How do the Organisms Reproduce Class 10 Science Important Questions
Please refer to How do the Organisms Reproduce Class 10 Science Important Questions with answers below. These solved questions for Chapter 8 How do the Organisms Reproduce in NCERT Book for Class 10 Science have been prepared based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these solved problems properly as these will help them to get better marks in your class tests and examinations. You will also be able to understand how to write answers properly. Revise these questions and answers regularly. We have provided Notes for Class 10 Science for all chapters in your textbooks.
Important Questions Class 10 Science Chapter 8 How do the Organisms Reproduce
All How do the Organisms Reproduce Class 10 Science Important Questions provided below have been prepared by expert teachers of Standard 10 Science. Please learn them and let us know if you have any questions.
ONE MARK QUESTIONS
Question: Name the method by which Planaria reproduce under favourable conditions. Is this method sexual or asexual?
Answer: Regeneration. Asexual
Question. The process of fertilization helps in the re-establishment of the number of
Answer: Chromosomes and the DNA content in new generation.
Question. Name the mode of reproduction if an organism simply split into two equal halves?
Answer: Binary fission
Question: Name the method by which Spirogyra reproduce under favourable conditions. Is this method sexual or
Answer: Fragmentation. Asexual
Question: What is the advantage of reproducing through spores?
Answer: In the form of cyst, spore with a cell wall can survive in adverse conditions.
They can be easily dispersed through wind as they are more in number and light in weight.
Question: Why does the lining of uterus become thick and spongy every month?
Answer: To receive and nurture the growing embryo, lining of uterus become thick and spongy.
Question. What is germination?
Answer: Growth of new plants from seeds under favourable conditons
Question. What is pollination?
Answer: Transfer of pollen grains in flowers is known as pollination
Question. What is ovulation?
Answer: Release of matured egg from the ovary into oviduct
Question. How is it possible in some organisms, new individual organisms form from their body parts if they are cut into parts?
Answer: It is possible in some organisms, new individual organisms form from their body parts if they are cut into parts because of the presence of regenerative cells.
Question. What are unisexual flowers?
Answer: Flowers which contain either stamen or pistil are called unisexual flowers. Example: papaya, watermelon
Question. ____________ is a protozoan in which binary fission occurs in a definite orientation.
Question. What is pistil?
Answer: Female reproductive organ of a flower
Question. Name the surgical methods of contraception.
Answer: Vasectomy ( vas deferens in male is blocked) and tubectomy ( fallopian tube in female is blocked)
TWO MARKS QUESTIONS
Question: Differentiate between asexual and sexual reproduction.
Question: What is binary and multiple fission? Name the organisms in which they occur.
Answer: Binary fission is the division of one parent cell into two identical daughter cells. It takes place in Amoeba, Paramecium, Euglena and other protozoa.
In multiple fission one single celled organism divides into many daughter cells within a cyst. These are released when the cyst breaks. This takes place in Plasmodium (malarial parasite).
Question: What is regeneration? Name two organisms that can reproduce by regeneration.
Answer: Many fully differentiated organisms have the ability to give rise to new organisms from their body parts by being cut or broken into many pieces. This is known as regeneration. All organisms do not have the capacity to reproduce by regeneration.
Hydra and Planaria can reproduce by the process of regeneration.
Question: What is vegetative propagation? What are its advantages?
Answer: The process by which some plants can reproduce asexually by their vegetative parts like roots, stem and leaves is called vegetative propagation. It has many advantages.
Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds. Plants that have lost the capacity to produce seeds like banana,
rose and jasmine can be propagated by this method. All plants produced by this method are genetically similar to the parent plant.
Question: Name two plants that can reproduce asexually by formation of spores.
Answer: Bread mould (Rhizopus) and ferns reproduce asexually by formation of spores.
Question: What is the significance of sexual reproduction?
Answer: (a) A sexual reproduction results in new combination of characters and increases genetic variations.
(b) It promotes diversity of characters in the offspring.
(c) It speeds up the process of making variations in the population.
Question: State the advantages of seed formation in plants.
Answer: The seed contains the future plant or embryo which can develop into a seedling under appropriate conditions. The seed is in a state of dormancy and can be kept in secure state for long period of time.
Question: What is puberty?
Answer: Puberty is the age at which the gametes start forming in the male and female human beings. At this age boys and girls become sexually mature.
Question: Name the agents of pollination.
Answer: The agents that bring about pollination are wind, water, birds and insects.
Question: What happens when the egg is fertilised?
Answer: When the egg is fertilised zygote is formed, it starts dividing and gets implanted in the lining of the uterus.
Question: State one function each performed by the following organs in human beings:
(b) Prostate gland
Answer: a. Formation of sperms takes place in testes.
b. Prostate gland contributes fluid to the semen.
Question: What kind of contraceptive methods prevents STD and how?
Answer: Barrier method prevent STD By this method there is no direct contact of genital organs of male and female and thus it prevents transmission of any infection.
Question: List any two reasons why the Government has banned prenatal sex determination by law.
Answer: a. People may get female foetus aborted.
b. Reckless female foeticide has disturbed malefemale ratio in society.
Question: Give two differences between a male and a female gamete.
Answer: a. Male gamete is smaller in size or compared to the female gamete.
b. Male gamete is motile whereas female gamete is non-motile.
Question: Mention the functions of (a) placenta (b) fallopian tube in the human female , reproductive system.
Answer: a. Placenta:
(i) Helps in transporting glucose and oxygen from the mother to the embryo.
(ii) Waste generated by the embryo is removed by transferring it to the mother’s blood.
b. Fallopian tube:
(i) Helps in carrying the egg from the ovary to the uterus.
(ii) Fertilization occurs here.
Question: What is the name of the reproductive process which involves (i) two parents
(ii) only one parent?
Answer: (i) The reproductive process which involves two parents is called sexual reproduction. In this process, both the male and the female genders are required for producing the new generation.
(ii) Asexual reproduction in the process of reproduction, where only one parent is involved. This means that an individual organism is capable of generating new generation.
Question: Name the agencies through which cross-pollination take place.
Answer: The transfer of pollen grains, in flowering plants, from one flower to another, is called cross-pollination. The agencies which carry out cross-pollination are wind, water and animals.
Question: Give one word for each phrase:
(i) A sexually transmitted disease caused by a virus.
(ii) The reproductive organ cut and ligated for male sterilisation.
(iii) The biological end of a full term gestation.
(iv) The type of disease to which Trichomoniasis belongs.
Answer: One word for each given phrase is as follows:
(ii) Vas deferens
(iv) Sexually transmitted protozoan disease.
Question: Leaves of Bryophyllum fallen on the ground produce new plants whereas the leaves of rose do not. Why?
Answer: The leaves of Bryophyllum have notches on their margins, which produce buds. When these leaves fall on the ground, the buds develop into a new plant by process of vegetative reproduction, under favourable conditions.
The leaves of rose don’t have this property. They don’t produce any buds over them and hence cannot produce new plants by vegetative reproduction. Instead, the stems and branches of rose plant are used for the purpose.
THREE MARKS QUESTIONS
Question: Give two examples each of the following:
a. Plants having unisexual flowers
b. Agents of pollination
c. Physical changes on puberty that are common to both boys and girls.
Answer: a. Papaya, watermelon
b. Insects, air, water, etc.
c. (i) Appearance of pubic hair.
(ii) Skin becomes oily and may develop pimples.
Question: Write the full form of DNA. Name the part of the cell where it is located. Explain its role in the process of reproduction of the cell.
Answer. The full form of DNA is deoxyribonucleic acid. It is the genetic material found in the chromosomes, which are present in the nucleus of a cell.
Role of DNA in the process of repro¬duction of the cell:
DNA plays an important role in the reproduction of a cell. The reproducing cell produces an identical copy of DNA through some cellular mechanism. Since the newly formed copy of DNA lacks an organised cellular structure, the cell gets divided to provide cell cover to the newly formed DNA. Thus, two daughter cells are formed from the single cell as a result of the copying of DNA.
Question: List six specific characteristics of sexual reproduction.
Answer: Characteristics of sexual reproduction:
a. Two parents are involved.
b. Two dissimilar gametes are formed by meiosis.
c. Variations are produced.
d. Occurs in all the higher and some of the lower organisms.
e. Fertilization / fusion of gametes leading to zygote formation.
Question: Name the two types of germ-cells present in human beings. How do they structurally differ from each other? Give two differences.
Answer : The two types of germ-cells present in human beings are sperm and ova. The sperm of human have either X or Y chromosome. The ova always carry X chromosome. The sperm is structurally long with a tail. The ova is round in structure.
Question: List any three differences between pollination and fertilisation.
Question: Why is DNA copying an essential part of the process of reproduction?
Answer : DNA copying is an essential part of the process of reproduction because:
(i) DNA copying provides cellular apparatus in the daughter cells.
(ii) DNA in daughter cells will be able to control the functioning of daughter cells.
(iii) DNA copies will retain the traits.
Question: State one genetically different feature between sperms and eggs of humans. What is its consequence?
Answer : The sex chromosome of human male is XY. A sperm of human male carries either an X chromosome or one Y chromosome.
The sex chromosome of human female is XX and hence, the egg always carries the X chromosome.
If a sperm carrying X chromosome fertilises an egg which carries X chromosome, then the’ child born will be a girl. If a sperm carrying Y chromosome fertilises an egg which carries X chromosome, then the child born will be a boy.
Question: Draw a longitudinal section of a flower and label the following parts:
(i) Part that produces pollen grain.
(ii) Part that transfers male gametes to the female gametes.
(iii) Part that is sticky to trap the pollen grain.
(iv) Part that develops into a fruit.
Question: Define the terms unisexual and bisexual giving one example of each.
Answer : Unisexual is the plant whose flowers contain either stamens or carpels but not both.
Example: Papaya, Watermelon.
Bisexual is the plant whose flowers contain both stamens and carpels. Example: Hibiscus, Mustard.
Question: What is ‘reproduction’? Mention the importance of DNA copying inreproduction.
Answer : Reproduction is the process of producing new individuals of the same species by existing organisms of a species, i.e. parents. The importance of DNA copying in reproduction are as follows:
(i) DNA copying is called DNA replication. In this process, one copy each of replicated DNA will be passed to daughter cells.
(ii) Variations may be introduced during DNA copying. This inbuilt tendency for variation during reproduction forms the basis of evolution.
Question: Write any two differences between binary fission and multiple fission in a tabular form as observed in cells of organisms.
Question: What does HIV stand for? Is AIDS an infectious disease? List any four modes of spreading AIDS.
Answer :HIV stands for Human Immunodeficiency Virus.
Yes, AIDS is an infectious disease.
Four modes of spreading AIDS are as follows:
(i) By having sexual contact with an infected person.
(ii) By the transfusion of blood from an infected person.
(iii) Through infected needles used for injection.
(iv) Through the placenta from the mother to child during pregnancy.
Question: What is regeneration? State a reason why a more complex organism cannot give rise to new individuals through this method.
Answer : Regeneration is the ability of a fully differentiated organism to give rise to new individual organisms from its body parts. More complex organisms cannot give rise to new individuals through regeneration because:
(i) their body is highly complicated.
(ii) there are specific organs to do specific functions.
(iii) there is a labour division in the body of complex organisms.
(iv) regeneration is carried out by specialised cells which are not present in complex organisms.
Question: (a) What is fragmentation in organism?
Name a multicell-ular organism which reproduces by this method.
(b) What is regeneration in organism? Describe regeneration in Planaria with the help of a suitable diagram.
Answer. (a) Fragmentation: Multicellular organisms with simple body organisation such as filamentous algae-Spirogyra breaks up into two or more small pieces or fragments upon maturation. These fragments grow into new individuals.
(b) Regeneration: It is the ability of a fully differentiated organism to give rise to new individual organisms from its body parts.
• Small cut or broken parts of the organism body grow or regenerate into separate individuals.
• Planaria can be cut into any number of pieces and each piece grows into a complete organism.
• Regeneration is carried out by specialised cells which proliferate and make large number of cells thus, undergoing changes to become various cell types and tissues.
• The changes taking place in an organised sequence is development.
Question: Expand AIDS. List any four methods of prevention (control) of AIDS.
Answer : AIDS stands for Acquired Immune Deficiency Syndrome.
Four methods of prevention or control of AIDS are as follows:
(i) Use condom during sex.
(ii) Avoid sharing of needles.
(iii) Test blood for AIDS before transfusion.
(iv) Avoid sexual contact with unknown person.
Question: Define the term puberty. List two changes observed in girls at the time of puberty.
Answer : The period, when the rate of general body growth begins to slow down and reproductive tissues begin to mature, is called puberty.
Two changes observed in girls at the time of puberty are:
(i) The breast size begin to increase, (ii) Menstruation starts.
Question: Name one sexually transmitted disease each caused due to bacterial infection and viral infection. How can these be prevented?
Answer : Sexually transmitted disease caused due to
(i) Bacterial infection is gonorrhoea, and
(ii) Viral infection is AIDS (Acquired Immune Deficiency Syndrome). These diseases can be prevented by responsible sexual behaviour such as use of condom during intercourse, etc.
Question: “DNA copies generated during reproduction will be similar but may not be identical to the original.” Justify this statement.
Answer : DNA copies generated will be similar, but may not be identical to the original as some variations are so drastic that new DNA copy cannot work with the cellular apparatus it inherits.
Such a newborn cell will simply die. Therefore, there could be many other variations in the DNA copies that would not lead to such a drastic outcome. Thus, the surviving cells are similar but slightly different from each other. This tendency of variation during reproduction is the basis for evolution.
Question: What is reproduction? What are its two types? Which one of the two confers new characteristics on the offsprings and how?
Answer : Reproduction is the process of producing new individuals of the same species by existing organisms of a species, z.e. parents. Its two types are: Asexual reproduction and Sexual reproduction.
Sexual reproduction confers new characteristics on the offspring due to variation in DNA copying.
Question: List and explain in brief three methods of contraception.
Answer : Methods of contraception are:
Use of condom for penis or for vagina as a mechanical barrier for the sperms to reach the egg.
Use of oral pills which change the hormonal balance so that eggs are not released.
Surgical method where either the vas deferens of male is blocked or the fallopian tube of female is blocked.
Question: Why are the testes located outside the abdominal cavity? Mention the endocrine and exocrine function
Answer: Sperm formation requires a lower temperature than the normal body temperature. This temperature is 1-3°C lower than the temperature of the body. Testes are thus located outside so that scrotum provides an optimal temperature for the formation of the sperms.
Endocrine function: Production of male hormone (testosterone).
Exocrine function:Production of male gametes (sperms).
Question: a. Trace the path of sperms from where they are produced in human body to the exterior.
b. Write the functions of secretions of prostate gland and seminal vesicles in humans.
Answer: a. The formation of sperms takes place in testes and delivered through the vas deferens which unites with a tube coming from urinary bladder to form urethra from where they are excreted out of the body.
b. Prostate gland and seminal vesicles add their secretions to make the sperms motile in a fluid which makes their transport easier and provides nutrition.
Question: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.
a. Prevent STDs.
b. Advantage of small family.
c. Less mortality among new-borns.
d. Reduces the cases of maternal mortality.
Areas which have improved:
a. Family Planning.
b. Decrease in STD cases.
Question: What is placenta? Explain its function in human female.
State the role of placenta in the development of embryo.
What is placenta? Describe its structure. State its functions in case of a pregnant human female.
Answer: Placenta is a specialized tissue embedded in the uterine wall. It contains villi on the embryo’s side and blood spaces on the mother’s side.
a. Helps in passing of nutrients from mother to foetus.
b. Exchange of oxygen and carbon dioxide gases.
c. Passing of waste materials from embryo to the mother.
Question: Write one main difference between asexual and sexual mode of reproduction. Which species is likely to have comparatively better chances of survival- the one reproducing sexually or the one reproducing asexually? Justify your answer.
How is sexual reproduction better than asexual reproduction?
Answer: a. Asexual reproduction does not involve genetic fusion while sexual reproduction involves fusion of male and female gametes to form a zygote.
b. Species reproducing sexually have better chances of survival.
Sexual reproduction gives rise to more variations which are essential for evolution as well as survival of species under unfavorable conditions.
Question: What is meant by tissue culture? How this technique is performed? In which area this technique is finding its application?
Answer: Tissue culture is a technique of growing new plants from cells or tissue from the growing tip of already existing plant, in an artificial medium. The process of tissue
culture is as follows:
1. Cells or tissue from the growing tip of a plant are removed or separated.
2. These cells are placed in an artificial medium, where they divide to form a group of cells called callus.
3. The callus is then transferred to a medium, which has hormones for growth and differentiation.
4. This results in growth of small plantlets, which are then placed in the soil to grow into mature plants.
This technique is finding its application in the propagation of ornamental plants, or for growth of plants from a single parent, in disease-free condition.
Question: Name two bacterial diseases which are sexually transmitted. Name their causal organisms, symptoms and preventive measures.
Answer: Two bacterial, sexually transmitted diseases are gonorrhoea and syphilis.
Gonorrhoea It is caused by Neisseria gonorrhoeae. Symptoms, if produced include burning with passage of urine, discharge from penis or vagina, pain in the pelvic region. The disease can be prevented by the use of condoms during sex or having sex with only one, uninfected partner.
It is caused by Treponema pallidum species. Symptoms include the presence of a firm skin ulcer, without pain or itching. This disease can be prevented by use of condoms.
FIVE MARKS QUESTIONS
Question: Answer the following:
a. How is zygote formed?
b. State the function of placenta in the mother’s body.
c. At what interval the egg is formed in human female ovary?
d. Name two STDs caused by bacterial infection.
e. Why is prenatal sex determination prohibited?
Answer: a. Zygote is formed by the fusion of male and female gamete.
b. Placenta is a special tissue through which the developing embryo/foetus gets nutrition from mother’s blood. It also transports wastes of the embryo into mother’s blood.
c. Ovulation releases mature ovum from ‘ the ovary. It happens once during a menstrual cycle that is for roughly 28 days.
d. STDs caused by bacterial infection are Gonorrhoea and Syphilis.
e. Prenatal sex determination is misused and it may be the reason for female foeticide.
Question: Name the type of asexual reproduction demonstrated by the following organisms:
a. Binary fission
b. Spore formation
d. Multiple fission
e. Vegetative propagation
Question: a. List two reasons for the appearance of variations among the progeny formed by sexual reproduction.
b. (i) Name the part marked A in the diagram.
(ii) How does “A” reaches part B?
(iii) State the importance of , the part C.
(iv) What happens to the part marked D after fertilization is over?
Answer: a. Sexual reproduction confers new characteristics on the offspring due to genetic recombination occurring during gamete formation in the sex organs. Moreover it involves union of two gametes coming from two parents which different genetic combination. Thus it ensures more diversity in characteristics.
b. (i) Pollen
(iii) Pollen tube carries male gametes to the ovule in ovary.
(iv) Ovule turns into seeds.
Question: ‘Grafting is a common method of obtaining a superior plant from two different plants’. Explain.
Answer: Grafting is a technique of horticulture which uses the property of vegetative reproduction for cultivation of new plants. In grafting, the desirable characters of two or more plants are combined to produce a new and better plant. The shoot of one plant (called scion) is joined by vascular combination, to the root (called rootstock) of another plant. Some branches or buds of different plants can also be combined with the scion.
This process has many benefits like:
•Plants raised by this method produce flowers and fruits earlier than those grown by seeds
•This method helps in growing plants that have lost their capacity to produce seeds.
•Plants produced are genetically similar to parent plant, and thus have all the desirable
characters in them.
Question: How do the ornamental plants propagate? Mention the method of
propagation for the following:
(i) Jasmine (ii) Rose
(iii) Bougainvillea (iv) Hibiscus
Answer: The ornamental plants propagate by vegetative reproduction methods. These include layering, budding, cutting, grafting, etc.
The method of propagation of given plants is:
(i) Jasmine – layering
(ii) Rose – cutting
(iii) Bougainvillea – layering
(iv) Hibiscus- layering
Question: Why is it said that ‘sexual reproduction promotes, diversity of characters in the offsprings’?
Answer: The DNA replication processes, though precise are not absolutely accurate and thus mistakes can be made. These mistakes in DNA copying mechanism result in variations in the population, which are necessary for the survival of individual in a population. This process of creating variations speeds up in sexual reproduction. Here, two individuals of a population, with different patterns of accumulation of variations, interact and participate in producing a new generation. These variations are unique. Thus, the diversity in characters of offsprings is promoted in sexual reproduction.
Question: Justify the statement ‘Primary sex organs control the growth, function and maintenance of secondary sex organs’.
Answer: Primary sex organs are those organs of reproductive system, which directly participate in the process of reproduction. In humans males, the primary sex organs are testes, and in females, the primary sex organs are ovaries. Apart from producing sperms and ovum, these organs also release some reproductive hormones, namely, testosterone (from testis) and estrogen and progesterone (from ovaries), which control the growth, function and maintenance of other reproductive system organs, like epididymis, vas deferens (in males) fallopian tube and uterus (in females), also called
the secondary sex organs. Hence primary sex organs control the growth, function and maintenance of secondary sex organs.
Question: “DNA copies generated will be similar, but may not be identical to the original.” Explain.
Answer: The DNA copying mechanism, also called the DNA replication processes, are highly precise, but they are not completely accurate. Each time when the DNA is copied, some changes or mistakes might take place in formation of the new DNA strand. These mistakes account for the variations that occur amongst the individuals in a population. In sexual reproduction, these changes increase in rate of occurrence due to involvement of two individuals with different patterns of accumulation of variations.
The variations hence created, are unique in nature. Thus, the DNA copies generated are similar, but not identical to the original.
Question: What is a seed? How does it help in reproduction in plants?
Answer: The zygote, after fertilisation in plants, divides several times to form an embryo, which is the future plant. This embryo is enclosed inside the ovule. The ovule, gradually hardens and develops into a small, tough and persistent structure, which encloses the embryo, called the seed.
This seed, when under favourable conditions of soil, water and air, develops into a seedling, a process known as germination. This germinated seedling further is involved in the development of new plant. This way, the seed helps in reproduction.
Question: What causes joining up of stock and scion in grafting? Name one positive trait that the plant contributing scion should have and one positive trait that the plant contributing the stock should have.
Answer: The combining up of vascular compartments of scion and stock cause joining of the two parts in grafting.
The plant contributing scion should be able to produce flowers and fruits quicker than those plants which are planted through seeds.
The plant contributing root stock should be able to keep the plant more resistant to diseases and pests.
Question: How can the reproductive health be maintained and sexually transmitted disease (STDs) be prevented?
Answer: Reproductive health can be maintained mainly by spreading awareness regarding the process of reproduction, and promoting safe sexual habits. Introduction of sex education in schools, use of birth control measures, prevention of sexual abuse and sex-related crimes will also help in maintaining reproductive health.
Sexually transmitted diseases can be prevented by use of condoms and avoiding sex with multiple partners.3. Enlargement and erection of penis.
Question: Fertilisation is possible if ovulation has taken place during middle of the menstrual cycle. Give reasons.
Answer: Fertilisation is the process of union of the sperm and the ovum inside the female reproductive tract. The site of fertilisation in humans is the junction between ampulla and isthmus of the fallopian tube. Thus, for fertility, it is necessary that the ovum be present at this site, when the sperm reaches and has not crossed it. As the release of ovum from the ovaries takes place between 11th to 16th day of menstrual cycle, which is roug hly the middle of the cycle, the chances of ovum being present in fallopian tube at that time is high. Hence, fertilisation is possible when ovulation occurs, in the middle of menstrual cycle.
Question: What changes are noticed on sexual maturity of human beings?
Answer: The changes that occur in humans on sexual maturity are collectively referred to as secondary sexual characters. Some of these changes are common to both the genders, whereas some changes occur specific to one gender.
The changes common to both sexes are:
1. Growth of thick hair in armpits and genital area.
2. Darkening of armpits and genital area.
3. Growth of thin hair on arms, legs and face.
The changes occurring in girls:
1. Enlargement of breasts
2. Darkening of the area of nipple
3. Beginning of menstruation.
The changes occurring in boys are:
1. Appearance of thick hair on face.
2. Cracking of voice.
Question: Due to heavy rise in demand for tea in international market and simultaneous incentive given by government on tea plantation, a tea company wants to go for a large-scale expansion of its tea plantation in Assam. To implement the project, the company need a large number of sapling and a huge motivated work force.
(a) What is the best option for the company to arrange large number of sapling?
(b) What are the minimum facilities that the company should provide to its workers?
(c) What additional step can the company take to motivate the workers to put
extra effort into successful expansion of the plantation?
Answer: (a) The best option for the company to arrange large number of saplings is by vegetative reproduction, through cutting of tea plant, or by tissue culture methods.
(b) The company must provide adequate salary to its workers. They must be made to work only for fixed hours, which can be rotatory in nature, healthy working environment must also be provided.
(c) The incentives received from cover can be distributed amongst the workers, their working environment can be made happy and healthy so as to motivate them to put extra efforts. They can be made a part of planning and management, where their ideas and opinions can be valued.
Question: Draw diagrams showing reproduction in yeast in proper sequence.
Answer: Diagram showing reproduction in yeast by budding:
Question: Give one example each of unisexual and bisexual flowers. Differentiate between the two types of pollination that occur in flowers.
What happens when a pollen lands on a suitable stigma? Write about the events that occur till the seed formation in the ovary.
Answer: An example of unisexual flower is Papaya, water melon (write any one) and of bisexual flower is Hibiscus, mustard (write any one).
Differences between the two types of pollination that occurs in plants, namely, self pollination and cross-pollination is given below:
Following events take place when a pollen lands on a suitable stigma:
(1) Pollen grains which are deposited on the stigma form tubes called pollen tubes.
(2) One pollen tube grows through the style and reaches the ovary where the ovules are located.
(3) The pollen tube normally enters the ovule through a small opening called micropyle.
(4) Inside the ovule, the pollen tube releases two male gametes into the embryosac which contains the egg.
(5) Fertilization of male and female gametes takes place inside the embryosac.
(6) After fertilization, the zygote divides several times to form an embryo within the ovule.
(7) The ovule develops a tough coat and is gradually converted into a seed, which contains the food store.
(8) The ovary grows rapidly and ripens to form a fruit.
Question: (A) Write the functions of the following parts in human female reproductive system:
(ii) Fallopian tube
(B) Describe the structure and functions of placenta.
Answer: (A) Function of following parts in human female reproductive system is given below:
(1) Ovary: Ovaries are the female primary reproductive organs which perform dual functions of production of female gamete or ovum and the secretion of female sex hormones, estrogen and progesterone.
(2) Fallopian tube: These are a pair of long convoluted tubes that carry ova or eggs from the ovary to the uterus and is also the site of fertilization of the ovum.
(3) Uterus: It is a hollow, pear-shaped organ within which the embryo develops after implantation. After fertilization has taken place, the embryo moves down to reach the uterus and gets attached to its thickened wall.
(B) Structure and functions of placenta:
(1) It is a special disc like tissue which develops between uterine wall and the embryo after implantation.
(2) It contains villi on the embryo’s side of the tissue and blood spaces surrounding the villi on the mother’s side.
(1) It is through the placenta that all the development needs of the foetus are met from the mother’s body.
(2) It provides a large surface area for glucose and oxygen to pass from the mother to the embryo.
(3) The waste substances generated by the developing embryo is also removed through the placenta.
Question: How do variations arise in organisms?
‘‘Variation is useful for the survival of species.”
justify this statement with the help of an example.
Answer: Variations arise in organisms during creation of DNA copy which is the basic event in reproduction. Cells use chemical reactions to build copies of their DNA but this process of copying the DNA will have some variations due to which the DNA copies will be similar but not identical to the original.
Variations which are favourable increase the chances of survival of the species. If anorganism can withstand a higher temperature, then the variation goes on accumulating in its future generations. Hence, these organisms can survive sudden rise in the temperature. This ensures the survival of the species. But other organisms (variants) without this variation may not survive due to sudden rise in temperature.
So, variation is beneficial to the species, but not necessarily for individual.
Question: (A) Write the functions of the following parts of the human male reproductive system:
(i) Testis (ii) Vas deferens (iii) Urethra
(B) List any two common pubertal changes that appear in human males.
Answer: (A) The functions of the various parts of the human male reproductive system are given below:
(1) Testis: The formation of germ-cells or sperms takes place in the testes.
It secretes the male hormone, called testosterone, which regulates the formation of sperms and brings about changes in appearance in boys at puberty.
(2) Vas deferens: It is a long tube which arises from each testes and carries sperms into organs called seminal vesicles, where the sperms get nourished and stored.
(3) Urethra: It is a common passage for both urine and spermatic fluid. The vasdeferens unites with a duct coming from the urinary bladder to form urethra.
(4) Prostate: It is a gland that secretes an alkaline fluid which gives lubrication and nutrition for the sperm.
(B) Common pubertal changes appearing in human males:
(1) Growth of thicker hair in armpits and genital area between the thighs.
(2) Growth of thinner hair on legs and arms.
(3) Skin becomes oily and pimples develop.
(4) There is thick hair growth on the face.
(5) Cracking of voice.
(6) Penis occasionally gets erect and enlarged.
Question: (A) What is meant by fragmentation in organisms? Name a multicellular organism which reproduces by this method.
(B) How does regeneration take place? Why is this process not possible in all animals?
Answer: (A) The breaking up of the body of a simple multicellular organisms into two pieces on maturing, each of which subsequently grows to form a complex new organism is called fragmentation.
Spirogyra simply breaks up into smaller pieces upon maturation. These pieces or fragments grow into new individuals. This happens without forming any gametes. Fragmentation in Spirogyra
Question: In our country the legally prescribed minimum age for marriage is 18 years for females and 21 years for males. Why is it essential to fix the minimum age for marriage? Give three reasons to justify your answer. List three methods for preventing unwanted pregnancy.
Answer: Setting a minimum age of marriage are an important way to safeguard boys and girls from being married before they are ready (physically, mentally, sexually) methods for preventing unwanted pregnancy are:
(1) Chemical Method: Use of oral pills to change the hormonal balance of the female.
(2) Barrier Methods: Use of condoms,Diaphram, to prevent the meeting of sperm and ova.
(3) Surgical Methods: Block the vasdeferns in males (vasectomy) or oviduct in females (Tubectomy).
IUCs: Loop or copper T (CuT) placed in uterus, to prevent pregnancy.
Question: What are chromosomes? Explain how the number of chromosomes in the progeny is maintained in sexually reproducing organisms.
Answer: Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid During the process of formation of germ cells in sexually reproducing organisms, meiosis cell division takes place in the reproductive organs,
due to which the male and female germ cells or gametes will have half the number of chromosomes as compared to their parent cells. When fertilisation takes place by the fusion of the two germ cells, the normal number of chromosomes and DNA content is thus restored in the progeny. So, the progeny will have the same number of chromosomes as its parents.
Question: Draw neat diagram of human female reproductive system. Label oviduct and uterus on it. State the role of placenta. How the waste generated by the developing embryo removed?
Role of Placenta: Placenta is a special tissue connection between embryo and uterine wall.
It acts as an endocrine gland:
(1) It possess villi that increase the surface area for absorption of nutrients.
(2) Waste substances produced by embryo are removed through placenta into mother’s blood.
(3) Cocilitate passage of nutrition and oxygen to embryo from mother through blood.
The waste generated by the developing embryo removed through placenta into mother’s blood.
Question: State the basic requirement for sexual reproduction? Write the importance of such reproductions in nature.
Answer: The basic requirement for sexual reproduction is the involvement of two sexes, namely, male and female and incorporates a process of combining DNA from two different individuals during reproduction.
Importance of sexual reproduction:
(1) It promotes diversity and new combination of characters in the off springs.
(2) It leads to variations which helps the survival of species in extreme environmental conditions.
(3) It is necessary for evolution.
(4) It plays an important role in the origin of new species.
Question: (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 fertilisation occurs.
(C) Explain how the developing embryo gets nourishment inside the mother’s body.
Answer: (A) The organ that produces sperms as well as secretes a hormone in human males is testes.
Hormone secreted by testes is testosterone hormone.
Functions of testosterone hormone:
(1) Regulates formation of the male gametes, sperms.
(2) Develops secondary sexual characteristics such as increased muscle and bone mass, deep voice and the growth of body and facial hair.
(3) Develops male reproductive tissues such as testes and prostate gland.
(B) In human female reproductive system, fertilization occurs in the Fallopian tube and implantation takes place in uterus.
(C) The developing embryo gets nourishment inside the mother’s body through the placenta which is a disc-shaped tissue embedded in the uterine wall.
Placenta contains villi on the side of the embryo and blood vessels surrounding villi on the side of the mother. Oxygen and glucose pass from the mother to the embryo through the placenta.
Question: What happens when:
(A) Accidently, Planaria gets cut into many pieces?
(B) Bryophyllum leaf falls on the wet soil?
(C) On maturation sporangia of Rhizopus bursts ?
Answer: (A) When Planaria accidentally gets cut into many pieces, many of these pieces grow into separate organisms. This is known as regeneration. Plauaria reproduces asexually by the method of regeneration.
(B) When Bryophyllum leaf falls on wet soil,buds produced in the notches along the leaf margin develop into new plants. This is a form of vegetative propagation.
(C) When sporangia of Rhizopus burst on maturation, the spores are released which develop into new Rhizopus individuals when they come in contact with a moist surface and begin to grow.
Question: What is vegetative propagation? List with brief explanation three advantages of practising this process for growing some types of plants. Select two plants from the following which are grown by this process:
Banana, Wheat, mustard, jasmine, Gram.
Answer: Vegatative Propagation: It is the development of a new plant from the vegatative part like roots, stem and leaves of a plant.
Advantages of vegetative propagation are:
(1) Such plants can bear flower earlier than those produced from seeds.
(2) Allows propagation of plants that have lost capacity to produce seeds,
(3) All plants produced are genetically similar to the parent plant and hence have all its characters.
Banana and jasmine are the two plants–
Question: What is sexual reproduction? List its four significances.
Answer: Sexual-Reproduction: The Type of reproduction in which male gametes and female gametes fuse together to form zygote which change into embryo and new organism, is called sexual Reproduction.
Significance of Sexual Reproduction
(1) Increases genetic variations.
(2) Promotes diversity in offsprings.
(3) Play a role in origin of new species.
(4) Genetic variations leads to survival of the species.
(5) Variations play an important role in the process of evolution.
Question: (A) What changes are observed in the uterus if fertilisation does not occur?
(B) List in tabular form two distinguishing features between a sperm and an ovum.
Answer: (A) In female, ovary produces one egg every month. The uterus also prepares itself to receive a fertilised egg. So, the wall of uterus becomes thick and spongy containing lots of blood capillaries. If egg gets fertilised with sperm, then fertilised egg gets attached with uterus wall and gets nourishment from it. In case, egg is not fertilised, then this lining is no longer needed. The inner lining of uterus breaks down and comes out in the form of blood and mucous through the vagina. This cycle occurs every month and is called menstruation. It usually lasts for about 2 to 8 days.
Mensuration in human females occurs in a cycle of 28 days.
Question. Write two points of difference between asexual and sexual types of reproduction.
Describe why variations are observed in the offspring formed by sexual reproduction.
During sexual reproduction, two types of gametes fuse. Although the gametes contain the same number of chromosomes their DNA is not identical. This situation generates variations among the offsprings. Due to lot of variations, sexual reproduction allows species to change to more advanced forms from one generation to the next and speed up evolution.
Question. (A) What changes are observed in the uterus if fertilisation does not occur?
(B) List in tabular form two distinguishing features between a sperm and an ovum.
Answer : (A) In female, ovary produces one egg every month. The uterus also prepares itself to receive a fertilised egg. So, the wall of uterus becomes thick and spongy containing lots of blood capillaries. If egg gets fertilised with sperm, then fertilised egg gets attached with uterus wall and gets nourishment from it. In case, egg is not fertilised, then this lining is no longer needed. The inner lining of uterus breaks down and comes out in the form of blood and mucous through the vagina. This cycle occurs every month and is called menstruation. It usually lasts for about 2 to 8 days.
Mensuration in human females occurs in a cycle of 28 days.
(B) (Table 202)
Question. Draw diagrams showing reproduction in yeast in proper sequence.
Answer : Diagram showing reproduction in yeast by budding:
Question. Mrs. Seghal’s family was very happy after the birth of their second child. Her friend, Mrs. Raman, suggested her to undergo tubectomy.
(A) What is tubectomy?
(B) Why do you think rs. Raman gave her such a suggestion?
(C) Can tubectomy prevent the spread of sexually transmitted diseases?
(D) Give reason for your answer. Why is there a need of adopting contraceptive methods?
Answer : (A) Tubectomy is a surgical method of birth control in females. In females, a small portion of the oviducts is removed by surgical operation and the cut ends are tied. This prevents the ovum or egg from entering into the oviducts. This prevents fertilization, which prevents the pregnancy.
(B) Mrs Raman gave advice for tubectomy to Mrs Sehgal because she knows that a small family is a happy family. If a couple has only two children, it can provide good food, clothes, and education to each child. This will keep parents as well as children happy. Mrs Raman also knows that having fewer children also keeps the mother in good health.
(C) No, tubectomy does not prevent the spread of sexually transmitted diseases.
(D) Since, there will be no physical barrier during sexual contact, there is every chance of a person (with tubectomy) getting infected with sexual transmitted diseases during sexual contact with an infected person. The need of adopting contraceptive methods is to avoid getting infected with sexually transmitted disease and for birth control. These are also used to avoid unwanted pregnancy.
Question. Give reasons: (A) Blocking of vas deferens prevents pregnancy.
(B) Wind acts as a pollinating agent.
(C)Use of condoms prevents pregnancy. (D) Blocking of fallopian tubes prevents pregnancy.
Answer : (A) Blocking of vas deferens is a surgical method of birth control in males. A small portion of the vas deferens is removed by surgical operation and both the cut ends are tied properly. This prevents sperms from ejaculating during sexual contact and prevents pregnancy.
(B) The blowing wind carries pollen grains from one flower to another flower and helps in cross-pollination.
(C) Condom prevents sperms from fertilizing the ovum by acting as a barrier between them.
(D) In females, a small portion of the fallopian tube is removed by surgical operation and the cut ends are tied. This prevents the ovum from travelling further into the fallopian tube. As a result, the sperm never meets the ovum during sexual contact and the chances of pregnancy become nil.
Question. (A) List two reasons of using contraceptive methods by married couples.
(B) Write in proper sequence the process going on in the different organs of the reproductive system of a human female starting from the time of egg production to childbirth.
Answer : (A) Married couples use contraceptive methods:
(1) To avoid unwanted pregnancy
(2) To have proper time gap between two children.
(3) To limit the number of children in the family.
(4) To prevent transmission of many of sexually transmitted diseases. (Any two)
(B) In human female reproductive system, there are two ovaries. One egg is produced every month by one of the ovaries during ovulation:
(1) The ovum egg goes into the oviduct or fallopian tube.
(2) The sperms released by the human male during copulation or mating are deposited at the top of the vagina close to the cervix of uterus. The sperms travel through the uterus to the top of fallopian tube.
(3) The fertilization of the ovum or egg takes place in the oviduct and a zygote is formed.
(4) The zygote divides rapidly as it moves down slowly in the oviduct and forms a hollow ball of hundreds of cells called embryo. The close attachment of embryo to the uterine wall is called implantation.
(5) After implantation, a number of development changes takes place in embryo as well as in the wall of uterus. When body features are seen clearly, the developing embryo is called foetus.
(6) A disc-like special tissue develops between the uterine wall and the foetus which is called placenta. The exchange of nutrients, oxygen and waste products between the embryo and the mother takes place through the placenta.
(7) The time period from the fertilization up to the birth of baby is called gestation. The average gestation period in humans is about nine months or 40 weeks or 280 days from the first day of the last menstruation.
(8) The rhythmic contraction of uterus muscles gradually pushes the baby out of the mother’s body through vagina which is called parturition. This is how a child is born.
Question. (A) Identify the modes of asexual reproduction in each of the following organisms:
(B) List three advantages of vegetative propagation.
(C) Why can fertilisation not take place in flowers if pollination does not occur?
Answer : (A) Modes of reproduction in:
(i) Hydra—Regeneration or budding
(iii) Amobea—Binary fission
(v) Rhizopus—Spore formation
(B) Advantages of vegetative propagation
(i) Plants can bear flowers and fruits earlier than those produced from seeds.
(ii) All the plants produced are genetically similar and have all the characteristics as those of parent plant.
(iii) Plants such as banana, orange, rose jasmine etc. that do not produce viable seeds can be propagated.
(iv) Desirable traits of fruits and flowers can be maintained.
(v) It is a cheaper, rapid and convenient method for growing plants.
(vi) Plants can easily be introduced in new areas by this method. (Any three)
(C) Fertilization cannot take place in flowers if pollination does not occur because for the male gamete to be able to combine with the female gamete, it is necessary that the pollen grains from the anther of stamen should be carried to the stigma of carpel. The transfer of pollen grains from the anther of a stamen to the stigma of a carpel is called pollination. 94. Based on the given diagram answer the questions given below:
Question. Based on the given diagram answer the questions given below:
(A) Label the parts A, B, C and D.
(B) Name the hormone secreted by testis and mention its role.
(C) State the functions of B and C in the process of reproduction.
Answer : Copy the figure and Label
(B) Hormone secreted by testis: Testosterone Role of testosterone: It brings about changes in appearance seen in boys at the time of puberty (secondary sexual characteristics).
(C) functions of B (Seminal vesicle): Along the path of vas deference, seminal vesicle along with prostrate gland add their secretions which make the transport of sperms easier and this fluid provides nutrition to sperms.
The transport of sperms easier and this fluid provides nutrition to sperms.
Functions of C (Urethra): Urethra carries urine from the bladder and sperms through vas deference through the penis.
Question. (A) Name the mode of reproduction of the following organisms and state the important feature of each mode :
(B) We can develop new plants from the leaves of Bryophyllum. Comment.
(C) List two advantages of vegetative propagation over other modes of reproduction.
Answer : (A) Mode of reproduction in:
(1) Planaria: Regeneration
Regeneration is carried out by specialised cells. Planaria if somehow gets cut into three pieces, after sometime, each cut piece of body of planaria grows into new planaria.
Question. Draw a neat diagram showing fertilisation in a flower and label (a) Pollen tube, (b) Male germ cell and (c) Female germ cell, on it.
Explain the process of fertilisation in a flower.
What happens to the (i) ovary and (ii) ovule after fertilisation?
Fertilization in a flower plant
Process of fertilization in a flower
During the process of pollination pollen grains land on the stigma of the carpel. Pollen grains form pollen tubes and one of the pollen tubes grows into the stigma, passes through the style and enters the ovary and finally to embryosac through an opening called micropyle.
Two non-motile male gametes (male germ cells) are formed in the pollen tube during its growth through the style.
Pollen tube releases two male gametes into the embryosac.
The mature embryosac consist of an egg apparatus having one haploid egg (Female germ cell, two synergids and two polar nuclei).
During the process of fertilization, one male gamete fuses with the female germ cell (egg) to form the diploid zygote. The process is called fertilization or syngamy. The zygote finally develops into embryo.
The other male gamete fuses with two polar nuclei and this process is called triple fusion.
In the ovary two fusions take place so this process is called double fertilization.
(i) The ovary grows rapidly and ripens to form a fruit.
ii) The ovule develops a tough coat and is gradually converted to seed.
At the same time, the petals, sepals, stamens, style and stigma may strive and fall off.
Question. (a) List three different categories of contraception methods.
(b) Why has Government of India prohibited prenatal sex determination by law? State its benefits in the long run.
(c) Unsafe sexual act can lead to various infections. Name two bacterial and two viral infections caused due to unsafe sex.
Answer : (A) Three different categories of contraception methods are:
(1) Barrier methods
(2) Surgical methods
(3) Intrauterine Contraceptive Device (IUCD)
(4) Natural methods.
Question. Distinguish between a gamete and zygote. Explain their roles in sexual reproduction.
Answer : (Table 191)
Importance of gametes and zygote in sexual reproduction:
Gametes are the reproductive cells which actually take part in sexual fertilisation. The gametes are carriers of the genetic material from one generation to the other and also help in the maintenance of the chromosome number of a species. The two fusing gametes possess characters of their parents in their DNA. Fertilisation brings characters of both the parents into one zygote cell.
Zygote is the name given to the cell produced by fertilisation of male and female gametes in sexual reproduction. It represents the first cell of the next generation which subsequently grows into a new individual and carries genetic information from both the parents involved.
It is divided repeatedly to give rise to a new individual. Gametes are a product of meiosis and hence carry half the chromosome number as that of parent cells. This chromosome number is restored during fertilisation and zygote formation. Hence, gamete and zygote are the two phases of sexually reproducing organisms that help maintain a constant chromosome number in each species.