Heredity and evolution class 10th Questions
- 1. C l a s s : X t h HEREDITY & EVOLUTION P a g e | 1 of 8 1. “father of genetics” : Gregor Johann Mendel 2. DNA was isolated by Frederick Meisherfor the very first time. 3. Heredity is the transference of the characters and traits from one generation to other. 4. Miller and Urey provided the experimental evidence to supportthe theory of origin of life from in animate matter. 5. Sex determination is regulated by environmental factors in turtle and lizard. 6. Gene:It is a segmentof DNA which is located on DNA and act as the information carriers from one generation to another. 7. What are the features that Archaeopteyrx has in common to the reptiles? Ans: Archaeopteyrxhas teeth, scales on the bodyand tail like a reptile. 8. What does the presence of 21st extra chromosome cause? Ans: The presence of 21st extra chromosome causes Down's syndrome.The presence of this chromosomecauses mental disorderin the child. 9. In what way are the off springs produced through sexual reproduction different from those produced by asexual reproduction? Ans: Asexual reproduction produces identical offspringwhile sexual reproduction does not produce offspring that are exactly similar to the parents. 10.Why is the decreasing number of surviving tigers a cause of worry from the point of view of genetics? Ans: As the populationof tigers is decreasing,there is a loss of genes from the gene pool and hence,there can’t be recombinationand variations,thus no evolution. 11.When Mendel crossed a Tall plant with a dwarf plant, no medium height plants were obtained in F1 generation. Why? Ans No medium heightplants were obtained in F1 generation because dominant genes express themselves and suppress the effect of recessive genes.There is no mixing of alleles in the F1 generation. 12. Differentiate between homologous and analogous organs. (Ans) HOMOLOGOUS ORGANS ANALOGOUS ORGANS The organswith similar structure and origin but different functions are known as homologous organs. The organs with similar function but different structures and origin are known as analogous organs. Example:forelimbs of frog, wings of birds, forelimbs of man. Example:wings of butterfly, wings of a bird. 13. What do you mean by organic evolution?
- 2. C l a s s : X t h HEREDITY & EVOLUTION P a g e | 2 of 8 Ans The branch of science which deals with wide variety of organisms and gradual change occurring in them since beginningof life is known as organicevolution. 14. Are forelimbs of man and frog analogous organs? Why or why not? Ans No, forelimbs of man and frog are not analogous organs becausethey are similar in structure and origin but differentin function. Forelimbs offrog are used for jumpingand hoppingwhile in man these areused for walking. 15. What are vestigial organs? Give examples. (Ans) The organs which are presentin the bodybut are functionless are known as vestigial organs.These organs are homologousto the organs which were functioning in our ancestors.For example:Vermiform appendixin human beings. 16. What do you mean by autosomes? Ans: Autosomes are the chromosomes which are associated with the functioningof the cells and determinationof characters and traits of the individual.There are22 pairs of autosomal chromosomesin human beings. 17. Which abnormal behavior of chromosomes cause Down’s syndrome? Ans: A 21st extra chromosomecauses Down'ssyndrome.It is a chromosomal disordercaused by the presence of all or part of an extra 21st chromosome.It is also known as trisomy 21. 18. Explain Speciation. How does geographical isolation results in speciation? Ans Speciation is the evolutionaryprocess by which new biological species arise. When the numberof variations accumulates in a generation,the process may lead to birth of new species entirelydifferent from the existing ones. Geographicisolation is the separationof two (or more) biological populations bya geographical barriereg. river, mountain range,ocean,desert etc. The effect of geographicisolation is that the two populations are subjected to different selection pressures and gene flow betweenthem would cease and the two separate populations would evolve independentlyas different species. 19. Why are the traits acquired during the lifetime of an individual not inherited? (Ans) Traits acquired during the lifetime of an individual are not inherited because change in non-reproductive tissue or somatic cells cannotbe passed on to the DNA of the germ cells. Thus,the acquired trait will be eliminated with the death of the individual.It is therefore non-heritableand cannotbe passed on to its progeny. 20. How can we calculate the age of a fossil? (Ans) There are two methods of detectingfossil’s age:
- 3. C l a s s : X t h HEREDITY & EVOLUTION P a g e | 3 of 8 i. Relative method:When we dig into the earth, the fossils we find closer to the surface are more recent than the fossils we find in the deeperlayers. ii. By detecting the ratios of differentisotopes of the same elementin the fossil material. 21. (i) State one of the evolutionary forces that lead to the origin of a new species according to the synthetic theory of evolution. (ii) What is the evolutionary significance of Archaeopteryx? Ans (i) Origin of new species is based on natural selection acting on genetic variations that appearamongthe members of a population. (ii) Archaeopteryxis the connectinglink between reptiles and birds. It has both reptilian and avian features. 22. a) Arrange the following according to their evolutionary closeness: Broccoli, cauliflower, wild cabbage, cabbage, gorilla b) Whose DNA among the above do you think is most similar to that of humans. Ans a) Wild cabbage - Cabbage- Broccoli - Cauliflower. b) DNA of gorilla is most similarto that of humans. 23.What are fossils? Of what interest are fossils to the evolutionary biologists? Ans A fossil is the remnantor impression ofan organism that lived in the past. Evolutionarybiologists study fossils for understandingthe phylogenyand the evolutionaryhistory. The fossil records help in buildinga broad historical sequence of the biological evolution. 24. What evidence does fossil provide about our evolution? Ans Fossils are the petrified remains of the ancientlife found preserved in rocks. The fossils provide evidences aboutour evolution.Forexample:A bird called Archaeopteyrxhas features of birds as well as reptiles. It has wings and beaklike a bird but teeth, scales on the body and tail like a reptile. 25. How does the mechanism of heredity work? Ans CellularDNA (genes) is the information source which regulates metabolism and makes protein in the cell. It also controls the characters of the progeny.During sexual reproduction,both the parents contribute equallyto the DNA of the progeny. Thus all the cells have two copies of chromosomes,one from male and the other from female.When the two germ cells combine they maintain the total numberof chromosomes and ensure the stabilityof DNA of the species. Thus the progeny inherits the traits of the parents.
- 4. C l a s s : X t h HEREDITY & EVOLUTION P a g e | 4 of 8 26. Who gave the concept of Natural selection? How does the process of natural selection relate to organic evolution? Ans The theory of Natural selection was proposed by Charles Darwin in 1859. Natural selection is the process by which favorable heritable traits become more common in successive generationsof a populationof reproducingorganisms and unfavorableheritable traits become less common,due to differential reproduction of genotypes. According to Darwin's theorydue to suitabilityof environmentthere is an increase in population.This leads to struggle for existence resultingin survival of the fittest and origin of species,which is termed as organic evolution. 27. Explain DNA’s utility in the process of reproduction of the cell. It carries genetic information and required by the cells to divide and produce proteins for regulation, structural and functional roles.During the gamete formation, DNA creates its exact copies which are passed to the gametes.The fusion of male and female gamete results in the developmentof variations.Thus, it is the DNA which acts as the blue print that is passed from generation to generation. 28. (a) What is the function of genes in an organism? (b) Who proposed the theory of natural selection? Why was this theory criticized? (Ans) (a) Genes are the segments of DNA which control the traits and characteristics of an individual. (b) Darwin proposed the theory of natural selection.Darwin’s theoryof natural selection was unable to explain mechanism for inheritance of traits from one generation to the next. 29. We have 23 pairs of chromosomes but still numerous characters are found in humans. How can we justify this? Ans There are only23 pairs of chromosomes in humans,but30,000 to 40,000 genes are presentin the DNA. This implies that each chromosome carries numerous genes on it. These genes are responsiblefor all the characteristic features.This is the reason that we have numerous characters,definitelyexceeding46 in number. 30. What are the causes of variations in the clones? Ans Causes of variations in the clones are: i. Inaccuracies during DNA copying. ii. Effect of environmenttermed as acquired variation. iii. Mutations are sudden stable changes thatare discontinuousinheritableas produced due to the changes in genetic make-up. 31. Is it true to say evolution is progressive from lower forms to higher forms. Ans Evolution can not be said to 'progress' from lower forms to higherforms. Rather, evolution seemsto have given rise to more complex bodydesigns even
- 5. C l a s s : X t h HEREDITY & EVOLUTION P a g e | 5 of 8 while simpler bodydesigns continue to flourish and grow. Many simplerand older body designs still survive. Thus, there is no real progress in the evolution,but only more complexbody designs have emerged over time. 32. 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? (Ans) a) Possible genotypesof the father are BB, Bb b) Genotype of the man: Bb Genotype of the mother: bb 33. Distinguish between acquired and inherited traits, giving one example of each. Ans Acquired trait Inherited trait A trait (or characteristic) of an organism that is ‘not inherited’ but develops in response to the environmentis called an acquired trait. A trait (or characteristic) of an organism that is caused by a change in its genes (or DNA) is called an inherited trait. The traits of an organism cannotbe passed on to its future generations. The inherited traits of an organism are passed on to its future generations. E.g. low weight of beetle,cut tail of a mouse. E.g., red colour of beetles,fur coat of guinea pigs. 34. What is Darwin’s theory of evolution? Ans According to Darwin's theory of evolution: (i) Within any population,there is natural variation. (ii) In spite of reproduction,the population becomes fairly constant. (iii) This is due to the struggle between the individuals of various species for food, space and mate. (iv) Due to this struggle, only the better ones are selected by nature. (v) The selected individuals pass on their favourable variations to their offsprings. (vi) These variations whenaccumulated overa long period of time lead to origin of new species. 35. A boy has parents with two different hair colors: one with red hair and the other with black hair. The boy has black hair. If we consider the black colour dominating over the red colour, what could be the possible genotypes of the boy? (c) Case-I Let BB be the genotype of father and bb of mother.
- 6. C l a s s : X t h HEREDITY & EVOLUTION P a g e | 6 of 8 Their offspring will be of followinggenotype: B B b Bb Bb b Bb Bb The possible genotype of the boy will be:- Bb The boy will have black hair colour as it is the dominantallele. Case-II Let Bb be the genotype of father and bb the genotype of mother. B b b Bb bb b Bb bb The possible genotypes ofthe boy will be: 2: Bb 2: bb Phenotype:There are 50% chances of boy havingblack hair and 50% chances of boy havingred hair. As the boyhas black hair, the genotype will have to be Bb. 36. An elephant learns a trick at the circus. Will his children also know the trick by birth? Support your answer with reasons. Ans A trick that an elephantlearns at a circus is not inherited by its progeny because it is an acquired trait. Any trait that does not change the genome of an organism will not be inherited.In this case, the trait is knowledgethat is acquired over the life time of an organism.It is just like a cut on skin, which will not be inherited. 37. What are the chances of having a baby boy in a marriage between a man with blood group O and a woman with blood group AB? Give reasons. Ans In any human marriage betweena man and a woman,the chances of a baby boy is 50%.This is irrespective of any other inheritablecharacters presentin the parents.So, whateverbe the blood group, the chances of a baby boy will be 50%. 38. Do you think adaptations can bring about evolution? How? Ans Adaptations can bring aboutevolution in a populationif the environmental conditions causingthose adaptationspersist. Adaptations are inheritable traits and will be carried from one generationto next changing the whole population.This creates a uniform populationat each generation which are different from the parent generation.This is evolution.
- 7. C l a s s : X t h HEREDITY & EVOLUTION P a g e | 7 of 8 39. What is natural selection? How can it help an organism to be ‘selected’? (Ans) Natural selection is the selection process that occurs when there is an environmental conditionprevailingin a geographical area.The organisms residingat that area will have to fight that condition for survival. Only those which are suited to withstand that condition will survive. Others will be eliminated.The ones that survive will reproduce and their numberwill increase day by day. Thus, they are ‘selected’ in the particular environmental condition. 40. How can we say that there is no ‘progress’ in the concept of evolution? Ans Evolution means creation of diversity (in potential individuals)and nurturing that diversity to suit in the changingenvironment.Eventuallyif the environmental conditions persist, the diversity survives, if not, it gives way to anothermore suited variation. Thus,evolution does not indicate progress; it only indicates survival of one diversity or the other. 41. Where in the world did human beings originate and in what form? Ans Human beings originated in the African continent.The first human being resemblingmodern humans appeared in Africa and is now called Australopithecine. 42.How are wings of a sparrow and flippers of a whale related? Ans The wings of a sparrow and flippers of a whale on anatomical study shows similar type of bone composition.Thus,though they perform different functions,they have a same origin and have diversified in the course of evolution later on. Thus,these two are homologous organs. 43. What do you understand by evidences of evolution? Give three examples. (Ans) Evidences of evolution mean those specimens orcharacters which indicate an evolutionaryrelationshipbetweentwo organisms. Three examples include: Fossil records , Anatomical similarities Geographical distribution 44. What is excavation and how is it related to study of evolution? Ans Excavation means the digging out of fossil specimens from the earth’s crust. Careful excavation will give very intact remains of hard structures in the body of the specimen. This can be used to study evolution as they are proofs of the existence of that specimen in the remote past.