.

4.) Offspring formed by asexual method of reproduction have greater similarity among themselves because

(i) asexual reproduction involves only one parent

(ii) asexual reproduction does not involve gametes

(iii) asexual reproduction occurs before sexual reproduction

(iv) asexual reproduction occurs after sexual reproduction

(a) (i) and (ii) (b) (i) and (iii)

(c) (ii) and (iv) (d) (iii) and (iv)

Answer: Answer is A, asexual reproduction involves only one parent and asexual reproduction does not involve gametes which is opposite to sexual reproduction.

5.) Characters transmitted from parents to offspring are present in

(a) cytoplasm

(b) ribosome

(c) golgi bodies

(d) genes

Answer: Answer is D. Because the gene are the major source of heredity.

6.) Characters that are transmitted from parents to offspring duringreproduction show

(a) only similarities with parents

(b) only variations with parents

(c) both similarities and variations with parents

(d) neither similarities nor variations

Answer: Answer is C. Because 2 parents are involved and blending of characters take place.

7.) A feature of reproduction that is common to Amoeba, Spirogyra and Yeast is that

(a) they reproduce asexually

(b) they are all unicellular

(c) they reproduce only sexually

(d) they are all multicellular

Answer: Answer is A, some of them are unicellular or multicellular, and no on reproduces sexually, therefore the answer is A.

8.) In Spirogyra, asexual reproduction takes place by

(a) breaking up of filaments into smaller bits

(b) division of a cell into two cells

(c) division of a cell into many cells

(d) formation of young cells from older cells.

Answer: Answer is A Fragmentation is a process of sexual reproduction majorly takes place in spirogyra.As the spirogyra gets mature, the body of spirogyra can be broken down into several pieces.

9.) The ability of a cell to divide into several cells during reproductionin Plasmodium is called

(a) budding

(b) reduction division

(c) binary fission

(d) multiple fission

Answer: Answer is D. Because several division can occur via multiple fission and not other methods.

10.) The correct sequence of reproductive stages seen in flowering plants is

(a) gametes, zygote, embryo, seedling

(b) zygote, gametes, embryo, seedling

(c) seedling, embryo, zygote, gametes

(d) gametes, embryo, zygote, seedling

Answer: Answer is A. First the gametes will form, the fusion of gametes will lead to formation of zygote, as the stage goes, the zygote will progress into an embryo and seedling starts.

11.) The number of chromosomes in parents and offsprings of aparticular species remains constant due to

(a) doubling of chromosomes after zygote formation

(b) halving of chromosomes during gamete formation

(c) doubling of chromosomes after gamete formation

(d) halving of chromosomes after gamete formation

Answer: Answer is B. halving of chromosomes during gamete formation which is meiosis also called as reductional division.

12.) In Rhizopus, tubular thread-like structures bearing sporangia attheir tips are called

(a) filaments

(b) hyphae

(c) rhizoids

(d) roots

Answer: Answer is B, hyphae are present at tip all other parts are present on roots.

13.) Vegetative propagation refers to formation of new plants from

(a) stem, roots and flowers

(b) stem, roots and leaves

(c) stem, flowers and fruits

(d) stem, leaves and flowers

Answer: Answer is Bstem, roots and leaves because fruits and flowers are involved in sexual reproduction.

14.) Factors responsible for the rapid spread of bread mould on slicesof bread are

(i) large number of spores

(ii) availability of moisture and nutrients in bread

(iii) presence of tubular branched hyphae

(iv) formation of round shaped sporangia

(a) (i) and (iii) (b) (ii) and iv)

(c) (i) and (ii) (d) (iii) and (iv)

Answer: Answer is A. As they get nutrients on moist bread therefore the environment becomes favourable for their growth.

15.) Length of pollen tube depends on the distance between

(a) pollen grain and upper surface of stigma

(b) pollen grain on upper surface of stigma and ovule

(c) pollen grain in anther and upper surface of stigma

(d) upper surface of stigma and lower part of style

Answer: Answer is B, pollen grain on upper surface of stigma and ovule on this factor majorly length of pollen tube depends.

16) Which of the following statements are true for flowers?

(i) Flowers are always bisexual

(ii) They are the sexual reproductive organs

(iii) They are produced in all groups of plants

(iv) After fertilisation they give rise to fruits

(a) (i) and (iv) (b) (ii) and (iii)

(c) (i) and (iii) (d) (ii) and (iv)

Answer: Answer is D, they are the sexual reproductive organs and after fertilisation they give rise to fruits, these 2 answers are correct.

17.) Which among the following statements are true for unisexual flowers?

(i) They possess both stamen and pistil

(ii) They possess either stamen or pistil

(iii) They exhibit cross pollination

(iv) Unisexual flowers possessing only stamens cannot produce fruits

(a) (i) and (iv) (b) (ii), (iii) and (iv)

(c) (iii) and (iv) (d) (i), (iii) and (iv)

Answer: Answer is B, unisexual flower are those which contain only one type of gamete, therefore self pollination is not possible.

18.) Which among the following statements are true for sexualreproduction in flowering plants?

(i) It requires two types of gametes

(ii) Fertilisation is a compulsory event

(iii) It always results in formation of zygote

(iv) Offspring formed are clones

(a) (i) and (iv) (b) (i), (ii) and (iv)

(c) (i), (ii) and (iii) (d) (i), (ii) and (iv)

Answer: Answer is C, for sexual reproduction in flowering plants the two gametes required and when this 2 gametes fuse zygote formation occurs.

19.) In Figure 8.1, the parts A, B and C are sequentially

(a) cotyledon, plumule and radicle

(b) plumule, radicle and cotyledon

(c) plumule, cotyledon and radicle

(d) radicle, cotyledon and plumule

Answer: Answer is C.

20.) Offspring formed as a result of sexual reproduction exhibit morevariations because

(a) sexual reproduction is a lengthy process

(b) genetic material comes from two parents of the same species

(c) genetic material comes from two parents of different species

(d) genetic material comes from many parents

Answer: Answer is B.genetic material comes from two parents of the same species, in which two parent are involved and fusion of gametes takes place.

21.) 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: Answer is D, yes for continuity of life reproduction is important.

22.) During adolescence, several changes occur in the human body.Mark one change associated with sexual maturation in boys

(a) loss of milk teeth

(b) increase in height

(c) cracking of voice

(d) weight gain

Answer: Answer is C. At the onset of maturation the voice of the male changes.

23.) In human females, an event that reflects onset of reproductivephase is

(a) growth of body

(b) changes in hair pattern

(c) change in voice

(d) menstruation

Answer: Answer is D.

24.) In human males, the testes lie in the scrotum, because it helps in the

(a) process of mating

(b) formation of sperm

(c) easy transfer of gametes

(d) all the above

Answer: Answer is D.

25.) Which among the following is not the function of testes at puberty?

(i) formation of germ cells

(ii) secretion of testosterone

(iii) development of placenta

(iv) secretion of estrogen

(a) (i) and (ii) (b) (ii) and (iii)

(c) (iii) and (iv) (d) (i) and (iv)

Answer: Answer is C. Placenta is present in pregnant woman and estrogen is female sex hormone.

26.) The correct sequence of organs in the male reproductive systemfor transport of sperms is

(a) testis ® vasdeferens ® urethra

(b) testis ® ureter ® urethra

(c) testis ® urethra ® ureter

(d) testis ® vasdeferens ® ureter

Answer: Answer is A.

27.) Which among the following diseases is not sexually transmitted?

(a) Syphillis

(b) Hepatitis

(c) HIV – AIDS

(d) Gonorrhoea

Answer: Answer is B. Hepatitis can transmit through blood or vector.

Short Answer Questions

28.) In a bisexual flower inspite of the young stamens being removedartificially, the flower produces fruit. Provide a suitable explanationfor the above situation.

Answer: In a bisexual flower inspite of the young stamens being removed artificially, the flower produces fruit, because removal of stamen means male part but flower still contains female part so fruit can be obtained.

29.) Can you consider cell division as a type of reproduction in unicellular organism? Give one reason.

Answer: yes,cell division as a type of reproduction in unicellular organism, because one cell divides into two cells.

30.) What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?

Answer: Clone can be defined as the method of asexual reproduction in which offsprings are genetically identical to the parent therefore offsprings formed by asexual reproduction exhibit remarkable similarity

31.) Explain how, offspring and parents of organisms reproducingsexually have the same number of chromosomes?

Answer: offspring and parents of organisms reproducing sexually have the same number of chromosomes due to presence of cell division called as meiosis or also called as reductional division.

32.) Colonies of yeast fail to multiply in water, but multiply in sugarsolution. Give one reason for this.

Answer: Colonies of yeast fail to multiply in water, but multiply in sugar solution because yeast get all the nutrition to grow in sugar and the energy provided by glucose.

33.) Why does bread mould grow profusely on a moist slice of breadrather than on a dry slice of bread?

Answer: bread mould grow profusely on a moist slice of breadrather than on a dry slice of bread because nutrition is provided by moist slice of bread.

34.) Give two reasons for the appearance of variations among theprogeny formed by sexual reproduction.

Answer:

1)The human reproduces sexually with the formation of gametes and fusion of gametes.  Both the parents are involved in the sexual reproduction. Therefore both the parents have different reproductive organs and reproductive processes.

2) Due to presence of 2 parents, the characters are getting blend so the appearance of variations among theprogeny formed by sexual reproduction.

35.) Would a Planaria cut vertically into two halves regenerate into twoindividuals? Complete Figure 8.2 D and E by indicating theregenerated regions.

Fig. 8.2

Answer: The planaria will regenerate.

36.) From the internet, gather information about the chromosome numbers of five animals and five plants. Correlate the number with the size of organism and answer the following questions.

(a) Do larger organisms have more number of chromosomes/cells?

(b) Can organism with fewer chromosomes reproduce more easilythan organisms with more number of chromosomes?

(c) More the number of chromosomes/cells greater is the DNA

content. Justify.

Answer: (a) Do larger organisms have more number of chromosomes/cells? No, because some small animals have more number of chromosomes than human.

(b) Can organism with fewer chromosomes reproduce more easilythan organisms with more number of chromosomes? No, there should no any relation in between these two terms.

(c) More the number of chromosomes/cells greater is the DNAcontent. Yes, as the number of chromosomes increases the number of DNA would be more.

37.) In tobacco plant, the male gametes have twenty four chromosomes.

What is the number of chromosomes in the female gamete?

What is the number of chromosomes in the zygote?

Answer: the number of chromosomes in the female gamete will be 24.

number of chromosomes in the zygote will be 48.

38.) Why cannot fertilisation take place in flowers if pollination doesnot occur?

Answer: fertilization does not take place in flowers if pollination doesnot occur because if there is no pollen grain then the process of fertilization will not takes place.

39.) Is the chromosome number of zygote, embryonal cells and adultof a particular organism always constant? How is the constancymaintained in these three stages?

Answer:  Yes, the chromosome number of zygote, embryonal cells and adult of a particular organism always constant because there is always a mitosis occur, in which there is no reduction in chromosome.

40.) Where is the zygote located in the flower after fertilization?

Answer: Zygote in the flower is present in the ovule inside region of ovary.

41.) Reproduction is linked to stability of population of a species.Justify the statement.

Answer: Reproduction can be defined as production or generation of new offspring that are genetically similar to their parents. Reproduction is the characteristics of living organisms. It is essential for continuity of life. Every living organism reproduces by different methods. The method of reproduction will vary from unicellular microorganism to complex human being.

Every living organism contains the genetic material. The genetic material transmits from one generation to next generation. The genetic material can be divided into two types such as DNA (Deoxyribose nucleic acid) and RNA (Ribonucleic acid).

All the living organisms contain the genetic material that is either DNA or RNA but both. The DNA or RNA (genetic material) present within the nucleus of the cell.

The DNA or RNA contains chromosomes. The number of chromosomes differs from organism to organism.

  1. It is essential for continuity of life of living organisms.
  2. The variation can be produced from reproduction; it leads to generation of new characteristics.
  3. It is the fundamental powers for heredity.

42.) How are general growth and sexual maturation different from eachother?

Answer: The general growth and sexual maturation different from eachother because general growth includes growth of the body in all aspects but in case of sexual maturation, the sexual organs develop and changes in the body which are occurred during puberty.

43) Trace the path of sperm during ejaculation and mention the gland and their functions associated with the male reproductive system.

Answer: The male reproductive system basically, contains 3 types of glands such as seminal vesicle, prostrate gland, bulbourethral gland.

1) Seminal vesicle : The seminal vesicle it contains fluid and sugar called as fructose.

This fructose gives energy to sperm.

2) Prostrategland : With the help of prostrate gland secretion, the sperm are able to move from one location to another.

3) Bulbourethral gland : The bulbourethral gland also called as cowper’s gland. It provides lubrication during sexual intercourse for secretion of whitish mucus fluid.

testis to vasdeferens to urethra is the correct sequence of path of sperm.

44.) What changes are observed in the uterus if fertilisation does not occur?

Answer: if fertilisation does notoccur the next cycle of menstruation will continue and the layer of endocarp will generate.

45.) What changes are observed in the uterus subsequent toimplantation of young embryo?

Answer: Due to implantation there will no menstrual cycle and will lead to initiation of formation of placenta.

46.) What are the benefits of using mechanical barriers during sexualact?

Answer: the benefits of using mechanical barriers during sexualact safe to use and prevent pregnancy and the sexually transmitted disease will prevented.

48.) What would be the ratio of chromosome number between an eggand its zygote? How is the sperm genetically different from the egg?

Answer: The ratio of chromosome number in egg and zygote will be 1:2. the sperm genetically different from the egg on the basis of the nature of sex chromosome that is XY.

Long Answer Questions

49.) Why are budding, fragmentation and regeneration all consideredas asexual types of reproduction? With neat diagrams explain theprocess of regeneration in Planaria.

Answer:

1.) Budding: Budding is the common type of asexual reproduction in which the offspring develops from outgrowth of parent cell from a particular site.

2.) Regeneration: This is a type of asexual reproduction in which generation of new part form a lost part of living organisms. Some organisms have ability of regeneration for example, lizard tail.

3.) Fragmentation: This type of asexual reproduction seen in spirogyra. In which, from the broken part of body, new organisms can arise.

50.) Write two points of difference between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction.

Answer:

Asexual Reproduction:

Sexual Reproduction:

It can be defined as the process where there is no fusion of gametes and only single parent involved. There are various types of asexual reproduction such as budding, regeneration, fission, etc.

The reproduction that takes place in plants, animals and humans. In the process, fusion of gametes and involvement of two parents are present.

 

Asexual mode of reproduction can be predicted as simplest form of reproduction, no involvement of gametes and therefore, gamete formation does not takes place. Such process is called as asexual method of reproduction.

Sexual reproduction occurs when male gamete fuses with the female gamete that is fusion of gametes.

The human reproduces sexually with the formation of gametes and fusion of gametes.  Both the parents are involved in the sexual reproduction. Therefore both the parents have different reproductive organs and reproductive processes. Therefore variations are observed in the offspring formed by sexual reproduction.

51.) Distinguish between pollination and fertilisation. Mention the siteand product of fertilisation in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule.

Answer:

Pollination

Fertilization

It is the transfer of pollen grain from anther to stigma.

When male and female gamete fuses fertilization takes place.
Occurs out of ovary.

Occurs in the ovary.

52.) Distinguish between a gamete and zygote. Explain their roles insexual reproduction.

Answer:

Gamete Zygote
The sex cells or germ cells called as gamete. When male and female gamete fuse there is formation of zygote.
Gametes are also called as unfertilized cells. It is also called as fertilized cells.

The role of gametes and zygote in sexual reproduction is due to sexual intercoarsemal and female gamete come into contact with each other and forms a zygote.

53.) Draw the diagram of a flower and label the four whorls. Write thenames of gamete producing organs in the flower.

Answer:

54.) What is placenta? Mention its role during pregnancy?

Answer: The placenta can be defined as an organ which forms in the female body during pregnancy to share or give the nutrients fetus and provides nourishment to growing baby. It is formed within the uterus.

55.) What are various ways to avoid pregnancy? Elaborate any onemethod.

Answer: The pregnancy can be avoid by various ways such as Use of condom, family planning , contraceptive tablets, intrauterine device and contraceptive injection.

56.) How does fertilisation take place? Fertilisation occurs once in amonth. Comment.

Answer: Fertilization can take place at the 14 day or around the 14th day of menstrual cycle, out of millions of sperm only one sperm can fuse with ovum and fertilization occurs.

57.) Reproduction is essentially a phenomenon that is not for survivalof an individual but for the stability of a species. Justify.

Answer: Reproduction can be defined as production or generation of new offspring that are genetically similar to their parents. Reproduction is the characteristics of living organisms. It is essential for continuity of life. Every living organism reproduces by different methods. The method of reproduction will vary from unicellular microorganism to complex human being.

Every living organism contains the genetic material. The genetic material transmits from one generation to next generation. The genetic material can be divided into two types such as DNA (Deoxyribose nucleic acid) and RNA (Ribonucleic acid).

All the living organisms contain the genetic material that is either DNA or RNA but both. The DNA or RNA (genetic material) present within the nucleus of the cell.

The DNA or RNA contains chromosomes. The number of chromosomes differ from organism to organism.

Importance of Reproduction:

1.) It is essential for continuity of life of living organisms.

2.) The variation can be produced from reproduction; it leads to generation of new characteristics.

3.) It is the fundamental powers for heredity.

Updated: May 15, 2021 — 6:15 pm

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