NCERT Solutions Class 10 Science Chapter 8 How do Organisms Reproduce
NCERT Solutions Class 10 Science Chapter 8 How do Organisms Reproduce: National Council of Educational Research and Training Class 10 Science Chapter 8 Solutions – How do Organisms Reproduce. NCERT Solutions Class 10 Science Chapter 8 PDF Download.
NCERT Solutions Class 10 Science Chapter 8: Overview
Board |
NCERT |
Class |
10 |
Subject |
Science |
Chapter |
8 |
Chapter Name |
How do Organisms Reproduce |
Topic |
Exercise Solutions |
NCERT Solutions Class 10 Science Chapter 8 – How do Organisms Reproduce
Questions from boxes:
Page 128
1) What is the importance of DNA copying in reproduction?
Ans. DNA copy is the first step that occurs during the formation of germ cells. DNA copy helps to maintain the particular characteristics in different generations of the same species. This process also produces variations among the offsprings which are useful for the survival of the species for long time. Without coping DNA, the act of reproduction cannot takes place.
2.) Why is variation beneficial to the species but not necessarily for the individual?
Ans. variation helps the members of the species to continue their existance even when the environmental condition gets changed. However, the variations are useful when evolution takes place which requires long time to occur. An individual has short life period as compared to the evolution. Hence, variation is beneficial to the species but not necessarily for the individual.
Page 133
1) How does binary fission differ from multiple fission?
Ans. An organism gets divided and forms two different individuals in binary fission by mitotic division. Ex- Amoeba whereas, in multiple fission, the parent cell get divided into many daughter cells at the same time. Ex- Plasmodium. Hence, by the method of multiple fission, rapid increase in number of individuals takes place.
2) How will an organism be benefited if it reproduces through spores?
Ans. The spores are covered by thick walls around the which protects them from unfavourable environmental conditions. These spores remain dormant until they come into contact with favourable environmental conditions and then they begin to grow.
3) Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Ans. More complex organisms cannot give rise to new individuals through regeneration due to the following reasons:
- Their body design is highly complicated as compared to that of the simple organisms which is not suitable for regeneration.
- There are specific organs to do specific functions unlike simple organisms where specialization in function is not found in cells.
- There is division of labour in the body of complex organisms unlike simple organisms which can perform every function.
4.) Why is vegetative propagation practised for growing some types of plants?
Ans. Vegetative reproduction produces genetically and morphologically similar organisms. To conserve the typical shape, size and colour of the various parts of plants like flower, stem, leaf and fruit, the vegetative propagation is practised for growing some types of plants.
5.) Why is DNA copying an essential part of the process of reproduction?
Ans. DNA copying is essential part in the process of reproduction because the information stored in DNA is used to make the required proteins in the cell. Synthesis of different types of different proteins will lead to altered body design of the organism. For a species to be continue, the baby should look like parent. Hence, DNA copying is an essential part of the process of reproduction
Page 140
1.) How does the embryo get nourishment inside the mother’s body?
Ans. The embryo grows inside the mother’s womb and hence it is dependent on its mother for all its nourishment. The embryo gets nourishment inside the mother’s body through placenta. Placenta connects the body of embryo with its mother which have villi to increase the contact area. Diffusion of all the nutrients takes place through the placenta and gets nourished.
Exercise:
1.) Asexual reproduction takes place through budding in
(a) amoeba.
(b) yeast.
(c) Plasmodium.
(d) Leishmania.
Ans. b. Yeast
Hint: Budding occurs in yeast only from the above options. Hence, correct ans. is yeast. Amoeba reproduces by binary fission, Plasmodium by multiple fission and Leishmania by binary fission.
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
Hint: vas deference is a part of male reproductive system whereas ovary, uterus and fallopian tube is part of female reproductive system.
3.) The anther contains
(a) sepals.
(b) ovules.
(c) pistil.
(d) pollen grains.
Ans. d. Pollen grains
Hint: Pollen grains are produced in anther. Hence, anther consists of pollen grains.
4.) What are the advantages of sexual reproduction over asexual reproduction?
Ans. Sexual reproduction provides a basis for exchange of genetic material which forms the basis for variation leading to evolution in species.
Alternative Answer –
The sexual process in which two parents are involved and create offspring which is similar to organism which produced from the parents then the process is known as sexual reproduction. Whereas the process in which single parent is involved then the process is known as asexual reproduction. Comparing to asexual reproduction, In sexual reproduction, variation is greater, resulting in more diverse species in the population that survive longer. And both male and female characteristics are processed in the new different species produced by the fusion of gametes. And the process of evolution is also possible in the species which are produced by the sexual reproduction.
In case you are missed :- Previous Chapter Solution
5.) What are the functions performed by the testis in human beings?
Ans. Testis are the sites for the production of male gametes called as sperms.
Alternative Answer –
In a male reproductive system, an part which produce germ- cells or sperm for reproduction called as testes. Testes produce sperm whereas others portions are deliver the sperm to the site of fertilisation. The testies are present in the outside the abdominal cavity in scrotum because in the production of sperm it requires the low temperature than the normal body temperature. We notice that in the age of puberty in boys there is some changes will appear, it is because of testosterone, during the integration of male and female the testicles are produces sex hormones in male body.
6.) Why does menstruation occur?
Ans. Menstruation occurs in females when the egg produced remains unfertilized. Every month, female reproductive system makes uterus lining more thickened to support the fertilized egg and provide it suitable site for its implementation and forms a new network of blood capillaries. But sometimes, the egg remains unfertilized as it does not fuse with the male gamete/ sperm. So, the thick lining of the uterus aling with all the blood capillaries are shed off along with the unfertilized egg at the end of the month. Hence, menstruation/ bleeding occurs.
Alternative Answer –
In female body the ovary produce one egg every month. And the uterus is ready to receive fertilised egg in every month therefore the lining becomes thick and spongey but when ling of the uterus does not fertilise then the lining is slowly breakdown and come out from vagina with blood mucous this process is known as menstruation. This cycle of menstrual happen every month and when egg is not fertilise then its life period is about oneday.
7.) Draw a labelled diagram of the longitudinal section of a flower.
Ans.
8.) What are the different methods of contraception?
Ans: Contraception methods
- Using contraceptive injection.
- Using oral contraceptives.
- Surgical contraception methods.
- Contraceptive patches.
- Using male / female condoms.
9.) How are the modes for reproduction different in unicellular and multicellular organisms?
Ans. unicellular organisms reproduce by asexual method of reproduction involving only one parent. For example- binary fission and multiple fission, fragmentation, etc. Multicellular organisms reproduce by both asexual and sexual mode of reproduction. Asexual reproduction takes place by vegetative propagation and sexual by fusion of male and female gametes.
Alternative Answer –
In unicellular organisms the creation of new individuals lead by cell division or fission. In this organisms, reproduction is done by manly asexual reproduction method. The cells division is the process in which unicellular organisms split into two equal halves and create new individuals for example Amoeba.
Where as in multicellular organisms the creation of new individuals lead by gametic fusion. The multicellular are plants, animals and humans. In humans and animals both parents are involve sexual process and create new offspring, but in plants they create their offspring by asexual reproduction even they are multicellular organisms. In multicellular organisms they perform asexual or sexual reproduction.
10.) How does reproduction help in providing stability to populations of species?
Ans. Stability to the population species living in a particular geographical area is provided by equalizing the birth ration and the death ratio. Thus, the rate of birth should approximately be equal to the rate of death in order to make the population stable. Reproduction fills the gap generated due to the loss occured by death in a popuation. So that, the population to be remain stable for long time.
Alternative Answer –
When an organism of a species produce another organism like itself, such a process is called reproduction. The process of reproduction of a species results in the production of new organisms, and when those new organism reproduce after some time, new organisms are produced. On the one hand, the death of organisms also happens, in this way the rate of birth and death is balanced. Reproduction is the only way for all organisms to maintain their existence. In this way reproduction is helpful in maintaining the existence of individual species.
11.) What could be the reasons for adopting contraceptive methods?
Ans – Reasons for adopting contraceptive methods
- To control the birth rate or population growth.
- To protect against sexually transmitted diseases.
- To prevent from the unwanted pregnancy.
In case you are missed :- Next Chapter Solution