NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution - Future Study Point

NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution

class 10 heredity

NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution

NCERT Solutions of Class 10 Science Chapter 9 Heredity and Evolution is the most important chapter of biology section of class 10 science NCERT text book for the examination perspective.It is very important for every students to clear the concept of this chapter  by studying its NCERT solutions,the students should have thorough knowledge about the new terms used in this chapter for proper understanding of the question and answers based on Heredity and Evolution.The chapter 9-Heredity and Evolutions is a basic chapter on the heredity ,so these NCERT solutions are mandatory for all students that will help you not only in  10 class CBSE board exam but also the proper understanding  of the chapter needed them for studying higher class biology.

class 10 heredity

Important terms used in the NCERT Solutions of Class 10 Science Chapter 9 Heredity and Evolution

You can also download PDF-NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution

PDF-Class X science best explained NCERT solutions of the chapter 9

Heredity: We look like our parents due to the process of heredity, heredity is the transmission of the traits from one generation to the next generation, as an example colour of the eye, blood group or diseases like diabetes etc.

Genes: Heredity is determined by genes, genes are transmitted from one generation to the next generation in the form of pair of traits known as alleles, alleles are copies of genes. One copy of the gene from the sperm and other copy from the egg is transmitted to the next generation.

Homozygous and Heterozygous traits: When transmitted copies of the genes (alleles) are identical then it is a homozygous trait for that gene and when both transmitted copies are different then it is heterozygous for that gene.

Dominant and Recessive trait: The traits which are highlighted in next-generation are known as dominant traits and the traits which are suppressed in next-generation are known as Recessive traits.

NCERT Solutions of Class 10 Science Chapter 9 Heredity and Evolution

Page 143

Q1. If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the population, which trait is likely to have arisen earlier?

Ans. In asexual reproduction, the parent cell reproduces a similar daughter cell. It is given to us that trait B exists in 60 %  of the population of a species and trait A exists in 10 % of the total population of the species since trait B represents a larger population as compared with trait A therefore trait B is likely to have arisen earlier.

Q2. How does the creation of variations in a species promote survival?

Ans. The creation of variation in a species promote survival because variation protects the species from adverse atmospheric condition, in changing atmospheric condition the variation causes the species to adapt themself, as an example bacteria variants that are fitted in adverse condition like heat and cold survive better, such bacteria spreads faster compared to those bacteria which couldn’t fit in that condition. Therefore the creation of variation in a species promotes survival.

Page 147

Q1. How do Mendel’s experiments show that traits may be dominant or recessive?

Ans. Mendel shows that traits may be dominant or recessive through his experiment of monohybrid cross (single trait). In his first experiment, he considered a single trait i.e tallness of pea plant, for that he fertilized a tall plant(TT)  to a dwarf plant (tt), which results in all tall plants in the F1 generation, thereafter he fertilized two TT plants of F1 generation through artificial pollination and found the result in F2 generation that one-fourth plants were seen, dwarf. Mendel concluded to that fact the tall plants produced in F1 generation were not the real tall TT plants which he had taken for the experiment, practically those plants of the F1 generation were Tt plants means the dwarfness of the plants were not seen, here in F1 generation tallness of pea plants shown is a dominant trait and since dwarfness is not seen in F1 so it is a recessive trait.

Plants taken for experiments =(TT),(TT)

F1 generation = (Tt),(Tt),(Tt),(Tt), in Tt, T trait is dominant, t trait is recessive

F2 generation =(Tt),(Tt),(Tt),(tt), in Tt, T trait is dominant, t trait is recessive and in tt, t trait is dominant and T is recessive.

Q2. How do Mendel’s experiments show that traits are inherited independently?

Ans. Mendel’s experiments show that traits are inherited independently, for this experiment he took two pea plants differing from each other by two characters, he crossed one plant with yellow and rounded seed to another plant with green and wrinkled seed. In (F1) first-generation, it results in the plants with yellow rounded seeds, and F2 generation results in the plants with round yellow, round green, and wrinkled yellow seeds, thus Mendel concluded to the fact that traits are inherited independently.

Q3. A man with blood group A marries a woman with blood group O and their daughter had blood group O, Is this formation enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?

Ans. The information that a man with blood group A marries a woman with blood group O and their daughter had blood group O is not sufficient to tell that blood group A or O is dominant. The father’s blood group A tells that it may have homozygous traits AA or heterozygous AO, mother’s blood group O tells that she may have homozygous trait OO or AO. Since genotypically 50-50 % of traits has to be transferred to next-generation, In both the cases the daughter must have the blood group O, therefore we can’t say which of traits A or O is dominant since generally A, B and AB traits are dominant and O is recessive.

NCERT Solutions of Class 10 Science Chapter 9 Heredity and Evolution

Q4. How is the sex of the child determined in human beings?

Ans. In a human being, the male has the XY chromosomes where x shows the trait of female and y shows the trait of male and a female has XX chromosomes where both traits show the trait of girls. Therefore in males, 50 % of chromosomes are of each one X and Y, when fertilization occurs Y chromosomes in sperm fuse X chromosomes in eggs,a boy is produced, and when X chromosome in sperm fuses X chromosome in female a girl is produced.

sex determine

Page 150

Q1. What are the different ways in which individuals with a particular trait may increase in a population?

Ans. The population of an individual with a particular trait may increase in a population in the following ways.

(i). The trait is beneficial to the population: A group of species use camouflage to blend into their surrounding, it helps them to defend from predators, such traits help them to increase their population. For example, the green colour in beetles is favourable as it helps them camouflage against predators.

(ii). Genetic drift: if a population faces an accident such that majority of its members get killed, the remaining members will pass on their traits to the subsequent generations. This will lead to an increase of the trait in the population.

(iii). By mutation: In reproduction during cell division the mistake in DNA copying is beneficial for the species to survive in changing circumstances, thus helps the species to increase their population.

(iv). Naturally Selection: If a trait is useful to the population, it will increase naturally. It may be direct the evolution of species population by adaptions to fit their environment better.

Q2. What are traits acquired during the lifetime of an individual not inherited?

Ans. The acquired traits during a lifetime of an individual are influenced by the surroundings. These traits are not coded by the DNA of the germ cells, this happens because an acquired trait involves a change in non-reproductive tissues(somatic cells) which cannot be inherited.

Q3. Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?

Ans 1. The small number of surviving tigers is a cause of worry because it can result in the loss of genetic variability. This sudden extinction of the tigers and their genes will affect the diversity of nature. The decrease in the tiger population results in a decrease in the genetic pool of tigers. This might even lead to extinction.

2. During the long process of evolution, these tigers carry the genes which have made them adapt to the particular environment. Genes responsible for the survival would not be able to contribute to future generations survival if the tigers became extinct due to any disease or by hunting.

Page 151

Q1. What factors could lead to the rise of a new species?

Ans. There are many factors that lead to the rise of a new species. Listed below are a few factors:

1. Genetic drift

2. Natural selection

3. Genetic mutation

4. Reproductive isolation

5. Environmental factors on the isolated populations.

6. Quantum of genetic variant inherited from one generation to the next generation.

Q2. Will geographical isolation to be a major factor in the speciation of a self-pollinating plant species? Why or why not?

Ans. No, geographical isolation will not be a major in the speciation of self-pollinating plant species. Geographical isolation creates the separation of the population. It is because in self-pollinating species, new variants are not formed and they do not show any variation in the population. After self-pollination, the homozygous line evolve. In contrast, after cross-pollination, the homozygous line evolves and it results in the variation of traits in the population.

Q3. Will geographical isolation to be a major factor in the speciation of an organism that reproduces asexually? Why or why not?

Ans. No, geographical isolation will not be the major factor in the speciation of asexually reproducing organisms. This is because there is no exchange of genetic material with the other species in such organisms. They pass on the parent DNA to the offspring which leaves no chance of speciation.

NCERT Solutions of Class 10 Science Chapter 9 Heredity and Evolution

Page 156

Q1. Give an example of characteristics being used to determine how close two species are in evolutionary terms.

Ans. In the example of man and ape, both of these two organisms are closed to each other in evolutionary terms because they have similar body designs as an example the hair in their body and mammary glands. In the case of the fish and man, the fish have jaws, vertebral columns and a brainbox which is matched with the man but the fish looks quite different from the man leads to the distant relationship between both of the organisms. There are two characteristics to determine how close are two species are in evolutionary terms.

Homologues and analogues organs are two characteristics to determine how close are two species are in evolutionary terms.

Homologous organs are similar organs in basic structure but perform different functions, this characteristic shows divergent evolution.

Analogous organs are different organs in basic structure but perform the same function, these characteristics show convergent evolution.

Q2. Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?

Ans. No, the wings of the bat and the wings of the butterfly should not be considered as homologous organs because they have different structures and origins but have the same function of flying so they are analogous organs.

Q3. What are fossils? What do they tell us about the process of evolution?

Ans. Fossils are the preserved remains or traces of animals, plants and other organisms from the past.

Fossils help us in many ways like:

1. They give great insight into the evaluation. For example, the pattern of fossil distribution gives us an idea of the time in history when various species were formed and extinct.

2. They help us in establishing evolutionary relations between present organisms. Example: Archaeopteryx (connecting link between reptiles and birds).

Page 158

Q1. Why are human beings who look so different from each other in terms of size, colour and looks said to belong to the same species?

Ans. All human beings, even though they have different sizes, colour and looks, belong to the same species because they have similar DNA sequences and have descended from the same ancestors. Also, they are capable of reproducing among themselves. These variations may have arisen due to environmental factors, mutation and mixing characteristics during reproduction.

Q2. In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better’ body design? Why or why not?

Ans. No, we cannot say that there is a better body design as these organisms evolved according to their needs to survive in the environment. If a chimpanzee has strong limbs capable of multiple actions, the bacteria can survive in extreme conditions where other organisms cannot. Hence there is no better body design.

Page 159

NCERT Solutions of Class 10 Science Chapter 9 Heredity and Evolution

Exercises

Question no.1 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q1. A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short.

This suggests that the genetic make-up of the tall parent can be depicted as:

(a) TTWW

(b) TTww

(c) TtWW

(d) TtWw

Ans. (c) TtWW

Question no.2 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q2. An example of homologous organs is:

(a) our arm and a dog’s fore-leg

(b) our teeth and an elephant’s tusks

(c) potato and runners of grass

(d) all of the above

Ans. (d) All of the above

Question no.3 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q3. In evolutionary terms, we have more in common with:

(a) a Chinese school-boy 

(b) a chimpanzee

(c) a spider

(d) a bacterium

Ans. (a) a Chinese school-boy

Question no.4 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q4. A study found that children with light-coloured eyes are likely to have parents with light coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?

Ans. Let the trait of light -coloured eye is represented by LL, in this study children have the trait LL with their parents having the traits LL, in this case, it is obvious that parents with LL will produce children with LL trait, in homozygous LL of parent we can’t say that light eye colour trait is dominant or recessive until we have the information of at least three generations.

Question no.5 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q5. How are the areas of study evolution and classification interlinked?

OR

Two areas of study namely ‘evolution’ and classification are interlinked. Justify this statement.

Ans. Classification of organisms tells us how closed are organism to each other that information feeds us about their common ancestor. The differentiation among the organisms tells us the distant relationship among them, these variations among the species enable them to adapt to particular environmental conditions, this is all about evolution.

Question no.6 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q6. Explain the terms analogous and homologous organs with examples.

Ans. Analogous Organs: The organs which have a different basic structure to each other between two organisms but perform the same functions. As an example, the wings of birds and insects are different in structure, both of them are evolved independently but the wings of both of them are used for flight.

Homologous organs: The organs which have a similar structure between two organisms but perform different functions. As an example, the wings of birds and fins of fish, both of them evolved from the same origin, but fins of fish are used to swim and wings are used to flight.

Question no.7 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q7.Outline a project which aims to find the dominant coat colour in dogs.

Ans. We choose one male dog of homozygous black colour(BB) and a female dog of homozygous white colour (ww) and cross them, then observing the colour coat in the offspring.

First-generation of such parent dogs shows (Bw, Bw, Bw, Bw), all are heterozygous black where black colour is dominated

If we cross two heterozygous black dogs, then puppies in the next generation will be (BB, Bw, Bw,ww),1 homozygous black, two heterozygous black where black colour is dominated and 1 homozygous white dog.

The ratio between the dogs of different pair of genes are 1:2 :1

If total puppies produced in second generations are 40 in number

The number of homozygous black puppies are =(1/4)×40=10

The number of heterozygous black puppies are =(2/4)×40=20

The number of homogeneous white puppies are =(1/4)×40=10

Question no.8 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q8.Explain the importance of fossils in deciding evolutionary relationships.

Ans. The fossils give us the following information

(i)  Evolutionary process of life in the earth.

(ii) The structure of the organism that enables us to link with present creatures available on the earth.

(iii) Fossils of theropods dinosaurs and dinosaurs with features give us an idea that birds are descended from the dinosaurs.

(iv) Wich animals evolved earlier and which were evolved later

(v) The fossils which were found near the surface are more complex than the fossils which were found deeper inside the earth.

Question no.9 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q9.What evidence do we have for the origin of life from inanimate matter?

Stanley L. Miller and Harold C. Urey gave proof with respect to the beginning of life from inanimate matter. They managed an environment like that that existed on early earth. The environment had molecules like ammonia, methane, hydrogen sulfide and water, but no oxygen.

The blend was kept up at a temperature just underneath 100°C and sparkes were passed through the combination of gases. They observed the result after a weak, 15% carbon from methane had been changed over to simple molecules of carbon like amino acids which make up protein particles. In this way, life emerged on earth.

Question no.10 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q10.Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?

Ans. Sexual reproduction gives rise to more viable variations than asexual reproduction because in asexual reproduction there is neglected error in DNA that results in neglected variations in the offspring, In asexual reproductions, the progeny is either more or less similar to the parents. So there are more chances of the organism to be extinct due to lack of variations.

In sexual reproduction during gamete, formation meiosis occurs between homologous chromosomes of male and female and cell division takes place which brings about new gene formation which is transferred to a new generation, in this matter natural selections is processed, in the natural selection those variations which have more adaptive value undergoes to the formation of new species.

Question no.11 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and

Q11.How is the equal genetic contribution of male and female parents ensured in the progeny?

Ans. In the human cell, there is a total of 46 chromosomes or 23 pairs of chromosomes. During the process of reproduction, each pair of chromosomes contributes one chromosome to the offspring, thus half of the chromosomes are transferred to children from each parent. Among 23 pairs of chromosomes, 22 pairs are the same in male and female which are known as autosomes and the rest one pair is sex chromosomes that are different in male and female and decide the sex of the child. In males, there is a pair of  XY chromosomes and female XX pair. When X of male reproduces X of female then offspring is a female and when Y of female reproduces X or female then the offspring is a male.

Question no.12 exercises NCERT Solutions of Class 10 Science Chapter 9 Heredity and Evolution

Q12.Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?

Ans. In sexual reproduction, the variations that confer an advantage to an individual will survive in a population. All the variation occurring are not beneficial for the survival of the organism, only those variables which have more adaptive value in changing environment causes the survival of the species.

Variation among the species makes them fit for changing environments. The organism which is adamant about the changes themselves can’t survive in changing environment.

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Extract

Students are required to study each NCERT Solutions for class 10 chapter 9 Heredity and Evolution ,some of questions are advised to study minutely for the preparation of the exams.

Q2. How does the creation of variations in a species promote survival?(page 143)

Q1. How do Mendel’s experiments show that traits may be dominant or recessive?(page 147)

Q4. How is the sex of the child determined in human beings?(page 147)

Q3. Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?(page 150)

Q1. What factors could lead to the rise of a new species?(page 151)

Q1. A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short.

This suggests that the genetic make-up of the tall parent can be depicted as:

(a) TTWW

(b) TTww

(c) TtWW

(d) TtWw

Q4. A study found that children with light-coloured eyes are likely to have parents with light coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?

Q5. How are the areas of study evolution and classification interlinked?

Q6. Explain the terms analogous and homologous organs with examples.

Q8.Explain the importance of fossils in deciding evolutionary relationships.

Q9.What evidence do we have for the origin of life from inanimate matter?

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Chapter 1- Chemical reactions and equationsChapter 9- Heredity and Evolution
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Chapter 1-Relations and FunctionsChapter 9-Differential Equations
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