Class 10 Science · 58 questions · 57 with answers
In the list of organisms given below, those that reproduce by the asexual method are (i) banana (ii) dog (iii) yeast (iv) Amoeba
(b) (i), (iii) and (iv)
In a flower, the parts that produce male and female gametes (germ cells) are
(c) anther and ovary
Which of the following is the correct sequence of events of sexual reproduction in a flower?
(c) pollination, fertilisation, embryo, seedling
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)
Characters transmitted from parents to offspring are present in
(d) genes
Characters that are transmitted from parents to offspring during reproduction show
(c) both similarities and variations with parents
A feature of reproduction that is common to Amoeba, Spirogyra and Yeast is that
(a) they reproduce asexually
In Spirogyra, asexual reproduction takes place by
(a) breaking up of filaments into smaller bits
The ability of a cell to divide into several cells during reproduction in Plasmodium is called
(d) multiple fission
The correct sequence of reproductive stages seen in flowering plants is
(a) gametes, zygote, embryo, seedling
The number of chromosomes in parents and offsprings of a particular species remains constant due to
(b) halving of chromosomes during gamete formation
In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called
(b) hyphae
Vegetative propagation refers to formation of new plants from
(b) stem, roots and leaves
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
(c) (i) and (ii)
Length of pollen tube depends on the distance between
(b) pollen grain on upper surface of stigma and ovule
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
(d) (ii) and (iv)
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
(b) (ii), (iii) and (iv)
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
(c) (i), (ii) and (iii)
In Figure 8.1, the parts A, B and C are sequentially
This question refers to a figure in the original PDF.
(c) plumule, cotyledon and radicle
Offspring formed as a result of sexual reproduction exhibit more variations because
(b) genetic material comes from two parents of the same species
Reproduction is essential for living organisms in order to
(d) continue the species generation after generation
During adolescence, several changes occur in the human body. Mark one change associated with sexual maturation in boys
(c) cracking of voice
In human females, an event that reflects onset of reproductive phase is
(d) menstruation 68 E XEMPLAR P ROBLEMS – SCIENCE
In human males, the testes lie in the scrotum, because it helps in the
(b) formation of sperm
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
(c) (iii) and (iv)
The correct sequence of organs in the male reproductive system for transport of sperms is
(a) testis → vasdeferens → urethra
Which among the following diseases is not sexually transmitted?
(b) Hepatitis
In a bisexual flower inspite of the young stamens being removed artificially, the flower produces fruit. Provide a suitable explanation for the above situation.
The pistil is intact. Cross pollination has occurred leading to fertilisation and formation of fruit.
Can you consider cell division as a type of reproduction in unicellular organism? Give one reason.
Yes, because it results in the formation of two daughter cells, that is, it results in the production of more individuals of the organism.
What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?
Clone refers to offspring of an organism formed by asexual method of reproduction. Since they possess exact copies of the DNA of their parent, clones exhibit remarkable similarity.
Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes?
Reduction division (meiosis) during gamete formation halves the chromosome number in both male and female gametes. Since these two gametes fuse during fertilisation, the original number of chromosomes (as in the parent) is restored in the offspring.
Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give one reason for this. HOW DO ORGANISMS REPRODUCE? 69
Sugar provides energy for sustaining all life activities in yeasts. In water, it fails to reproduce because of inadequate energy in its cells.
Why does bread mould grow profusely on a moist slice of bread rather than on a dry slice of bread?
Moisture is an important factor for the growth of hyphae. Moistened bread slice offers both moisture and nutrients to the bread mould, hence it grows profusely. Dry slice of bread offers nutrients but not moisture hence hyphae fail to grow.
Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.
(a) Sexual reproduction involves two parents with different sets of characters (b) The gene combinations are different in gametes.
Would a Planaria cut vertically into two halves regenerate into two individuals? Complete Figure 8.2 D and E by indicating the regenerated regions. Fig. 8.2
This question refers to a figure in the original PDF.
Yes, shaded part in Figures D and E represent the regenerated halves.
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 easily than organisms with more number of chromosomes?
(c) More the number of chromosomes/cells greater is the DNA content. Justify.
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?
Number of chromosomes in female gamete is 24 Number of chromosomes in zygote is 48
Why cannot fertilisation take place in flowers if pollination does not occur?
In a flower fertilisation requires both male and female gametes. If pollination does not occur, male gamete is not available hence fertilisation cannot take place.
Is the chromosome number of zygote, embryonal cells and adult of a particular organism always constant? How is the constancy maintained in these three stages?
Yes, the constancy is maintained because cells in all these three structures undergo only mitotic divisions.
Where is the zygote located in the flower after fertilization?
Zygote is located inside the ovule which is present in the ovary.
Reproduction is linked to stability of population of a species. Justify the statement.
In reproduction, DNA passes from one generation to the next. Copying of a DNA takes place with consistency but with minor variations. This consistency leads to stability of species.
How are general growth and sexual maturation different from each other?
General growth refers to different types of developmental process in the body like increase in height, weight gain, changes in shape and size of the body but sexual maturation is specific to changes reflected at puberty like cracking of voice, new hair patterns, development of breast in female etc.
Trace the path of sperm during ejaculation and mention the gland and their functions associated with the male reproductive system. 70 E XEMPLAR P ROBLEMS – SCIENCE
Sperm comes out from testis into the vas deferens and then passes through urethra before ejaculation. The secretions of seminal vesicle and prostrate glands provide nutrition to the sperms and also facilitate their transport.
What changes are observed in the uterus if fertilisation does not occur?
The thick and spongy lining of the uterus slowly breaks and comes out through the vagina as blood and mucus.
What changes are observed in the uterus subsequent to implantation of young embryo?
The uterine wall thickens that is richly supplied with blood. A special tissue called placenta develops which connects embryo to the uterine wall that provides nutrients and oxygen to it. ANSWERS 151
What are the benefits of using mechanical barriers during sexual act?
Mechanical barriers like condom prevents the sperms from reaching the egg. Thus it is an effective method to avoid pregnancy. It also prevents transmission of infections during sexual act.
In the given Figure 8.3 label the parts and mention their functions
This question refers to a figure in the original PDF.
(a) Production of egg
(b) Site of fertilisation
(c) Site of implantation
(d) Entry of the sperms Fig. 8.3
What would be the ratio of chromosome number between an egg and its zygote? How is the sperm genetically different from the egg? .QPI #PUYGT 3WGUVKQPU
The ratio is 1 : 2. Sperms contain either X or Y chromosome whereas an egg will always have an X chromosome. .QPI#PUYGT3WGUVKQPU
Why are budding, fragmentation and regeneration all considered as asexual types of reproduction? With neat diagrams explain the process of regeneration in Planaria.
Budding, fragmentation and regeneration are considered as asexual types of reproduction because all of them involve only one parent and gametes are not involved in reproduction Regeneration in Planaria 152 E XEMPLAR P ROBLEMS – SCIENCE
Write two points of difference between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction.
Asexual reproduction Sexual reproduction (a) Involves only one parent (i) Often involves two (b) Gametes are not parents produced (ii) Gametes are produced (c) No fertilisation and (iii) Fertilisaton and zygote zygote formation formation is observed. (d) Meiosis does not occur (iv) Meiosis occurs at the at anytime during time of gamete reproduction formation During sexual reproduction two types of gametes fuse. Although the gametes contain the same number of chromosomes, their DNA is not identical. This situation generates variations among the offsprings.
Distinguish between pollination and fertilisation. Mention the site and product of fertilisation in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule.
The process or mechanism of transfer of pollen grains from the anther to the stigma is termed pollination. The fusion of male and female gaemtes giving rise to zygote is termed fertilisation The site of fertilisation is ovule. The product of fertilisation is zygote.
Distinguish between a gamete and zygote. Explain their roles in sexual reproduction.
Gamete represents the sex cell or germ cell in sexual reproduction. There are two types of gametes, male and female. Zygote is the product of fertilisation in which a male and a Pollen tube growth and female gamete fuse with each other. its entry into the ovule The two fusing gametes possess characters of their parents in their DNA. Fertilisation brings characters of both parents into one zygote cell. Zygote is the first cell of the next generation. It divides to form an embryo which subsequently grows into a new individual. Male gamete forming part – anther/stamen Female gamete forming part – pistil/ovary/ovule ANSWERS 153
Draw the diagram of a flower and label the four whorls. Write the names of gamete producing organs in the flower. HOW DO ORGANISMS REPRODUCE? 71
What is placenta? Mention its role during pregnancy?
Hints— (a) Special tissue connection between embryo and uterine wall (b) Possesses villi that increases the surface area. (c) Facilitate passage of nutrition and oxygen to embryo from mother through blood. (d) Waste substances produced by embryo are removed through placenta into mother’s blood.
What are various ways to avoid pregnancy? Elaborate any one method.
Hints— (a) Contraceptive methods are used such as (i) mechanical (ii) drugs (as pills) (iii) loop or copper T and (iv) surgical method. (b) Pills change the hormonal balance and thus prevent the release of egg, hence fertilisation is prevented.
How does fertilisation take place? Fertilisation occurs once in a month. Comment.
Hints— (a) Sperm enters through the vaginal passage during sexual intercourse and moves upwards. (b) Egg released from the ovary reaches the oviduct. (c) Sperm encounters egg in the oviduct and fertilization takes place. (d) Egg is released once every month by ovary.
Reproduction is essentially a phenomenon that is not for survival of an individual but for the stability of a species. Justify.
Hints— (a) Organisms need energy for survival which they obtain from life processes such as nutrition and respiration. (b) Reproduction needs a lot of energy. (c) Genetic material is transferred from one generation to the next as a result of reproduction through DNA copying. (d) DNA copying takes place with high constancy and considerable variations, that is, advantages to the species for stability in the changing environment.
Describe sexually transmitted diseases and mention the ways to prevent them. 72 E XEMPLAR P ROBLEMS – SCIENCE
Hints— (a) These are infectious diseases transmitted during sexual contact. (b) They may be bacterial like or viral like. (c) Use of mechanical barrier like condom prevents transmission of infection. 154 E XEMPLAR P ROBLEMS – SCIENCE %*#26'4 ANSWERS /WNVKRNG%JQKEG3WGUVKQPU