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Solved the very best collection of How do Organisms Reproduce Class 10 Science Important Questions and Answers Chapter 8 Pdf from the latest NCERT edition books, It will help you in scoring more marks in CBSE Exams.
Class 10 Science Chapter 8 Important Questions with Answers How do Organisms Reproduce
Class 10 Chemistry Chapter 8 Important Questions with Answers How do Organisms Reproduce
How do Organisms Reproduce Class 10 Important Questions Very Short Answer Type
Question 1.
“Cell division is a type of reproduction in unicellular organisms.” Justify. (2013 D)
Answer:
Cell division is a type of reproduction in unicellular organisms because many unicellular organisms split into two identical halves during cell division leading to the creation of new organisms.
Question 2.
Name the body part where fertilisation occurs in human female. (2013 OD)
Answer:
Fallopian tube.
Question 3.
List two functions performed by the testis in human beings. (2015 D)
Answer:
Two functions of testes are:
- To produce the male sex cells (gametes) called sperms.
- To secrete the male sex hormone called testosterone which is responsible for secondary sexual changes in males.
Question 4.
Name the life process of an organism that helps in the growth of its population. (2015 OD)
Answer:
Reproduction is the process that helps in the growth of population of an organism.
Question 5.
Name two simple organisms having the ability of regeneration. (2015 OD)
Answer:
Two simple organisms having the ability of regeneration are Planaria and Hydra.
Question 6.
Name the part of Bryophyllum where the buds are produced for vegetative propagation. (2016 D)
Answer:
The leaves produce buds in Bryophyllum which are used for vegetative propagation.
Question 7.
What happens when a Planaria gets cut into two pieces? (2016 D)
Answer:
When a Planaria gets cut into two pieces, then each piece regenerates into a new planaria.
Question 8.
What happens when a mature spirogyra filament attains considerable length? (2016 OD)
Answer:
When a mature spirogyra filament attains considerable length, it breaks up into smaller fragments or pieces, and each fragment grows into a new filament or individual.
Question 9.
What are those organisms called which bear both the sex organs in the same individual? Give one example of such organism. (2016 OD)
Answer:
Organisms having both the sex organs in the same individual are called Hermaphrodite. E.g., Earthworm.
Question 10.
List two functions of ovary of human female reproductive system. (2016 OD)
Answer:
Two functions of ovary:
- To produce female gamete ovum
- To secrete female hormones estrogen and progesterone.
How do Organisms Reproduce Class 10 Important Questions Short Answer Type I
Question 1.
Write any two differences between binary fission and multiple fission in a tabular form as observed in cells of organisms. (2011 D)
Answer:
Difference between Binary fission and Multiple fission
Binary Fission:
- The parent organism splits to form two new organisms.
- This method of reproduction can take place in any plane in unicellular organisms like amoeba. It takes place during normal life conditions.
Multiple Fission:
- The parent organism splits to form many new organisms at the same time.
- In this method of reproduction a protective wall is formed around the cell of a single celled organism like in plasmodium during unfavourable conditions.
Question 2.
List any four modes of asexual reproduction. (2011 D, 2014 D)
Answer:
Four modes of asexual reproduction:
- Fission:
(i) Binary fission
(ii) Multiple fission - Budding
- Spore formation
- Fragmentation
Question 3.
How does an embryo get nourishment inside the mother’s body? (2011 OD)
Answer:
After implantation, a disc-like special tissue develops between the uterus wall and the embryo called placenta. The exchange of nutrients, oxygen and waste products between the embryo and the mother takes place through the placenta.
Question 4.
List two advantages of vegetative reproduction practised in case of an orange plant. (2012 D)
Answer:
Advantages of vegetative reproduction in case of an orange plant:
- In case an orange plant is grown from seeds it may take many years before it starts to bear fruit. But if the plant is grown from vegetative reproduction, it starts bearing fruits much earlier.
- Seedless oranges can be obtained by this method.
Question 5.
How does a growing embryo get nutrition from the mother’s blood? (2012 D)
Answer:
There is a special tissue developed between the uterus wall and embryo called placenta. It is through the placenta that all the requirements of the developing foetus like nutrition, respiration and excretion etc. are met from the mother’s body.
Question 6.
Define the term puberty. List two changes observed in girls at the time of puberty. (2012 D)
Answer:
Puberty: The age at which the sex hormones (or gametes) begin to be produced and the boy and girl become sexually mature (able to reproduce) is called puberty.
Generally boys attain puberty at the age of 13 to 14 years while girls reach puberty at the age of 10 to 12 years.
Changes observed in girls at the time of puberty are mammary glands develop and enlarge; menstruation starts.
Question 7.
What is meant by asexual reproduction? List its any two different forms. (2012 D)
Answer:
Asexual reproduction. The production of a new organism from a single parent without the involvement of sex cells is called asexual reproduction.
Different forms:
- Fission
- Budding.
Question 8.
Mention the two functions of human testis. (2013 D)
Answer:
Functions of human testis:
- Testes make male sex hormones called testosterone.
- Testes produce male sex gametes, i.e., sperms.
Question 9.
List two advantages of growing grapes or banana plants through vegetative propagation. (2013 OD)
Answer:
Two advantages of growing grapes or banana plant through vegetative propagation:
- The fruit trees grown through vegetative propagation bear fruits much earlier.
- Banana and grapes produce either very few seeds or do not produce viable seeds. Therefore their plants are grown by vegetative propagation.
Question 10.
(a) How do Leishmania and Plasmodium reproduce?
(b) State one difference in their mode of reproduction. (2013 OD)
Answer:
(a) Leishmania and Plasmodium reproduce by fission (asexual mode of reproduction).
(b) (i) Leishmania reproduce by binary fission in which the parent organism splits to form two new organisms.
(ii) Plasmodium reproduce by multiple fission in which the parent organism splits to form many new organisms at the same time.
Question 11.
List four advantages of vegetative propagation. (2014 D)
Answer:
advantages of vegetative propagation:
- Plants grown by vegetative propagation grow much faster than those grown from seeds.
- A large number of plants can be produced by the method of vegetative propagation.
- The plants grown by vegetative propagation usually need less attention in their early years than the plants grown from seeds.
- Seedless plants can also be grown from this method.
How do Organisms Reproduce Class 10 Important Questions Short Answer Type II
Question 1.
(a) List two sexually transmitted diseases in each of the following cases:
(i) Bacterial infections
(ii) Viral infections
(b) How may the spread of such diseases be prevented?
Answer:
(a) sexually transmitted diseases:
- Bacterial infections. Gonorrhoea, Syphilis
- Viral infections. Warts, AIDS (Acquired Immuno Deficiency Syndrome)
(b) Barrier method of contraception provides protection against STDs like AIDS, Syphilis etc.
Observing hygienic conditions.
Question 2.
What does HIV stand for? Is AIDS an infectious disease? List any four modes of spreading AIDS. (2011 OD)
Answer:
HIV. Human Immuno Deficiency Virus
This virus causes AIDS which is an infectious disease.
Modes of spreading AIDS:
- The AIDS disease usually spreads through unprotected sexual contact with an infected person carrying AIDS virus.
- The AIDS disease also spreads through the transfusion of blood contaminated with AIDS virus.
- The AIDS disease also spreads through the use of infected needles for injections.
- An AIDS infected mother can transmit the virus to her child during pregnancy or during birth.
Question 3.
What are sexually transmitted diseases? Write two examples each of sexually transmitted diseases caused by (i) virus, (ii) bacteria. Explain how the transmission of such diseases be prevented? (2012 D, 2013 D, 2015 D)
Answer:
Diseases which are transmitted from an infected person to a healthy person due to sexual contract are called Sexually Transmitted Diseases (STD).
Sexually transmitted diseases caused by
(i) Virus:
- AIDS (Acquired Immuno Deficiency Syndrome)
- Genital warts
(ii) Bacteria:
- Gonorrhoea
- Syphilis
Transmission of such diseases can be prevented by the following ways:
- Screening tests for blood donors
- Mutually faithful monogamous relationships
- Educating people in high risk groups
- Using condoms etc.
Question 4.
(a) State the role of placenta in the development of embryo. (2012 OD)
(b) What happens when the egg is not fertilized?
Answer:
(a) Role of placenta. After implantation, a disc like special tissue develops between the uterus wall and the embryo called placenta.
The exchange of nutrients, oxygen and waste products between the embryo and the mother takes place through the placenta.
(b) If the egg does not get fertilised (due to non-availability of sperms in the female body) then the thick and soft inner lining of uterus along with the blood vessels and the dead egg comes out of the vagina in the form of bleeding called menstruation.
Question 5.
List and explain in brief three methods of contraception. (2012 OD)
Answer:
Three different methods of contraception:
1. Barrier methods. In these methods, physical devices such as condoms, diaphragm and cervical caps are used. These devices prevent the entry of sperm in the female genital tract, thus acting as a barrier between them.
2. Surgical methods. There are surgeries that can be carried out in males and females. In males, a small portion of the sperm duct (vas deferens) is blocked by surgical operation. It prevents the egg to reach the uterus. In both the cases, fertilisation will not take place.
3. Chemical methods. This category of contraceptives acts by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. Females use two types of pills for preventing pregnancies, i.e., oral pills and vaginal pills.
The oral pills contain hormones which stop the ovaries from releasing ovum into fallopian tube. This is also called oral contraceptives (OC).
Other contraceptive devices such as loop or the copper-T are placed in the uterus to prevent pregnancy.
Question 6.
(a) Explain the process of regeneration in Planaria.
(b) How is regeneration different from reproduction? (2013 D, 2013 OD)
Answer:
(a) Planaria, a flatworm, possesses great power of regeneration. If the body of planaria gets cut into a number of pieces, then each body piece can regenerate into a complete planaria by growing all missing parts.
The process of getting back a full organism from its body parts is called regeneration.
(b) Regeneration is different from reproduction because most simple animals would not depend on being cut into pieces to be able to reproduce.
Question 7.
(a) Name the following: (2013 D)
(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 the structure and the function of the structures released from the ‘blobs’ in Rhizopus.
Answer:
(a) (i) Thread like non-reproductive structures present in Rhizopus is hyphae.
(ii) Blob like structure at the tip of hyphae is sporangia.
(b) Thread like non-reproductive parts develop on the substrate (like bread) called hyphae. At the tip of the hyphae tiny blob like structures develop called sporangia which contain spores. These spores can develop into new Rhizopus individuals. The spores are covered by thick walls that protect them until they come into contact with another moist bread and can begin to grow.
Question 8.
Explain budding in Hydra with the help of diagrams only. (2013 OD, 2015 D)
Answer:
Budding in Hydra. Hydra reproduces by budding which is an asexual type of reproduction.
During this type of reproduction, a bulb like projection arises from the parent body which is known as bud. The bud may be unicellular or multicellular formed by mitotic division of its cells. This bud then grows gradually to form a small hydra. And finally, the tiny new hydra detaches itself from the body of the parent hydra and lives as a separate organism. Thus, the parent hydra produces a new hydra.
Question 9.
List any four methods of contraception used by humans.
How does their use have a direct effect on the health and prosperity of the family?
(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. (2013 OD, 2014 D, 2016 D)
Answer:
Methods of Contraception:
1. Barrier methods. In these methods, physical devices such as condoms, diaphragm and cervical caps are used. These devices prevent the entry of sperm in the female genital tract, thus acting as a barrier between them.
2. Surgical methods. There are surgeries that can be carried out in males and females. In males, a small portion of the sperm duct (vas deferens) is blocked by surgical operation. This presents the sperms from coming out. In females a small portion of the fallopian tubes (oviducts) is blocked by a surgical operation. It prevents the egg to reach the uterus. In both the cases, fertilisation will not take place.
3. Chemical methods. This category of contraceptives acts by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. Females use two types of pills for preventing pregnancies, i.e,, oral pills and vaginal pills.
The oral pills contain hormones which stop the ovaries from releasing ovum into fallopian tube. This is also called oral contraceptives (OC).
Other contraceptive devices such as loop or the copper-T are placed in the uterus to prevent pregnancy.
Effect of these methods on health of the family. Contraceptive methods are used to prevent the spreading of STDs like syphillis, AIDS, etc.
Effect of these methods on the prosperity of the family. If a couple has less number of children, they can provide good clothes, good food and a good education to each child. This will make the parents as well as children happy.
Question 10.
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 organism in which a similar process can be observed. (2014 D)
Answer:
The process of getting back a full organism from its body parts is called regeneration. The simple animals like hydra and planaria show regeneration.
Diagram for regeneration in planaria. The process of getting back a full organism from its body parts is called regeneration. The simple animals like hydra and planaria show regeneration.
Explanation: If the body of planaria gets cut into a number of pieces, then each body piece can regenerate into a complete planaria by growing all the missing parts. The regeneration of an organism from its cut body part occurs by the process of growth and development. The cells of cut body part divide rapidly to make a ball of cells. The cells then become specialised to form different types of tissues which again form various organs and body parts.
Question 11.
(a) Write the names of those parts of a flower which serve the same function as the following do in the animals: (2014 D)
(i) testis (ii) sperm (iii) ovary (iv) egg
(b) State the function of flowers in the flowering plants.
Answer:
(a) (i) testis – anther
(ii) sperms – pollen grains
(iii) ovary – ovary
(iv) egg – egg or ovum
(b) The function of flower in flowering plants is to assist in sexual reproduction, i.e., to make male and female gametes and to ensure that fertilisation will take place to make new seeds for the reproduction in plants.
Question 12.
On cutting the body of an organism into many pieces it was observed that many of these pieces developed as new individuals. Name the process and list two organisms in which this process may be observed. Draw a schematic diagram to illustrate the changes that are likely to be observed during the development of new individuals in any one of the organisms named. (2014 D)
Answer:
Process is Regeneration.
Examples. The simple animals like hydra and planaria show regeneration.
Diagram for Regeneration in Planaria:
Question 13.
Which species is likely to have better chances of survival the one reproducing asexually or the one reproducing sexually? Justify your answer. (2014 OD)
Answer:
The survival of animal reproducing sexually has better chance of survival:
1. Modes of sexual reproduction allow for greater variations to be generated which are useful for ensuring the survival of the individuals of species during the struggle for existence. Sexually reproductive young ones are more healthy than those reproduced by asexual methods.
2. In asexual reproduction, the offsprings are almost identical to their parent because they have the same genes as their parent, so much genetic variation is not possible in asexual reproduction. This is a disadvantage because it inhibits the further evolution of the organism.
Question 14.
List six specific characteristics of sexual reproduction. (2015 OD)
Answer:
Characteristics of sexual reproduction are:
- In sexual reproduction, two parents are involved (male and female).
- The new organism produced is genetically different from both parents.
- During gamete formation meiosis occurs. After fertilization all divisions are mitotic.
- Sexual reproduction helps in evolution.
- Fertilization of gametes leads to zygote formation. This zygote grows and develops to form a new organism.
- Humans, fish, dogs, hens, cats, cows, horses, deer, rabbit; lions and tigers all reproduce by the method of sexual reproduction. Most of the flowering plants also reproduce by sexual reproduction.
Question 15.
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. (2015 OD)
The significance of reproductive health of society are:
- Regular medication and check-ups have led to development of reproductive health. Healthy mothers give birth to healthy children.
- Reproductive health should be maintained in order to prevent sexually transmitted diseases (STDs).
- Family planning by using various contraceptives enables a couple to decide on the number of children they want to have and when to have them. If a couple has less number of children they can provide good food, clothes and education to each child. So a small family is a happy family.
- Having fewer children also keeps the mother in good health. This will reciuce the cases of maternal mortality as well as new born mortality.
Areas which have improved:
- Better family planning has led to reduction in family size and better economic stability.
- Decrease in STD cases due to more awareness and wider use of contraceptives.
Question 16.
Name the parts A, B and C shown in the following diagram and state one function of each. (2016 D)
Answer:
A → Anther. It produces pollen grains which are the male gametes.
B → Style. It provides the path through which the polien tube grows and reaches the ovary.
C → Ovary. It contains ovules and each ovule has an egg cell/female gamete. It develops into fruit after fertilization.
Question 17.
What is multiple fission? How does it occur in an organism? Explain briefly. Name one organism which exhibits this type of reproduction. (2016 D)
Answer:
Multiple fission. The process of asexual reproduction in which many individuals are produced from the parent cell.
Process: Sometimes during unfavourable conditions a protective wall or cyst is formed around the cell of a single celled organism (like in plasmodium). Inside the cyst, the nucleus of the cell splits several times to form many smaller nuclei called daughter nuclei. Each nucleus gathers a bit of cytoplasm around itself, develops a membrane around each structure. Thus many daughter cells develop which on liberation grow into adult organisms.
Plasmodium exhibits multiple fission.
Question 18.
What are the functions of testes in the human male reproductive system? Why are these located outside the abdominal cavity? Who is responsible for bringing about changes in appearance seen in boys at the time of puberty? (2016 D)
Answer:
Functions of testes are:
1. to make male sex cells (or male gametes) called sperms.
2. to make the male sex hormone called testosterone.
3. The testes of a man lie in a small muscular pouch called scrotum outside the abdominal cavity of the body. This is because the sperm formation requires a lower temperature than the normal body temperature.
Being outside the abdominal cavity, the temperature of scrotum is about 3° C lower than the temperature inside the body and thus the testes are provided an optimal temperature for the formation of sperms. The male sex hormone testosterone is responsible for bringing about changes in appearance seen in boys at the time of puberty.
Question 19.
Define reproduction. How does it help in providing stability to the population of species? (2016 OD)
Answer:
The production of new organisms from the existing organisms of the same species is known as reproduction. It is essential for the survival of a species on earth. It helps in replacing the lost section of the population due to death and various other causes.
- Populations of organisms live in well defined places called niches in the ecosystem using their ability to reproduce.
- Reproduction involves DNA copying which is the source of information for making proteins thereby controlling body design.
- These body designs allow the organism to use a particular niche for the stability of the population of a species.
- Minor variations may also lead to the stability of the species.
Question 20.
Explain the term “Regeneration” as used in relation to reproduction of organisms. Describe briefly how regeneration is carried out in multicellular organisms like Hydra. (2016 OD)
Answer:
Regeneration is a mode of asexual reproduction in some organisms. The process of getting back a full organism from its body parts is called regeneration. The simple multicellular animals like hydra and planaria show regeneration.
Regeneration in hydra:
- If the body of hydra gets cut into a number of pieces, then each body piece can regenerate into a complete hydra by growing all the missing parts.
- The regeneration of an organism from its cut body part occurs by the process of growth and development.
- The cells of cut body parts divide rapidly to make a ball of cells.
- The cells then become specialised to form different types of tissues which again form various organs and body parts.
Question 21.
(a) List two reasons for the appearance of variations among the progeny formed by sexual reproduction. (2016 OD)
(b)
(i) Name the part marked ‘A’ in the diagram.
(ii) How does ‘A’ reach part ‘B7
(iii) State the importance of part ‘C’.
(iv) What happens to the part marked ‘D’ after fertilisation is over?
Answer:
(a) The appearance of variations among the progeny formed by sexual reproduction is due to the following reasons:
(i) Sexual reproduction takes place by the combination of two germ cells produced by two different individuals. Fusion of the male and female gametes.
(ii) Each time zygote is formed by the new combination of variants.
(b) (i) A ⇒ Pollen grains
(ii) Pollen grains, i.e., ‘A’ reach part ‘B’, i.e., stigma of the carpel by the process of pollination.
Pollination is carried out by insects (like bees, butterfly, etc.), birds, wind, water, etc.
(iii) ‘C’ ⇒ Pollen tube
Pollen tube grows downward through the style towards the female gamete in the ovary. Pollen tube helps the male gamete reach the egg or ovule (female gamete).
(iv) ‘D’ ⇒ Fertilised egg or Zygote
The fertilized egg (or zygote) divides several times to form an embryo within the ovule.
Question 22.
In the context of reproduction of species state the main difference between fission and fragmentation. Also give one example of each. (2016 OD)
Answer:
Difference between Fission and Fragmentation
Fission:
- Fission is the process of reproduction in which a unicellular organism splits (or divides) to form two (or more) new organisms.
- Many unicellular organisms like amoeba, paramecium, leishmania, etc. carry out fission.
Fragmentation:
- Fragmentation is the process of breaking up of the body of a simple multicellular organism into two (or more) pieces on maturing, each of which subsequently grows to form a complete new organism.
- The organisms like spirogyra, sea anemones can reproduce by fragmentation.
Question 23.
State the basic requirement for sexual reproduction? Write the importance of such reproduction in nature. (2017 D)
Answer:
The basic requirement for sexual reproduction is sexual interaction of male and female parents to cause fusion of male gamete with female gamete to form zygote. Then from the zygote develops the new child. Importance of such reproduction.
Such sexual reproduction leads to more variation in the offsprings for their successful living in the changing environmental conditions. More variations also lead to evolution of new species after some generations. It leads to diversity in the population which helps in natural selection.
Question 24.
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? (2017 OD)
Answer:
Three techniques to prevent pregnancy are:
- Barrier method. Use of condoms either by male or female during sexual mating.
- Use of copper-T device by the females in their uterus.
- Surgical method by male or female.
Use of copper-T is not meant for males. By use of these techniques a family will have lesser number of children so their economic condition will be better. Such family will have healthy children as lesser number of children in a family will get more attention from the parents and will be cared for in a better way. It also helps to control the population.
How do Organisms Reproduce Class 10 Important Questions Long Answer Type
Question 1.
(a) Draw a diagram of the longitudinal section of a flower and label on it sepal, petal, ovary and stigma.
(b) Write the names of male and female reproductive parts of a flower. (2011 D)
Answer:
(a)
(b) Male reproductive part. Stamen
Female reproductive part. Carpel
Question 2.
(a) What is fragmentation in organisms? Name a multicellular organism which reproduces by this method.
(b) What is regeneration in organisms? Describe regeneration in Planaria with the help of a suitable diagram. (2011 D)
Answer:
(a) Fragmentation: It occurs in multicellular organisms with relatively simple body organisation, for example, in spirogyra (an algae plant). The body breaks up on maturation into two or more smaller pieces and each piece then develops into a new individual.
(b) The process of getting back a full organism from its body parts is called regeneration. The simple animals like hydra and planaria show regeneration.
Explanation: If the body of planaria gets cut into a number of pieces, then each body piece can regenerate into a complete planaria by growing all the missing parts. The regeneration of an organism from its cut body part occurs by the process of growth and development. The cells of cut body part divide rapidly to make a ball of cells. The cells then become specialised to form different types of tissues which again form various organs and body parts.
Question 3.
With the help of suitable diagrams, explain the various steps of budding in Hydra. (2011 OD)
Answer:
Hydra reproduces by budding which is an asexual type of reproduction.
During this type of reproduction, a bulb like projection arises from the parent body which is known as bud. The bud may be unicellular or multicellular formed by mitotic division of its cells. This bud then grows gradually to form a small hydra. And finally, the tiny new hydra detaches itself from the body of the parent hydra and lives as a separate organism. Thus, the parent hydra produces a new hydra.
Question 4.
What is binary fission in organisms? With the help of suitable diagrams, describe the mode of reproduction in Amoeba. (2011 OD)
Answer:
Binary fission. Binary fission is an asexual method of reproduction in which the parent organism splits to form two new daughter organisms.
Reproduction in amoeba: Unicellular organisms like amoeba and paramecium reproduce by binary fission. During this reproduction process, first the nucleus divides into two daughter nuclei followed by the division of cytoplasm.
Question 5.
Define the terms pollination and fertilisation. Draw a diagram of a pistil showing pollen tube growth into the ovule and label the following:
pollen grain, male gamete, female gamete, ovary. (2012 D)
Answer:
Pollination: Pollination is the transfer of pollen grains from the anther of a stamen to the stigma of a carpel. Pollination occurs only in plants. Pollination can occur in two ways:
- Self pollination
- Cross pollination.
It is a physical process.
Fertilisation: The fusion of a male gamete with a female gamete to form zygote is called fertilisation. Fertilisation occurs in plants as well as in animals. Fertilisation is also of two types:
(a) external fertilisation and
(b) internal fertilisation. It is a biochemical process.
Diagram:
Question 6.
Describe in brief the role of (i) testis, (ii) seminal vesicle, (iii) vas deferens, (iv) ureter and (v) prostate gland in human male reproductive system. (2012 D)
Answer:
Role in human male reproductive system:
(i) Testis: Testis is the main reproduction organ of the male reproductive system. There are two testes located outside the abdominal cavity in scrotum because sperm forma-tion requires a lower temperature than the normal body temperature. So testis pro-duces male germ cells (sperms). Testis also produces male sex hormone (testosterone).
(ii) Seminal vesicle: Seminal vesicle is a pair of male reproductive glands present between the rectum and urinary bladder. It secretes seminal fluid which is alkaline and neutralises the acidity of urine and activates sperms.
(iii) Vas deferens: Vas deferens or sperm duct is a long tube which joins the testes with another tube called urethra coming from the bladder. The sperms formed in the testis are delivered through the vas deferens to urethra.
(iv) Ureter: These are a pair of long, narrow, thin-walled and tubular structures which start from the hilum of the kidneys, run downward and open in urinary bladder. These conduct the urine from the kidneys to urinary bladder.
(v) Prostate gland: It is a single, large sized & lobulated gland present just below the urinary bladder. It adds its secretion to the seminal fluid which provides nutrition to the sperms.
Question 7.
Distinguish between unisexual and bisexual flowers giving one example of each. Draw a diagram showing the process of germination of pollen grains on stigma and label the following parts:
(i) Female germ cell; (ii) Male germ cell; (iii) Ovary (2012 OD)
Answer:
Difference between Unisexual and Bisexual flowers
Unisexual flowers:
- The flowers which contain only one sex organ, either stamen or carpel are called unisexual flowers.
- Example: The flowers of papaya and watermelon are unisexual flowers.
Bisexual flowers:
- The flowers which contain both the sex organs, stamen as well as carpel are called bisexual flowers.
- Example: The flowers of hibiscus and mustard plants are bisexual flowers.
Diagram:
Question 8.
Draw a diagram of human female reproductive system and label the part
(i) that produces eggs.
(ii) where fusion of egg and sperm takes place.
(iii) where zygote is implanted.
What happens to human egg when it is not fertilised? (2012 OD)
Answer:
Human female reproductive system:
(i) part that produces eggs – Ovary
(ii) where fusion of egg and sperm takes place – Fallopian tube
(iii) where zygote is implanted – Uterus
When human egg is not fertilised then the thick and soft inner lining of uterus is no longer needed and hence it breaks down in the form of vaginal bleeding known as menstruation. Unfertilized egg also passes out along with menstrual bleeding.
Question 9.
(a) List three distinguishing features between sexual and asexual types of reproduction. (2014 OD)
(b) Explain why more variations are observed in the offsprings of sexually reproducing organisms? (2013 D)
Answer:
Difference between Unisexual and Bisexual flowers
Asexual reproduction:
- Only one organism is required.
- New organism produced is genetically similar to the parent organism.
- All divisions involved are mitotic.
- It does not help in evolution.
Sexual reproduction:
- Two separate individuals, male and female are required.
- New organism produced is genetically different from both.
- During gamete, formation meiosis occurs. After fertilization, all divisions are mitotic.
- It helps in evolution.
(b) Reason: There is always a possibility of diversity of characters in the offsprings because the offspring is formed as a result of fusion of two gametes produced by two different individuals the male and the female parents. So there is an opportunity for new combinations of characters.
Question 10.
(a) Identify A, B and C in the given diagram and write their functions. (2013 D, 2015 D)
(b) Mention the role of gamete and zygote in sexually reproducing organisms.
Answer:
(a) A – Stigma. The top part of carpel is called stigma. Stigma is for receiving the pollen grains from the anther of stamen during pollination.
B – Pollen tube. When a pollen grain falls on the stigma, it bursts open and grows a pollen tube downward through the style towards the female gamete in the ovary. A male gamete moves down the pollen tube.
C – Female gamete (ovum). It is a special reproductive female sex cell which combines with male gamete to form zygote.
(b) Sexual reproduction takes place by the combination of special reproductive cells called sex cells. These cells are of two types – male sex cells and female sex cells, which are coming from two different parents – a male and a female. The cells involved in sexual reproduction are called gametes.
In sexual reproduction, a male gamete fuses with a female gamete to form a new cell called zygote. This zygote then grows and develops into a new organism in due course of time.
Question 11.
(a) What is placenta? Explain its function in human female. (2013 D, OD)
(b) List four ways of preventing pregnancy. State two advantages of using such preventive methods.
Answer:
(a) After fertilisation, zygote is formed which develops into an embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. On the mother’s 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. In this way, embryo gets its nutrition.
(b) Methods to prevent pregnancy:
1. Barrier methods. In these methods, physical devices such as condoms, diaphragm and cervical caps are used. These devices prevent the entry of sperm in the female genital tract, thus acting as a barrier between them.
2. Surgical methods. There are surgeries that can be carried out in males and females. In males, a small portion of the sperm duct (vas deferens) is blocked by surgical operation. It prevents the egg to reach the uterus. In both the cases, fertilisation will not take place.
3. Chemical methods. This category of contraceptives acts by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. Females use two types of pills for preventing pregnancies, i.e., oral pills and vaginal pills.
The oral pills contain hormones which stop the ovaries from releasing ovum into fallopian tube. This is also called oral contraceptives (OC)
Other contraceptive devices such as loop or the copper-T are placed in the uterus to prevent pregnancy.
Advantages of using preventive methods:
- Contraceptive methods are used to prevent the spreading of sexually transmitted diseases like syphillis, AIDS etc.
- Contraceptive methods are also used to control human population by checking the unwanted pregnancies during sexual activities.
Question 12.
(a) Draw a sectional view of human female reproductive system and label the following parts:
(i) Where the development of egg occurs.
(ii) Where fertilisation takes place.
(b) Describe the changes the uterus undergoes:
(i) to receive the zygote.
(ii) if zygote is not formed. (2013 D, 2014 OD)
Answer:
(a) Human female reproductive system.
(i) Development of egg occurs – Ovary
(ii) Fertilisation takes place – Fallopian tube
(b) (i) When the uterus receives the zygote, zygote divides rapidly by mitosis and forms a hollow ball of hundreds of cells called embryo which gets embedded in the thick lining of the uterus. This process is called implantation. After implantation, a disc like special tissue develops between the uterus wall and the embryo which is called placenta. The exchange of nutrients, oxygen and waste products between the embryo and the mother takes place through placenta.
(ii) If zygote is not received by the uterus, then the thick and soft uterus lining having lot of blood capillaries in it is not required. The unfertilised ovum dies within a day and the uterus lining also breaks down. The breaking of the uterus lining produces blood along with tissues in the form of bleeding through the vagina. This vaginal bleeding is called menstrual flow or menstruation. Unfertilized egg also passes out along with menstrual bleeding.
Question 13.
Write the two causes of human population explosion. Explain with the help of suitable examples how this explosion can be checked. (2013 OD)
Answer:
There are three main causes of human population explosion:
- Decline in death rate from 13.8 per 1,000 in 1985 to 8 per 1,000 in 2001.
- Increase in longevity.
- Increase in birth rate.
The uncontrolled growth of human population causes many socio-economic problems. To mitigate the various ill-effects of increasing population, there is a need of population control by reducing the birth rate through family planning programmes.
1. By adopting various methods of contraception:
- Barrier methods – Physical devices such as condoms, diaphragm and cervical caps are-used.
- Surgical methods
- Chemical methods – Oral and vaginal pills used by females.
2. People in reproductive age group should be educated about the advantages of a small family with the help of mass media like radio, T.V., newspapers, etc. and educational institutions.
3. Marriage age should be increased.
4. Social organisations should be involved in family planning programmes.
5. Literacy rate, especially that of females should be increased.
Question 14.
What is pollination? How does it occur in plants? How does pollination lead to fertilization? Explain. (2013 OD)
Answer:
The transfer of pollen grains from anthers (male sexual parts) of a flower to the stigma part of the pistil (female sexual part) is known as pollination. Pollination is done by insects, birds, wind and water.
Pollination can occur in two ways:
- Self pollination. When the pollen grains from the anther of a flower are transferred to the stigma of the same flower or another flower on the same plant, it is called self pollination.
- Cross pollination. When the pollen grains from the anther of a flower on one plant are transferred to the stigma of a flower on another similar plant, it is called cross pollination.
When a pollen grain falls on the stigma of the carpel, it grows a pollen tube downwards through the style towards the female gamete in the ovary. A male gamete moves down the tube. When the pollen tube enters the ovule, its tip bursts open and male gamete comes out of the pollen tube and combines with the nucleus of the female gamete and forms zygote. This process is known as fertilization.
Question 15.
(a) Give one example each of a unisexual and a bisexual flower.
(b) Mention the changes a flower undergoes after fertilisation.
(c) How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals? (2014 D)
Answer:
(a) Unisexual Flower – Papaya
Bisexual Flower – Hibiscus
(b) After fertilisation, the fertilised egg divides several times to form an embryo within the ovule. The ovule develops a tough coat around it and is gradually converted into a seed (containing the baby plant along with food). The ovary of flower develops and becomes a fruit (with seeds inside it). The other parts of flower like sepals, petals, stamens, stigma and style dry up and fall off. Only the ovary is left behind.
(c) In sexual reproduction, though the genetic material DNA from two gametes, male and female gametes, combine together to form a new cell ‘zygote’ but the amount of DNA in zygote does not get doubled. This is because the gametes are special type of cells which contain only half the amount of DNA as compared to the normal body cells of an organism. So the new cell zygote formed by two gametes cells will have the normal amount of DNA.
Question 16.
(a) Name the respective part of human female reproductive system:
(i) that produces eggs.
(ii) where fusion of egg and sperm takes place, and
(iii) where zygote get implanted.
(b) Describe in brief what happens to the zygote after it gets implanted. (2014 D)
Answer:
(a) Part of human female reproductive system:
(i) that produces eggs – Ovary
(ii) where fusion of egg and sperm takes place – Fallopian tube
(iii) where zygote get implanted – Uterus
(b) After zygote gets implanted, a disc like special tissue develops between the uterus wall and embryo (foetus) which is called placenta. The foetus is connected to the placenta in the mother’s body through the umbilical cord. The exchange of nutrients, oxygen and waste products between the embryo and the mother takes place through the placenta.
Question 17.
(a) Write the name of the human male reproductive organ that produces sperms and secretes a hormone. Name the hormone secreted and state its function? (2014 D)
(b) Write the site of fertilization and the part where the zygote gets implanted in the human female.
Answer:
(a) Testes is the human male reproductive organ that produces sperms and secretes male sex hormone – testosterone. The function of testosterone hormone is to control the development of male sex organs and male features such as deeper voice, moustache, beard and more body hair during male puberty.
(b)
- Site of fertilisation: Fallopian Tube.
- Zygote gets implanted in uterus of human female.
Question 18.
(a) Name the human male reproductive organ that produces sperms and also secretes a hormone. Write the functions of the secreted hormone.
(b) Name the parts of the human female reproductive system where
(i) fertilisation takes place,
(ii) implantation of the fertilised egg occurs.
Explain how the embryo gets nourishment inside the mother’s body. (2015 OD, 2017 D)
Answer:
(a) Testis produces sperms and secretes male hormone – testosterone.
Function of testosterone hormone is to control the development of male sex organs and male features such as deeper voice, moustaches, body hair, etc. All these changes caused by testosterone are associated with male puberty which the boys attains at an age of 13 to 14 years. It also controls the formation of male gamete, i.e., sperm.
(b) (i) Fertilisation takes place in fallopian tube (oviduct).
(ii) Implantation of the fertilised egg occurs in the uterus.
Nourishment of embryo. After fertilisation, zygote is formed which develops into an embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue.
On the mother’s 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. In this way, embryo gets its nutrition.
Question 19.
(a) Write the functions of the following parts in human female reproductive system:
(i) Ovary (ii) Oviduct (iii) Uterus (iv) Fallopian tube
How does the embryo get nourishment inside the mother’s body? Explain in brief.
(b) Describe the structure and function of placenta. (2015 D, 2016 D, 2017 OD)
Answer:
(a) (i) Ovary: The ovaries produce thousands of eggs in the female body.
- It produces female hormones called estrogen.
- It produces female gamete ova.
(ii) Oviduct:
- Transfer of female gamete (egg) from the ovary to the uterus takes place through the oviduct (or fallopian tube).
- The fertilisation of egg (or ovum) by a sperm takes place in the oviduct.
(iii) Uterus: The growth and development of a fertilised ovum into a baby takes place in the uterus.
(iv) Fallopian tube: This is the site of fertilisation of the egg with sperm (male gamete). It also helps in the transfer of female gamete from the ovary.
After fertilisation, zygote is formed which develops into an embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. It contains finger-like projections called villi on the embryo’s side of the tissue.
On the mother’s 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. In this way, the embryo gets its nutrition.
(b) Structure of placenta: Placenta is the link between the mother’s body and the baby (embryo). It is a disc like structure embedded in the uterine wall connected to the embryo. It has villi on the embryo’s side of the tissue and on the mother’s side, it has blood spaces which surround the villi.
Function of placenta: It provides a large surface area for nutrients (glucose) and oxygen to pass from the mother’s side to the embryo and waste substances from the embryo’s side to the mother’s blood.
Question 20.
What is placenta? Describe its structure. State its functions in case of a pregnant human female. (2016 OD)
Answer:
Placenta: It is a special tissue that helps human embryo in obtaining nutrition from mother’s blood. It serves as a link between the mother’s body and the baby.
Structure and function: After fertilisation, zygote is formed which develops into an embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. It contains thousands of villi on the embryo’s side of the tissue, on the mother’s side are blood spaces, which surround the villi.
This provides a large surface area for glucose, nutrients and oxygen to pass from the mother to the embryo. In this way, embryo gets its nutrition. The wastes produced by the foetus are also removed through the placenta. It also functions as an endocrine gland and secretes hormones necessary for maintaining pregnancy.