How do organisms reproduce class 10 biology ncert MCQ & SAQ

How do organisms reproduce class 10 biology  NCERT solution:

1. What is the importance of DNA copying in reproduction?

DNA is the genetic material present in the cells of all organisms. The genetic information from generation to generation is carried by DNA. It is therefore possible for the organism to produce organisms of its own type due to DNA copying only. For the inheritance of traits of the parent, DNA copying is a must. DNA copying also brings about variation ,which forms the basis for the origin of new species.

 

2. Why is variation beneficial to the species but not necessarily for the individual?

Variations are more beneficial to the species than individual because sometimes for a species, the environmental conditions change so drastically that their survival becomes difficult. For example, if the temperature of water increases suddenly, then most of the bacteria living in that water would die. Only a few variants that are resistant to heat would be able to survive. However, if these variants were not there, then the entire species of bacteria would have been destroyed. Thus, these variants help in the survival of the species. However, all variations are not necessarily beneficial for the individual organisms.

 

 

 

1. How does binary fission differ from multiple fission?

In binary fission a single cell divides into two equal halves.Amoeba and Bacteria divide by binary fission.

In multiple fission, a single cell divides into many daughter cells simultaneously. Plasmodium divides by multiple fission.

 

2. How will an organism be benefited if it reproduces through spores?

Advantages of spore formation:

→ Large numbers of spores are produced in one sporangium.

→ Spores are distributed easily by air to far-off places to avoid competition at one place.

→ Spores are covered by thick walls to prevent dehydration under unfavorable conditions.

 

3. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Higher complex organisms cannot give rise to new individuals through regeneration because complex organisms have an organ-system level of organization. All the organ systems of their body work together as an interconnected unit. They can regenerate their lost body parts such as skin, muscles, blood, etc. However, they cannot give rise to new individuals through regeneration.

 

4. Why is vegetative propagation practiced for growing some types of plants?

Vegetative propagation is practiced for growing some types of plants because of following advantages:

→ It is used to grow a plant in which viable seeds are not formed or very few seeds are produced such as Orange, Banana, Pineapple.

→ It helps to introduce plants in new areas where the seed germination fails to produce mature plants due to change in environmental factors and the soil.→ It is a more rapid, easier and cheaper method.

→ By this method a good quality of a race or variety can be preserved.

 

5. Why is DNA copying an essential part of the process of reproduction?

 

DNA copying is an essential part of reproduction as it passes genetic information from parents to offspring. It determines the body design of an individual. The reproducing cells produce a copy of their DNA through some chemical reactions and result in two copies of DNA. The copying of DNA always takes place along with the creation of additional cellular structure. This process is then followed by division of a cell to form two cells.

 

1. How is the process of pollination different from fertilization?

Pollination is the process of transfer of pollen from anther to stigma. It occurs with the help of certain pollinators such as air, water, birds, or some insects.

Fertilization is the fusion of the male and female gametes. It occurs inside the ovule and leads to the formation of zygotes.

2. What is the role of the seminal vesicles and the prostate gland?

The secretions from seminal vesicles and prostate glands lubricate the sperm and provide a fluid medium for easy transport of sperm. Their secretion also provides nutrients in the form of fructose, calcium, and some enzymes.

 

3. What are the changes seen in girls at the time of puberty?

The changes seen in girls at the time of puberty are:

→ Increase in breast size and darkening of the skin of the nipples present at the tips of the breasts.

→ Appearance of hair in the genital area.

→ Appearance of hair in other areas of skin like underarms, face, hands, and legs.

→ Increase in the size of uterus and ovary.

→ Beginning of menstrual cycle.

→ More secretion of oil from the skin, which results in the appearance of pimples.

 

4. How does the embryo get nourishment inside the mother's body?

 

After fertilization the lining of the uterus thickens and is richly supplied with blood to nourish the growing embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called the placenta. It is embedded in the uterine wall. The Placenta contains Villi on the embryo’s side of the tissue and blood spaces on the mother's side surrounding the villi. This provides a large surface from mother to the embryo and waste products from embryo to mother.

 

5. If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?

No, because copper-T will not prevent contact with body fluids. Thus it will not protect her from sexually transmitted diseases.

 

 

Exercise

 

1. Asexual reproduction takes place through budding in

(a) amoeba.

(b) yeast.

(c) plasmodium.

(d) leishmania.

► (b) yeast.

 

2. Which of the following is not a part of the female reproductive system in human beings?

(a) Ovary

(b) Uterus

(c) Vas deferens

(d) Fallopian tube

► (c) Vas deferens

 

3. The anther contains

(a) sepals.

(b) ovules.

(c) carpel.

(d) pollen grains.

► (d) pollen grains.

 

4. What are the advantages of sexual reproduction over asexual reproduction?

Advantages of sexual reproduction:

→ In sexual reproduction, more variations are produced. Thus, it ensures survival of species in a population.

→ The new formed individual has characteristics of both the parents.

→ Variations are more viable in sexual mode than in asexual one. This is because in asexual reproduction, DNA has to function inside the inherited cellular apparatus.

 

5. What are the functions performed by the testis in human beings?

Functions of testes:

→ Produce sperm, which contains a haploid set of chromosomes of the father.

→ Produce a hormone called testosterone, which brings about secondary sexual characters in boys.

 

6. Why does menstruation occur?

Menstruation is a process in which blood and mucous flows out every month through the vagina. This process occurs every month because one egg is released from the ovary every month and at the same time, the uterus (womb) prepares itself to receive the fertilized egg. Thus, the inner lining of the uterus gets thickened and is supplied with blood to nourish the embryo. If the egg does not get fertilized, then the lining of the uterus breaks down slowly and gets released in the form of blood and mucous from the vagina.

 

7. Draw a labeled diagram of the longitudinal section of a flower.

 

8. What are the different methods of contraception?

The contraceptive methods can be broadly divided into the following types:

→ Natural method: It involves avoiding the chances of meeting sperm and ovum. In this method, the sexual act is avoided from day 10th to 17th of the menstrual cycle because during this period, ovulation is expected and therefore, the chances of fertilization are very high.

→ Barrier method: In this method, the fertilization of ovum and sperm is prevented with the help of barriers. Barriers are available for both males and females. Condoms are barriers made of thin rubber that are used to cover penis in males and vagina in females.

→ Oral contraceptives: In this method, tablets or drugs are taken orally. These contain small doses of hormones that prevent the release of eggs and thus fertilization cannot occur.

→ Implants and surgical methods: Contraceptive devices such as the loop or Copper-T are placed in the uterus to prevent pregnancy. Some surgical methods can also be used to block the gamete transfer. It includes the blocking of vas deferens to prevent the transfer of sperm known as vasectomy. Similarly, fallopian tubes of the female can be blocked so that the egg will not reach the uterus, known as tubectomy.

 

9. How are the modes for reproduction different in unicellular and multicellular organisms?

In unicellular organisms, reproduction occurs by the division of the entire cell. The modes of reproduction in unicellular organisms can be fission, budding, etc. whereas in multicellular organisms, specialized reproductive organs are present. Therefore, they can reproduce by complex reproductive methods such as vegetative propagation, spore formation, etc. In more complex multicellular organisms such as human beings and plants, the mode of reproduction is sexual reproduction.

 

10. How does reproduction help in providing stability to populations of species?

Reproduction is the process of producing new individuals of the same species by existing organisms of a species, so, it helps in providing stability to the population of a species by giving birth to new individuals as the rate of birth must be at par with the rate of death to provide stability to the population of a species.

 

11. What could be the reasons for adopting contraceptive methods?

Contraceptive methods are mainly adopted because of the following reasons:

→ To prevent unwanted pregnancies.

→ To control population rise or birth rate.

→ To prevent the transfer of sexually transmitted diseases.

How do organisms reproduce class 10 biology ncert MCQ :

1. The ability of a cell to divide into several cells during reproduction in Plasmodium is called

(a) budding

(b) multiple fission

(c) binary fission

(d) reduction division

► (b) multiple fission

 

2. When an organism breaks into a number of parts and each part develops into an individual, it is called:

a) Budding

b) Binary fission

c) Regeneration

d) Spore formation

► c) Regeneration

 

3. During favorable conditions, Amoeba reproduces by

(a) multiple fission

(b) binary fission

(c) budding

(d) fragmentation

► (b) binary fission

 

4. In a potato, vegetative propagation takes place by:

(a) root

(b) leaf

(c) stem tuber

(d) grafting

► (c) stem tuber

 

5.  In vegetative reproduction, the new individuals are genetically –

a) Similar

b) Dissimilar

c) Abnormal

d) None of these

► a) Similar

 

6. In Rhizopus, tubular thread like structures bearing sporangia at their tips are called

(a) filaments

(b) hyphae

(c) rhizoids

(d) roots

► (b) hyphae

 

7. Spirogyra reproduce by

(a) budding

(b) fragmentation

(c) regeneration

(d) fission

► (b) fragmentation

 

8. The process of release of eggs from the ovary is called

(a) menstruation

(b) reproduction

(c) insemination

(d) ovulation

► (d) ovulation

 

9. The seed that contains the future plant is called the

(a) cotyledons

(b) seed coat

(c) germ cells

(d) embryo

► (d) embryo

 

10. During grafting, the portion of plant that is grafted is called –

a) Stock

b) Scion

c) stalk

d) stem

► b) Scion

 

11. The flower of the Hibiscus plant is

(a) bisexual

(b) unisexual

(c) neuter

(d) very small

► (a) bisexual

 

12. Plants like banana, rose, jasmine, orange have lost the capacity to produce

(a) seeds

(b) buds

(c) flower

(d) roots

► (a) seeds

 

13. In man, fertilization of ovum takes place in

a) Vagina

b) ovary

c) uterus

d) Fallopian tubes

► d) Fallopian tubes

 

14. Along the path of the vas-deferens the secretions of which glands provide nutrition to the sperm.

(a) Prostate glands

(b) Seminal vesicles

(c) Scrotum

(d) Urinary bladder

► (b) Seminal vesicles

 

15. Anemophily is the pollination by –

a) Birds

b) Rain

c) insects

d) Wind

► d) Wind

 

16. Which among the following diseases is not sexually transmitted?

(a) Syphilis

(b) Hepatitis

(c) HIV-AIDS

(d) Gonorrhea

► (b) Hepatitis

 

17. The period during adolescence when the reproductive tissues begin to mature is called

(a) ovulation

(b) puberty

(c) germination

(d) propagation

► (b) puberty

 

18. Which of the following is not an artificial method of vegetative propagation?

(a) Cutting

(b) Layering

(c) Budding

(d) Grafting

► (c) Budding

 

19. There is a greater possibility for the evolution of a new species in organisms which reproduce by

(a) binary fission

(b) budding

(c) fertilization

(d) regeneration

► (c) fertilisation

 

20. The normal duration of menstrual cycle is

a) 7 – 8 days

b) 13 – 15 days

c) 3 – 4 days

d) 28 days

► d) 28 days

 

21. A common feature of reproduction in Amoeba, spirogyra and yeast is that:

a) Asexual reproduction occurs after sexual reproduction

b) Asexual reproduction occurs before sexual reproduction

c) Asexual reproduction does not involve gametes

d) Asexual reproduction involves only one parent

► (d) Asexual reproduction involves only one parent.

 

22. The ability of an organism to develop the whole body from a broken piece or fragment is called

(a) binary fission

(b) budding

(c) multiple fission

(d) regeneration

► (d) regeneration

 

23. Which is the most common method of reproduction in the majority of fungi and bacteria?

(a) Budding

(b) Spore formation

(c) Binary fission

(d) Multiple fission

► (b) Spore formation

 

24. Which of the following method of contraception protects from acquiring sexually transmitted diseases?

(a) Surgery

(b) Condoms

(c) Copper-T

(d) Oral-pills

► (b) Condoms

25. Anemophily is the pollination by:

a) Birds

b) Rain

c) insects

d) Wind

► d) Wind

 

26. The embryo in humans gets nutrition from the mother’s blood with the help of a special tissue called

(a) Placenta

(b) Villi

(c) Uterus

(d) Womb

► (a) Placenta

 

27. Which part of the flower forms the fruit?

a) Whole flower

b) Only stamens and carpel

c) Only ovary

d) Only carpel

► c) Only ovary

 

28. Fertilization in plants occurs in the:

a) Embryo sac

b) Style

c) Pollen tube

d) Stigma

► a) Embryo sac

 

29. The ability to reproduce is lost in a female after

(a) fertilization

(b) menstruation

(c) gamete formation

(d) menopause

► (d) menopause

 

30. Pollen grains are produced by

(a) ovary

(b) ovule

(c) anther

(d) corolla

► (c) anther

 

31. When the fetus is growing inside the uterus it needs nutrients. Which part provides these nutrients?

(a) Placenta

(b) Amniotic sac

(c) Oviduct

(d) Uterus

► (a) Placenta

 

32. Where does fertilization take place?

(a) Uterus

(b) Vagina

(c) Fallopian tube

(d) Cervix

► (c) Fallopian tube

 

33. Which of these is seminal fluid?

a) Prostate gland

b) Cowper’s gland

c) Seminal vesicle

d) all of these

► c) Seminal vesicle

 

34. What marks the beginning of the reproductive life of a woman?

(a) Menopause

(b) Menarche

(c) Fertilization

(d) Ovulation

► (b) Menarche

 

35. At the time of entering into ovule, pollen tube has

a) three male nuclei

b) two male nuclei

c) one gamete nucleus

d) four male gametes

► b) two male nuclei

 

36. Which of the following is a primary sex organ in a mammal?

(a) Ovary

(b) Vagina

(c) Uterus

(d) Mammary glands

► (a) Ovary

 

37. When a sperm is deposited into the vagina which route does it travel?

(a) Vagina → Oviduct → Uterus → Cervix

(b) Vagina → Ovary → Uterus → Oviduct

(c) Vagina → Cervix → Uterus → Oviduct

(d) Vagina → Uterus → Cervix → Oviduct

► (c) Vagina → Cervix → Uterus → Oviduct

 

38. The fertilization of human egg by the sperm takes place in

(a) vagina

(b) uterus

(c) ovary

(d) oviduct

► (d) oviduct

 

39. Many unicellular organisms reproduce by the process of

(a) fission

(b) ovulation

(c) regeneration

(d) nondisjunction

► (a) fission

 

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

(a) process of mating

(b) formation of sperms

(c) easy transfer of gametes

(d) secretion of estrogen

► (b) formation of sperms

 

41. A pair of duct arising from testis, which carry sperms are

(a) fallopian tube

(b) vas deferens

(c) oviduct

(d) urethra

► (b) vas deferens

 

42. The anther contains

(a) Sepals

(b) Ovules

(c) Carpel

(d) Pollen grains.

► (d) Pollen grains.

 

43. Assertion: In male reproductive system, transport of sperm takes place in a fluid which also provides nutrition.

Reason: Protective glands and seminal vesicles secret in the vas deferens.

(a) Both A and R are true and R is the correct explanation of A.

(b) Both A and R are true but R is not the correct explanation of A.

(c) A is true but R is false.

(d) A is false but R is true.

(e) Both A and R are false.

► (a) Both A and R are true and R is the correct explanation of A.

 

44. Assertion: Ovary releases one egg every month.

Reason: The lining of the uterus is always thick and spongy.

(a) Both A and R are true and R is the correct explanation of A.

(b) Both A and R are true but R is not the correct explanation of A.

(c) A is true but R is false.

(d) A is false but R is true.

(e) Both A and R are false.

► (c) A is true but R is false.

 

45. Assertion: In human beings, the female. play a major role in determining the sex of the offspring.

Reason: Women have two X chromosomes.

(a) Both A and R are true and R is the correct explanation of A.

(b) Both A and R are true but R is not the correct explanation of A.

(c) A is true but R is false.

(d) A is false but R is true.

(e) Both A and R are false.

► (d) A is false but R is true.

 

46. Assertion: Amoeba reproduces by fission

Reason: All unicellular organisms reproduced by asexual method.

(a) Both A and R are true and R is the correct explanation of A.

(b) Both A and R are true but R is not the correct explanation of A.

(c) A is true but R is false.

(d) A is false but R is true.

(e) Both A and R are false.

► (a) Both A and R are true and R is the correct explanation of A.

 

Question : An animal which can reproduce by budding is

a) Bryophyllum b) Yeast

c) Hydra d) All of the above

Answer : C

 

Question : Male reproductive organ in a flowering plant is

a) Carpel b) Stamen

c) Corolla d) Ovary

Answer : B

 

Question : A fertilized ovule develops into a _____ in an angiosperm plant

a) seed b) fruit

c) flower d) cotyledon

Answer : A

 

Question : Where are sperms formed in the human body?

a) Vas deferens b) Prostate gland

c) Ovary d) Testis

Answer : D

 

Question : The place where fertilization takes place in the human body is

a) Uterus b) Oviduct

c) Ovary d) vagina

Answer : B

 

Question : Pre- natal sex determination has been prohibited by law due to

a) High cost charged by doctors

b) Possible danger of mother’s health

c) Increasing cases of female foeticide

d) Increasing cases of male foeticide

Answer : C

 

Question : Copper T and Loops are

a) Contraceptive devices b) Conventional devices

c) Conducive devices d) Contaminating devices

Answer : A

 

Question : An unisexual flower

a) Do not have carpal b) Do not have stamen

c) Has either carpel or stamen d) Has either petal or sepal

Answer : C

 

Question : _______ is a common tube for urine and sperm in human male.

a) Urethra b) Uterus 

c) Ureter d) None of the above

Answer : A

 

Question : Eggs starts developing in human female

a) When she attains puberty b) Only after her birth

c) After the first menstruation d) When she is in her mother’s womb

Answer : D

How do organisms reproduce class 10 biology ncert SAQ:

Q.1. Write one difference between asexual and sexual mode of reproduction. Which species is likely to have comparatively better chances of survival - the one reproducing asexuaily or the one reproducing sexually? Give reason to justify your answer.    [CBSE 2018]

Ans. 

• Differences between asexual and sexual mode of reproduction.

• The species reproducing sexually will have better chances of survival because genetic variation is created during sexual reproduction; in case of an adverse environmental change, atleast some variants will survive and continue the race.

 

 

 

Q.2. List three techniques that have been developed to prevent pregnancy. Which one of these techniques is not meant for males? How does the use of these techniques have a direct impact on the health and prosperity of a family?    [Al 2017]

Ans. The techniques to prevent pregnancy include:

(i) Creation of mechanical barriers.

(ii) Changing the hormonal balance of the body.

(iii) Use of intrauterine contraceptive devices.

(iv) Surgical methods.

Use of intrauterine devices is not meant for males.

Impact of use of contraceptives: 

(i) Use of mechanical barriers like-condoms can prevent the spread of sexually-transmitted diseases.

(ii) Pregnancy will make major demands on the body and mind of the woman and if she is not ready for it, her health will be adversely affected; such a condition can be avoided.

(iii) By having a small family, the standard of living can be improved.

 

Q.3. State the changes that take place in the uterus when: 

(a) Implantation of embryos has occurred. 

(b) Female gamete/egg is not fertilized.    [Delhi 2017]

Ans. 

(a) After implantation, the cell divisions continue to occur.

Placenta develops and the embryo gets nutrition from the mother’s blood through the placenta.

The complete development of the fetus occurs in about nine months.

(b) When the female gamete is not fertilized, the thickened and spongy lining of the items is not required any more.

Hence, the lining along with its blood vessels, breaks and comes out through the vagina as blood and mucus, in the process, called menstruation.

 

Q.4. State the basic requirement for sexual reproduction? Write the importance of such reproductions in nature.     [Delhi 2017]

Ans. Sexual reproduction requires male and female individuals of the species.

New genetic variations are created, where each variation would be novel, as sexual reproduction combines DNA (genetic material with accumulated variations) from two different individuals. Such genetic variations are useful in ensuring survival of species.

 

Q.5. What is vegetative propagation? State two advantages and two disadvantages of this method.   [Al 2017]

Ans. Vegetative propagation refers to the development of new plants from vegetative parts (roots, stem or leaves) of an existing plant.

Example of Vegetative Propagation

Advantages of vegetative propagation 

(i) Vegetative propagation is a cheaper, easier and more rapid method of propagation in plants than growing plants from their seeds.

(ii) Better quality of the plants can be maintained by this method.

(iii) it results in propagation of those plants which do not produce viable seeds or produce seeds with prolonged periods of dormancy.

(iv) The plants generated from vegetative means require less time to grow and have the advantage of being more uniform and genetically similar to the parent stock.

Disadvantages:

(a) No genetic variation is created.

(b) Continued vegetative propagation can lead to loss of vigor.

 

 

 

Q.6. What is regeneration? Give one example of an organism that shows this process and one organism that does not. Why does regeneration not occur in the latter?    [Foreign 2017] 

Ans. 

• Regeneration is defined as the ability of any small part of the body to give rise to a new individual. 

• Example:
  (a) Hydra and Planaria show regeneration.
  (b) Amphibians and human beings do not show regeneration.

• 

  Regeneration is carried out by certain specialized cells, which can proliferate to make a large number of cells and different cells undergo development to become various cell types and tissues.

• Such regenerative cells are not found in amphibians and humans.
  
  

Q.7. What is asexual reproduction? Write the process of budding in Hydra.     [Delhi 2017(C)] 

Ans. Reproduction in Hydra:

• Hydra reproduces by budding using regenerative cells.

• A bud develops as an outgrowth in Hydra due to repeated cell division at one specific site.

• When fully mature, the bud detaches itself from the parent body and develops into a new independent individual.

 

 

Q.8. Reproduction is one of the most important characteristics of living beings. Give three reasons in support of the statement.    [AI 2017]

Ans. (a) Reproduction is necessary to maintain the continuity of species.

(b) Reproduction is linked to the stability of populations of species, which occupy well defined places called niches in the ecosystems.

(c) The variations created during reproduction are responsible for survival of a species in case of an adverse change in the environment and evolution.

 

Q.9. Name the method by which spirogyra reproduces under favorable conditions. Is this method sexual or asexual?    [Delhi 2017]

Ans. Spirogyra reproduces by fragmentation.

It is an asexual method of reproduction.

 

Q.10. Name the organs producing sperms and ova respectively in humans. [Foreign 2017] 

Ans. Tests produce sperm and ovary produces ova.

 

Q.11. What is meant by pollination ? Name and differentiate between the two modes of pollination in flowering plants.    [Delhi 2016]

Ans. Pollination is the transfer of pollen grains from the anther of a stamen to the stigma of a carpel. The two modes of pollination are self pollination and cross pollination.

 

Q.12. Name the three parts A, Band C of the flower shown in the following diagram and state one function of each.    [AI 2017(C); Delhi 2016]

Ans. A = Another stamen.

Function: Anther contains two pollen sacs within which numerous pollen grains are produced.

B = Carpel

Function: It is the female reproductive organ of a flower which receives pollen grains that moves through the style and causes fertilization in the ovaries.

C = Ovule

Function: Ovule contains female gamete, egg.

 

Q.13. List any four modes of asexual reproduction.    [CBSE 2016-17 C] 

Ans. Four modes of asexual reproduction are : 

(a) Fission - Parent cell divides to form two or more daughter cells.

(b) Fragmentation - Multicellular organisms break into pieces and each undergo cell division to develop into complete organisms.

(c) Regeneration - Multicellular organisms break into pieces and each undergoes cell division and differentiation (by specialized cells) to form complete organisms.

(d) Budding - A small outgrowth on the parent body detaches when mature and develops into a new individual.

 

Q.14. Name the three parts A, B and C of the flower shown in the figure and state one function of each.    [CBSE 2016-17 C]

Ans.

A.  Anther

Function: Anther contains two pollen sacs within which numerous pollen grains are produced.

B. Style

Function: Guides pollen tube to reach egg cell.

C. Ovary

Function: Has the embryo sac where egg is filtered to form zygote leading to formation of seed.

 

Q.15. (a)  Write the functions of the following parts of the human male reproductive system: 

(i) Testis ; (ii) Vas deferens ; (iii) Urethra ; (iv) Prostate. 

(b) List any two common pubertal changes that appear in human males.    [CBSE 2016-17 C]

Ans. (a) Functions of the following in human male reproductive system -

(i) Testis - Production of male hormones i.e., testosterone and male game test.e., sperms.

(ii) Vas deferens - Delivers sperms.

(iii) Urethra - Helps in transporting sperm out of the m ale reproductive tract, is a common passage for both sperm and urine.

(iv) Prostate - Adds its secretion to the sperm so that they are in fluid medium which provides them with nutrition and makes the transport easier.

(b) Two changes in males during puberty -

(i) Appearance of facial hair.

(ii) Voice begins to crack.

(iii) Occasional enlargement of penis.

(iv) Muscular body.

 

Q.16. In the given figure label the concerned with 

(а) production of egg 

(b) site of fertilization

(c) site of implantation 

(d) site of entry of sperm.     [CBSE 2017]

Ans.

 

Q.17. In the given figure label the parts numbered 1 to 6.    [CBSE 2011,2016-17 C]

Ans. 

1. Pollen grain

2. Stigma

3. Pollen tube

4. Style

5. Ovaiy

6. Synergids

 

Q.18. Explain how spirogyra reproduces. [CBSE 2013,2017] 

Ans. Spirogyra breaks up into smaller pieces upon maturation. These fragments grow into new individuals. Hence, it reproduces by fragmentation.

 

Q.19. List two reasons for the appearance of variations among the progeny formed by sexual reproduction.    [CBSE 2016]

Ans. Sexual reproduction involves gametes from two different individuals. Thus their genetic makeup is different and hence gametes carry different alleles.

It leads to formation of greater variation, so better adaptability and evolution.

 

Q.20. What happens when 

(a) Planaria gets cut into two pieces? 

(b) A mature Spirogyra filament attains considerable length? 

(c) On maturation sporangia burst?    [Foreign 2016] 

Ans. (a) When Planaria is cut into two pieces, each piece grows into a complete organism.

(b) A mature Spirogyra on attaining considerable length breaks up into two or more small pieces. Each piece then grows into a new individual.

(c) When sporangia bursts, spores are released, each one of which develops into a new individual.

 

Q.21. What changes are observed in the uterus if fertilization does not occur ? [CBSE 2016]

Ans. If fertilization fails to take place the thick and spongy lining of the uterus which is formed to receive the fertilized ovum breaks and comes out through the vagina as blood and mucus. This cycle takes place every month and is known as the menstrual cycle.

 

Q.22. In which part of the female reproductive organs of human females does fertilization take place and what happens to the fertilized egg ?    [CBSE 2017]

Ans. In human females, fertilization takes place in the fallopian tube. After fertilization, the fertilized ovum travels to the uterus and gets attached to the wall of the uterus for further development. This is called implantation.

 

Q.23. What happens when a mature Spirogyra filament attains considerable length ?    [CBSE 2016]

Ans. Its filament breaks up into smaller fragments or pieces, and each fragment grows into a new filament/individual.

 

Q.24. Define reproduction. How does it help in providing stability to the population of species?     [DoE, AI 2016]

Ans. Reproduction: It is the process of producing new individuals of the same species by existing organisms of a species, i.e. parents.

Reproduction helps in providing stability to the population of species because reproduction is a process by which organisms increase their populations. The rate of birth and death in a given population determine its size.

 

Q.25. What are those organisms called which bear both the sex organs in the same individual. Give one example of such an organism.    [AI 2016]

Ans. Organisms which bear both the sex organs are called hermaphrodite/bisexual.

Example: Earthworm

 

Q.26. Name the part of Bryophyllum where the buds are produced for vegetative propagation.    [Delhi 2016] 

Ans. Vegetative part, leaf is used in the propagation of Bryophyllum.

 

Q.27. Name the method by which Hydra reproduces. Is this method sexual or asexual?    [Foreign 2016] 

Ans. Hydra reproduces by budding. It is an asexual method.

 

 

 

 

 

 

 

 

 

Q.28. List any four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of a family ? [CBSE 2014,2015]

Or

Suggest three contraceptive methods to control the size of human population which is essential for the health and prosperity of a country. State the basic principle involved in each.    [CBSE 2016]

Ans. 

Four methods of contraception are :

(i) Mechanical barrier - So that sperm does not reach the egg. e.g., condom.

(ii) OCPs - Oral Contraceptive Pills act by changing hormonal balance so that eggs are not released.

(iii) IUD - Intrauterine device like copper-T to prevent pregnancy.

(iv) Surgical method - Blocking vas deferens or fallopian tube.

Since pregnancy makes major demands on a woman's body and mind, her health suffers. By using contraceptive methods a woman is in a better state of health to look after herself and her family. Spacing children will result in healthier and happier children and will also be more economical for the family to look after, giving a good life, and education to fewer children.

 

Q.29. Draw diagrams to explain the regeneration that takes place in each of the body parts of Planaria when its body is cut into three pieces. Name any other organisms in which a similar process can be observed.    [CBSE 2014,2016]

Ans. See Fig. 8.9.

However, multicellular organisms with cell differentiation, when cut in small pieces, may regrow into complete organisms with the help of specific cells, e.g., Planaria and Hydra. This process is known as regeneration.

Regeneration is also seen in Hydra.

 

Q.30. (a) Name an organism in which binary fission occurs in a definite orientation.

(b) Draw a neat diagram of a germinating seed and label on it the following : Cotyledon, Plumule, Radicle.

Or

Draw a germinated seed and label the future root, future shoot and structure that stores food.

Or

Draw a diagram of a germinating seed and label the following parts :

(i) Part that gives rise to shoot system

(ii) Part that gives rise to the root system.

(iii) Part that contains stored food.    [CBSE 2012,2016]

Ans. (a) Leishmania.

(b)

 

 

 

 

 

 

Q.31. ‘Different species use different strategies to determine sex of a newborn individual. It can be environmental cues or genetically determined/ Explain the statement by giving examples for each strategy.    [CBSE 2016] 

Ans. Different species use very different strategies for this. Some rely entirely on environmental cues. Thus, in some animals, the temperature at which fertilized eggs are kept determines whether the animals developing in the eggs will be male or female. In other animals, such as snails, individuals can change sex, indicating that sex is not genetically determined. However, in human beings, the sex of the individual is largely genetically determined. In other words, the genes inherited from our parents decide whether we will be boys or girls.

 

Q.32. Name the organ where ova are formed inside the body. Trace their pathway from their formation to fertilization. Name the organ where they go after fertilization.    [CBSE 2012,2013,2015]

Ans. Organ where ova are formed is the ovary. Ova are released from the ovary into the fallopian tube which leads into the uterus. The ovum gets fertilized in the fallopian tube, where sperm travel to fertilize the egg from the cervix, through the uterus, to the fallopian tube.

The fertilized egg, i.e., zygote, gets implanted in the uterus after fertilization.

 

Q.33. State the changes that take place in the uterus subsequent to implantation of the embryo ? How does this embryo get nourishment inside the mother’s body ?    [CBSE 2012,2015]

Ans. After implantation -The uterine wall thickens and is richly supplied with blood.

A special tissue called placenta develops which connects the embryo to the uterine wall that provides nutrients and oxygen to it.

Placenta is a disc which is embedded in the uterine wall. It contains villi on the embryonic side. On the maternal side, are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.

 

Q.34. State in brief the role of the human male reproductive system. Why is it called the ‘urogenital’ system ? [CBSE 2012,2015]

Ans. The primary reproductive organ in males are testis. Testis produce male gamete and testosterone.

They are located in the scrotum, outside the abdominal cavity, to maintain a temperature 1-3 °C lower than body temperature. This is essential for the production of sperm.

The sperms are formed and delivered through vas deferens which unite with the ureter coming from the urinary bladder.

The prostate glands and seminal vesicles release their secretions which are essential for sperm transport and nutrition.

This opens into the urethra through which both urine and sperm are released.

Hence, the human male reproductive system is also called urino-genital system as urine and semen are released from the same tract.

 

Q.35. List four points of significance of reproductive health in a society. Name any two areas related to reproductive health which have improved over the past 50 years in our country.    [CBSE 2015] 

Ans. Significance of reproductive health in a society :

(i) Reproductively healthy individuals will give rise to a healthy new generation.

(ii) There will be fewer sexual transmitted diseases.

(iii) Healthy mothers mean happy households.

(iv) Healthy individuals mean more productive and prosperous families and society at

 

Q.36. List three distinguishing features between sexual and asexual types of reproduction, in tabular form.    [DoE; Al 2015]

Ans. Distinguishing features between sexual and asexual reproduction:

 

Q.37. List four categories of contraceptive methods.

State in brief two advantages of adopting such preventive methods.    [Al 2015]

Ans. Four methods of contraception used by humans are:

(a) Mechanical barriers such as condoms.

(b) Surgical methods such as vasectomy or tubectomy.

(c) Chemical method such as oral or vaginal pill.

(d) Copper-T.

Advantages of using contraceptives.

(a) It helps in avoiding unwanted pregnancy.

(b) Condom helps in preventing transmission of STDs.

 

Q.38. List six specific characteristics of sexual reproduction.    [AI 2015] 

Ans. Specific characteristics of sexual mode of reproduction. 

(i) Sexual reproduction promotes diversity of characters in the offsprings.

(ii) It results in new combinations of genes brought together in the gamete and this reshuffling increases genetic variation.

(iii) It plays a prominent role in the origin of new species.

(iv) The sexual mode of reproduction incorporates process of combining DNA from two different individuals during reproduction.

(v) It needs two parents to produce an offspring.

(vi) Sex cells are used in sexual reproduction.

 

Q.39. Identify A, B and C in the given diagram and write one function of each.    [AI 2015]

Ans. A = Stigma

B = Pollen tube

C = Female germ cell

Function of stigma: Stigma helps in receiving the pollen grains from the anther of stamen during pollination.

Function of pollen tube: The pollen tube facilitates movement of male germ cells through it to reach female germ cells.

Function of the female germ cell: It meets with the male germ cell to form a zygote which divides many times to form an embryo.

 

Q.40. Name the two reproductive parts of a bisexual flower which contain the germ cells. State the location and function of its female reproductive part.    [Foreign 2015]

Ans. The two reproductive parts of a bisexual flower are stamen and carpel. Stamen is the male reproductive part of the plant. They are the little stalks with swollen tops just inside the rings of petals in a flower.

It is made up of two parts, i.e. a filament and another. Filament is the stalk of stamen and it bears another and consists mainly of conducting tissue. Others are sac-like structures which produce male garnets known as pollen.

The carpel is the female reproductive organ located at the center of a flower. It consists of ovary, style and stigma. The ovary is the swollen part at the bottom of the carpel. The elongated part in the center of the carpel is the style. The stigma is sticky so that it can trap pollen grains easily. Pollen tube that grows from the pollen grain to the ovary aids fertilization.

 

Q.41. (a) Name the following:     [Delhi 2015] 

(i) Thread-like non-reproductive structures present in Rhizopus. 

(ii) ‘Blobs’ that develop at the tips of the non-reproductive threads in Rhizopus, 

(b) Explain how these structures protect themselves and what is the function of the structures released from the ‘blobs’ in Rhizopus.

Ans. (a) (i) Hyphae (ii) Sporangium

(b) Spores are enclosed within sporangia which protect the spores.

Spores when released from sporangia develop into new Rhizopus.

 

 

 

 

 

 

 

 

Q.42. Explain the process of regeneration in Planaria. How is this process different from reproduction?    [Foreign 2015; Delhi 2013]

Ans.

In regeneration, the organism needs to be cut into pieces to get more organisms. In reproduction, the organism need not be cut to multiply.

 

Q.43. What are chromosomes? Explain how in sexually reproducing organisms the number of chromosomes in the progeny is maintained.    [AI 2015]

Ans. ‘Chromosomes’ are long thread-like structures which contain hereditary information of the individual and are thereby the carriers of genes. Chromosomes are located in the nucleus of a cell.

The parents are diploid (2n) as each of them has two sets of chromosomes. They form haploid (In) male and female gametes through the process of meiosis. The haploid gametes have one set of chromosomes. These two gametes fuse during fertilization and the offspring become diploid (2n) which is the same as the parents chromosome number.

 

Q.44. Name the parts of a bisexual flower that are not directly involved in reproduction. [Foreign 2015] 

Ans. Parts of a bisexual flower which are not directly involved in reproduction are (i) Petal, (ii) Sepal and (iii) Stem.

 

Q.45. Name two simple organisms having the ability of regeneration.    [Al 2015]

Ans. Hydra and Planaria.

 

Q.46. Name the causative agent of the disease “Kalaazar” and its mode of asexual reproduction.    [Foreign 2015]

Ans. Leishmania causes kala-azar. It reproduces by binary fission.

 

Q.47. What is DNA copying?    [Delhi 2015] 

Ans. DNA in the cell nucleus is the information source for making proteins and different proteins lead to different body designs. During reproduction, a similar copy of DNA is generated and the process is called DNA copying.

 

Q.48. Where is DNA found in a cell?    [DoE; AI 2015] 

Ans. DNA is found in the nucleus.

 

 

 

 

 

 

Q.49. What is DNA?   [Foreign 2015]

Ans. The full form of DNA is deoxyribonucleic acid. DNA lies in the cell nucleus which is the information source for making proteins, and different proteins lead to different designs.

 

Q.50. Name the life process of an organism that helps in the growth of its population.    [AI 2015] 

Ans. Reproduction

How do organisms reproduce class 10 biology ncert  long question:

Q.1. (a) Identify the given diagram. Name the parts 1 to 5.

(b) What is contraception? List three advantages of adopting contraceptive measures.    [Delhi 2019]

Ans. (a) 1. Oviduct

2. Ovary

3. Uterus

4. Cervix

5. Vagina

(b) The prevention of pregnancy in women is called contraception.

(i) It helps in maintaining the health of women as frequent pregnancies have adverse effects on the health of the mother.

(ii) It helps in preventing sexually transmitted diseases such as AIDS, syphilis, gonorrhoea, etc.

(iii) It helps in birth control. If a family is small then each child will get proper resources like attention, education, food, clothes, etc.

Q.2. (a) Write the functions of the following parts in the human female reproductive system:

(i) Ovary 

(ii) Oviduct 

(iii) Uterus 

(b) Describe the structure and function of the placenta.    [CBSE 2018, AI 2017,17(C), Delhi 2016]

Ans. (a) (i) Ovary

- It produces the female gametes or germ cells, called ova.

- It secretes the female sex hormones such as oestrogen and progesterone.

(ii) Oviduct

- It transports the ova from the ovary to uterus/womb.

- Fertilization occurs in the oviduct.

(iii) Uterus

- Implantation of the embryo occurs in the lining of the uterus and; the complete development of the foetus occurs here.

- the contractions of the muscles of the uterus help in childbirth.

(b) Structure of placenta:

- Placenta is a disc-like structure embedded in 7 the uterine wall.

- It contains villi on the embryo’s side and on the mother’s side there are blood spaces, which surround the villi; this arrangement provides a large surface area for exchange of materials.

Functions of placenta: 

- It transfers glucose and oxygen from the mother’s blood to the fetus.

- It also rem oves the wastes (CO2 and nitrogenous wastes) generated by the fetus to the mother’s blood.

Q.3. (a) Name the organ that produces sperms as well as secretes a hormone in human males.

Name the hormone it secretes and write its functions.

(b) Name the parts of the human female reproductive system where fertilization occurs. 

(c) Explain how the developing embryo gets nourishment inside the mother’s body.     [Delhi 2017]

Ans. (a) The male organ is testis. It secretes the hormone testosterone and regulates the formation of sperms.

— It brings about changes in the appearance of boys at the time of puberty.

(b) Fertilization occurs in the oviduct.

(c) The developing embryo gets nourishment from the mother’s blood with the help of a special tissue, called placenta.

The placenta provides a large surface area for the passage of glucose and oxygen from the mother’s blood to the embryo.

Q.4. (a) What is pollination? Give its two types.

(b) Draw a longitudinal section of the female reproductive part of a flower showing germination of pollen grain. Label it the following:

(i) Stigma;

(ii) Pollen tube with a male germ cell;

(iii) Female germ cell.    [CBSE 2016-17 C]

Ans. (a) Pollination is the process of transfer of pollen grains from another of a flower to the stigma of a same flower or another flower of same species.

Depending on the flower, it is of two types :

(i) Self pollination - When pollen from the anther of the same flower lands on its stigma. (ii) Cross pollination - When pollen from one flower lands on the stigma of another flower of the same species, with the help of air, water, insects, birds or bats.

(b)

Q.5. List and. explain briefly any three methods of contraception.    [CBSE 2016-17 Cl

Ans. Three methods of contraception :

(i) Mechanical Barrier - Condoms on penis or vagina are a covering worn so as to create a barrier such that sperm do not reach the egg.

(ii) Oral Contraceptive Pills - They change the hormonal balance o f the body so that eggs are not released and fertilization does not take place.

(iii) Intrauterine Device - Devices like copper-T or loop are placed in the uterus which change the pH of the uterus and hence sperm cannot survive, thereby preventing pregnancy.

(iv) Surgical Method - Blocking vas deferens in males and fallopian tubes in females, would allow respective gametes to be released and hence act as contraceptive.

Q.6. (a) What is variation ? How is variation created in a population ? How does the creation of variation in a species promote survival ?

(b) Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes.    [CBSE 2017-18 C]

Ans. (a) Variation is the occurrence of differences between organisms.

Variations are created in a population in different ways :

(i) There may be minor changes/errors during the DNA copying mechanism which happens before any cell division. These variations may go on accumulating from previous generations, ultimately leading to visible changes.

(ii) In sexually reproducing organisms, the traits of two individuals combine and give rise to new combination in the progeny. This also leads to variation.

(iii) Thus combining variations from two or more individuals would thus create new combinations of variations.

Organisms with suitable variations will have better chances of survival. Depending on the nature of variation, different individuals would have different kinds of advantages.

(b) In sexually reproducing organisms each cell has two copies of each chromosome, one each from the male and female parent. During gamete formation, one chromosome from each pair goes to a gamete. Hence, the gametes have half the number of chromosomes, but one chromosome of each pair. When two gametes combine, they restore the normal number of chromosome in the progeny

Q.7. What is placenta? Describe its structure. State its functions in case of pregnant human females.    [CBSE 2012,2013,2016,2017]

Ans. For implantation of the foetus, a special tissue called the placenta develops from the maternal uterine wall. It is a disc shaped structure, in the uterine wall with villi on the embryonal side and large blood spaces on the maternal side.

Functions :

(i) It provides a large surface area for glucose and O2 to pass from the mother's blood to the embryo.

(ii) It also removes embryonal metabolic wastes.

Q.8. (a) Differentiate between pollen grains and ovule.

(b) State in brief the functions of the following parts of the human female reproductive system : 

(i) Ovary 

(ii) Fallopian tube 

(iii) Uterus.     [CBSE 2012,2015,2017 C]

Ans.

(a) (b) (i) Ovary — Involved in production of ova and female sex hormone estrogen.(ii) Fallopian tube - Receives ovum after ovulation and is the site of fertilisation.

(iii) Uterus - Embryo gets implanted and its development till child birth takes place here.

Q.9. (a) Mention the role of the following organs in the human male reproductive system :

(i) Testis

(ii) Scrotum

(iii) Vas deferens

(iv) Prostate glands

(b) State the reasons why testes are located outside the abdominal cavity.     [CBSE 2011,2012,2013,2015,2016-17 C]

Ans. (a) (i) Male gametes (sperms) and male hormone testosterone are produced by testis. (ii) Sperm formation requires a lower temperature than the normal body temperature. This temperature is 1-3°C lower than the temperature of the body. Testis are located outside the abdominal cavity, in the scrotum to provide the right temperature.

(iii) The sperms formed are delivered through the vas-deferens which unite with a tube coming from the urinary bladder.

(iv) The prostate glands secrete the fluids which provide nutrition to the sperms and make their transport easier.

(b) They require a lower temperature than the human body temperature for the formation of sperms.

Q.10. (a) Draw a sectional view of the human female reproductive system and label the following parts :

(i) where the development of egg occurs,

(ii) where fertilization takes place,

(iii) where fertilized eggs get implanted.

(b) Describe the changes the uterus undergoes :

(i) to receive the zygote.

(ii) if zygotes are not formed.     [CBSE 2013,2014,2015,2016-17 C]

Ans. (a)

(b) (i) The zygote gets implanted in the uterus which thickens its walls and increases blood supply.

(ii) If zygotes are not formed, the lining of the uterus slowly breaks and is shed along with blood and mucus and comes out through vagina in the form of menstrual flow.

Q.11. Discuss briefly the different types of reproduction.    [CBSE 2017-18 C]

Ans. Living organisms reproduce mainly by two methods :

(1) Asexual reproduction : In this mode of reproduction, the offspring arises from a single individual parent. Asexual type of reproduction takes place in unicellular organisms, some plants, and certain multicellular animals like sponges and Hydra.

Main types of asexual reproduction are :

(i) Fission.

(ii) Budding.

(iii) Spore formation.

(iv) Regeneration.

(v) Vegetative propagation.

(2) Sexual reproduction : For sexual reproduction, involvement of the two sexes, male and female, is essential. Sexual reproduction involves union of sperm (male gamete) and egg (female gamete). These gametes are produced by gonad testes in males and ovary in females.