NCERT Exemplar Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce (MCQ, SAQ and LAQ)
Chapter Name | NCERT Exemplar Solutions for Class 10 Science Ch 8 How do Organisms Reproduce |
Topics Covered |
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Related Study |
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Objective Type Questions for How do Organisms Reproduce
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 which embryo is formed. Seedling comes out from 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)
Asexual reproduction involve single parent and there will be no exchange of gametes hence 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 reproduce by binary fission, Spirogyra reproduce by fragmentation, yeast reproduce 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 reproduce by fragmentation. Spirogyra simply breaks up into smaller pieces upon maturation. 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 divide into many daughter cell by binary multiple fission. In Multiple fission nucleus of the cell divides multiple times by mitosis 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
Gametes fuse to form a zygote during fertilization. After fertilization embryo will be formed which will lead 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
Because of halving of chromosome during gamete formation number of chromosome remain same as somatic cell of an organism. Halving of gametes in a chromosomes is called diploid number of chromosomes.
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 occur in plants. In vegetative reproduction new plant is produced from vegetative parts of the plants such as roots, stem, leaf and buds. In vegetative reproduction plants produced are genetically similar enough to the parent plant to have all its characteristics.
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 ensure a few spore 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
Length of pollen tube ensures 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 hence statement i) is wrong. Only angiosperms produces flowers hence statement iii) is wrong.
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)
Cross pollination is necessary is unisexual flowers as they possess either stamen or pistil. Flowers possessing only stamens cannot produce fruits because fruit is a mature ovary.
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 from sexual reproduction cannot be clones hence statement (iv) is wrong.
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
In sexual reproduction zygote is formed by gametes produces by a male and a female. A male and a female gamete fuse to form a zygote which fertilizes to produce new offspring. Because of contribution of two parents off-springs incur more variations.
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 the 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, following changes occur in boys
- Growth of hairs in new parts of the body such as armpits, on chest and between thighs near genital organ, face, legs and on arms.
- Creaking of voice
- Skin becomes oily and pimples will start appearing
- Occasionally penis will erect especially while dreaming.
(a) growth of body
(b) changes in hair pattern
(c) change in voice
(d) menstruation
(d) menstruation
- Growth of hairs in new parts of the body such as armpits, between thighs near genital organ thin hairs on face, legs and on arms.
- Start menstruation
- Skin becomes oily and pimples will start appearing
- Breast size will increase
(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 → vas deferens → urethra
(b) testis → ureter → urethra
(c) testis → urethra → ureter
(d) testis → vas deferens → ureter
(a) testis → vas deferens → urethra
(a) Syphilis
(b) Hepatitis
(c) HIV - AIDS
(d) Gonorrhoea
(b) Hepatitis
Short Answer Questions for How do Organisms Reproduce
When stamens of a bisexual flower are removed. Cross pollination can take place which results in fertilization and production of fruit.
Reproduction is creation of new individual. In unicellular organism cell division leads to formation of new individuals. Hence cell division is a type of reproduction in unicellular organisms.
Clone are the aggregate of cell or organisms which are produced asexually. Asexual reproduction involve single parent and there will be no exchange of gametes hence offspring looks similar to their parent.
Because of halving of chromosome during gamete formation number of chromosome remain same as somatic cell of an organism. Halving of gametes in a chromosomes is called diploid number of chromosomes.
Yeast requires energy for its growth and cell division. Water does not provide required energy whereas sugar provide energy hence yeast multiplies in sugar solution.
Spores of bread mould needs moisture to germinate and grow. Hence, mould grow profusely on a moist slice of bread.
- Gametes are contributed by two individuals of the same species.
- Crossing over occur during meiosis.
Yes, Planaria cut vertically into two halves can regenerate into two individuals.
(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.
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Animals |
Chromosome numbers |
Plants |
Chromosome numbers |
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Man |
46 |
Corn |
20 |
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Cat |
38 |
Cotton |
52 |
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Horse |
64 |
Garden pea |
14 |
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Rabbit |
44 |
Mango |
40 |
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Elephant |
56 |
Onion |
16 |
Number of chromosomes in both the gametes are equal hence number of chromosomes in a female gamete of tobacco plant is 24. Combining both number of chromosomes in a zygote is 48.
Pollination is a process in which transfer of pollen grains from anthers to stigma takes place. If there is no pollination then there will be no fusion of gametes and fertilization do not take place.
Meiosis is a way of cell division in which number of chromosomes get halved. After fertilization chromosomes become equal to that of somatic cells. After fertilization Mitosis takes place for the rest of the stages of life. Hence chromosomes remain constant.
After fertilization zygote will be located in the ovary.
Competition for food, predation are common in nature. If there is no reproduction species would have become extinct. Hence reproduction linked to population of the species.
General growth is all about growth of size. Sexual maturation is about achieving the ability to reproduce. General growth begins with growth of an organism whereas sexual maturity is attained at certain stage of life called as adolescence.
Sequence of organs in the male reproductive system for transport of sperms is:
testis → epididymis → vas deferens → prostate→ urethra.
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Gland associated with male reproductive system |
Function |
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Testes |
Secretion of testosterone |
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Prostate gland |
Makes the medium of semen alkaline |
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Seminal vesicle |
Addition of fluid content to semen |
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Cowper’s gland |
Urethra lubrication and neutralizes acidic traces of urine. |
Following changes occur in the uterus if fertilization does not occur
- Extra lining of Uterus degenerates
- Uterus lining fragments gets discharged through vagina
- Unfertilized egg gets discharged
- Menstruation takes place
Following changes are observed in the uterus subsequent to implantation of young embryo.
- Uterine lining thickens to support to developing embryo. (PLACENTA)
- Uterine lining is richly supplied with blood vessels so that nutrition and oxygen could be supplied to the developing foetus.
- Mechanical barriers prevents unwanted pregnancy
- Mechanical barriers prevent sexually transmitted
(a) Ovary
The ratio of chromosome number between an egg and its zygote is 1:2.
Long Answer Questions for How do Organisms Reproduce
In Budding, fragmentation and regeneration only a single parent is involved and there are no formation of gametes hence they are considered as asexual types of reproduction.
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Sexual reproduction |
Asexual reproduction |
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Two parents are involved |
Single parent is involved |
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Gametes are formed |
Gametes are not formed |
- Gene pool are contributed by two parents
- Crossing over that occur during meiosis results in more variation
- DNA replication also contributes for the variation
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Pollination |
Fertilization |
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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. |
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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. |
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Leads to fertilization |
Lead to formation of seeds |
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Pollination is an external process |
Occurs in the ovary of female. |
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Gamete |
Zygote |
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Formed after Meiosis |
Formed by fusion of two gametes. |
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Gametes produces haploid number of chromosomes |
Produces diploid number of chromosomes |
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Male and female parts produces gametes |
Zygote formaton takes place in female |
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Gametes are required for sexual reproduction |
Zygote is the precursor for embryo formation |
Ovary produces female gametes. Anthers produces male gametes.
(a) Physical barrier
(b) Copper-T
(c) Hormone Pills
(d) Surgical procedure
Barrier method: In the barrier methods of preventing pregnancy, the physical devices such as diaphragm (or cap) and condoms are used. Diaphragm (or Cap) is used by human females which is put over the cervix. Condoms are used by males.
Once in a month one egg is released from either of the ovaries. The egg gets transferred to fallopian tube from the ovaries. Sperms swims towards fallopian tube and only one sperm can penetrate the egg at a time. This process is called fertilization.
A menstrual cycle is composed of about 28 days. This means only one egg is available for fertilization in one menstrual cycle. Hence, it can be said that fertilization can occur only once in a month.
Competition for food, predation are common in nature. If there is no reproduction species would have become extinct. Hence reproduction linked to population if a species. New individuals carries lineage of their parents. More number of organisms produces counterbalances the mortality that arises due to various factors. Like this reproduction helps in maintain stability of a species.
Disease that gets spread from person to person through sexual means are called sexually transmitted diseases. These include bacterial infections such as gonorrhoea and syphilis, and viral infections such as warts and HIV-AIDS.
Below are the ways to prevent sexually transmitted diseases
- Use of condoms or other physical barriers.
- Avoiding sexual contacts with unknown partners.
- Avoid sharing towels or underclothing.
- Get a vaccination for hepatitis B.