NCERT Exemplar Class 10 Science Chapter 8 How do Organisms Reproduce? Solutions
NCERT Exemplar Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce covers all the important questions and answers as well as advanced level questions. It helps in learning about the sexual and asexual reproduction, pollination, reproduction in flowers, fertilization, genetics and human reproductive system.
The NCERT Exemplar solutions for class 10 science is very important for board exams. NCERT Exemplar Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce is provided by our experts. They prepared the best solutions which help the students in understanding the solutions in an easy way. This chapters also covers the other topics like chromosomes, physical barriers, sexually transmitted diseases.
Chapter Name | Chapter 8 How do Organisms Reproduce |
Book Title | NCERT Exemplar for Class 10 Science |
Related Study |
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Topics Covered |
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NCERT Exemplar Solutions for Chapter 8 How do Organisms Reproduce Class 10 Science
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)
Solution
(b) (i), (iii) and (iv)
Dog reproduce sexually, yeast reproduce by budding, Amoeba reproduce sexually and cultivated banana also reproduce asexually.
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
Solution
(c) anther and ovary
3. Which of the following is the correct sequence of events of sexual reproduction in a flower?
(a) pollination, fertilisation, seedling, embryo
(b) seedling, embryo, fertilisation, pollination
(c) pollination, fertilisation, embryo, seedling
(d) embryo, seedling, pollination, fertilization
Solution
(c) pollination, fertilisation, embryo, seedling
Pollination leads to fertilization. After this embryo is formed. Seedling comes out from the embryo.
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)
Solution
(a) (i) and (ii)
Single parent is involved in asexual reproduction and thus there will be no exchange of gametes. This is the reason why offspring looks similar to their parent..
5. Characters transmitted from parents to offspring are present in
(a) cytoplasm
(b) ribosome
(c) golgi bodies
(d) genes
Solution
(d) genes
6. Characters that are transmitted from parents to offspring during reproduction show
(a) only similarities with parents
(b) only variations with parents
(c) both similarities and variations with parents
(d) neither similarities nor variations
Solution
(c) both similarities and variations with parents
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
Solution
(a) they reproduce asexually
Amoeba reproduces by binary fission, Spirogyra reproduces by fragmentation and yeast reproduces by budding.
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.
Solution
(a) breaking up of filaments into smaller bits
Spirogyra reproduces by fragmentation. Upon maturation, the spirogyra simply breaks up into smaller pieces. These pieces or fragments grow into new individuals.
9. 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
Solution
(d) multiple fission
Plasmodium divides into many daughter cells by binary multiple fissions. In multiple fission nucleus of the cell divides multiple times by mitosis and then separates to create multiple daughter cells.
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
Solution
(a) gametes, zygote, embryo, seedling
During fertilization, gametes fuse to form a zygote. Embryo will be formed after fertilization which leads to seedling in plants.
11. The number of chromosomes in parents and offsprings of a particular 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
Solution
(b) halving of chromosomes during gamete formation
The number of chromosome is halved during gamete formation. The number of chromosome remains the same as that in somatic cell of an organism.
12. In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called
(a) filaments
(b) hyphae
(c) rhizoids
(d) roots
Solution
(b) hyphae
Tiny blob-on-a-stick like structures involved in reproduction are called hyphae. The blobs are called sporangia, which contain cells, or spores, that can eventually develop into new rhizopus individuals.
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
Solution
(b) stem, roots and leaves
Vegetative propagation is a type of asexual reproduction which occurs in plants. Anew plant is produced from the vegetative parts of the plants such as roots, stem, leaf and buds. The plants produced in vegetative reproduction are genetically similar enough to the parent plant.
14. Factors responsible for the rapid spread of bread mould on slices of 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)
Solution
(c) (i) and (ii)
Large number of spores ensures that a few of them survive even in adverse conditions. Availability of moisture and nutrients in the bread provides necessary environment for spore to grow into mould.
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
Solution
(d) upper surface of stigma and lower part of style
The length of the pollen tube ensures that the pollens reach the stigma to conduct pollination.
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)
Solution
(d) (ii) and (iv)
Flowers are not always bisexual. Only angiosperms produce flowers.
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)
Solution
(b) (ii), (iii) and (iv)
Unisexual flowers possess either stamen or pistil, hence cross pollination is necessary. Fruit is a mature ovary, hence the flowers possessing only stamens cannot produce fruits.
18. Which among the following statements are true for sexual reproduction 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)
Solution
(c) (i), (ii) and (iii)
Off-springs produced by sexual reproduction cannot be clones.
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
Solution
(c) plumule, cotyledon and radicle
20. Offspring formed as a result of sexual reproduction exhibit more variations 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
Solution
(b) genetic material comes from two parents of the same species
Zygote is formed by gametes produced by a male and a female in sexual reproduction. Zygote on fertilization produces new offspring. Offsprings incur more variations as there is contribution from two parents.
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
Solution
(d) continue the species generation after generation
Reproduction is essential to the lineage of a species whereas other life processes are essential to keep the organism alive.
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
Solution
(c) cracking of voice
During adolescence the following changes occur in boys:
- Growth of hairs in armpits, between thighs, near genital organ, thin hairs on face, legs and on arms.
- Creaking of voice
- Skin becomes oily and pimples start appearing.
(a) growth of body
(b) changes in hair pattern
(c) change in voice
(d) menstruation
(d) menstruation
- Growth of hairs in armpits, between thighs, near genital organ, thin hairs on face, legs and on arms.
- Creaking of voice
- Skin gets oily and pimples appear.
(a) process of mating
(b) formation of sperm
(c) easy transfer of gametes
(d) all the above
(b) formation of sperm
(i) formation of germ cells
(ii) secretion of testosterone
(iii) development of placenta
(iv) secretion of estrogen
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
(c) (iii) and (iv)
(a) testis → vasdeferens → urethra
(b) testis → ureter → urethra
(c) testis → urethra → ureter
(d) testis → vasdeferens → ureter
(a) testis → vasdeferens → urethra
(a) Syphillis
(b) Hepatitis
(c) HIV - AIDS
(d) Gonorrhoea
(b) Hepatitis
Short Answer Questions
The pistil remains intact. Cross pollination might have occurred leading to fertilisation and formation of fruit.
Cell division can be considered as a type of reproduction in unicellular organisms because it results in the formation of two daughter cells. That is it results in the production of more individuals of the organism.
The offspring of an organism formed by asexual method of reproduction is referred to as a clone. Clones exhibit remarkable similarity as they possess exact copies of the DNA of their parent.
During gamete formation, deduction division (meiosis) halves the chromosome number in both male and female gametes. As these two gametes fuse during fertilisation, the original number of chromosomes (as in the parent)is restored in the offspring.
In yeasts, sugar provides energy for sustaining all life activities. Yeast fails to reproduce in because of inadequate energy in its cells.
For the growth of hyphae moisture is an important factor. Moistened bread slice offers both moisture and nutrients to the bread mould, hence it grows profusely. Hyphae fail to grow on dry slice of bread as it offers nutrients but not moisture.
- Two parents with different sets of characters are involved in sexual reproduction.
- In gametes, the gene combinations are different.
The shaded part in Figures D and E represent the regenerated halves.
(a) Do larger organisms have more number of chromosomes/cells?
(b) Can organism with fewer chromosomes reproduce more easily than organisms with more number of chromosomes?
(c) More the number of chromosomes/cells greater is the DNA content. Justify.
Animals | Chromosome numbers | Plants | Chromosome numbers |
Man | 46 | Corn | 20 |
Cat | 38 | Cotton | 52 |
Horse | 64 | Garden pea | 14 |
Rabbit | 44 | Mango | 40 |
Elephant | 56 | Onion | 16 |
Number of chromosomes in female gamete is 24.
Flower fertilisation requires both male and female gametes. Therefore, if pollination does not occur, male gamete won’t be available and hence fertilisation cannot take place.
Yes, the constancy is maintained as the cells in all these three structures undergo only mitotic divisions.
Zygote is located inside the ovule which is present in the ovary.
In the process of reproduction, DNA passes from one generation to the next. DNA copying takes place with consistency but with minor variations. This consistency leads to stability of species.
Different types of developmental process in the body like increase in height, weight gain, changes in shape and size of the body are referred to as general growth but sexual maturation is specific to changes reflected at puberty like cracking of voice, new hair patterns, development of breast in female etc.
From the testis the sperms come into the vas deferens and then pass through the urethra before ejaculation. The secretions from the seminal vesicle and prostrate glands provide nutrition to the sperms and facilitate their transport.
Gland associated with male reproductive system | Function |
Testes | Secretion of testosterone |
Prostate gland | Makes the medium of semen alkaline |
Seminal vesicle | Addition of fluid content to semen |
Cowper’s gland | Urethra lubrication and neutralizes acidic traces of urine. |
Following changes occur in the uterus if fertilization does not occur
- Slowly the thick and spongy lining of the uterus breaks and comes out through the vagina as blood and mucus.
- Unfertilized egg gets discharged
- Menstruation takes place
The uterine wall thickens as it gets richly supplied with blood. A special tissue called placenta develops. Placenta connects embryo to the uterine wall which provides nutrients and oxygen to it.
(a) Ovary
The ratio of chromosome number between an egg and its zygote is 1 : 2. Sperms contain either X or Y chromosome whereas an egg will always have an X chromosome
Long Answer Questions
Budding, fragmentation and regeneration involve only one parent and gametes are not involved in reproduction. Hence they are considered as asexual type of reproduction.
Sexual reproduction | Asexual reproduction |
Two parents are involved | Single parent is involved |
Gametes are formed | Gametes are not formed |
- Both the parents contribute to the gene pool.
- Crossing over during meiosis results in more variation.
- DNA replication also contributes for the variation.
Pollination | Fertilization |
It is the transfer of pollen grains from the anther to the stigma of a flower. | It is the fusion of male gamete with female gamete. |
Achieved by agents like a wind, water or animals. | Achieved by the growth of pollen tube so that the mail gamete reaches the female germ cells. |
Leads to fertilization | Lead to formation of seeds |
Pollination is an external process | Occurs in the ovary of female. |
Gamete | Zygote |
Formed after Meiosis | Formed by fusion of two gametes. |
Gametes produces haploid number of chromosomes | Produces diploid number of chromosomes |
Male and female parts produces gametes | Zygote formation takes place in female |
Gametes are required for sexual reproduction | Zygote is the precursor for embryo formation |
Ovary produces female gametes whereas anthers produce male gametes
A disc like structure embedded in the uterine wall is known as the placenta.
a) Physical barrier
b) Copper-T
c) Hormone Pills
d) Surgical procedure
Various ways to avoid pregnancy are as follows:
- Physical barrier
- Copper-T
- Hormone Pills
- Surgical procedure
One egg is released from either of the ovaries once in a month. From the ovaries the eggs get transferred to fallopian tube. The sperms swim towards the fallopian tube. At a time, only one sperm can penetrate the egg. This is known as fertilization. A menstrual cycle is composed of approximately 28 days. That is in one menstrual cycle only one egg is available for fertilization. Hence, it can be said that fertilization can occur only once in a month.
The species would get extinct if there is no reproduction. Thus reproduction is linked to the population of a species. New individuals carries lineage of their parents. More number of organisms produced counter balances the mortality that arises due to various factors. In this way reproduction helps in maintaining the stability of a species
Sexually transmitted diseases are the diseases that get spread from person to person through sexual means. These include bacterial infections such as gonorrhoea and syphilis, and viral infections such as warts and HIV-AIDS. Few methods to prevent sexually transmitted diseases are:
- Use of condoms or other physical barriers.
- Avoiding sexual contacts with unknown partners.
- Avoid sharing towels or underclothing.
- Get a vaccination for hepatitis B.