Important Questions for CBSE Class 10 Science Chapter 8 - Heredity and Evolution 2024-25

Very Short Answer Questions (1 Mark)

1. Select the group which shares the maximum number of common characters-

1. Two genera of two families

2. Two species of a genus

3. Two genera of a family

4. Two individuals of a species

Ans: (d) Two individuals of a species

2. Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds produce ${{F}_{1}}$ progeny having round, yellow (RrYy) seeds. When ${{F}_{1}}$ plants are selfed, the ${{F}_{2}}$ progeny will have the following combination of characters

1. 15:1

2. 9:3:3:1

3. 9:3:4

4. 12:3:1

Ans: (b) 9:3:3:1

3. Some dinosaurs had feathers although they could not fly birds have feathers that help them to fly. In the context of evolution, this means that-

1. Reptiles have evolved from birds

2. There is no evolutionary connection between reptiles and birds

3. Feathers are homologous structures in both the organisms

4. Birds have evolved from reptiles.

Ans: (d) Birds have evolved from reptiles.

4. What is a monohybrid cross?

Ans: The combination between two plants that display two different variants of a property (character).

5. What are autosomes and sex chromosomes?

Ans: There are 23 pairs of chromosomes in a human cell. 22 pairs are termed autosomes, while the remaining 1 pair, which determines a child's sex, is called sex chromosome.

6. Which of the following scientists gave the principles of inheritance?

1. Mendel

2. Griffin

3. Johanssen

4. Watson and Crick

Ans: (a) Mendel

7. Which of the following is not correct-

1. For every hormone, there is a gene.

2. For every protein, there is a gene.

3. For the production of every enzyme, there is a gene.

4. For every molecule of fat, there is a gene.

Ans: (a) For every protein there is a gene.

8. According to the evolutionary theory formation of a new species occurs generally due to-

1. Sudden creation by nature.

2. accumulation of variations over several generations

3. clones formed during asexual reproduction

4. Movement of individuals from one habitat to another.

Ans: (a) accumulation of variations over several generations.

9. Who coined the term ‘gene’?

Ans: The term gene was originated by Johannsen (1909).

10. What are dominant genes?

Ans: A dominant gene is one that expresses itself.

11. The concept of the origin of species by natural selection was given by.

1. Lamarck

2. Weismann

3. Darwin

4. Linnaeus

Ans: (c) Darwin

12. If a round green seeded pea plant (RRYY) is crossed with wrinkled yellow seeded pea plant (rr yy) the seeds to be produced in F1 generation will be.

1. Wrinkled and yellow

2. round and green

3. wrinkled and green

4. round and yellow.

Ans: (b) round and green

13. The genetic constitution of an organism is called.

1. Genotype

2. phenotype

3. variation

4. gene.

Ans: (a) Genotype

14. Write the scientific name of the plant on which Mendel carried out his experiments.

Ans: Pisum sativum

15. How many autosomes are present in human sperm?

Ans: 22

16. Two pink coloured flowers on crossing result in 1red, 2pink and 1white flower progeny. The nature of the cross is-

1. cross-fertilization

2. self-pollination

3. double fertilization

4. no fertilization

Ans: (a) cross-fertilization

17. A basket of vegetables contains carrot, potato, radish, and tomato. Which of them represent the correct homologous structure

1. carrot and potato

2. carrot and tomato

3. radish and carrot

4. radish and potato

Ans: (c) radish and carrot

18. Mendel proposed that every character is controlled by-

1. one factor

2. two factors

3. one chromosome

4. two chromosomes

Ans: (b) two factors

19. Who is called the father of genetics?

Ans: Gregor Mendel.

20. What is the scientific name of a human being?

Ans: Homo sapiens

21. The theory of chemical evolution of life was experimentally demonstrated by-

1. Oparin

2. Miller and Urey

3. Mendel

4. Darwin

Ans: (b) Miller and Urey

22. Genetics is the study of-

1. resemblances amongst individuals

2. heredity and environment

3. differences amongst individuals

4. Heredity and variations.

Ans: (d) Heredity and variations.

23. The wing of a bird and wing of an insect is

1. Homologous organs

2. analogous organs

3. vestigial organ

4. both (a) and (b)

Ans: (a) Homologous organs

24. What is heredity?

Ans: Heredity refers to the transmission of a person's personality from one generation to the next.

25. What are Mendelian factors?

Ans: Mendelian factors are heredity components that carry on a character from parents to offspring.

26. 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

1. TTWW

2. TTww

3. TtWW

4. TtWw

Ans: (c) TtWW

27. An example of homologous organs is

1. Our arm and a dog’s foreleg.

2. Our teeth and an elephant’s tusks.

3. Potatoes and runners of grass.

4. All of the above.

Ans: (d) All of the above.

28. In evolutionary terms, we have more in common with

5. A Chinese schoolboy.

6. A chimpanzee

7. A spider

8. A bacterium

Ans: (a) A Chinese schoolboy.

29. What happened when Mendel crossed two traits of a character in a pea plant?

Ans: Mendel discovered that each feature was inherited separately from the others, resulting in its own 3:1 ratio. 

30. Who provided experimental evidence to support the theory of the origin of life from inanimate matter?

Ans: Miller and Urey

31. A normal pea plant bearing coloured flowers suddenly starts producing white flowers. What could be the possible cause?

Ans: Mutation is responsible for the appearance of white flowers.

32. Mention any two recessive traits of a garden pea.

Ans: Dwarf (height of plant) and wrinkled seed.

33. What is called a phylogenetic system of classification?

Ans: Organisms are classified depending on their evolutionary relations.

34. What will be the percentage of ab gametes produced by AaBb parents?

Ans: 25 per cent

35. Mendel crossed a pure white recessive pea plant with a dominant pure red-flowered plant. What will be the first-generation f hybrids.?

Ans: Allred

36. Name the chemicals which were essential for the origin of life.

Ans: Proteins and nucleic acid

37. Why are males called heterogametic?

Ans: Males are called heterogametic because their y chromosomes are different.

39. What is the percentage possibility of a couple having daughters?

Ans: 50 per cent.

40. Name 2 organisms in which sex determination is regulated by environmental factors.

Ans: Turtle and lizard.

41. Clones of sheep are carbon copies of each other except for physical health. What kind of variation is it?

Ans: Phenotypic variation.

Short Answer Questions (2 Marks)

1. Why are acquired traits not inherited?

Ans: Acquired traits are those that organisms develop over the course of their lives. These characteristics can't be handed down because they're caused by non-reproductive tissue.

2. How evolution and classification are linked?

Ans: The organisation of organisms into groups based on their properties is known as classification. Characteristics are physical or behavioural characteristics. The most advanced and effective classification system is based on evolution. The division of organisms/species into groups reflects their shared origins, as well as their evolutionary relationship.

3. What are coacervates?

Ans: Coacervates are the first life molecules created when a membrane forms around amino acids, sugars, and nitrogenous bases aggregates. Coacervates continue to evolve, eventually leading to the origin of life.

4. How do the two factors for a character, present in diploid cells, behave at the time of gamete formation?

Ans: During gamete development, two components named X and Y separate. As a result, the gamete is either X or Y.

5. Give the pair of contrasting traits of the following characters in the plant and mention which one is recessive and which is dominant?

(a) yellow seed

Ans: Green seed- Dominant

Yellow seed- Recessive

(b) round seed

Ans: Wrinkled seed – Recessive

Round seed- Dominant

6. Mention two important features of fossils that help in evolution.

Ans: Two important features of fossils that help in evolution:

(i) Fossils are a type of ancient species preservation. 

(ii) Fossils aid in the identification of evolutionary relationships between creatures and their forefathers and mothers. 

7. What do you understand by the term natural selection?

Ans: Natural selection theory states that nature selects the fittest animals for breeding, while those who do not fit are removed by nature.

8. Mention the complement of a sperm and the egg which will determine the birth of a female child.

Ans: The X chromosome is found in both the sperm and the egg of a female child and it is the complement of a sperm and the egg which will determine the birth of a female child.

9. What is emasculation? Why is it done?

Ans: Emasculation is the removal of an anther to prevent pollination in an experimental plant.

10. What is a gene? Where are genes located?

Ans: The term "gene" refers to DNA segments.

Chromosomes are where genes are found.

11. How many contrasting characters did Mendel see in garden pea? Give any two of them.

Ans: In the pea plant, Mendel discovered seven distinct characteristics.

For example, axial and terminal flower positions. Round and wrinkled seed form.

12. What is the phenotypic ratio obtained by Mendel by monohybrid cross? Answer with the help of a diagram.

Ans: Mendel's monohybrid cross's phenotypic ratio isa3:1. A monohybrid cross happens when fertilisation occurs between two true-breeding parents who differ exclusively in the feature being examined, and the resulting offspring are termed monohybrids. Mendel experimented with seven different forms of monohybrid crosses, each including opposing features for various phenotypes. The F1 offspring of such crosses all had one parent's phenotype, but the F2 offspring had a 3:1 phenotypic ratio.

Mendel hypothesised that each parent in a monohybrid cross provided one amongst two paired unit factors towards each offspring, and that any potential combination of unit factors seemed equally probable.

13. Why are acquired characters not inherited?

Ans: Acquired qualities are those that organisms develop over the course of their lives.

They are not passed down to future generations. Because these characteristics are caused by non-reproductive tissues, they cannot be handed forward.

14. How is the chromosome number restored in the zygote?

Ans: Male and female gametes each have N chromosomes. Gametes combine and form a zygote during fertilisation. The number of chromosomes in a zygote is 2N.

15. What are variations? Give their types.

Ans: Despite the fact that offspring of the same parents seem the same, they are not identical to their parents. There are three distinctions between them. Variations are the term for these disparities. There are two types of it:

(a) Reproductive- It is passed down from one generation to the next.

(b) Non-reproductive—not passed down from generation to generation.

16. Write the difference between Autosomes and Allosomes.

Ans: The difference between autosomes and allosomes is as given below,

17. What will be the sex of the embryo if an egg is fertilized by the sperm having?

(a) \[22+x\] and

Ans: Female

(b) \[22+y\] composition

Ans: Male.

18. Mention two sources of variation.

Ans: Two sources of variation are:-

1. DNA copying errors.

2. Fertilization at random.

19. What are monohybrid and dihybrid cross? Give one example of each.

Ans: Monohybrid cross- This is the simplest cross in which only one character's inheritance is investigated. A cross is created by crossing two plants with one contrasting characteristic, such as tall or dwarf.

Dihybrid cross- A dihybrid cross is a cross between two plants with two sets of opposing characters. Round and green seed, for example, crossed with yellow and wrinkled seed.

20. Why did Mendel choose a pea plant for his experimentation?

Ans: Mendel chose the garden pea for his experiment for the following reasons: 

1. Because this plant has a short life cycle, the results may be gathered and evaluated more quickly.

2. The garden pea possesses a number of features that are diametrically opposed to one another.

3. This plant is also tiny, easy to grow, and produces a big number of offspring.

21. If a trait A exists in \[\mathbf{10}%\] of a population of an asexually reproducing species and a trait B exists in \[\mathbf{60}%\] of the same population, which trait is likely to have arisen earlier?

Ans: Trait B.

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

Ans: Individuals with a certain attribute can increase in a variety of ways, including:

1. Natural selection- Certain differences give individuals in a group a survival edge in a changing context, resulting in population growth.

2. Genetic drift—In a small population, even if no survival benefit is gained, accidents can lead to an increase in the number of specific individuals.

23. Why are traits acquired during the lifetime of an individual not inherited?

Ans: Any changes in non-reproductive organs are not passed on to germ cell DNA. As a result, qualities acquired during a person's lifetime are not inherited.

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

Ans: The minimal number of living tigers is concerning because it could lead to a loss of genetic diversity. The abrupt demise of tigers and their genes will have an impact on natural diversity. Because the tiger population is declining, the genetic pool of tigers is shrinking. It will have an impact on the frequency of selection, which is necessary for survival. The population must have an indefinitely a vast number of individuals in order for selection to be effective.

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

Ans: The evolutionary distance between humans and apes can be determined using the example of humans and apes. Both of their bodies are similar in appearance. Both animals have hair on their bodies and mammary glands. As a result, these two animals are tightly linked in terms of evolution. 

• Homologous organs share a common origin and basic structure, although they serve diverse purposes in different organisms.

• Analogous organs have similar functions but vary in basic anatomy.

• Homologous organs have evolved in different ways.

• Analogous organs have evolved in a similar way. They form in creatures that are connected to one another.

26. Can the wing of a butterfly and the wing of the bat be considered homologous organs?

Ans: No, while the function of the wing is identical in both cases, the structural plan and origin are not.

27. 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: Humans differ from one another in terms of size and colour, but they are all members of the same species. This is due to the fact that, despite the tremendous diversity of human shapes and traits among different human races around the world, all human beings' genetic footprints can be traced back to the same common heritage of African origins. Humans are a single species that descended from the earliest members of the human species in Africa, Homo sapiens. Because there has been no well-defined geographical or reproductive isolation among members of the human species, this has resulted in a wide range of genetic makeups for features with minor differences.

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

Ans: We can't say whether germs, spiders, fish, or chimps have a "superior" body design in evolutionary terms. The idea that various animals have better bodily designs is unjustifiable. Because the evolutionary process considers the development of the most efficient and suitable elements in organisms' body designs for survival and adaptation to a specific niche. Organisms with a complex and ostensibly better body architecture, for example, may not be able to live in a given context. Bacteria, on the other hand, can survive in the most hostile and severe environmental circumstances, such as extremely hot, cold, or acidic, due to their rudimentary body design and simple microbial lifestyle. Bacterial microorganisms can be found deep beneath arctic ice, in deserts, near volcanic eruptions on the surface of the world, at thermal vents under the deep sea or on the surface of the globe, and even in outer space.

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

Ans: Organisms are categorised into categories based on the similarities and differences they have with one another. The more features that two species share, the more closely they are related. The proximity of the two species shows that they shared a similar ancestry. As a result, species taxonomy reflects their evolutionary relationship.

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

Ans: The importance of fossils in deciding evolutionary relationships:

1. The study of fossils allows us to estimate how far back creatures' evolutionary relationships go.

2. Knowing the age of fossils allows us to determine which organisms evolved first and which evolved later.

31. Write the characteristics on the basis of which duck-billed platypus is considered as a link between reptiles and mammals.

Ans: Laying of eggs is a feature that resembles reptiles, whereas the presence of mammary glands is a characteristic that resembles mammals.

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

Ans: As the tiger population declines, genes are lost from the gene pool, which means there can be no recombination or variants, and hence no evolution.

33. How one is adopted to perform different functions? Give one example

Ans: One modification that occurred early in evolution is now utilised to accomplish additional functions. Feathers, for example, evolved for warmth before being modified for flying.

34. Why are asexually reproducing organisms capable of showing hereditary features?

Ans: Asexual reproduction tends to preserve the genetic similarities among all members of a line of descent. As a result, asexually reproducing organisms can exhibit hereditary characteristics.

35. If the sperm bearing Y-chromosome fertilizes the egg, the child born will not be entirely like his father. Why is it so?

Ans: If the sperm bearing Y-chromosome fertilizes the egg, the child born will not be entirely like his father because the X-chromosome, the other sex chromosome, will also have an impact. Other egg autosomes will also display their properties.

36. In evolutionary terms, which among-bacteria, spiders, fish and chimpanzees have a “body design''? Why or why not?

Ans: Chimpanzees have a better bodily design than the other species. They have greater movement, communication, and reasoning abilities.

37. What is offspring?

Ans: Offspring are organisms that are raised as a result of gene segment crossing and exchange in sexual reproduction.

38. What have inherited traits? Give one example.

Ans: Inherited traits are characteristics that are passed on from parents to their children. For example, earlobes are both free and attached.

39. When Mendel crossed a tall plant with a dwarf plant, no medium height plants were obtained in F generation. Why?

Ans: When Mendel crossed a tall plant with a dwarf plant, no medium height plants were obtained in F generation because dominant genes express themselves and prevent recessive genes from having an influence. As a result, no plants of medium size were obtained.

40. The human hand, cat paw and horse foot when studied in detail show the same structure of bones and point towards a common origin.

i. What do you conclude from this?

Ans: We can deduce that these organs share a common ancestor.

ii. What is the term given to such structures?

Ans: Homologous organs are those that are identical to one another.

41. How do we know how old a fossil is?

Ans: There are two techniques:

1. Relative method: When we delve into the earth, we find that the fossils found closer to the surface are more recent than those found in deeper levels.

2. In the fossil material, by measuring the ratios of different isotopes of the same element.

42. What will be the sex of a baby if sperm carrying the X chromosome fertilizes the egg in human beings? Why?

Ans: It will be a female since the fusion of gametes containing X chromosomes produces a homozygous zygote with the XX composition.

43. Feather imprints were preserved along with the dinosaur’s bones but dinosaurs could not fly. What was the significance of feathers in reptiles and later on for other species?

Ans: Dinosaur feathers are thought to have offered protection in cold temperatures, but they eventually became beneficial for avian flight.

44. What will be the blood groups of offspring produced by the parents having the following genotype?

Male -II

Female 1

Ans:

Blood groups will be:

(i) A

(ii) A

(iii) B

(iv) AB

45. A woman with blonde curly hair married a man with black soft hair. All of their children in the first generation had black soft hair but in the next generation, children had different combinations in the ratio of 9:3:3:1. State the law that governs this Expression.

Ans: The law of independent assortment holds that the factors of various pairs of opposing traits are unaffected by one another. In terms of selection, they are unrelated to one another.

Short Answer Questions (3 Marks)

1. 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: Variations that benefit an individual organism may or may not survive in the population, depending on the organism's social behaviour. A variant in a sociable species, such as an ant, may not survive in a population, whereas a variation in a predatory animal, such as a leopard, may.

2. What are the different approaches to determine the evolutionary history of man?

Ans: There are three methods for reconstructing man's evolutionary history:

1. Fossil records provide direct evidence in the form of the historical approach. Carbon dating techniques can be used to establish the age of fossils.

2. Comparative method- By comparing multiple existing forms, we can build hypotheses about their common ancestors and reconstruct their history.

3. Analytic method: Observing vestigial organs in modern humans and examining their development from embryo to adult.

3. What is fossilization? How are fossils formed?

Ans: Fossilization is the term for the process of forming fossils. When organisms die, their corpses disintegrate and become fossilised. The body, or a portion of it, maybe in an environment that prevents it from fully decomposing. The mud will solidify over time and maintain the impression of the organism's bodily parts. This mud with the imprint will be referred to as an organism's fossil.

4. What are homologous and analogous organs? Explain with the help of an example.

Ans: Homologous organs have a similar basic structure and origin, but may perform diverse tasks. Human hands, for example, and avian wings, for example.

Organs that have a similar function but a different basic structure and origin are referred to as comparable organs.

For example, 

1. a bat's wing and a bird's wing.

2. a bird's wing and an insect's wing

5. Differentiate between convergent and divergent evolution.

Ans: The difference between convergent and divergent evolution is as given below:

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

Ans: Selection of environmental conditions for a species' survival are the factors that are responsible for raising a new species. If a variation exists in a population and the variation results in the organism surviving better in the prevailing natural conditions, the characteristic will be naturally selected and spread across the population.

7. What are the different theories about the origin of life?

Ans: Below given are the different theories about the origin of life:-

1. Special creation theory: This theory claims that the almighty god created life.

2. The idea of spontaneous generation- According to this theory, life sprang from non-living components by abiogenesis process including mud, decaying matter, the sun, air, and water, among other things.

3. Cosmozoic theory: According to this view, life came to Earth in the form of spores or seeds from distant celestial bodies.

4. Biogenesis—According to this hypothesis, life evolved from pre-existing life.

5. The modern view of life's genesis states that complex organic molecules can only be generated from simple inorganic molecules under certain conditions.

8. What is the difference between chemical evolution and organic evolution?

Ans: The difference between chemical and organic evolution is as given below,

9. Give the difference between homologous and analogous organs.

Ans: The difference between homologous and analogous organs is as given below:

10. State three laws of Mendel.

Ans: Mendel’s law-

1. Law of dominance- When two distinct character factors are present in an organism, only one (dominant factor) manifests itself, while the other (recessive factor) remains unexpressed.

2. Principle of segregation –At the moment of gamete formation, two elements of a character are separated, and each gamete receives only one factor for that character.

3. Principle of independent assortment-This concept asserts that one pair of contrasting qualities is independent of the other pair of contrasting traits when two or more pairs of contrasting traits are inherited.

11. Describe how the sex of the offspring is determined in the zygote ins human beings?

Ans: Males have the ability to create either X-type or Y-type gametes. The females only generate the X-type of gametes or ova. If X-type sperm unites with the ovum, the infant will have feminine sex. If Y-type sperm is used in conjunction with the ovum, the kid will be male. The baby's gender is determined at the time of conception. The baby's sex is determined at the time of conception.

12. Give a suitable explanation for “geographical isolation of individuals of a species lead to the formation of a new species?

Ans: Between the subpopulations, a reproduction barrier such as a river (geographical isolation) leads to:

1. Genetic drift, or chance changes in gene frequency, such as the selection of red or blue beetles over green beetles in the presence of crows.

2. Natural selection, or selection of the fittest by nature, e.g., in the presence of crows, green beetles are preferred over red beetles.

13. State the evolutionary force which leads to the origin of a new species.

Ans: The following are some of the evolution's elemental forces:

1. Mutation 

2. Recombination (crossing over during meiosis, random gene assortment during gamete production)

3. Survival of the fittest or natural selection

4. Genetic drift is a term used to describe the process of a person's

14. What is a fossil? How do fossils tell us about the process of evolution?

Ans: Fossils are the dead remains of former live species. Paleontology is the branch of biology concerned with the study of fossils. The study of fossils reveals that species evolved from pre-existing ones or that evolution has occurred and is still occurring in nature.

15. Give the difference between diploid and haploid.

Ans: The difference between diploid and haploid is as given below:

16. Who disproved Lamarckism and how?

Ans: August Weismann established that Lamark's acquired character could not be inherited. He began cutting the rat's tail at birth and proceeded for 21 generations. Tight-lipped rats, on the other hand, were never born. Because this feature does not alter the DNA of germ cells, it cannot be passed down the generations. As a result, alterations in an individual's non-reproductive tissue during their lifespan cannot be passed on to their progeny, and hence cannot direct evolution.

17. How does Archaeopteryx provide evidence for organic evolution?

Ans: Archeopteryx contains reptile-like characteristics, dinosaur-like characteristics, and bird-like characteristics such as wings. This demonstrates that birds and reptiles are closely linked. Reptiles may have evolved into birds.

18. What is divergent evolution? Explain with the help of an example.

Ans: Divergent evolution is the process of animals with distinct appearances evolving from common ancestors. This is also known as adaptive radiation, and it refers to the evolution of new forms in multiple directions from a common ancestor type. The evolution of wild cabbage is a current example of such a process. For more than 200 years, humans have cultivated wild cabbage as a food plant and used artificial selection to produce a variety of vegetables (such as cabbage, broccoli, cauliflower, kohlrabi, and kale). As a result, all of these distinct vegetable structures are descended from the same ancestor, which is wild cabbage.

19. What is the difference between reproductive and non-reproductive variations?

Ans: The difference between non-reproductive and reproductive variation is as given below:

20. Write similarities between Mendelian’s factors and genes.

Ans: Genes, like mendelian factors, contain information about phenotypes. They are the units of inheritance that transmit from one generation to the next without turning into children.

• Genes occur in the form of alleles of a gene situated on homologous chromosomes, identical to mendelian factors.

• During gamete development, alleles of a gene also segregate, and each gamete obtains just one amongst the two forms, identical to mendelian factors.

• One of the alternate versions of a gene is dominant over another that lowers its expression, similar to Mendelian factors.

• When genes are situated on distinct chromosomes or at a distance on the very same chromosome, they segregate and assort independently, similar to Mendelian factors.

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

Ans: Different individuals would have different sorts of advantages to adjust in a certain ecosystem depending on the nature of the variances. Variation allows individuals to create a variety of features that make creatures more bearable.

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

Ans: In a Mendel monohybrid cross between tall and dwarf pea plants, all progeny in the \[{{\text{F}}_{\text{1}}}\]  generation is tall, while \[75\] percent of pea plants in the \[{{\text{F}}_{2}}\] generation are tall but \[25%\] are dwarf. This demonstrates whether a characteristic is dominant or recessive.

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

Ans: When a round green seeded pea plant is crossed with a wrinkled yellow seeded pea plant in the \[{{\text{F}}_{\text{1}}}\] generation, all of the plants have round yellow seeds. However, two new features, round yellow and wrinkled green, develop in the \[{{\text{F}}_{2}}\] generation. This demonstrates that qualities are inherited separately.

24. A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits-blood group A or O- is dominant? Why or why not?

Ans: No, because the blood group is defined by a pair of genes, the information is insufficient. One came from the mother, while the other came from the father. In this situation, the youngster received the O blood group gene from both his mother and father.

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

Ans: A girl inheriting the X chromosome from her father will be a female, whereas a boy inheriting the Y chromosome will be a boy.

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

Ans: The following factors may contribute to the emergence of new species:

(a) In small breeding isolated populations, changes in gene frequency.

(b)Natural selection

(c) Changes in chromosome number.

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

Ans: No, because geographical barriers prevent breeding between sexually reproducing individuals in a community. Furthermore, asexually reproducing organisms pass on parental DNA to offspring, eliminating the possibility of speciation.

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

Ans: Yes, the two populations are separated due to geographical remoteness. The amount of gene flow between them will dwindle. The isolated population will breed with the local population, resulting in the isolated population being included in the new population.

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

Ans: Fossils are preserved evidence of living animals that are found closer to the earth's surface and are more recent in origin than fossils discovered in deeper layers. Fossils can also aid in the discovery of evolutionary relationships between creatures.

30. 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: No,1 because parents pass on two copies of qualities, one from the mother and the other from the father. We can't identify which is dominant and which is recessive unless we understand the nature of these two types of attributes. When both parents contribute a recessive gene, recessive features arise. We can only assume that both parents contribute a recessive gene based on this remark.

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

Ans: Analogous organs: These are organs that have similar functions but differ in structure and origin. For example, the wings of birds and insects.

Homologous organs: Organs with identical structure and origin, but with different functions. Frog, lizard, and bird forearms are examples.

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

Ans: Stanley L. Miller and Harold C. Urey provided testimony in 1953. They created an atmosphere above water that was expected to exist on early Earth. They kept it at a temperature slightly below \[100\] degrees Celsius and stimulated lightning by passing sparks through the combination of gases. They discovered that \[15%\] of the carbon had been transformed to simple carbon compounds, such as amino acids, which make up protein molecules, at the end of the week.

33. 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: Variations occur as a result of either DNA copying errors or sexual reproduction. Genetic heterogeneity in the population rises from generation to generation as a result of sexual reproduction. Because sexually reproducing organisms acquire half of their genes from each parent, this occurs. These differences are critical to the evolution process.

34. 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: No, various individuals have different kinds of advantages depending on the kind of variances. However, when the environment undergoes a radical shift, only those organisms in the population that have a beneficial variation in that population would be able to live in the new environment.

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

Ans: During sexual reproduction, both male and female parents contribute equally to the child. Each progeny trait is determined by a pair of alleles, and male and female gametes each have one allele. During fertilisation, each allele pair combines to determine phenotypes. As a result, child qualities are decided by equal genes from both male and female parents.

36. Is it true that when a new species emerges, the old species is eliminated and why?

Ans: No, it is not true that as a new species emerges, the old one dies off.

Because when a species changes, it only affects a portion or a few individuals of the population. If the newly created species is better in any way, it will have a better chance of surviving, but if the genetic mutation is harmful to the environment, it will perish. As a result, unmodified members of other species may survive and thrive in a changing environment.

37. Why are traits acquired during the lifetime of an individual not inherited?

Ans: Changes in nonreproductive tissue or somatic cells cannot be passed on to the DNA of germ cells, hence traits acquired during a person's lifetime are not inherited. As a result, the acquired trait will perish with the individual's death. As a result, it is non-heritable and cannot be passed on through the generations.

38. The gene type of green stemmed tomato plants are denoted as GG and that of purple stemmed tomato plants as GG when these two are crossed.

(i) What colour of the stem would you expect in \[~{{F}_{1}}\] progeny?

Ans: Green is the colour of the \[{{\text{F}}_{\text{1}}}\] progeny.

(ii) Give the percentage of purple stemmed plants if F is self-pollinated.

Ans: In the \[{{\text{F}}_{2}}\] generation, the percentage of purple stemmed plants was \[{\scriptscriptstyle 1\!/\!{ }_4}\] or \[25%\].

(iii) In what ratio would you find the gene types CG and Gg in the F progeny?

Ans: CG and Gg genotype ratio is \[1:2\].

37. What are the causes of variations in clones?

Ans: Below given are the causes of variation in clones:-

(i) Amid DNA copying inaccuracies

(ii) Acquired variation refers to the effect of the environment.

(iii) Mutations are unidirectionally inheritable, sudden stable alterations caused by changes in genetic make-up.

38. The only variation that confers an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?

Ans: We concur with the assertion. All of the variations do not have an equal chance of survival in their current environment. The nature of variation affects the probability of survival. Individuals benefit from a variety of advantages. In a heatwave, microorganisms that can endure heat will do better.

39. Study the given data and answer the questions following the data: Parental plants cross-fertilize and seeds collected \[~{{F}_{1}}\] First Generation offsprings  \[~{{F}_{2}}\]  of offsprings of self-pollination of \[~{{F}_{1}}\] Male parents always bare red flowers, Female parent always had white flowers, 330 seeds sown and observed, all 330 gave red flowers, out of 44 seeds 33 seeds gave plants with red flowers and 11 seeds gave plants with white flowers. 

(i) What is the term for this type of cross?

Ans: Monohybrid cross

(ii) What does the data of the column marked F indicate?

Ans: The red colour of the bloom takes precedence over the white flower.

(iii) Express the gene type of the (a) parents (b) \[~{{F}_{1}}\]  progeny and (c) \[~{{F}_{2}}\] progeny

Ans:

1. Parents – (RR) and (rr)

2. \[~{{F}_{1}}\] progeny – Rr

3.   \[~{{F}_{2}}\] progeny – RR, Rr and rr

40. Wild cabbage was converted into a 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?

Ans: Artificial selection is the term for this method. Because it is similar to natural selection, it plays a crucial role in biological evolution. It aids in the production of new species with beneficial features in a shorter amount of time.

41. How are variant genotypes produced?

Ans: Variant genotypes can be created using the following methods:

(i) Gene and chromosomal mutations.

(ii) Gene recombination is a process in which two or more genes combine to form offspring with combinations of traits.

(iii) Gene hybridization is a term used to describe the process of combining two or more genes.

42. Can geographical isolation lead to speciation? How?

Ans: Geographic isolation can, in fact, lead to speciation. As a result of genetic drift, members of two subgroups may not be able to interbreed due to geographical isolation. Natural selection works differently in these subgroups as well. Speciation occurs as a result of this.

Long Answer Questions (5 Marks)

1. Answer the following questions:

(i) Who provided the evidence of DNA as genetic material?

Ans: Mendel.

(ii) Why is DNA called polynucleotide?

Ans: DNA is made up of many different nucleotide units.

(iii) List three important features of the double-helical model of DNA.

Ans: Important features-

(a) In helical, both chains run antiparallel.

(b) Purine (A, G) and pyrimidine are two nitrogenous bases (T, C).

(c) A will always bind to T, and C will always bind to G.

2. Give the basic features of the mechanism of inheritance.

Ans: Characteristics of the inheritance mechanism-

(a) A pair of elements influence each character. It's possible that the factors are similar or dissimilar.

(b) When two distinct character factors are present in an organism, only one of them manifests itself, while the other remains silent.

(c) At the moment of gamete production, two elements of a character are separated, leaving only one factor for that character.

(d) Inheritance of two or more pairs of contrasting features in such a way that one pair is independent of the other pairs.

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

Ans: Dogs have a variety of coats. Select a pure-bred male and female dog with a black coat (hair) colour or a pure-bred male and female dog with a brown coat (hair) colour to find the dominant coat (hair) colour in dogs. Cross a homozygous male BB with a homozygous female BB, then look at the coat colour of the offspring (offspring). If all of the progeny are black, this indicates that in dogs, black will be the dominant coat colour, and if the progeny has brown coats, brown will be the dominant coat colour.

And, if we make the Punnett square of the \[~{{F}_{1}}\] generation, we obtain Bb, Bb, Bb, Bb, i.e., all progeny is black. As a result, the dominant colour is determined to be black.

Learn More About Heredity and Evolution

The important questions for class 10 science chapter heredity and evolution cover every topic that is given in the chapter.

Genes can be defined as the functional unit of heredity. According to solved important questions for Heredity and Evolution Class 10, every gene is responsible for controlling one or several characteristic features in different living organisms. Class 10 Science Heredity and Evolution important questions will help students to understand the topics easily.

Heredity can be defined as the process through which various features of an organism are passed from one generation to another. This process is carried out by genes. Another important topic from which many CBSE Class 10 Science Heredity and Evolution important questions are asked is Mendel’s work.

It should be noted that Gregor Johann Mendel, who is also known as the ‘Father of Genetics’, was an Austrian Monk who worked on pea plants to explore the concept of heredity. It was his work that laid the foundation for the modern field of genetics. According to Gregor Johann Mendel, there are three basic laws of inheritance. These laws are:

• The Law of Dominance

According to the law of dominance, a gene that has two contrasting alleles and the one gene always expresses itself is known as the dominant gene.

• The Law of Segregation

The law of segregation states that the traits get segregated completely during the formation of gametes without any mixing of alleles.

• The Law of Independent Assortment

According to the law of independent assortment, the traits can be segregated independently of different characters. This is done during the process of gamete formation.

Various concepts are related to this topic are as follows.

• Dominant Traits

Dominant traits are traits that can express themselves in an organism under every possible combination. In the experiment that was carried out by Mendel, the tall trait of pea plants was dominant over the short trait.

• Recessive Traits

Recessive traits are those traits that are not expressed in the presence of a dominant allele or dominant trait. Readers should remember that a recessive trait will not be expressed in the presence of a dominant allele.

• Monohybrid Cross

During the crossing over of genes of two organisms, if only one trait is considered, then that type of cross is known as a monohybrid cross. Also, the monohybrid ratio is the ratio of characters that arises out of the monohybrid cross at F2 generation. The monohybrid ratio is 3:1.

• Dihybrid Cross

If two characters are considered during a cross, then this type of cross is known as a dihybrid cross. The dihybrid ratio is the ratio of characters that arises out of a dihybrid cross at F2 generation. The dihybrid ratio is 9:3:3:1.

• Inheritance

It is the process of transfer of traits from one generation to another in biology.

• Sex Determination

Sex determination is the process in which the sex of an individual can be determined. This is done on the basis of the composition of genetic material. In various animals, the sex of an embryo is identified by considering different factors.

In human beings, the process of sex determination is carried out on the basis of the presence or absence of the Y chromosome. If XX chromosomes are present, then the child is a female and if XY chromosomes are present, then the child is a male.

• Traits

Traits are characteristic features of an organism. These features are visible in a physical form or in the physiological aspect of an organism.

The different types of characters or traits are:

• Acquired Characters: The characters that are acquired by an organism through experience or over the period of his or her lifetime are known as acquired characters. These characters might not be passed on to the next generation through genes.

• Inherited Characters: These characters are inherited by the offspring from the parent through genes. These characters might be expressed or not expressed depending on whether the trait is dominant or recessive. For example, skin colour, height, and eye colour.

• Genetic Variation

Genetic variations can be explained as the difference in the DNA sequences that are present among every organism. This leads to a varied and diverse gene pool. These differences also result in different physical characters and biochemical pathways.

• Natural Selection

Natural selection can be explained as the process by which a favorable trait is selected from a population of a species. This occurs due to the changing natural conditions, which further exert equal pressure on all living organisms.

This further leads to a scenario where the organisms or species that are better adapted to coping up with the exerted pressure survive. In other words, those organisms are selected by nature and cannot perish.

• Genetic Drift

Genetic drift is the process through which random fluctuations in gene variants occur due to various reasons. Genetic drift can also be defined as the change in the frequency of an existing allele in a small population. Due to genetic drift, a gene variant might completely disappear from a population. This also reduces genetic variation.

• Speciation

Speciation is the process through which new species are formed from existing species. This can be the result of various evolutionary forces like isolation of populations, genetic drift, and natural selection.

Students should also remember that Charles Darwin is known as the ‘Father of Evolution.’ He was an English biologist and naturalist. He wrote a theory of evolution, which was published in a book called Origin of Species in 1859.

Now, let’s move to the topic of evolution. Evolution can be best explained as a type of tangible change in the heritable characteristics of a population. This change occurs over several generations. For evolution, new species arise or the pre-existing species might become better at dealing with several environmental stressors.

There is also a theory on the origin of life. This theory was given by J. B. S. Haldane, who was a British scientist. According to this theory, life originated from lifeless and organic matter. This theory was proved to be correct by an experiment that was carried out by Urey and Miller. This theory is also known as the theory of abiogenesis. There is also much evidence that supports the theory of evolution. One of those evidences is fossils. Fossils can be defined as the preserved remains of ancient animals or plants that died millions of years ago. These fossils help scientists to understand the physiology and anatomy of organisms that existed millions of years ago on earth. This is the biggest evidence of how evolution worked and led to the formation of organisms that exist on earth today.

We know that humans belong to the primate family, and there are many studies that prove that humans have a very close genetic connection to chimps and other primate organisms. According to several theories on human evolution, it has been stated that some ancestors of human beings are Dryopithecurs, Ramapithecus, Homo erectus, Ramapithecus, neanderthalensis, and Cro-magnon man. Interestingly, the story of human evolution has also been traced back to Africa.

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