CBSE Class 10 Science Heredity and Evolution Assignment Set B

MCQ Questions for NCERT Class 10 Science Heredity and Evolution

Question. What is an allele?
(a) A gene
(b) A protein
(c) RNA
(d) None of the above
Answer : A

Question. Heredity refers to
(a) passing of characters from parents to offspring
(b) sterility
(c) the study of the pattern of passing of characters
(d) none of the above
Answer : A

Question. What is meant by gene flow?
(a) Floating of genes
(b) Exchange of genetic material
(c) Melting of genes
(d) None of the above
Answer : B

Question. Which is correct about autosomes?
(a) They contain genes for sexual characters.
(b) They contain genes for both sexual and vegetative characters.
(c) They contain genes for vegetative characters.
(d) None of the above
Answer : C

Question. What is applicable for Y chromosomes?
(a) They lack DNA.
(b) They lack histones.
(c) They contain genes for maleness.
(d) They contain genes for femaleness.
Answer : C

Question. A farmer saves the seeds from his best maize crop plants to sow for next year’s crop.
(a) artificial selection
(b) genetic engineering
(c) natural selection
(d) variation
Answer : A

Question. Which of the following would stop evolution by natural selection from occurring?
(a) If humans became extinct because of a disease epidemic
(b) If a thermonuclear war killed most living organisms and changed the environment drastically
(c) If ozone depletion led to increased ultraviolet radiation, which caused many new mutations
(d) If all individuals in a population were genetically identical and there was no genetic recombination, sexual reproduction, or mutation
Answer : D

Question. Which statement is true for a dominant allele?
(a) It cannot undergo mutation
(b) It gives a greater chance of survival than a recessive allele
(c) It gives the same phenotype in heterozygotes and homozygotes
(d) It is only responsible for male characteristics
Answer : C

Question. Which of the following features do humans lack that other primates have?
(a) Forward-facing eyes
(b) Short snouts
(c) Flexible shoulder and elbow joints
(d) Opposable big toes
Answer : D

Question. What is a result of natural selection?
(a) Dogs that are friendly to humans
(b) Grapes that contain no seeds
(c) Mosquitoes that are resistant to insecticides
(d) Onion crops that have a pleasant taste
Answer : C

Question. Which of the following evolutionary mechanisms acts to slow down or prevent the evolution of reproductive isolation?
(a) Natural selection
(b) Gene flow
(c) Mutation
(d) Genetic drift
Answer : B

Question. Which of the following are fossils?
(a) pollen grains buried in the bottom of a peat bog
(b) the petrified cast of a clam’s burrow
(c) the impression a clam shell made in mud, preserved in mudstone
(d) all of the above
Answer : D

Question. A recessive homozygote is crossed with a heterozygote of the same gene. What will be the phenotype of the F₁-generation?
(a) All dominant
(b) 75% dominant, 25% recessive
(c) 50% dominant, 50% recessive
(d) 25% dominant, 50% heterozygous, 25% recessive
Answer : C

Question. Which amongst the listed tools was used to study the law of inheritance in pea plant by Gregor J Mendel?
(a) Family tree
(b) Pedigree chart
(c) Punnett square
(d) Herbarium sheet
Answer : C

Question. Your arm is homologous with-
(a) a seal flipper
(b) an octopus tentacle
(c) a bird wing
(d) both a and c
Answer : D

Question. The genotype of the height of an organism is written as Tt. What conculsion may be drawn?
(a) The allele for height has at least two different genes
(b) There are atleast two different alleles for the gene for height
(c) There are two different genes for height, each having a single allele
(d) There is one allele for height with two different forms
Answer : B

Question. Mendel’s concept of segregation implies that the two members of an allelic pair of genes-
(a) are distributed to separate gametes
(b) may contaminate one another
(c) are segregated in pairs
(d) are linked
Answer : D

 

Fill in the blanks.

Question. According to Darwin the power of reproduction is ...... and this will lead to ...... for food and shelter.
Answer : enormous, struggle

Question. Allele is another name of ...... .
Answer : gene

Question. Genes that are not expressed are called ...... .
Answer : recessive

Question. The real source of variation is ...... .
Answer : mutation

 

Mark the statements true(T) or false(F).

Question. Genes assort independently.
Answer : true

Question. Vestigial organs are nonfunctional.
Answer : true

Question. Struggle for existence is always active.
Answer : true

Question. Sex is determined by different factors in various species.
Answer : True

Question. A factor which shows its effect in the hybrid is called recessive.
Answer : False

Question. At present time evolution is not possible.
Answer : False

Question. Tendril of a pea plant and phylloclade of Opuntia are homologous.
Answer : True

Question. Changes in the non-reproductive tissues caused by environmental factors are inheritable.
Answer : False

 

Assertion and Reason

DIRECTION : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.

Question. Assertion : Mutation is sudden change in the genetic material.
Reason : Variation is useful for the survival of species over time.
Answer : B

Question. Assertion : Among the primates, chimpanzee is the closest relative of the present day humans.
Reason : The banding pattern in the autosome number 3 and 6 of man and chimpanzee is remarkably similar.
Answer : A

Question. Assertion : Evolution is called as organic evolution.
Reason : Evolution involves the living organisms.
Answer : A

Question. Assertion : Human ancestors never used their tails and so the tail expressing gene has disappeared in them.
Reason : Lamarck’s theory of evolution is popularly called theory of continuity of germ plasm.
Answer : C

Question. Assertion : Changes in non-reproductive tissues can be passed on the the DNA of the germ cells.
Reason : Inherited traits include the traits developed during the lifetime of an individual that cannot be passed on to its propeny.
Answer : D

Question. Assertion : Chromosomes are known as hereditary vehicles.
Reason : The chromosomes are capable of selfreproduction and maintaining morphological and physiological properties through successive generations.
Answer : A

Question. Assertion : The sex of a child is determined by the mother.
Reason : Humans have two types of sex chromosomes: XX and XY.
Answer : D

Question. Assertion : DNA finger printing is a method in which polymerase chain reaction followed by DNA probe is used.
Reason : A DNA finger print is inherited and therefore, resembles that of parents.
Answer : A

Question. Assertion : Learning a skill such as dance and music is an acquired trati.
Reason : Acquired traits develops in the life time of an individual and do not pass to the progeny.
Answer : A

Question. Assertion : In humans, males play an important role in determining the sex of the child.
Reason : Males have two X chromosomes.
Answer : C

Question. Assertion : Mendel chose a number of varieties of garden pea as plant material for his experiments.
Reason : Garden pea has well defined characters and was bisexual.
Answer : A

Question. Assertion : The sex of the children will be determined by chromosome received from the father.
Reason : A human male has one X and one Y -chromosome.
Answer : A

Question. Assertion : The establishment of reproductive isoloations in an event of biological significance.
Reason : In the absence of reproductive isolation species can merge into single population.
Answer : A

Question. Assertion : Dominant allele is an allele whose phenotype expresses even in the presence of another allele of that gene.
Reason : It is represented by a capital letter, e.g. T.
Answer : B

Question. Assertion : Mendel selected the pea plant for his experiments.
Reason : Pea plant is cross-pollinating and has unisexual flowers.
Answer : A

Question. Assertion : Traits like eye colour or height are inherited traits.
Reason : Inherited traits are not transferred from parents to young ones.
Answer : C

Question. Assertion : The birds have large, light spongy bones with air sacs.
Reason : These adaptations help them during flight.
Answer : A

 

Matching Questions

Answer : A-p, B-q, C-r, D-s

Question. Match the physical evidence of evolution with the best description of that particular type of evidence.

Answer : A-p, B-q, C-r, D-s

Question.

Answer : A-p, B-q, C-r, D-s

Question.

Answer : A-p, B-q, C-r, D-s

Question.

Answer : A-w, B-v, C-u, D-t, E-s F-r, G-q, H-p

 

Very-Short-Answer Questions

Question. Name the book in which Lamarckism ismentioned.
Answer : Philozophie Zoologique 4. Origin of Species

Question. Who gave the first modern theory of organic evolution?
Answer : Darwin

Question. When does duplication of DNA take place?
Answer : Just before cell division

 

Short-Answer Questions

Question. State the importance of variations.
Answer : Variations are the differences in the characters among the individuals of a species. Variations enable the organisms to adapt themselves in the changing environmental conditions.
Variations form the raw materials for evolution and formation of new species.

Question. Define Genetics. What did Mendel’s contribution to genetics?
Answer : The science of heredity and variation is called Genetics.
Mendel conducted breeding experiments in a plant called garden pea (pisum sativum) with contrasting pair of characters, found that only one character of the pairs appeared in the first generation but both the characters appeared in the subsequent generation.
On the basis of these results of his experiments he put forth the various principals of inheritance. He also suggested that each character is controlled by a pair of factors which are now called as genes.

Question. What is environmental selection?
Answer : It is the selection within a population resulting from the influence exerted by the environment. It leads to a change in the composition of genes within a population.

Question. Which of the following are homologous and analogous organs?
(a) Wings of birds and insects. (b) Flippers of whale and fins of fish.
(c) Flippers of whale and wings of bat. (d) Our teeth and elephants tusks.
(e) Potato and runners of grass.
Answer : (a) — Analogous organs
(b) — Analogous organs
(c) — Homologous organs
(d) — Homologous organs
(e) — Homologous organs

Question. What is speciation? How does it occur?
Answer : Formation of new species from the existing ones over the period of time is called speciation.
Speciation takes place due to gene flow, genetic drift, reproductive isolation and finally natural selection.

Question. How do traits or characters get expressed?
Answer : Genes control the expression of a trait or a character in an organism. Genes produces proteins. The proteins act as enzymes which can directly control a character or help in the formation of a hormone which can control the expression of a particular character. 

Question. Describe briefly four ways in which individual with a particular trait may increase in population.
Answer : Four ways in which individual with a particular trait may increase in population are:
(a) Variations that occur in species helps in the survival of individuals.
(b) Organisms when show genetic drift which cope them to survive in the given environment.
(c) Adaptation and natural selection.
(d) Sexual reproduction results in variation.

Question. What is genetic drift?
Answer : Accidents in small populations can change the frequency of some genes in a population even if they give no survival advantage. This is genetic drift, which provides diversity without any adaptations. So, it is the random change in the frequency of alleles in a population over successive generation.

Question. How do we know how old fossils are?
Answer : We can find the relative of the fossil by the depth at which the fossil is found. The ones that are found near the surface are more recent than the fossils found in the deeper layer. The second way of dating fossils in detecting the ratios of different isotopes of the same element in the fossils material.

Question. Which of the following combinations of sex chromosomes produces a male or a female child—XX or XY?
Answer : XX combination produces a female child while the XY combination produces a male child.

Question. What is phylogeny and molecular phylogeny?
Answer : Phylogeny is the evolutionary history of an organism.
Molecular phylogeny traces the evolutionary relationships by comparing the differences in the DNA of different organisms.

Question. What is natural selection?
Answer : According to Darwin, natural selection is the process which brings about evolution of new species of plants and animals.
It consists of the following processes:
(i) He noted that the size of population tends to remain constant despite the fact that more offsprings are produced than needed.
(ii) Variations provide adaptations.
(iii) The best adopted survive in the changing environment (survival of the fittest).
(iv) Nature selects the best organisms with better adaptations and after many generations new species are formed (natural selection).

Question. What are fossils? What do they tell about the process of evolution?
Answer : Fossils are preserved traces or remains of living organism of geological past. Fossils help to trace the racial history of organisms. Fossils found closer to the surface are more recent than fossils found in the deepest layers.

Question. What term did Mendel use for genes? Where are the genes located?
Answer : Mendel used the term ‘factors’ for genes. Genes are portions of DNA which code for a single protein.

Question. Define variation in relation to a species: Why is variation beneficial is the species.
Answer : Variations are differences that occur between the organisms of the same species in spite of the same basic features. Variation in species promotes survival of an organism in changing environment by increasing the adaptability.

Question. ‘‘Variations that confer an advantage to an individual organism only will survive in population’’. Justify.
Answer : Variation is the difference in the characters or traits among the individuals of a species.
Sexual reproduction of organisms produces variation. The variations produced in organisms during successive generations gets accumulated in the organism. The significance of variations shows up only if it continues to be inherited by the offspring for several generation.

Heredity And Evolution

Question. a. What function is performed by human arms, forelimbs of dog and forelimbs of whales?
b. Which type of organs are these?
c. Why do we call them so?
Answer : a. Human arm : holding things Forelimbs of dog : running Forelimbs of whales : paddles
b. Homologous,
c. Same origin, different functions.

Question. How green beetles had colour advantage over red beetles? Explain.
Answer : Green beetle merge with green background of vegetation which give survival advantage to a species from elimination.
a. in the population of beetles, the new variation (green colour) get survival benefit / advantage to green beetles whereas other (red) perishes.
b. It is because of Natural selection — some variations are advantageous for an organism to adapt better in the prevailing conditions of habitat. It makes it easy to obtain food and mating partner by them.In this manner they are able to propagate more,transmitting their genes to next generation and producing more individuals with similar genetic

Question.What is DNA copying? State its importance.
Answer : A process where a DNA molecule produces two similar copies of itself in a reproducing cell.
Importance -
a. It makes possible the transmission of characters from parents to the next generation.
b. It causes variation in the population.the same species.
c. Inheritance from the previous generation provides both a common basic body design, and subtle changes in it, for the next generation. So the changes keep on accumulating generations after generations.

Question. In a pea plant, find the contrasting trait if:
a. the position of flower is terminal.
b. the flower is white in colour.
c. shape of pod is constricted.
Answer : a. Axial position of flower.
b. Purple colour of flower.
c. Inflated shape.

Question. Explain with an example for each, how the following provides evidences in favour of evolution in organisms:
a. Homologous organs
b. Analogous organs
c. Fossils
Answer : a. Homologous organs - study of homologous organs suggests that the organs having same structure but performing different functions have evolved from a common ancestor. Example: forelimbs of a frog, lizard, bird and man.
b. Analogous organs - show adoption of organs for common use. Example: wings of butterfly and wings of bat.
c. Fossils - provide the missing links between two species. Example: - Archeopteryx / fossils of some dinosaurs with feathers

Question.a. During evolution some changes may have occurred for a reason but proved to be useful for some other purpose. Cite one such example.
b. Has the evolutionary changes took place all of sudden. Elaborate.
Answer : a. Evolutions of feathers: Functional Advantage: A change that is useful for one property to start with can become useful later for quite a different function. Feathers, for example, can start out as providing insulation in cold weather. But later,they might become useful for flight. In fact, some dinosaurs had feathers, although they could not fly using the feathers. Birds seem to have later adapted the feathers to flight. This, means that birds are very closely related to reptiles, since dinosaurs were reptiles. Birds have evolved from reptile.
b. Evolution changes has not took place all of sudden. Evolution takes place in stages, i.e., bit by bit over generations. Even an intermediate stage, such as a rudimentary eye, can be useful to some extent. This might be enough to give a fitness advantage. In fact, the eye seems to be a very popular adaptation.
Insects have them, so does an octopus, and so do vertebrates. And the structure of the eye in each of these organisms is different - enough for them to have separate evolutionary origins

Question.“We cannot pass on to our progeny the experiences and qualifications earned during our lifetime”. Justify the statement giving reason and examples.
Answer : Acquiring knowledge / skill in one’s lifetime such as learning dance, music, physical fitness or any other suitable example.
Reason:
a. Such characters / experiences acquired during one’s lifetime do not bring any change in the DNA of the reproducing c$ll/germ cell.
b. Only germ cells are responsible for passing on the characters from the parents to the progeny.

Question. Explain the term homologous organ with an example.
Answer : The organs which have similar basic structure and mode of origin but perform different functions in different animals are called homologous organs. E.g.,
Forelimbs of amphibians, reptiles, birds and mammals. Homologous organs give an evidence of common ancestory and evolutionary relationship between apparently different species.

Question. a. Insects, octopus and vertebrates all have eyes. Can we group eyes of these animals together to establish a common evolutionary origin? Justify your answer.
b. “Birds have evolved from reptiles”. State evidence to prove the statement.
Answer : a. No, the structure of the eye in each of the organisms is different.
b. Fossils of certain dinosaurs/reptiles show imprints of feathers along with their bones but they could not fly presumably using the feathers for insulation.
Later they developed / evolved and adapted feathers for flight, thus becoming the ancestors of present day birds.

Question.An organ like a wing in birds are an advantage to an organism. Did they appear in different stages or were formed due to a single sudden change in them.
Answer : Feathers in dinosaur were long and they could not fly using feathers. It gave them protection from cold weather and warmth. Birds seem to have later adapted the feathers to flight.

Question. a. “Chromosomes are heredity carriers.” Why do we say so?
b. Which vital function is not controlled by autosomes?
Answer : a. Chromosomes are made-up of DNA. Genes are located on the chromosomes. It is the DNA copy which transfers from both the parents to their offspring. Therefore, chromosomes made-up of DNA and containing genes are said to be the heredity carriers.
b. Sex of the child is not controlled by autosomes.

Question.What are chromosomes ? Explain how in sexually reproducing organisms the number of chromosomes in the progeny is maintained.
Answer : Chromosomes - Thread like structures made up of DNA found in the nucleus. The original number of chromosomes becomes half during gamete formation.
Hence, when the gametes combine, the original number of chromosomes gets restored in the progeny. (or same thing explained in the form of a flow chart).

Question.With the help of suitable examples, explain why certain traits cannot be passed on to the next generation. What are such traits called?
Answer : Example: Acquiring knowledge by reading/change in body weight. Reason: Because such changes do not bring any change in the DNA of the germ cells/ such changes take place only in the non-reproductive tissues. Traits: Acquired traits.

Question. An angiosperm plant having red coloured flowers when crossed with the other having the same colour produced 40 progenies, out of which 30 plants were with red coloured flowers, 10 plants were with white coloured flowers. Find out:
a. What is the possible genotype of parent plants?
b. Which trait is dominant and recessive?
c. What is this cross called as and what is its phenotypic ratio?
Answer : a. Rr and Rr.
b. Red colour of flowers is the dominant trait while white colour is the recessive trait.
c. Monohybrid cross, phenotypic ratio is 3 : 1.

Question. How are fossils formed? Describe, in brief, two methods of determining the age of fossils.
Answer : Fossils are formed when dead organisms are not completely decomposed. The organisms may get trapped in resins of tree, lava of volcanoes or hot mud which when hardens, retains the animal’s parts thus,forming fossils.
Two methods of determining the age of fossils:
a. Relative method: By estimating the age of the layer of earth’s crust where the fossil is found. Fossils near the surface are recent and those in the
deeper layers are more ancient.
b. Radio-carbon dating method: By detecting the ratios of different isotopes of carbon in the fossils.
Fossils help in determining the connecting links between various groups and their origin from their primitive ones, e.g., Archaeoptyrx.

Question. Rekha is very dark in colour. She stays very quiet at home and in her class also. She is always seeing for the beauty products which can help her to become fair. Her friend Lila talks to her about excessive use of beauty products and tells her that they are very harmful and colour comes by birth and she is not responsible for her dark colour.
a. What might have caused Rekha’s colour to be dark?
b. Is it possible that all the family members of Rekha’s family were dark?
c. What value do you learn?
Answer : a. Her dark colour may be due to the genetic inheritance.
b. All may not be dark, depending upon the genes inherited and the environmental conditions that each one of them living in.
c. Awareness, logical thinking, scientific temperament.

Question. If a population of red beetles, living on green bushes,is being eaten by crows. During sexual reproduction,
a green beetle is found in progeny:
a. What is the future of new trait?
b. Will it survive in the new habitat?
Answer :  
a. Among progeny, when green beetle is found, it escaped attack of crows as it merged with green colour. Green beetles increased, red decreased.
b. New trait will survive.

Question. Clones of sheep are carbon copy of each other except physical health. What kind of variation is it? 
Answer : Phenotypic variation

Question. If a pure tall pea plant is crossed with a pure dwarf pea plant, then in F₁ generation only tall plants appear. What happens to the traits of the dwarf plant?
Answer : Although in F₁ generation only the tall plants appear, both the tallness and dwarfness traits are inherited in the F₁ plants but as the tallness trait is dominant, it is expressed, whereas,

Question. The gene type of green stemmed tomato plants is denoted as GG and that of purple stemmed tomato plants as gg. What colour of stem would you expect in F₁ progeny when these two are crossed?
Answer : As green stem is a dominant trait as compared to purple stem, the colour of stem would be green in F₁ progeny.

Question. All the human races like Africans, Asians, Europeans, Americans and others might have evolved from a common ancestor. Provide a few evidences in support of this view. 
Answer : All human beings have evolved from a common ancestor as they have the maximum number of common characters. Moreover, all human beings can interbreed with each other, which shows that all of them belong to the same species. Some of the common characters of all human beings are:
(1) Common body plan, structure, physiology and metabolism.
(2) All of them have a constant chromosome number i.e., 46.
(3) Their genetic makeup is also similar i.e., almost 99.9% DNA is nearly the same in all humans.
(4) All the humans; can freely inter-breed to produce offspring. All these evidences clearly indicate that all of us, whether Africans, Asians, Europeans, Americans, etc., have evolved from a common ancestor.

Question. (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.
Answer : (A) The differences in characteristics between individuals of the same species is called variation. Variations arise in organisms during the process of copying the DNA due to which the DNA copies will be similar but not identical to the original. Variation is created in a population consisting of sexually reproducing organisms as

Question. Name the plant Mendel used for his experiment. What type of progeny was obtained by Mendel in F1 and F2 generation when he crossed the tall and short plants? Write the ratio he obtained in F2 generation plants.
Answer : Mendel used Pisum sativum (Pea plant) for his experiment.
Mendel took a tall pea (TT) plant and a short pea plant (tt) plant. When he crossed both, in F₁ generation all plants were tall. When F₁ progeny was self pollinated, all plants obtained in F₂ generation were not tall. Instead 3 tall and I short pea plant was obtained.

 

 

Question. What will be the sex of a baby if sperm carrying X chromosome fertilizes egg in human beings. Why?
Answer : It will be a baby girl because fusion of gametes having X chromosomes leads to homozygous condition producing zygote with XX composition.

Question.How did Mendel explain that it is possible that a trait is inherited but not expressed in an Organism?
Answer : (i)In Mendel’s experiment, when pure tall pea plants were crossed with pure dwarf pea plants, only tall pea plants were obtained in F₁ generation.
(ii)On self pollination the pea plants of F₁ generation both tall and dwarf pea plants were obtained in F₂ generation.
(iii)Reappearance of the dwarf pea plants in F₂ generation proves that the dwarf trait was inherited but not expressed in F₁ generation.

 

Question. Feather imprints were preserved along the dinosaur’s bones but dinosaurs could not fly. What was the significance of feathers in reptiles and later on for other species? 
Answer : It is believed that feathers in dinosaurs might have provided insulation in cold weather but later on became useful for flights in birds.

Question. A zygote which has an X-chromosome inherited from the father will develop into a
(a) Boy
(b) X-chromosome does not determine the sex of a child.
(c) Girl
(d) either boy or girl
Answer : Correct option(c)

Question. Wild cabbage was converted into number of variants like cauliflower, broccoli and cabbage by man. What is this process known as? Does it play an important role in organic evolution? 
Answer : This process is known as artificial selection. It plays an important role in organic evolution because it is parallel to natural selection. It helps to produce new species having useful traits in less time.

Question. Which of the following is not a direct conclusion that can be drawn from Mendel’s Experiment?
(a)Only one parental trait is expressed
(b)Two copies of each trait is inherited in sexually reproducing organism
(c)For recessive trait to be expressed, both copies should be identical
(d)Natural selection can alter frequency of an inherited trait
Answer : Correct option (d)

Question. How are variant genotypes produced? 
Answer :  Variant genotypes can be produced by:-
1. Mutation in genes and chromosomes.
2. Recombination of genes.
3. Hybridization of genes.

Question. Why is variation important for a species?
Answer : Survival of species over time.

Question. Can geographical isolation lead to speciation? How? 
Answer : Yes, geographical isolation can lead to speciation. Due to geographical isolation, the members of two sub groups may not be able to interbreed as a result of genetic drift. Natural selection also operates differently in these subgroups. This leads to speciation.