Class 10 CHAPTER HOW DO ORGANISMS REPRODUCE SOLVED QUESTIONS
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![]() HOTS: (High Order Thinking Skill) Questions with Answers: Q.1. Why is variation beneficial to the species but not necessary for the individual? Ans- Variation is beneficial to the species as it enables a species for its survival. A favourable variation makes an organism to live better in a changed environment and an unfavourable variation will not. So it is not necessarily true that a variation is beneficial to the individual always. Q.2. What is the advantage of reproduction through spores in the case of Rhizopus? Ans: The spores are covered by thick walls that protect them until they come into contact with another moist surface and can begin to grow. Q.3. The simple animals such as planaria can be cut into number of pieces and each piece grows into a complex organism. What is this process known as? Ans: Regeneration Q.4) Name the unicellular organism which caused the disease known as kala-azar. Ans : Leishmania Q.5) Which process taking place in the nucleus of a cell leads to variation in the offspring during reproduction? Ans : DNA copying Q.6. What causes joining up of stock and scion in grafting technique of vegetative propagation in plants? Define the terms stock and scion. Name one positive trait each of the plant contributing scion and stock should have. Ans : The stock and scion unite due to cambial cavity. Stock is the portion on which grafting is done and it provides the roots. Scion is the portion of the plant which is grafted on the other plant and it contributes the stem. The plant contributing scion should have large sized fruits and the plant contributing stock should have deep root system. Q.7 . Which type of layering is done in Jasmine? Ans : Air Layering (Gootee) Q.8 . Where does fertilization takes place in human female? Ans : Oviduct (fallopian tube) Q.9 . Why is it said that “sexual reproduction promotes diversity of characters in the offsprings”? Ans : It is because sexual reproduction results from the fusion of two gametes coming from two different and sexually distinct individuals. This leads to variation, is necessary for evolution. Q.10. What happens if the fallopian tubes are partially blocked and the ovulated eggs are prevented from reaching the uterus? Ans : Fertilization may take place but the zygote may develop in the tube instead of uterus. Q.11 . Name the causative organism of syphilis and gonorrhoea. Ans : Treponema pallidum and Nisseria gonorrhoeae. Q.12 . Why are variation possible in progeny of sexually reproductive individuals? Ans-Variations are possible in progeny of sexually reproductive individuals because copy of DNA in newly formed cell is not identical to copy DNA of original cell. 10th NCERT Solution Intex and Exercise Questions 10th CBSE NCERT Question(1 mark) Solved 10th CBSE NCERT Question( 2 marks) Solved 10th CBSE NCERT Question( 3 marks) Solved 10th CBSE NCERT Test Paper (Solved) Click to download these files ![]() HEREDITY AND EVOLUTION SOLVED EXERCISES QUESTIONS [Biology Term-2 CHAPTER - 13] VERY SHORT ANSWER QUESTIONS (1 mark) 1. Who proposed the theory of inheritance of acquired characters. Answer: J.B. Lamarck. 2. State one of the evolutionary forces leading to the origin of a new species according to the synthetic theory of evolution. Answer: Origin of new species is based on natural selection acting on genetic variations that appear among the members of a population. 3. Give an example of a vestigial organ present in human body. Answer: Vermiform appendix. 4. What is the evolutionary significance of the fossil Archaeopteryx? Answer: Archaeopteryx is the connecting link between reptiles and birds. It has both reptilian on features and avian(bird-like) features. 5. Who proposed the double helical model of DNA? Answer: Watson and Crick. 6. Who proposed the theory of natural selection? Answer: Charles Darwin. 7. What is retro virus? Answer: A virus with RNA as the genetic material eg: HIV is a retro virus. 8. What is a genetically modified organism (GMO)? Answer: The organism that contains a segment of foreign DNA. 9. Name any two genetic diseases. Answer: Hemophilia and colour blindness. 10. One of the examples of two analogous organs can be the wing of parrot and a) Flippers of whale. c)Foreleg of horse b) Front leg of frog d)Wing of housefly Answer: Wing of housefly SHORT ANSWER QUESTIONS (2 marks) 1. What are transgenic organisms? Which property of DNA is used as a tool in genetic engineering? Answer: The organisms that contain a segment of foreign DNA are known as transgenic organisms.The complimentary property of the nucleotides of DNA.is the most powerful tool in genetic engineering. 2. Explain how the sex of the child is determined at the time of conception in human beings. Answer: Male human beings have XY sex-chromosomes and female human beings have XX sex-chromosomes. If a sperm carrying x-chromosome fertilizes with the ovum, then sex of the baby will be female. If a sperm carrying y-chromosome fuses with the ovum, the sex of the baby will be male. 3. By comparing the similarity of nucleotide sequences in DNA of different kinds of organisms, evolutionary relationships can be established. a) Arrange the following according to their evolutionary closeness (You may use your knowledge of classification also) Cockroach, mango tree, gorilla, fish. b) Whose DNA among the following do you think is most similar to that of humans. Answer: (a) cockroach – fish – gorilla ( b) Gorilla 4. Mention the ways by which variant genotypes are produced in organism? Answer: a) gene mutation b) Crossing over c) Hybridization 5. In human beings blue eye colour is recessive to brown eye colour . If a brown eyed man has a blue eyed mother then find a) What are the possible genotypes of his father? b) What is the genotype of the man and his mother? Answer: BB , Bb B. Man: Bb, mother: bb 6. What are fossils? Of what interest are fossils to the evolutionary biologists? Answer: A fossil is the remnant or impression of an organism that lived in the Remote past. Use of Fossils a) Phylogeny, the evolutionary history can be reconstructed from the fossils. b) The fossil record has helped in building the broad historical sequence of biological evolution. SHORT ANSWER QUESTION (3 marks) 1. a) Who isolated DNA for the first time from pus cells? b) Why is DNA called polynucleotide? c) Name two purine nitrogenous bases found in a DNA molecule. Answer: a) F.Meishcer, named it nuclein. b)DNA is called polynucleolide because it is a polymer or long chain of nucleolide. c)Purine:- Adenine and Guanine. 2. a) Who put forward the double helical model of DNA? b) What are the three chemically essential parts of nucleotides constituting a DNA? Answer: a) Watson and Crick. b)Nucleotide constituting –DNA Nitrogen bases (Purines and Pyrimidines), Pentose sugar(Deoxyribose sugar) and a phosphate molecule. 3.Guinea pig having black colour when crossed with guinea pig having same colour produced 80 offspring, out of which 60 were black and 20 were white. Now,find out: a)What is the possible genotype of the guinea pigs? b)Which trait is dominant and which trait is recessive? c)What is this cross called as and what is its phenotypic ratio? Answer: a) Bb x Bb b)Black is dominant and white is recessive. c) Monohybrid cross, phenotypic ratio=3:1 4. Write a brief account on . Who disproved this theory? Answer: salient points of Lamarck‘s theory: 1.The use and disuse of an organ leads to acquiring of change in the features of that organ. 2. These changes are inherited by the offspring. 3. Favourable variations result in evolution of new species. August Weisman disproved this theory. 5. Distinguish between acquired and inherited traits giving one example of each. Answer: Acquired traits 1) A trait (or characteristic) of a organism which is not inherited‘ but develops in response to the environment is called an acquired trait. (2) The acquired traits of an organism cannot be passed on to its future generations. e.g. low weight‘ of beetle, cut tail‘ of a mouse. Inherited traits 1) A trait (or characteristic) of an organism which is caused by a change in its genes (or DNA) is called an inherited trait. 2) The inherited traits of an organism are passed on to its future generations. e.g. red colour of beetles, fur coat of guinea pigs. 6. Why did Mendel chosen pea plant for his experiments? T-II 2015 Answer: Mendel chose pea plant for his experiments because it is: (a) Easy to grow (b) Short lifespan (c) Easily distinguishable characters (d) Larger size of flower (e) Self-pollinated. HEREDITY AND EVOLUTION [SOLVED][Biology Term-2] Click Here 10th Science SA-2 Chapter wise Test Papers Links 1. Carbon and Its Compounds 6. The Human Eye and the Colorful World 2. Periodic Classification of Elements 7. Our Environment 3. How Do Organisms Reproduce? 8. Management of Natural Resource 4. Heredity and Evolution 9. Science Sample papers 5. Light - Reflection and Refraction 10. X Science NCERT SOLUTIONS ![]() Q1) What is the importance of DNA copying in reproduction? Ans- DNA is the genetic material present in the cells of all organisms. The genetic information from,generation to generation is carried by DNA .It is therefore possible for the organism to produce organism of its own type due to DNA copying only. For the inheritance of traits of the parent,DNA copying is a must.DNA copying also brings about variation ,which forms the basis for the origin of new species. Q2) What are the changes seen in girls at the time of puberty? Ans: i) Enlargement of breasts with the darkening of skin of the nipples . ii) growth of hair in the genital region and in armpits occurs. iii) onset of menstruation . Q3) If a woman is using a copper-Twill it help in protecting her from sexually transmitted diseases(STD’s)? Ans- No,using copper-T will not protect a woman against catching STD.Copper-T is a device which will only guard her against pregnancy . Q4)Sexual reproduction is considered advantageous over asexual reproduction? Explain Ans Sexual reproduction ensures that large number of variations appear in the daughter organism constituting a population. This is made possible by the appearance of many new gene combinations which are contributed by the two parents. Sexual reproduction also ensures that the rate of appearance of new variations is speed up which is not achieved due to asexual reproduction. Q5) Mention the changes observed in flower after fertilization. Ans- a) ovary ripens and developed into fruit. b) ovules develop into seed. c) petals and sepals wither and drop. d)stigma, style and stamens dry up and fall off. Q6) Give the advantages of vegetative propagation. Ans- 1) it is much easier,lowcost,quicker method compared to sexual reproduction. 2) plants which produce non viable seeds or too few seeds or have lost the ability to produce seeds can be made to reproduce vegetatively to produce daughter organisms. 3) plants produced by vegetatively reproduction are genetically similar to the parent plant and show all the characteristics of the parent. Q7) What is placenta? Give the significance of placenta Ans-placenta is a disc like mass of nutritive tissue which develops on the inner wall of uterus where the fertilized egg is implanted. Placenta performs the following functions: 1)it provides all the nutrients such as glucose,proteins,minerals and vitamins to the foetus. 2)ti provides antibodies through the mother’s blood to the foetus.these antibodies provide immunity to the child after its birth against a number of diseases. 3)it also meets the oxygen requirement of the foetus and removes carbon dioxide and other metabolic waste generated in the body of the foetus. These metabolic wastes are ultimately removed and excreted by mother’s excretory system. Q8) Why is reproduction essential for a species? Ans Reproduction is necessary for species in order to increase their numbers otherwise it will become extinct. Q9) Name an organism which shows binary fission and another that shows multiple fission. Ans-binary fission-Amoeba, multiple fission-material parasite.e.,plasmodium Q10) Name a unicellular organism and also a multi-cellular organism that show budding process. Ans-Unicellular-yeast, multicellular-hydra. Q11)How do oral contraceptive pills prevent pregnancy? Ans-oral pills do not allow release of ovum from the follicle to occur, so fertilization does not take place. Q12)Which is the most effective contraceptive method which will not allow sexually transmitted diseases(STD’s) to spread? Ans-mechanical barrier by condoms, cervical caps, etc. Q13)Give one difference between zygote and embryo. Ans-Zygote is single celled fusion product of sperm and ovum. Embryo is a multicellular product produced by mitotic divisions from zygote. 14)How does the embryo derive nutrition after getting implanted in the walls of uterus? ans-the embryo derives nutrition after getting implanted in the walls of uterus through a disc like tissues called placenta which has villi like projections on embryo side and blood spaces on mother’s side. This enables transport of materials like amino acids,glucose and oxygen from mother to child. Q15)What happens if the ovum does not fertilized in female body? Ans-when the ovum does not get fertilized it lives for one day.As the preparations of the uterine lining are not needed any more, the lining breaks and comes out along with the unfertilized ovum through the vaginal path in form of blood discharge. This is known as menstruation as it happens once in a month and it lasts for 2-8 days. Q16)What is the function of seminal vesicles and prostate gland in the male body? Ans-they add their secretions to sperms in order to make the sperms lie in a fluid which makes their flow and transport easier and also provides nutrition to sperms. Q17)Why are pair of testes located outside the male body? Ans-the pairs of testes are located outside the body of the males because a temperature of 2-3 degrees C,less than the body temperature is required for production of sperms. Q18) Give example of two bacterial and two viral diseases which are transmitted through sexual contact? Ans-bacterial diseases-gonorrhoea and syphilis, viral diseases-AIDS and genital warts. Q19)What factors have lead to adoption of contraceptive methods? give at least four factors. Ans-factors are: 1)growing human population. 2)spread of sexually transmitted diseases like AIDS. 3)gap between children in a family so that both mother and child get proper nutrition. 4)maintenance of sexual health. Q20) How do sperms reach the female genital tract? where does fertilization and implantation of the embryo takes place. For how long does the embryo remain attached to uterine walls. Ans-sperms travel upwards through uterus to oviduct where they may meet an ovum and hence fertilize it. Fertilization takes place in oviduct to give rise to single celled zygote. The zygote divides to become multicellular embryo which gets fixed in uterus. The embryo remains attached in uterine walls throughout gestation period which is 40 weeks in humans. full post Chapter - 8 How Do Organisms Reproduce ?
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