Class 10 Science Chapter 8 Board Questions

Class 10 Science Chapter 8 Board Questions of How do Organisms Reproduce. There are one mark, two marks, three marks and five marks questions with answers given in the form of sets. All the questions are answered properly with suitable examples. Long questions and short questions are answers according to their marks. This is the collection of last 5 years’ paper’s questions and important questions from last 10 years CBSE board papers. Very short questions for 1 mark, short questions for 2 marks and long answers questions for 5 marks are available with answers and explanation. Most of the questions are taken from last five years CBSE Board Papers but the important questions from last ten years are also included for practice.

In Uttar Pradesh, students are also using NCERT Books, so these questions are also helpful for UP Board students also.

Class 10 Science Chapter 8 Board Questions for Exams

Class: 10Science
Contents:10th Science Chapter 8 Board Questions

Class 10 Science Chapter 8 Board Questions for Practice

Practice here with Class 10 Science Chapter 8 Board Questions, last ten years CBSE Board exams questions with answers. Answers of all questions are described properly. Students can take an idea about the questions which are asked in CBSE Board exams. All the answers are taken from Class 10 NCERT Books only.

10th Science Chapter 8 Board Questions Set – 1 (1 Mark)

What happens when a mature spirogyra filament attains considerable length? [CBSE 2016]

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

Name any two sexually transmitted diseases. What advice is given to prevent them? [CBSE 2008]

Gonorrhoea, syphilis and AIDS.
Advice to prevent them:
(i) Use of condoms.
(ii) Do not share injection needles/syringe.

Define reproduction. [CBSE 2012, 2013]

Reproduction is a process by which new individuals of the some species are produced by existing organisms(parents).

What are the two main methods of reproduction? [CBSE 2013]

Asexual and sexual.

Write the source of making proteins in the cell information. [CBSE 2013]

DNA on the chromosome.

Difference between budding in hydra and budding in yeast. [CBSE 2012]

Budding in HydraBudding in Yeast
(i) Buds produced are multicellular.(i) Buds produced are multicellular.
(ii) Buds get detached from parent body.(ii) Buds may remain attached to the parent body.

10th Science Chapter 8 Board Questions Set – 2 (1 Mark)

Name a plant that has lost the capacity to produce seeds. [CBSE 2013]

Banana.

“Cell division is a type of reproduction in unicellular organisms.” Justify. [CBSE 2013]

Unicellular organisms, e.g., Amoeba, reproduce by cell division. A parent cell can divide into two or more daughter cells during this. This is called fission. So, cell division is a type of reproduction in unicellular organisms.

State the mode of reproduction in plasmodium. [CBSE 2011]

Multiple fission.

Protozoans reproduce by binary fission as well as multiple fission. In your opinion which process is better and why? [CBSE 2011]

In my opinion multiple fission is better because at a time many daughter cells will be produced.

List two plants which are grown by vegetative propagation of stem. [CBSE 2012]

(i) Jasmine (ii) Rose

Difference between Binary fission and Multiple fission

Binary Fission

The organisms splits into two daughter cells example Amoeba.

Multiple Fission

The organisms splits into many daughters cells example Plasmodium.

10th Science Chapter 8 Board Questions Set – 3 (1 Mark)

Give one example for each of the following: (i) Plants in which vegetative propagation occurs by grafting? (ii) Plants in which vegetative propagation occurs by leaves? [CBSE 2008, 2012]

(i) Rose
(ii) Bryophyllum.

Name any two plants that reproduce by grafting. [CBSE 2012]

(i) Rose
(ii) Sugarcane.

In which part of the human female reproductive system does the implantation of embryo take place? [CBSE 2013]

Uterus.

Name two plants which bear unisexual flowers. [CBSE 2013]

Papaya, watermelon

Give one example of wind pollinated plant. [CBSE 2013]

Grass, Maize.

Questions are divided in to 1 mark, 2 marks, 3 marks and 5 marks according to short or long questions. It includes almost all the expected questions from 10th Science Chapter 8 for board exams.

10th Science Chapter 8 Board Questions Set – 4 (1 Mark)

What should be the female-male ration in a healthy society? [CBSE 2013]

1:1

What is the swollen sticky terminal end of the carpel called? [CBSE 2013]

Stigma.

Name an STD which damages the immune system of human body. [CBSE 2011]

AIDS, Acquired Immuno Deficiency Syndrome.

What does a seed contain? [CBSE 2011]

Seeds contains the future plant in the form of embryo that develops into seeding in favourable condition.

What is the duration of pregnancy in human female? [CBSE 2012]

280 days about 40 weeks (nine months).

Difference between Sperms and Eggs of human [CBSE 2014]

Main difference between sperm and egg is that all eggs are of one type, bearing X chromosomes while sperms are two types 50% having X chromosome while other 50% having Y chromosome.
This is important when X carrying sperm fertilises egg, it result in female zygote whereas when Y carrying sperm fertilises egg, it result in male zygote.

10th Science Chapter 8 Board Questions Set – 5 (1 Mark)

What does ovary of a plant contain? [CBSE 2011]

The ovary contains embryo sac which has an egg- the female gamete.

Name different part of flower that has green cells. [CBSE 2011]

Stamen and pistil have germ cell.

Name the part that produces egg and the one that carries it to the womb. [CBSE 2012]

Ovary produces egg and fallopian tube carries it to the womb.

Mention two modes of reproduction. [CBSE 2013]

(i) Sexual reproduction.
(ii) Asexual reproduction.

Why are testes located outside the abdominal cavity? [CBSE 2013]

Sperm production require little lower temperature compared to body temperature hence testis are located outside.

Gene

A part of DNA on chromosome, capable of coding for a polypeptide.

10th Science Chapter 8 Board Questions Set – 6 (1 Mark)

Name one sexually transmitted diseases each caused due to bacterial infection and viral infection. How can these be preserved? [CBSE 2008]

Sexually transmitted diseases each caused due to bacterial infection and viral infection is gonorrhea. These diseases are curable. Disease caused by viral infection is AIDS. This disease is not curable. These can be prevented by use of condoms during sexual act.

In which part of the female reproductive organs of human female does fertilisation take place and what happens to the fertilized egg? [CBSE 2017]

In human female, fertilisation takes place in the fallopian tube After fertilisation, the fertilised ovum travels to uterus and gets attached to the wall of uterus for further development. This is called implantation.

What changes are observed in the uterus if fertilisation does not occur? [CBSE 2016]

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

Fallen leaves of Bryophyllum on the ground produce new plants whereas the leave of rose do not? Explain the difference between two plants. [CBSE 2012]

In bryophullum, vegetative propagation occurs through leaves where buds occur while in rose leaves do not form buds. Thus its fallen leaves do not produce new plants.

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

In bryophullum, vegetative propagation occurs through leaves where buds occur while in rose leaves do not form buds. Thus its fallen leaves do not produce new plants.

Reproduction in Spirogyra [CBSE 2013, 2017]

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

10th Science Chapter 8 Board Questions Set – 7 (2 Marks)

Small piece of root tissue was taken from the rose plant and placed in a nutrient medium. Each root tissue produced a new rose plant. Name the reproduction process involved. What type of genes will be possessed by new rose plant? [CBSE 2012]

This process is called Tissue culture.
Genes possessed by new plant will be same as that of parent plant, resulting in formation of clones.

The organisms formed by asexual reproduction are considered as clones why? State the advantages of sexual reproduction over asexual reproduction. [CBSE 2011]

Organisms produced by asexual reproduction contain exactly the same chromosomes as the parent cell have. Hence they look like clones because the trait remains preserved. Sexual reproduction results in the mixing of gametes of two individuals, hence variation occurs in offspring leading to evolution.

Explain why pollination may occur without fertilisation but fertilisation will not take place without pollination. [CBSE 2012]

Pollination is landing of pollen grain on suitable stigma. It may not always result in fertilisation. However, fertilisation requires both male and female gametes. If pollination does not occur male gamete is not available. Hence fertilisation cannot taken place.

List any two common pubertal changes that appear in both boys and girls. [CBSE 2013]

(i) Appearance of pubic hair.
(ii) Skin become oily and may break into pimples.

Differentiate between germination and fertilization. [CBSE 2011]

Germination: The development of the embryo contained in the seed into seedling under favourable condition is called germination.
Fertilization: The fusion of male germ cell with the female gamete is known as fertilization.

Differentiate between fission of Leishmania and Plasmodium. [CBSE 2013]

Fission of Leishmania

Binary fission occurs in definite orientation in relation to whip like structure.

Fission of Plasmodium

Multiple fission occurs.

10th Science Chapter 8 Board Questions Set – 8 (3 Marks)
What is reproduction? Mention the importance of DNA copying in reproduction. [CBSE 2008, 2015]

Reproduction is the process by which an organism produces new individuals that looks very much like themselves.
Importance of DNA copying in reproduction:
(i) Copying or duplication of genetic material through faithful replication is called DNA copying. It can be inherited by the progeny.
(ii) The process of DNA copying brings some variation each time. The surviving cells are similar to but subtly different from each other. This inbuilt tendency for variation during reproduction bring variations among individuals of the same species. This is useful for ensuring survival of the species.

(a) In the human body what is the role of (i) seminal vesicles and (ii) prostate gland? (b) List two functions performed by testes inhuman beings. [CBSE 2008, 2013]

(a) The role of seminal vesicles and prostate gland are as follows:
(i) Seminal vesicles produce seminal plasma with in the form of fluid makes the transport of sperm smooth.
(ii) Prostate gland secretes prostatic fluid take keeps the sperms alive and help them to swim vigorously.
(b) In human being testes perform dual function:
(i) Production of sperm
(ii) Secretion of male hormone testosterone.

Identify among the following organisms which is reproduced by sexual and which by asexual method: Amoeba, Human being, Whale, Hydra, Spirogyra, Dog.[CBSE 2013]

Amoeba- Asexual reproduction
Human being – Sexual reproduction
Whale– Sexual reproduction
Hydra– Asexual reproduction
Spirogyra– Asexual reproduction
Dog– Sexual reproduction

List three reason for growing plant by vegetative propagation. [CBSE 2012]

(i) Plant grown by vegetative propagation are genetic similar to the parent plant.
(ii) They can bear fruit and flower faster than those plants that are produced by seeds.
(iii) Plants that do not produce seeds too can be multiple by this method.

What happen to the pollen when it transferred on the stigma? What happens to ovary and ovule after fertilisation? [CBSE 2012, 2013]

Pollen on landing on a suitable stigma grows the pollen tube so as to reach the female gamete in the ovary. The pollen tube carries two male gametes in it, which fuse with the egg cell to form zygote and other male gamete fuses with secondary nucleus to form PEN.
After fertilisation the ovary grows rapidly and ripens to form a fruit. After fertilisation the ovule develops a tough coat and it gradually converted into a seed.

Difference between Budding and Spore Formation
BuddingSpore Formation
1. Process of asexual reproduction where bud develops as an outgrowth of body due to repeated cell division example Yeast, Hydra.1. Spore formation is the process.
2. Buds can be unicellular or multi-cellular.2. Spores are always unicellular.
3. Buds do not have any wall.3. Spores are thick walled.
10th Science Chapter 8 Board Questions Set – 9 (3 Marks)
Describe the process of budding as seen in yeast? [CBSE 2012]

Yeast a unicellular fungus reproduces by budding.
When a yeast cell grows to became an adult cell, a small protuberance appears on it. The nucleus splits and the daughter DNA is given into this bud. The bud may detach as an independent yeast cell from parent cell or remain attached on the parent cell as a chain.

(a) Specify the events which occur in reproductive system of human female: (i) If egg is fertilised. (ii) If egg is not fertilised. (b) Mention the changes that take place in uterus in both the above events. [CBSE 2011]

(a)
(i) Pregnancy
(ii) Mensturation
(b) In first case the lining of uterus became thick and spongy richly supplied with blood helps in implantation of embryo.
In second case the lining brakes along with blood vessels and come through vagina as menstrual flow.

(a) Name the structure in human male reproductive system that delivers the sperm from the testes to the urethra. (b) Name the structure in human female reproductive system which delivers the egg from the ovary to the uterus. [CBSE 2012]

(a) Vas deference deliver the sperms from the testis to the urethra.
(b) The egg is transferred through fallopian tube from ovary to uterus.

Name any two sexually transmitted diseases. How do these infectious diseases spread from one person to other? Give two symptoms of STDs. [CBSE 2012]

Syphilis, Gonorrhoea, AIDs, wants are sexually transmitted disease.
These infectious diseases spread from one person to other by sexual contact with an infected person.
Fluid discharge, burning sensation while urination, sores in genital area etc., some of the symptoms of STDs.

Which parts/organs of the human reproductive systems perform the following functions: (a) Production of fluid to provide a medium for sperms. (b) Secretes the hormone that regulates formation of sperms. (c) Provide nutrition from mother’s blood to embryo. (d) Carries egg from ovaries to the womb. [CBSE 2012]

(a) Seminal vesicles/prostate gland
(b) Testes
(c) Placenta
(d) Fallopian tube

Difference between Human Male Gamete and Female Gamete [CBSE 2013]
Male GameteFemale Gamete
1. Produced in large numbers each times.1. Only one gamete produced at a time.
2. They are smaller.2. They are larger as they have food reserve.
3. They are motile.3. They are non-motile.
4. They are two types.4. They are of one type only.
10th Science Chapter 8 Board Questions Set – 10 (3 Marks)
List four advantages of vegetative propagation. [CBSE 2014]

(i) Plants raised by vegetative propagation bear flower and fruits earlier.
(ii) Plants that do not produce seeds can be propagated by this method.
(iii) All plants produced are genetically identical.
(iv) Any vegetative plant part can be used. Thus many new plants can be produced at a time.

Reproduce is one of the most important characteristics of living beings. Give three reasons in support of the statement. [CBSE 2017]

(i) Organisms reproduce and create new individuals of their kind. This is essential for perpetuation of species.
(ii) Information the inheritance of features from parent to next generation is present within chromosomes in the form of DNA. The DNA is information source for making proteins, which if changes will change the original body design.
(iii) DNA copying is as essential process toward formation of new cells. This may not always be accurate and thus results in variations. Variations are essential for evolution, but very slow in this case.

What is vegetative propagation? State two advantage and two disadvantage of this method. [CBSE 2017]

Many plants can give rise to new plants through their vegetative parts as roots, stem and leaves. This is known as vegetative propagation.
Following are the advantages (any two):
(i) Plants grown by vegetative propagation are genetically similar to the parent plant.
(ii) Plants that do not produce seeds too can be multiplied by this method.
(iii) Plants raised by vegetative propagation can bear flower and fruits earlier than those produced from seeds.
(iv) Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that have lost the capacity to produce seeds.
(v) Thus, desirable features of parent plant can be retained and expressed without any change in future generation.
Following are the disadvantages:
(a) All plants are genetically identical to the parent plant and hence no variation.
(b) Because of no variation they would not show any evolution if propagated solely by vegetative propagation.

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

Different methods of contraception are:
(i) Barrier method- Where physical like condoms (worn over penis), diaphragm (used by female), cervical cap and Copper-T (an IUCD) are used.
(ii) Chemical method- Spermicidal applications by women, vaginal pills or oral contraceptive pills (OCP)s are used. OCPs are hormonal preparations which alter the hormonal level in female body. Use of OCPs is not meant for males.
(iii) Surgical method- Portion of vas deferens in male (vasectomy) or portion of fallopian tube in female (tubectomy) is cut or ligated. This stops releases of gametes, preventing fertilisation.
Contraceptive methods should be adopted as:
(i) They help in spacing two children.
(ii) Thus helps in maintaining a woman’s health.
(iii) Better care of mother and child.
(iv) Also prevention of sexually diseases on using condoms.
(v) This results in better productivity of a family and hence more prosperity.

What is meant by pollination? Describe its various types along with names of various pollinating agents. [CBSE 2012, 2016, 2017, 2018]

The transfer of pollen grains from the anther to suitable stigma is termed pollination. Pollination is of two types:
(i) Self-pollination: The transfer of pollen grain from the anther of a flower to the stigma of the same flower is known as self-pollination.
(ii) Cross-pollination: The transfer of pollen grain from the anther of one flower to the stigma of another flower growing on same or another plant of the same species is called cross-pollination.
Agencies of pollination are- wind, water, insects, birds and animals.

Differences between Pollination and Fertilisation
PollinationFertilisation
1. Transfer of pollen grain from anther to stigma.1. It is the process of fusion of male gamete and female gamete resulting in formation of zygote.
2. Pollination facilitates formation of pollen tube which carries male gamete to the ovule.2. Zygote later develops into seeds which contains embryo.
3. Occurs only in higher plants.3. Occurs in plant as well as in animals.
10th Science Chapter 8 Board Questions Set – 11 (3 Marks)
Explain vegetative propagation with the help of two examples. List two advantages of vegetative propagation. [CBSE 2008, 2010]

In vegetative propagation new plant can be obtained from vegetative parts such as stem, root and leaves. Examples:
(i) Sugar came is grown by using stem cuttings.
(ii) Leaf of Bryophyllum has buds on its margins. When it falls or touches the soil, new plants arise from these buds.
Two advantages of vegetative propagation:
(i) It is the only means of propagating such plants which do not produce visible seeds or produce very few seeds such as banana, orange, grape, rose and pineapple.
(ii) Many identical plants having same characters can be raised from a single parent, by from a single plant, this method.

Name the organ where the sperms are produced and name the hormone produced by it. Why do sperms have tail but ovum does not? [CBSE 2011]

The organ that produce sperms is Testis. Hormone produced by testis is testosterone. Sperms have to swim to reach the female gamete, which is stationary. Hence they have tails.

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

Organ where ova are formed is ovary. Ova are released from ovary into the fallopian tube which lead into the uterus. The ovum gets fertilised in the fallopian tube where sperms travel to fertilise the egg from cervix, through uterus, to fallopian tube.
The fertilised egg, i.e., zygote gets implanted in the uterus after fertilisation.

What are chromosomes? Explain how in sexually reproducing organisms the number of chromosome in the progency is maintained. [CBSE 2015, 2016, 2017]

Chromosome are carries of genetic information which is inherited from generation to generation.
Number of chromosomes in sexually reproducing organisms is maintained. This has been achieved by having special lineages of cells in specialised organs which have only half the number of chromosomes and thus half the amount of DNA. Thus, when this germ cells from two individuals combine during sexual reproduction to form a new individual, it results in reestablishment of the number of chromosome and DNA content in the new generation.

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

Significance of reproductive health in a society:
(i) Reproductive healthy individuals will give rise to healthy new generation.
(ii) There will be fewer sexual transmitted diseases.
(iii) Healthy mothers mean happy households.
(iv) Healthy individuals mean more productive and prosperous families and society at large.
In last 50 years, government has strictly imposed ban on child marriage and hence maternal mortality rate and infant mortality rate has gone down.

Fertilization

The process of fusion of one male gametes with that of a female gametes(egg) is known as fertilization.

10th Science Chapter 8 Board Questions Set – 12 (3 Marks)
List two reasons for the appearance of variations among the progency formed by sexual reproductive. [CBSE 2016]

Sexual reproductive involves gametes from two different individuals. Thus their genetic make up is different and hence gametes carry different alleles.
It leads to formation of greater variation, so better adaptability and evolution.

(a) Write the functions of the following parts of human male reproductive system: (i) Testis (ii) Vas deferens (iii) Urethra (iv) Prostate. (b) List any two common pubertal changes that appear in human males. [CBSE 2016, 2017]

(a) Functions of the following in human male reproductive system-
(i) Testis- Production of male hormone i.e., testosterone and male gametes i.e., sperms.
(ii) Vas deferens- Delivers sperms.
(iii) Urethra- Helps in transporting sperm out of the male reproductive tract, is common passage for both sperms and urine.
(iv) Prostate-Adds its secretion to the sperm so that they are in fluid medium which provides them with nutrition and makes the transport easier.
(b) Two changes in males during puberty-
(i) Appearance of facial hair.
(ii) Voice begins to crack.
(iii) Occasional enlargement of penis.
(iv) Muscular body.

List any four modes of asexual reproduction. [CBSE 2016, 2017]

Four mode of asexual reproduction are:
(a) Fission- Parent cell divides to form two or more daughter cells.
(b) Fragmentation- Multicellular organisms breaks into pieces and each undergoes cell division to develop into complete organisms.
(c) Regeneration- Multicellular organisms breaks into piece and each undergoes cell division and differentiation (by specialised cells) to form complete organisms.
(d) Budding- A small outgrowth on the parent body detaches when mature and develops into a new individual.

(a) What is pollination? State its significance. (b) how does fertilisation occurs in flowers? Name the parts of the flower that develop into (i) Seed and (ii) fruits after fertilisation. [CBSE 2014]

(a) The transfer of pollen from anther to stigma of suitable flower is pollination.
This results in fertilisation and hence formation of next generation.
(b) After pollination, the pollen germinates to form pollen tube that carries male germ cells. It grows to reach embryo sac, where these germ cells are released and fertilisation takes place.
(i) Embryo sac forms seed.
(ii) Ovary forms the fruit.

What is the role of seminal vesicle and the prostate gland? [CBSE 2016]

Along the path of the vas deference these glands add their secretions so that the sperms are now in fluid which make their transport easier and this fluid also provides nutrition to sperms.

Reproduction and Regeneration

Process of formation of individual organism takes place by sexual or asexual method where as new organism develop from the body parts of certain organism.

10th Science Chapter 8 Board Questions Set – 13 (5 Marks)
Discuss briefly the different types of reproduction. [CBSE 2017, 2018]

Living organisms reproduce mainly by two methods:
(i) Asexual reproduction: In this mode of reproduction, the offspring arises from a single individual parent. Asexual type of reproduction takes place in unicellular organisms, some plants and certain multicellular animals like sponges and Hydra.
Main types of asexual reproduction are:
(a) Fission.
(b) Budding.
(c) Spore formation.
(d) Regeneration.
(e) Vegetative propagation.
(ii) Sexual reproduction: For sexual reproduction, involvement of the two sexes, male and female, is essential. Sexual reproduction involves union of sperm (male gamete) and egg (female gamete). These gametes are produced by gonads testis in males and ovary in females.

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? [CBSE 2017]

(a) Multicellular organisms with cell differentiation, when cut in small pieces, may regrow into complete organisms, e.g. Planaria and Hydra. This process is known as regeneration.
Regeneration is also seen in Hydra
(b) Adventitious buds present on the leaf margin at notches begin to grow to give rise to a new plant, when Bryophyllum leaf falls on wet soil.
(c) In many fungi, like Rhizopus, spore formation takes place in spore sacs called sporangia. These spores, being thick walled, survive harsh conditions and can grow into a complete organism under favourable conditions.
Spore formation is the most common method of asexual reproduction seen in fungi and bacteria. During spore formation, a structure called sporangium develops from the fungal hypha. The nucleus divides several times within the sporangium and each nucleus with a bit of cytoplasm, develops into a spore.
The spore is liberated and they develop into hypha after reaching the ground e.g., Rhizopus, Mucor and Penicillium.

(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. [CBSE 2010]

(a) Placenta is a special tissue having disc like shape which remains embedded in the uterine wall. It contains villi on the embryo side of the tissue. On the mother’s side are blood spaces which surrounds the villi. This provides a large surface area for glucose and oxygen to pass from the mother. The developing embryo also generate waste substances which can be removed by transferring them into the mother’s blood through placenta. Apart from it placenta also secretes certain hormones which maintain the pregnancy.
(b) Bacterial diseases transmitted through sexual contact:
(i) Gonorrhoea
(ii) Syphilis
Viral diseases:
(i) Warts
(ii) HIV-AIDS
Use of condoms is the most effective contraception device to prevent STD’s.

(a) Mention the role of following organs of human male reproductive system: (i) Testis (ii) Scrotum (iii) Vas deferens (iv) Prostate glands (b) State the reasons why testes are located outside the abdominal cavity. [CBSE 2011, 2012, 2013, 2015, 2016, 2017]

(a) (i) Male gametes (sperms) and male hormone testosterone are produced by testis. This
temperature is 1-3 0 C lower than the temperature of the body. Testis are located outside the abdominal cavity, in the scrotum to provide right temperature.
(iii) The sperms formed are delivered through the vas-deferens which unites with a tube coming from the urinary bladder.
(iv) The prostate glands secrete the fluids which provides nutrition to the sperms and make their transport easier.
(b) They require a lower temperature than the human body temperature for the formation of sperms.

All the questions which come in the CBSE Board Exams may further come in future exams. So, student should practice well these questions of Class 10 Science for better practice for terminal test or exams.

10th Science Chapter 8 Board Questions Set – 14 (5 Marks)
(a) Which device prevents implantation by irritating the lining of uterus? (b) What could be the possible reason for declining female male sex ratio in our country? suggest two measures to achieve 1:1 ratio. (c) Name those parts of a flower which serve the same function as the following do in animals: (i) Testis (ii) Ovary (iii)Eggs (iv) Sperms. [CBSE 2011]

(a) Intra Urine Contraceptive Device (IUCD) like Copper-T prevents implantation.
(b) Selective Medical Termination of Pregnancy (MTP) of female foetus using amniocentesis is the main reason behind decline female-male sex ratio in our country. This is because many sections of our society considered girl child as a burden.
Measures to achieve 1:1 ratio.
(i) Generating awareness about girls begin equal helping bands in the family income.
(ii) Banning prenatal sex determination tests.
(iii) Banning certain ill practices in our society like dowry system.
(c) (i) Testis-Anther
(ii) Ovary-Ovary
(iii) Egg-Female gamete/egg
(iv) Sperms-Male gamete in pollen tube.

What is placenta? Describe its structure. State its function in case of pregnant human female. [CBSE 2012, 2013, 2016, 2017]

For implantation of foetus, a special tissue called placentae develops from the maternal uterine wall. It is a disc shaped structure, in the uterine wall with villi on the embryonal side and large blood spaces on maternal side.
Functions:
(i) It provides large surface area for glucose O2 to pass from mother’s blood to the embryo.
(ii) It also removes embryonal metabolic wastes.

(a) What is variation? How is variation created in a population? How does the creation of variation in a species promote survival? (b) Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes. [CBSE 2017, 2018]

(a) Variation is occurrence of differences between organisms.
Variation are created in a population in different ways:
(i) There may be minor changes/errors during DNA copying mechanisms which happens before any cell division. These variations may go on accumulating from previous generations, ultimately leading to visible changes.
(ii) In sexually reproducing organisms, the traits of two individuals combine and give rise to new combination in the progency. This also leads to variation.
(iii) Thus combining variations from two or more individuals would thus create new combination of variations.
Organisms with suitable variations will have better chances of survival. Depending on the nature of variations, different individual would have different kind of advantages.
(b) In sexually reproducing organisms each cell has two copies of each chromosomes one each from the male and female parent. During gamete formation one chromosomes from each pair goes to a gamete. Hence the gametes have half the number of chromosomes but one chromosomes of each pair. When two gametes combine they restore the normal number of chromosomes in the progeny.

What is Pollination? How does it occur in plants? Explain how pollination leads to fertilisation. [CBSE 2017, 2018]

Pollination is the process of transfer of pollen grains from anther to stigma of the same flower or of different flower of same species.
It occurs with the help of various biotic and abiotic agencies. For example,
Biotic- Birds, insects and bats help in pollination.
Abiotic- Air and water also help in pollination.
Step lading from pollination to fertilisation.
(i) Pollen grain lands on suitable stigma, grows out pollen tube carrying the two male gametes.
(ii) First male gametes fuse with the egg cell resulting in formation of the diploid zygote. The zygote develops to form embryo which later forms complete plant.
(iii) The second male gamete fuses with the two polar nuclei to form triploid PEN. Primary endosperm nucleus to develop zygote.

Methods of Contraception.
    • (i) Mechanical Barrier- Condoms on penis or vagina in a covering worn so as to create a barrier such that sperms do not reach the egg.
    • (ii) Oral Contraceptive Pills- They change the hormonal balance of the body so that eggs are not released and fertilisation does not take place.
    • (iii) Intra Uterine device- Devices like coper T or loop are placed in the uterus which change the pH of uterus and hence sperm cannot survive thereby prevent the pregnancy.
    • (iv) Surgical method- Blocking vas deference in males and fallopian tube in females would allow respective gametes to be released and hence act as contraceptive.

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