Class 10 Science Chapter 8 How Do Organisms Reproduce? The answer to each chapter is provided in the list so that you can easily browse throughout different chapters NCERT Class 10 Science Chapter 8 How Do Organisms Reproduce? and select need one.
Class 10 Science Chapter 8 How Do Organisms Reproduce?
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How Do Organisms Reproduce?
Chapter – 8
TEXTUAL QUESTIONS AND ANSWERS
Page – 128
Q.1. What is the importance of DNA copying in reproduction?
Ans :- The consistency of DNA copying during reproduction is important for the maintenance of body design features that allow the organism to use the particular niche.
Q.2. Why is variation beneficial to the species but not necessarily for the individual?
Ans :- Temperatures on earth can go up or down, water levels can very, or there could be meteorite hits, to think of a few examples. If a population of reproducing organisms were suited to a particular niche and if the niche were drastically altered, the population could be wiped out.
However , if some variations were to be present in a few individuals in these populations , there would be some change for them to survive .
Thus , if there were a population of bacteria living in temperate waters , and if the water temperature were to be increased by global warming most of these bacteria would die , but the few variants resistant to heat would survive any grow further . Variation is thus useful for the survival of species over time .
Q.1. How does binary fission differ from multiple fission?
Ans :- In binary fission , the parent organisms splits to form two new organisms .
In multiple fission , the parent organism splits to form many new organisms at the same time .
Q.2. How will an organism be benefited if it reproduces trough spores ?
Ans :- The reproduction by spores takes place in plants . Spores are covered by hard protective coat which enables them to survive under unfavourable condition like lack of food , lack of water and extreme temperatures . But when the conditions become favourable then the spores can grow to produce new plants . Thus , the reproduction by spores benefits the plants because by surviving under adverse conditions , the spores make these plants live forever .
Q.3. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration ?
Ans :- The tissues in complex organisms can not regenerate a new individual as they highly differentiated to perform specialised functions . For example , human skin cannot regenerate into a new individual as it is a highly differentiated tissue performing a designated function .
Q.4. Why is vegetative propagation practised for growing some types of plants ?
Ans :- Plants raised by vegetaive propagation can bear flowers and fruits earlier than those produced from seeds . Such methods also make possible the propagation of plants such as banana , orange , rose and jasmine that have lost the capacity to produce seeds . Another advantage of vegetative propagation is that all plants produced are genetically similar enough to the parent plant to have all its characteristics .
Q.5. Why is DNA copying an essential part of the process of reproduction ?
Ans :- Importance of DNA copying in a sexual reproduction is that the characteristics of the parent organisms are transmitted to its offsprings and at the same time some occasional variations are also produced in the offsprings .
Q.1. How is the process of pollination different from fertilisation ?
Ans :- Pollination is the transfer of poller grains from the anther of stamen of a flower to the stigma of a carpel in the same flower or another flower of the same species . On the other hand , fertilisation occurs when the male gamete present in the pollen grain joins with the female gamete present in ovule to form a zygote .
Q.2. What is the role of seminal vesicles and prostrate gland ?
Ans :- Seminal vesicles secrete a viscous fluid which forms most of the part of semen . It also lubricates the passage through which the sperms travel . This fluid also protects the sperms from the acids normally present in the urethra and female reproductive duct . Prostate gland produces prostatic fluid which is discharged into urethra through more than two dozen fire ducts . There is more secretion during sexcual act when they are forcefully ejected by contraction of muscular and elastic tissues .
Q.3. What are the changes seen in girls at the time of puberty ?
Ans :- The various changes which occur in girls at puberty are : Hair grow under armpits and pubic region . Breasts develop and enlarge . The hips broaden . Extra fat is deposited in various part of the body like hips and things . Fallopian tubes , uterus and vagina enlarge ovaries start to release eggs . Menstruation start . Feelings and sexual drives associates with adulthood begin to develop .
Q.4. How dose the embryo get nourishment inside the mother’s body ?
Ans :- The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta . Placenta is a disc – shapeel tissue which is embedded in the uterus wall . It has villi on the embryo side of the tissue . On the mother’s side are blood spaces which surround the villi . Placenta provides a large surface area for glucose and oxygen to pass from the mother to the embrague . The developing embryo also produces waste substances which can be removed by transferring them into the mother’s blood through the placenta .
Q.5. If a women is using a copper – T , will it help in protecting her from sexually transmitted diseases ?
Ans :- No , the use of copper – T for contraception will not protect a women from sexually transmitted diseases.
Q.1. COM Asexual reproduction takes place through budding in :
( a ) Amoeba.
( b ) Yeast.
( d ) Plasmodium.
( d ) Leishmania.
Ans :- ( b ) Yeast.
Q.2. Which of the following is not a part of the female reproductive system in human beings ?
( a ) Ovary.
( b ) Uterus.
( c ) Vas deferens.
( d ) Fallopian tube.
Ans :- ( c ) Vas deferens .
Q.3. The anther contains
( a ) Sepals.
( b ) Ovules.
( c ) Carpel.
( d ) Pollen grains.
Ans :- ( d ) Pollen grains .
Q.4. What are the advantages of sexual reproduction over a sexual reproduction ?
Ans :- In asexual reproductrion , the offsprings are almost identical to their parent because they have the same genes as their parent . So , much genetic variation is not possible in asexual reproduction . This is a disadvantage of a sexual reporoduction because it inhabits the further evolution of the organism . In sexual reproduction the offsprings , although similar to their parents are not identical to them or to one another . Because the offsprings receive some genes from the mother and some from the father . Because of the mixing of genes of mother and father in various different combination , all the offsprings hae genetic variations . In the way sexual reproduction leads to a greater variety in population .
Q.5. Why are the functions performed by testes in human beings .
Ans :- Testes are the primary reproductive organs in man . The function of testes is to make the male sex cells called sperens and also to make the male sex hormone called testosterone .
Q.6. Why does menstruation occur ?
Ans :- The ovary release one egg every month and the uterus prepares for the implantation of the zygote by thickening its walls . If the egg is not fertilised , the uterine living slowly breaks down and comes out through the vagina as blood and mucus . This cycle takes place roughly roughly every month as menstruation and lasts for about two to eight days .
Q.7. Draw a labelled diagram of the longitudinal section of a flower .
Q.8. What are the different methods of contraception ?
Ans :- The various method of contraception are : – Barrier methods , chemical methods , use of Loop or copper – T and surgical method .
In the barrier methods of preventing pregnancy , the physical devices such as condoms and diaphragm are used .
In the chemical methods of preventing pregnancy , the femalls use oral pills.
The loop or copper – T are also very effective in preventing pregnancy . A loop or copper – T is placed inside the uterus by a doctor or a trained nurse .
Surgical methods of birth control are available for males as well as females . In males , a small portion of the sperm duct is removed by surgical operation and both the cut ends are ligated property . In females , a small portion of the oviducts is removed by surgical operation and the cut ends are ligated .
Q.9. How are the modes of reproduction different in unicellular and multicellular organisms ?
Ans :- The modes for reproduction in unicellular organisms are binary fission and multiple fission .
The modes for reproduction in multicellular organisms are : regeneration , fragmentation and sexual reproduction .
Q.10. How does reproduction help in providing stability to populations of species ?
Ans :- Reproduction induces variations in the population which help the population to tide over adverse environmental conditions and adapt to changing environment . Reproduction also helps generate copies of individuals which are suited to a particular environment .
Q.11. What could be the reasons for adopting contraceptive methods ?
Ans :- The use of contraceptive methods helps in family planning . By adopting contraceptive methods , a couple can avoid unwanted pregnancy . They can choose how many children to have and when to have them .
Some of the contraceptive methods also provide protection to a person from sexually transmitted diseases .
Additional Quesetions and Answers
Q.1. What is reproduction ? What is its importance ?
Ans :- The production of new organisms from the existing organisms of the same species is known as reproduction.
Reproduction is essential for the survival of a species on this earth .
Q.2. What are the two main methods of reproduction ?
Ans :- ( i ) asexual reproduction .
( ii ) sexual reproduction .
Q.3. What is asexual reproduction ? Give example .
Ans :- The production of a new organism from a single parent without the involvement of sex cells in called asexual reproduction .
Examples :- binary fission in Amoeba , budding in Hydra, fragmentation in spirogyra etc.
Q.4. What is sexual reproduction ? Give examples .
Ans :- The production of a new organism from two partents by making use of their sex cells is called sexual reproduction .
Examples :- The humans , fish , frogs etc are reproduce by the method of sexual reproduction .
Q.5. Differentiate between sexual reproduction and asexual reproduction .
Ans :- ( i ) In asexual reproduction only one parent is needed whereas two parents are needed in sexual reproduction .
( ii ) No sex cells are involved in asexual reproduction but sex cells take part in sexual reproduction .
Q.6. Name the types of asexual reproduction .
Ans :- There are six types of asexual reproduction . These are –
( i ) Fission.
( ii ) Budding.
( ii ) Spore formation.
( iv ) Regeneration.
( v ) Fragmentation.
( vi ) Vegetative propagation .
Q.7. Write a difference between fission and fragmentation .
Ans :- The main difference between fission and fragmentation is that in fission , a unicellular organism breaks up to form two or more daughter organisms , whereas in fragmentation , a multicellular organism breaks up to form two or more daughter organisms .
Q.8. Which of the following organisms reproduce by sexual method and which by asexual method ?
Amoeba, Cats , Humans , Hydra , Birds .
Ans :- Sexual method : – Cats , Humans , Birds .
Asexual method : – Ameoba , Hydra .
Q.9. What is meant by regeneration ? Name two animals which can regenerate fully from their cut body parts .
Ans :- The process of getting back a full organism from its body parts is called regeneration .
The animals Hydra and Planaria show regeneration.
Q.10. What is Zygote ? Name the two types of gametes.
Ans :- In sexual reproduction , a male gamete fuses with a female gamete to form a new cell called zygote .
The two types of gametes are : male gametes and female gametes .
Q.11. Write the name of the main parts of flower .
Ans :- The main parts of flowers are :
( i ) Receptacle.
( ii ) Sepals.
( iii ) Petals.
( iv ) Stamen.
( v ) Carpel.
Q.12. What is carpel ? What are the parts of carpel ?
Ans :- Carpel is the female reproductive organs of the plant . A carpel is made of three parts . These are –
( i ) Stigma.
( ii ) Style.
( iii ) Ovary.
Q.13. Which flowers are unisexual ? Give examples .
Ans :- The flowers which contain only one sex organ either stamens or carpels are called unisexual flowers .
Examples : – Papaya , watermelon .
Q.14. Which flowers are bisexual ? Give examples .
Ans :- The flowers which contain both the sex organs stamens as well as carpel , are called bisexual flowers .
Examples :- The flowwers Hibiscus and mustard plants are bisexual flowers .
Q.15. What is seed ?
Ans :- A seed is the reproductive unit of a plant which can be used to grow a new plant .
Q.16. What do you mean by fertilisation ? Write the types of fertilisation .
Ans :- The fusion of a male gamete with a female gamete to form a zygote during the sexual reproduction is called fertilisation .
There are two types of fertilisation :
( i ) Internal fertilisation.
( ii ) External fertilisation.
Q.17. Define internal fertilisation and external fertilisation .
Ans :- The fertilisation which occurs inside the female body is called internal fertilisation .
The fertilisation which occurs outside the female body is called external fertilisation .
Q.18. Define puberty .
Ans :- The reproductive systems in human beings become functional or start functioning at a definite ages called puberty .
Q.19. What is sexually transmitted diseases ? Give examples .
Ans :- The diseases which are spread by sexual contact with an infected person are called sexually transmitted diseases .
Examples :- Gonorrhoea , syphilis and AIDS .
Q.20. What do you mean by menstruation ?
Ans :- The breakdown and removal of the inner , thick and soft lining of the uterus along with its blood vessels in the form of vaginal bleeding is called menstrual flow or menstruation .
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