Please see Chapter 10 How do the Organisms Reproduce Exam Questions Class 10 Science below. These important questions with solutions have been prepared based on the latest examination guidelines and syllabus issued by CBSE, NCERT, and KVS. We have provided Class 10 Science Questions and answers for all chapters in your NCERT Book for Class 10 Science. These solved problems for How do the Organisms Reproduce in Class 10 Science will help you to score more marks in upcoming examinations.
Exam Questions Chapter 10 How do the Organisms Reproduce Class 10 Science
ONE MARK QUESTIONS
Question: Name the type of cells which undergo regeneration.
Answer: Regenerative cells can proliferate and make large number of cells.
Question: List two functions of ovary of human female reproductive system.
Answer: In human female, ovary contains thousands of eggs.
One egg is produced every month one of the ovaries. Ovary also secretes estrogens hormone for development of sexual characteristics at puberty.
Question: When a cell reproduces, what happens to its DNA?
Answer: Its DNA first doubles up followed by its equal and accurate division between two daughter cells.
Question: Name the method by which Plasmodium reproduce under favourable conditions. Is this method sexual or asexual?
Answer: Multiple Fission. Asexual
Question: Where is DNA found in a cell?
Answer: Genes/Chromosomes.
Question: What are those organisms called which bear both sex organs in the same individual. Give one example of such organism.
Answer: Bisexual. For example: earthworm, leech, starfish, hibiscus, mustard. (Any one)
Question: Name the life process of an organism that helps in the growth of its population.
Answer: Reproduction.
Question: Name the causative organism of the disease “Kalaazar”and its mode of asexual reproduction.
Answer: Leishmania, Binary fission.
Question: List two functions performed by testis in human beings.
Answer: a. Testis produce sperms.
b. Produces male sex hormone, testosterone.
Question Give an advantage of vegetative propagation.
Answer: Vegetative propagation can be practised for growing such plants which usually do not produce seeds or produce non-viable seeds.
Question: How can the chromosomes be identified?
Answer: Chromosomes can be seen as thread like structure when cell is dividing.
Question: What are sexually transmitted diseases? Name an STD which damages the immune system of human Download more materials in free at : body.
Answer: a. Diseases that spread through the sexual contact.
b. AIDS
Question: Organisms have a varied body design. Name the property which gives the basic difference in body design.
Answer: Errors in DNA copying (variations).
Question: Why is temperature of scrotal sac 2°C less than the body temperature?
Answer: Because testes require temperature 2°C less than the body temperature for the production of sperms.
Question: Organisms have a varied body design. Name the property which gives the basic difference in body design.
Answer: Errors in DNA copying (variations).
Question: Regeneration is not possible in all types of animals.Why?
Answer: Regeneration is carried by specialised cells. The organisms which have those cells only can show regeneration.
Question: What is the importance of DNA copying in reproduction?
Answer: DNA copying is an important phenomenon of reproduction through which the organisms pass on their characteristics to their offspring. It maintains the characteristics in different generations of the species. It also produces variations which are useful for the survival of species for long time.
Question: How does binary fission differ from multiple fission?
Answer: Binary Fission: An organism is divided into two individuals. Mitotic division takes place resulting in two identical individuals or daughter cells. e.g., Amoeba.
Multiple Fission: Mitotic division takes place. The nucleus divides repeatedly to form a number of equal sized and similar individuals, e.g., Plasmodium.
Question: Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Answer: More complex organisms cannot give rise to new individuals because:
1. Their body design is highly complicated.
2. There are specific organs to do specific functions.
3. There is a labour division in the body of complex organisms.
4. Exception is lizard, which can regenerate its tail.
Question: Why is DNA copying an essential part of the process of reproduction?
Answer: DNA copying is needed because information stored in DNA is used to make protein.
Synthesis of different proteins will lead to altered body design. Thus, reproduction at its most basic level involves making copies of the blueprints of body design.
Question: What is the role of seminal vesicles and prostate gland?
Answer: Seminal vesicles are a pair of thin-walled muscular and elongated sacs which secrete a fluid for nourishment of sperms.
Prostate glands also produce a fluid which is released in the urethra along with secretion of seminal vesicle. It affects the vaginal pH so that sperms move smoothly inside the vagina.
Question: How does the embryo get nourished inside the mother’s body?
Answer: The embryo grows inside the mother’s womb and gets nourishment from its mother’s blood through placenta. Placenta contains villi which connects the embryo with the mother’s blood. These villi provides a large surface area for glucose and oxygen to pass from mother to the embryo.
TWO MARKS QUESTIONS
Question: State the changes that take place in the uterus when a. implantation of embryo has occurred
b. female gamete/egg is not fertilized
Answer: a. Uterus wall becomes thicker due to development of blood vessels and glands in it and placenta develops from the side of foetus so that it can derive nutrition from mother and pass the waste to mother’s blood.
b. Uterus lining gets peeled and shed off along with mucus, blood, dead ovum during menstruation.
Question: Give reasons as to why the following processes are different from each other:
a. Fission in Amoeba and Plasmodium .
b. Binary fission and Fragmentation.
Answer: a. In Amoeba during binary fission the cell divides into two daughter cells while in Plasmodium multiple fission occurs, where the cell divides into many daughter cells.
b. In binary fission, a cell divides into two daughter cells while in fragmentation, the body of a multicellular organisms divides into two or more Download more materials in free at : parts which grow further.
Question: “Variations” are seen in the organisms. State the two main causes of variation.
Answer: Variations are caused by:a. Change in the genetic material, i.e., DNA at the time of DNA copying.
b. Environmental factors viz., light, temperature, nutrition, wind and water supply, etc.
c. Mutations.
Question: a. What is the location of the following:
(i) DNA in a cell (ii) Gene
b. Expand DNA.
Answer:
a. (i) Nucleus. (ii) Located on the chromosomes.
b. Deoxyribo Nucleic Acid.
Question: Define the following processes of asexual reproduction:
a. Spore formation
b. Regeneration
c. Multiple fission
Answer: a. Reproduction seen in organisms by formation of spores.
b. Organisms are cut into any number of pieces and each piece grows into a complete organism.
c. Unicellular organisms divide into many daughter cells simultaneously.
Question: What happens when the following situations are initiated:
a. A Planaria is cut into three different pieces.
b. Leaf of the Bryophyllum with notches falls on the soil.
c. Testosterone is released in the male reproductive system.
Answer: a. Each piece grows into a complete organism.
b. Develops into new plants.
c. Changes occurs in the appearance at the time of puberty.
Question: Explain how do organisms create an exact copy of themselves.
Answer: To build the copies of DNA or the genetic material, the cells use biochemical reactions. Additional cellular apparatus along with the DNA copies are separated and so a cell divides to give rise to two almost identical cells.
Question: What does the diagram given below correctly illustrate? Give reason in support of your answer.
Answer:
Binary fission in Amoeba. The splitting of the two cells during division in Amoeba can take place in any plane.
Question: Draw labelled diagrams to illustrate budding in Hydra.
Answer: a. In sexual reproduction, fusion of male and female gametes takes place, these germ-cells/gametes contain half the number of chromosomes and by the fusion of these gametes the zygote is formed with full set of chromosomes.
b. When male and female gametes fuse at the time of fertilization, it restores the original number of chromosomes (of the parent), ensuring the stability of species.
Question: What is the main difference between sperms and eggs of human? Write the importance of this difference?
Answer: Sperms are motile and are produced in . large numbers by a male. Egg are non-motile and only one is produced at a time by the female.
Sperms are motile as they have to travel up to egg for fertilization. It becomes zygote, remains protected inside female’s body and gives rise to foetus and baby.
Question: “The chromosomal number of the sexually producing parents and their offspring is the same.” Justify this statement.
Answer: a. DNA copying is essential for formation of addition cellular apparatus, so that when DNA copies separate, each cell gets its own cellular apparatus.
b. The process of DNA copying results in variation each time. As a result, the DNA copies generated will be similar, but may not be identical to the original.
Question: Define variation in relation to a species. Why is variation beneficial to the species?
Answer: Variation means certain changes which occur in sexually reproducing organisms because of errors in DNA copying. Variations are beneficial for species because they given survival advantage even in the adverse environmental conditions.
Question: Why is vegetative propagation practised for growing Download more materials in free at : some types of plants?
or
Why is vegetative propagation practiced for growing some types of plant? List two plants which are grown by this method.
Answer: Advantages of vegetative propagation:
a. The plants bear flowers and fruits earlier than those propagated sexually.
b. Plants have lost capacity to form seeds hence they are propagated vegetatively. Such plants are genetically similar to parent plants and have all their characters.
Question: a.List any two methods of asexual reproduction.
b. Explain how Spirogyra reproduces.
Answer: a. (i) Budding in Hydra and Yeast.
(ii) Spore formation in Fungi.
b. Spirogyra breaks up into smaller pieces upon maturation. These fragments grow into new individuals
Question: How can pregnancy be prevented surgically?
Answer: Pregnancy can be prevented surgically by adopting:
a. Vasectomy: When vas deferens in males are blocked surgically, sperm transfer will be prevented.
b. Tubectomy: When fallopian tubes are blocked, eggs will not be able to reach the uterus.
Question: State the importance of chromosomal difference between sperms and eggs of humans.
Answer: Eggs always contain same type of sex chromosomes (both X). Sperms contain X or Y sex chromosomes.
Thus, sperm containing X chromosome when combines with X chromosome of egg results in a female child.
Whereas sperm containing Y chromosome when combines with X chromosome of egg results in a male child.
Question: ‘Regeneration is not reproduction’. Justify this statement with reason.
Answer: When a piece is cut from an organism, it grows into complete organisms. Regeneration is carried out by specialized cells. It is not reproduction since most organisms would not be able to grow through pieces.
Question: Why do we need to adopt contraceptive measures?
Answer: a. Contraceptive measures are needed to be adopted to prevent unwanted pregnancies.
b. To prevent sexually transmitted diseases.
c. Spacing between children.
d. For sound health of a mother.
THREE MARKS QUESTIONS
Question: List three techniques to prevent pregnancy. Which of them is not meant for males? How does the use of such techniques have an impact on health and prosperity of a family?
or
List any four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of a family?
Answer: Three techniques to prevent pregnancy:
a. Mechanical barrier — male or female.
b. Taking oral pills/i-pill/saheli – changing the hormonal balance of the body so that eggs are not released.
c. Use of the loop or the Copper-T.
d. Surgical method – tubectomy / vasectomy Use of hormonal preparations is not meant for males.
Effect on Health and Prosperity:
a. Health of women is maintained
b. Parents can give more attention to children
c. More resources can be made available.
Question: With the help of suitable diagrams, explain the various steps of budding in Hydra.
Answer : • Hydra reproduces by budding using the regenerative cells.
• A bud develops as an outgrowth in Hydra due to repeated cell division at one specific site.
• When fully matures, the bud detaches itself from the parent body and develops into new
indipendent individuals
Question: What is vegetative propagation? List two advantages and two disadvantages of vegetative propagation.
Answer: Method of producing new plants from vegetative parts like roots, stem and leaves is called vegetative propagation.
Advantages are:
a. The plants bear flowers and fruits earlier than those propagated sexually.
b. Plants have lost capacity to form seeds hence they are propagated vegetatively.
Disadvantages are:
a. Such plants are genetically similar to parent plants and are vulnerable to infections and diseases.
b. They do not have variations therefore do not adapt well to changing environment, the plant species does not evolve.
Question: (a) What is spore formation?
(b) Draw a diagram showing spore formation in Rhizopus.
(c) List two advantages for organisms to reproduce themselves through spores.
Answer.
(a) When a slice of bread is kept in moist dark place for a few days, spores of Rhizopus present in air settle on the bread to form new fungus plants of Rhizopus.
(b) The Rhizopus consists of fine thread-like projections called hyphae. It has a knob like structure which is involved in reproduction called sporangia, containing spores, that develop into new Rhizopus.
(c) Two advantages for organisms to reproduce themselves through spores are as follows:
(i) It is a faster mode of reproduc-tion.
(ii) Offsprings produced are identical.
Question: Mention the total number of chromosome along with sex chromosome. Explain how in a sexually reproducing organism chromosome number of parents and their offsprings is the same.
Answer: Total number chromosomes is 23 pairs. The last pair is called sex chromosome. If they are similar, they are termed as XX chromosome. They are present in the females. If they are dissimilar, they are called XY. They are present in the males. DNA doubling is always followed by cell division. But multicellular organisms have special linkages of cells in specialised organs which have only half the number of chromosomes and half the amount of DNA. Thus, when these germcells from two individuals combine during sexual reproduction to form a new individual, it results in re-establishment of number of chromosome and DNA content.
Question: Draw a diagram of a human female reproductive system and label the part
(i) that produces egg
(ii) where fusion of egg and sperm take place
(iii) where zygote is implanted
What happens to human egg when it is not fertilised?
Answer.
Question: Reproduction is one of the most important characteristics of the living beings. Give three reasons in support of your answer.
or
Define reproduction. How does it help in providing stability to the population of species?
Answer: a. Reproduction is the process of producing individuals of its own kind. Through reproduction, the continuity is maintained.
b. Members of population are eliminated due to old age, disease, accidents and other reason. They have to be replaced by new members in order to maintain a stable population.
c. Reproduction brings variation so that population may adapt better and evolution in species takes place. Ultimately new species originate from preexisting ones.
d. Reproduction is not essential for an individual as its survival is not dependent upon it but is essential for a species for its survival.
Question: What happens when:
a. Accidentally Planaria is cut into three different pieces.
b. Bryophyllum leaf fall on the wet soil.
c. On maturation sporangia of Rhizopus burst.
Answer: a. Three new Planaria will form due to regeneration.
b. New plantlets will form from these buds helping the plant to propagate vegetatively.
c. Spores are released which upon finding suitable substratum germinates to form new individual.
Question: State the basic requirement for sexual reproduction. Write the importance of such reproduction in nature.
Answer: Sexual reproduction takes place in multicellular organisms with complex body design. There are specialized (sex) organs in which through a special type of cell division, number of chromosome is reduced to half and male and female germ cells/gametes form.
These gamete fuse to form zygote on fertilization,thus the characteristic number of chromosome and the normal DNA content for a cell is regained.
Sexual reproduction gives rise to more variations which are essential for evolution as well as survival of species under unfavorable conditions. Species reproducing sexually have better chances of survival.
Question: List four steps in sexual reproduction. Write two of its advantages.
Answer: a. Four steps in sexual reproduction :
b. Formation of gametes in the sex organs.
c. Transfer of male gamete to female gamete which involves release of both types of gametes in the medium outside.
d. Fusion of gametes, either inside or outside the female parents body.
e. Development of zygote to embryo and then complete individual.
Advantages:
a. Variations are produced among the progeny.
b. Such populations are able to adapt well to
changing environment and thus evolves faster.
Question: Explain the term “Regeneration” as used in relation to reproduction of organisms. Describe briefly how regeneration is carried out in multicellular organisms like Hydra.
Answer:The ability to give rise to new individuals from the body parts of the parent individual is called regeneration, e.g., Hydra and Planaria, if their bodies get broken into many pieces, each piece is capable of re-growing into a complete individual.
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 asexually or the one reproducing sexually? Give reason to justify your answer The species having sexual mode of reproduction have better chances of survival because sexual reproduction leads to variations which give better survival advantage to the species over time.
Answer:
The species having sexual mode of reproduction have better chances of survival because sexual reproduction leads to variations which give better survival advantage to the species over time.
Question: Compare the following:
a. Unisexual and bisexual flower.
b. Self-pollination and cross pollination.
c. Style and filament.
Answer:a. Unisexual flowers have either stamens or carpels, e.g., Papaya and Watermelon. Bisexual Flowers have both stamens and carpels, e.g., Mustard and Hibiscus.
b. Self-Pollination is transfer of pollen grains from the stamen to the stigma of same flower. Cross Pollination is transfer of pollen grains to another flower by agents like wind, water or animals.
c. Style is the middle elongated part of the carpel. It acts as a passage for pollen to reach ovary for the fertilization. Filaments is the elongated part of stamen.
Question: “Regeneration is not same as reproduction”.
a. Justify the statement.
b. What is meant by regeneration?
c. How is this process different from fragmentation?
Answer: a. Regeneration is not the same as reproduction, since most organisms would not normally depend on being cut up to be able to reproduce.
b. The ability to give rise to new individuals from the body parts of the parent individual is called regeneration.
c. In fragmentation, the body of a simple multicellular organism breaks down onto many ‘fragments’. All cells undergo division and the organism develops from each fragment. Regeneration occurs only through some specialised cells.
Question: Explain the process of regeneration in Planaria. How is this process different from reproduction?
Answer : Regeneration is the ability to give rise to new individuals from the body parts of the parent individual e.g., Hydra and Planaria, if their bodies get broken into many pieces, each piece is capable of re-growing into a complete individual.
In some organism regeneration occurs but only to regain lost body parts like in tail of lizard, arm of a star fish. In the case of Planaria, it is a way of reproduction that is producing organisms of its own kind.
Question: In the process of reproduction as used by Spirogyra,the organism splits itself into small pieces.
a. What is this process of reproduction called?
b. Is this type of reproduction sexual or asexual?
c. Is this process same as regeneration?
Answer: a. Fragmentation.
b. Asexual as only one parent is involved,
c. In fragmentation, the body of a simple multicellular organism breaks down into many ‘fragments’. All cells undergo division and the organism develops from each fragment. In regeneration, body of a multicellular organism get broken into many pieces, each piece is capable of re-growing into a complete individual.
Question: Study the diagram given below:
a. Identify the process.
b. Which organism uses the above method of reproduction?
c. How is the above method different from the process of fragmentation?
or
In context of reproduction of species, state the main difference between fission and fragmentation. Also give one example of each.
Answer: a. Binary fission.
b. Amoeba.
c. Binary fission occurs in unicellular organisms only. In fragmentation the body of a simple multicellular organism breaks down into many
‘fragments’. All cells undergo division and the organism develops from each fragment.
Question: DNA content has the tendency to double itself during sexual reproduction due to combining of the genetic materials from the two parents. How the problem of DNA doubling can be solved to maintain the consistency of the genetic material throughout the species?
or“
The chromosome number of the sexually reproducing parents and their offsprings is the same”. Justify the statement.
Answer: DNA doubling is always followed by cell division. Due to this special cell division, gametes form with half the content of DNA and single set of chromosomes. These gamete fuse to form zygote on fertilization. Thus the characteristic number of chromosome and the normal DNA content for a cell is regained.
Thus the consistency of the genetic material throughout the species is maintained and for the same reason the chromosome number of the sexually reproducing parents and their offsprings is the same.
Question: Explain the structure of the female reproductive system of humans.
Answer: Female Reproductive System consists of ovaries, fallopian tubes, uterus and vagina.
a. Ovaries are located inside the abdominal cavity, near the kidney. It performs two functions:
• Produce female germ – cells/eggs. Every month one egg is produced
• Secrete hormones like Estrogens which stimulate the development of secondary sexual characteristics at puberty.
b. Fallopian Tubes carry the egg from ovary to the womb; egg gets fertilized in the oviducts only if it meets a sperm.
c. Uterus is a elastic bag like structure. The fertilized egg, the zygote gets implanted in the fining of uterus and develops into an embiyo.
d. Vagina (Birth Canal) receives the sperms as well as child is borne through it.
Question: Give the functions of the following in the process of reproduction:
a. Pollen tube.
b. ovary,
c. Stigma.
Answer: a. Pollen tube carries male gamete from stigma to ovule.
b. Ovary has ovule and forms fruit to protect and dispersal of seeds.
c. Stigma receives pollen during pollination.
Question: Justify the following statements:
a. Variation is beneficial for the species over a period of time.
b. New offsprings produced are similar to their parents but not identical.
c. Binary fission is different in Amoeba and Leishmania.
Answer: a. Variations help a population in the process of natural selection and accumulation of adaptations in a population. It leads to evolution of a species.
b. Offspring, especially when produced sexually, have minor differences or variations among themselves hence they may not look identical. By virtue of them being from same species they look similar.
c. Binary fission in Amoeba is in any plane but in Leishmania it is in a fixed plane.
Question: What happens when:
a. APlanaria is cut into three different pieces,
b. Leaf of the Bryophyllum with notches fall on the soil.
c. Testosterone is released in the male reproductive system.
Answer: a. Three new Planaria will form due to regeneration.
b. New plantlets will form from these buds helping the plant to propagate vegetatively.
c. The male shows masculine features and attains fertility. Sperm starts forming in testis.
Question: What is the effect of DNA copying, which is not perfectly ccurate, on the reproduction process? How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?
Answer: a. DNA copying leads to more variations in the offspring.
b. Sexually reproducing organisms have special lineage of cells which have only half the number of chromosomes as the parent cell.
c. When such germ cells fused, a new individual is formed with the same amount of DNA as that of parent.
Question: Differentiate between the following:
a. Placenta and uterus
b. Unisexual and bisexual flowers
c. Fertilization and germination
Answer: a. Placenta and uterus : The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta.
After fertilization, embryo gets attached to the walls of uterus.
b. Unisexual flowers contain either stamens or carpels. Bisexual flowers contain both stamens and carpels.
c. Fertilization and germination : The fusion of male gamete with female gamete leading to the formation of zygote is known as fertilization.
The growth of embryo (present in the seed) into seedling under appropriate conditions is known as germination.
Question: A part of the male reproductive system is shown below. Study the diagram and answer the questions that follow.
a. Two part have been incorrectly labelled. Identify them.
b. Give the function of urethra.
c. Which hormone is released by testis?
Answer: a. Testis, penis.
b. Urethra serves as a common passage for both sperms and urine.
c. Testosterone.
Question: Mention one function each of the following parts with respect to the female reproductive system:
a. Vagina
b. Ovary
Answer: a. The uterus open into vagina through the cervix.The sperms enter through the vaginal passage during sexual intercourse.
b. One egg (female gamete) is produced every month by one of the ovaries.
Question: List and explain in brief three methods of contraception.
or
List any four methods of contraception. How are they helpful to young couples?
Answer: Four methods of contraception:
a. Condoms
b. Copper-T
c. Diaphragm
d. Oral pills
All these help in family planning as it helps in keeping gap between two children. They help in proper utilization of family resources.
Question: (a) Explain the terms: (i) Implantation (ii) Placenta
(b) What is the average duration of human pregnancy?
Answer : (a) (i) Implantation: The embedding of a fertilised mammalian egg (embryo) into the inner thick wall of the uterus (womb) where it will continue its development is called implantation.
(ii) Placenta: It is a complex double-layered spongy vascular tissue in human female formed by the joint activity of maternal and foetal tissues in the wall of uterus that is meant for attachment, nourishment and waste disposal for the foetus.
(b) The average duration of human pregnancy is 40 weeks or 280 days.
Question: What are sexually transmitted diseases? Name four such diseases. Which one of them damages the immune system of human body?
Answer : Sexually Transmitted Diseases (STDs) are the diseases which are spread by sexual contact from an infected person to a healthy person. They are caused by various microorganisms that live in warm and moist environments of the vagina, urethra, anus and mouth.
The four sexually transmitted diseases are:
(i) Gonorrhoea
(ii) Syphilis
(iii) Trichomoniasis
(iv) AIDS (Acquired Immune Deficiency Syndrome).
AIDS damages the immune system of human body.
Question: List any four reasons for vegetative propagation being practised in the growth of some type of plants.
Answer :
(i) Vegetative propagation is a cheaper, easier and more rapid method of propagation in plants than growing plants from their seeds.
(ii) Better quality of plants can be maintained by this method.
(iii) It results in propagation of those plants which do not produce viable seeds or produce seeds with prolonged period of dormancy.
(iv) The plants generated from vegetative means are more uniform and genetically similar to the parent stock.
Question: (a) Explain the role of placenta in the development of human embryo.
(b) Give example of two bacterial and two viral sexually transmitted diseases. Name the most effective contraceptive which prevents spread of such diseases.
Answer : (a) Role of placenta in the development of human embryo: A special tissue develops between the uterine wall and the embryo (foetus) called placenta, where exchange of nutrients, glucose and oxygen takes place. The developing embryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta. The development of the child inside the mother’s blood takes approximately nine months.
(b) Sexually transmitted diseases (STDs) transmitted by bacteria are:
(i) Gonorrhoea (ii) Syphilis
STDs transmitted by virus:
(i) AIDS (ii) Genital warts
The most effective contraceptive which prevents the spread of these diseases is by the use of mechanical barriers such as physical devices like condoms.
Question: What is AIDS? Which microbe is responsible for AIDS infection? State one mode of transmission of this disease. Explain in brief one measure for the prevention of AIDS.
Answer : AIDS is the Acquired Immune Deficiency Syndrome.
It is caused by a virus called Human Immunodeficiency Virus.
AIDS is transmitted by sexual contact with an infected person.
AIDS can be prevented by avoiding sexual contact with infected person or by using condom during sex.
FIVE MARKS QUESTIONS
Question: How does vegetative propagation occur in nature? Explain with four different examples.
Answer: There are many plants in which parts like the root, stem and leaves develop into new plants under appropriate conditions. This is called as vegetative propagation. Examples of vegetative propagation:
a. Adventitious buds: In Bryophyllum, adventitious buds grow in the notches along the leaf margin,which when fall on the soil, develop into new plants.
b. Cutting: A piece of stem, root, leaf or even a bulb scale is placed partly under moist soil which grows into a new plant, e.g., rose.
c. Layering: A part of the stem is pulled out and buried in the soil. The layered stem grows into a new plant, e.g., Pudina.
d. Grafting: In grafting, two parts from two different plants are joined together so that they can unite and grow into a new plant, e.g., sugarcane.
Question: 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) Fertilization takes place,
(ii) Implantation of the fertilized egg occurs.
Explain how the embryo gets nourishment inside the mother’s body.
Answer: a Testis – secrete male hormone – testosterone.
Functions : (i) Formation of sperms, (ii)Development of secondary sexual characters.
b. (i) fallopian tube/oviduct. (ii) uterus.
Placenta is a special disc like tissue embedded in the mother’s uterine wall and connected to the foetus/embryo. Placenta provides a large surface area for glucose and oxygen/ nutrients to pass from the mother’s blood to the embryo/ foetus.
Question: a. Identify A,B,C and D in the given diagram and write their names.
b. What is pollination? Explain its significance.
c. Explain the process of fertilization in flowers. Name the parts of flower that develop after fertilization into (i) seed (ii) fruit
Answer: a. A – pollen grain; B – stigma; C – Pollen tube, D – Female germ cell/Egg cell.
b. Pollination – Transfer of pollen grains from anther to the stigma of a flower.
Significance of pollination – Process of pollination leads to fertilization as it brings the male and female gametes together for fusion.
c. After a pollen falls on a suitable stigma, the pollen tube grows out of the pollen grain and travels through the style to reach the ovule in the ovary.
Here the male germ cell (carried by the pollen tube) fuses with the female germ cell to form a zygote.
Question: a. Write the function of following parts in human
female reproductive system: (i) Ovary (ii) Oviduct (iii) Uterus
b. Describe in brief the structure and function of placenta.
or
Write the functions of the following in human female reproductive system: Ovary, oviduct, uterus How does the embryo get nourishment inside the mother’s body? Explain in brief.
Answer: a. Functions of Ovary, oviduct, uterus Functions of Ovary
(i) Production of female hormone, oestrogen and progesterone.
(ii) Production of female gamete / egg /germ cell.
Functions of Oviduct:
(i) Transfer of female gamete from the ovary.
(ii) Site of fertilization.
Functions of Uterus:
(i) Implantation of Zygote/ embryo.
(ii) Nourishment of developing embryo.
b. Placenta is a special disc like tissue embedded in the mother’s uterine wall and connected to the foetus / embryo.
Placenta provides a large surface area for glucose and oxygen/nutrients to pass from the mother’s blood to the embryo/ foetus.
Question: What happens when
a. Testosterone is released in the male reproductive system.
b. Pollen grain falls on the stigma of flower.
c. Egg fuses with the sperm cell.
d. A Planaria is cut into three different pieces.
e. Buds are formed on the notches of leaf of the Bryophyllum.
Answer: a. The male shows masculine features and attains fertility/ sperm starts forming in testis.
b. Pollen tube forms and male gametes are carried by it to the ovule.
c. Fertilization occurs and a zygote forms.
d. Three new Planaria will form due to regeneration.
e. New plantlets will form from these buds helping the plant to propagate vegetatively.
Question: Differentiate between:
a. Pollen tube and Style
b. Fission of Amoeba and Plasmodium
c. Fragmentation and regeneration
d. Bud of Hydra and bud of Bryophyllum
e. Vegetative propagation and spore formation.
Answer: a. Pollen tube forms and male gametes are carried by it to the ovule.
Style is part of female part- carpel through which pollen tube passes.
b. Amoeba shows binary fission where one cell splits into two equal halves.
Plasmodium (malarial parasite) shows multiple fission where one cell divides into many daughter cells simultaneously.
c. Fragmentation occurs in multi-cellular organisms with simple body organisation like Spirogyra (a filamentous alga). It involves breaking up of a filament into many fragments and each fragment growing into new individual.
Regeneration is the ability to give rise to new individuals from the body parts of the parent individual, e.g., Hydra and Planaria, if their bodies get broken into many pieces, each piece is capable of regrowing into a complete individual.
d. In Hydra, a bud is formed at a specific site by repeated cell division and develops into a tiny hydra.
In Bryophyllum, vegetative buds arise from the notches of its leaves and develops into a new plantlet.
e. Vegetative Propagation is the development of new plants from parts like root, leaf and stem under suitable conditions, e.g., Bryophyllum vegetative buds arise from the notches of its leaves. In potato, ginger, garlic etc. it occurs through stems.
Spore formation: A spore is a special cell protected by thick coating. It is capable of germinating into a new plant when comes in contact with suitable and environment conditions and moist surface, e.g., in Rhizopus (bread mould), they are formed inside reproductive, bob¬like sacs called sporangia.
Question: Explain what happens when:
a. Testosterone is released in males.
b. Pollen grain falls on the stigma of the flower.
c. Egg fuses with sperm cell.
d. Planaria is cut into many pieces.
e. Buds are formed on the notches of the Bryophyllum leaf.
Answer: a. (i) Formation of sperms, change in appearance.
(ii) Thick hair growth on the face and voice begin to crack.
b. A tube grows out of the pollen grain and travel through the style to reach the ovary.
c. Zygote is formed (fertilization).
d. Each piece grows into a complete organism.
e. Buds may fall on the soil and develop into new plants.
Question: a. Draw a sectional view of human female reproductive system and label the part where:
(i) Eggs develop
(ii) Fertilization takes place
(iii) Fertilized eggs get implanted.
b. Describe in brief, the changes the uterus undergoes:
(i) To receive the zygote
(ii) If zygote is not formed.
Answer:
(i) Ovary
(ii) Oviduct or fallopian tube
(iii) Uterus or uterus wall
b. (i) It becomes thicker due to development of
blood vessels and glands in it.
(ii) It gets peeled and shed off along with mucus,
blood, dead ovum during menstruation
Question: Define the following processes:
a. Fertilization
b. Menstruation
c. Binary fission
d. Vegetative propagation
e. Regeneration
Answer: a. The fusion of male gamete with female gamete is known as fertilization.
b. Menstruation cycle takes place every month when egg is not fertilized. It lasts for about two to eight days and during this cycle the lining of uterus slowly breaks and comes out through the vagina as blood and mucus.
c. Binary fission is the splitting of nucleus into two daughter cells which can take place in any plane. It can be observed in Amoeba.
d. When vegetative part of a plant like the root, stem or leaves develops into new plant under appropriate conditions, it is known as vegetative propagation.
e. When body of an organism cuts into any number of pieces and each piece grows into a complete organism. This is known as regeneration. Hydra and Planaria reproduce through this process.
Question: a. Identify the organisms A, B and the mode of asexual reproduction exhibited by them.
b. How will an organism be benefitted if it reproduces through spores?
c. Mention the two asexual methods by which hydra can reproduce. Explain briefly any one such method.
Answer: a. (i) Bryophyllum – vegetative propagation. (ii) Plasmodium – multiple fission.
b. Spores are covered with thick walls that protect them until they come into contact with a moist surface.
c. Budding and Regeneration.
Budding : A bud develops as an outgrowth due to repeated cell division at a specific site, these buds develop into tiny individuals, mature and detach from the parent to become new individuals.
Regeneration: Specialized cells divide to form large number of cells and undergo changes to become various cell types and tissues.
Question:a. Draw a diagram of the longitudinal section of a flower and label on it sepals, petal, ovary and stigma.
b. Write the names of male and female parts of a flower.
Answer:
b. Male Part : Stamen; Female Part : Carpel/pistil
Question: a. Identify the organisms in figure A, B, C and D.
b. Identify the life process commonly shown in all the figures,
c. How is this life process .advantageous to the organisms? Mention any two advantages.
Answer: a. (A) Hydra (B) Rhizopus
(C) Bryophyllum (D) Planaria
b. Asexual mode of reproduction
c. (i) Only one individual is required. (ii) Progeny is identical like parents (iii) Produced in large number (Any two)
Question. (A) What is 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) Fragmentation: This is a type of asexual reproduction in which a body breaks into several fragments, which later develop into complete organism. e.g.
etc. Spirogra is a multicellular organism which reproduces by fragmentation.
(B) Regeneration: Regeneration is a type of asexual reproduction in which the organism is capable of regrowing certain body parts or whole body e.g. sponge.
Regeneration is possible only for animals with simple cell structure. In complex cell structure, tissue structure is also different.
Therefore regeneration is not possible in complex organisms.
Question. How do organisms, whether reproduced asexually or sexually maintain a constant chromosome number through several generations? Explain with the help of suitable example.
Answer : When organism reproduce sexually, the organism produce gametes through a special type of division called meiosis or reductional division,in which the original number of chromosome becomes half. In sexual reproduction male gametes and female gametes are combined and forms zygote, and the original number of chromosomes is restored.
Male gametes(n) + female gametes(n)– zygote(2n)
(23) (23) (46)
In asexual reproduction, only mitotic divisions are involved and the chromosome number remain same.
Example: In humans, humans have 46.chromosome or 23 pair of chromosomes.
When the gametes formed through meiosis, the chromosomes number become half.
Question.
When the sperm and the egg fuse, the zygote has 46 or 23 pairs of chromosomes.
Sperm (23) + Egg (23) ⎯fuse⎯→ Zygote (46)
Question. (A) Write the functions of the following parts of the human male reproductive system:
(i) Testis (ii) Vas deferens (iii) Urethra (iv) Prostate
(B) List any two common pubertal changes that appear in human males.
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 vas deferens 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) Describe the various steps involved in the process of binary fission with the help of a diagram.
(B) Why do multicellular organisms use complex way of reproduction?
Answer :
(1)
(2) Multicellular organisms cannot reproduce by cell because they are not simple random collection of cells. In them, specialized cells are organized as tissues which are organized into orgAnswer : Cell-by-cell division would be impractical. Multicellular organisms, therefore, require to use more complex ways of reproduction.
(3) Multicellular organisms cannot reproduce by cell because they are not simple random collection of cells. In them, specialized cells are organized as tissues which are organized into orgAnswer : Cell-by-cell division would be impractical. Multicellular organisms, therefore, require to use more complex ways of reproduction.
Question. (A) Write the functions of the following parts in human female reproductive system:
(i) Ovary
(ii) Oviduct
(iii) Uterus
(B) Describe the structure and function of placenta.
Answer : (A) (i) Ovary → They produce egg for fertilisation.
→ Produce the reproductive harmones (Oestrogen & Progesterone).
(ii) Oviduct → It transfer the female gamete (egg) from the ovary.
→ It is the site of fertilization.
(iii) Uterus → Implantation of the zygote.
→ Nourishment of developing embryo.
→ Helps in placenta development.
(B) Structure of Placenta: Placenta is a special tissue connection between embryo and uterine wall. It acts as an endorine gland.
Functions of Placenta:
(i) It possess Villi that increase the surface area for absorption of nutrients.
(ii) Waste substances produced by embryo are removed through placenta into mother’s blood.
(iii) Facilitate passage of nutrition and oxygen to embryo from mother through blood.
Question. (A) Describe the role of prostate gland,seminal vesicle and testes in the human male reproductive system.
(B) How is the surgical removal of unwanted pregnancies misused?
(C) Explain the role of oral contraceptive pills in preventing conception.
Answer :
(A) Prostate glands and seminal vesicle : add their secretions so that the sperms are in a fluid and it makes their transport easier and also provides nutrition.Testes secrete testosterone which brings about changes in the appearances in the boys at the time of puberty.
(B) Female foeticides/illegal sex selected abortion of female foeticide.
(C) Interfere in release of egg and eggs are not released.
Question. Answer the following:
(A) Give an example of bisexual flower. What is its female reproductive part known as?
(B) Draw a diagram of its longitudinal section showing the process of germination of pollen on stigma and label the following on it:
(i) Male germ cell
(ii) Female germ cell
(iii) Ovary
(iv) Pollen tube
(C) Pollination may occur without fertilization but fertilization will not take place without pollination. Give reasons.
Answer : (A) A flower that contains both the male and female reproductive structure (stamen and pistil) is called a bisexual flower or hermaphrodite.
Example: rose, hibiscus
Its female reproductive part is known as carpel or pistil.
(B) Diagram of longitudinal section of flower showing the process of germination of pollen on stigma:
(i) Male germ cell
(ii) Female germ cell
(iii) Ovary
(iv) Pollen tube
(C) Pollination is just the transfer of pollen grains from the anther of stamen to the stigma of pistil. It is carried out by agents like wind, insect etc. For pollination to happen there is no need of fertilisation of gametes i.e. their union. Fertilisation is fusion of male and female gamete and this process is facilitated by pollination. By pollination pollens are brought to eggs so that they can fuse and fertilisation can take place. Therefore, Pollination may occur without fertilisation but fertilisation will not take place without pollination.
Question. (A) Define vegetative propagation. List its two methods.
(B) Why is this mode practised for growing some types of plants?
(C) Explain the process of budding in Hydra with the help of labelled diagrams.
Answer : (A) Vegetative propagation is a method of asexual reproduction in some higher plants in which a new plant develops from the vegetative parts of a plant such as root,stem or leaf.
Two methods are:
(1) From root as in Dahlia, sweet potato.
(2) From stem as in ginger, potato, onion.
(3) From leaf as in Bryophyllum
(4) Cutting as in grapes.
(5) Layering as in guava
(6) Grafting as in lemon
Question. (A) Although Amoeba and Leishmania, both show same mode of reproduction, but the process of reproduction is carried out in different ways.
Identify their mode of reproduction and mention the way it is carried out in the two species.
(B) What is regeneration? Explain with the help of a diagram how this process is carried out in Planaria.
(C) Name the part of Rhizopus in which spores are formed.
State the condition under which spores grow into a new individual.
Answer : (A) Mode of asexual reproduction in Amoeba and Leishmania is Binary Fission.
In Amoeba, during division splitting of the two cells can take place in any plane.
In Leishmania, binary fission occurs in a definite orientation in relation to the whip like structures present at one end of the cell.
(B) Regeneration is a process in which an
organism is broken/ cut into pieces, these pieces may grow into separate individuals.
Diagram:
(C) Spores are formed in Sporangia.
Spores grow into a new individual under moist conditions.
Question. List six specific characteristics of sexual reproduction.
Answer : Characteristics:
Two parents are involved,
Two dissimilar gametes are formed, gamete formation involves meiosis,Variations are produced, Occurs in all the higher and some of the lower organisms, Fertilization/fusion of gametes leading to zygote formation Slow.
Question. What are chromosomes? Explain how in sexually reproducing organisms the number of chromosomes in the progeny is maintained.
Answer : Chromosomes: thread like structures made up of DNA found in the nucleus.
The original number of chromosomes becomes half during gamete formation.
Hence, when the gametes combine, the original number of chromosomes gets restored in the progeny. (or same thing explained in the form of a flow chart).
