9. Heredity and Evolution SEBA/ASSEB Class 10 Science– Important Questions and Answers | Assam HSLC

SEBA/ASSEB Class 10 Science Chapter 9: Heredity and Evolution Important Questions and Answers | HSLC Assam

Chapter 9: Heredity and Evolution

Multiple Choose Question and Answer :

Question: A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because
(a) tallness is the dominant trait (b) shortness is the dominant trait
(c) tallness is the recessive trait (d) height of pea plant is not governed by gene ‘T’ or ‘t’
Answer : (a) Tallness is the dominant trait.

[ When a tall pea plant (TT) is crossed with a short pea plant (tt), all the offspring have the genotype Tt. Since tallness (T) is dominant over shortness (t), all the progeny are tall plants.]

Question: If a round, green seeded pea plant (RR yy) is crossed with wrinkled,yellow seeded pea plant, (rr YY) the seeds produced in F1 generation are
(a) round and yellow (b) round and green
(c) wrinkled and green (d) wrinkled and yellow
Answer : (a) Round and yellow.

[ In this cross, the round seed plant (RR yy) is crossed with the wrinkled yellow seed plant (rr YY). All offspring in the generation receive 'R' (round) and 'Y' (yellow) alleles, making them 'Rr Yy'. Since round (R) is dominant over wrinkled (r), and yellow (Y) is dominant over green (y), allseeds will appear round and yellow. ]

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

Answer: (b) Girl.

[ In humans, females have two X chromosomes (XX), and if a zygote inherits an X chromosome from the father, it will develop into a girl. ]

Question: The organs having different origin, similar appearance and similar function are : [SEBA 2016]

(a) Homologous (b) Analogous (c) Adjacent (d) Vestigeal

Answer: (b) Analogous.

[ Analogous organs have different evolutionary origins but similar appearances and functions.]

Question: Human originated in – [SEBA 2017]

(a) Asia (b) Africa (c) Australia (d) Europe

Answer: (b) Africa.

Question: Two pea plants one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds produce F1 progeny that have round, yellow (RrYy) seeds. When F1 plants are selfed, the F2 progeny will have new combination of characters. Choose the new combination from the following
(i) Round, yellow (ii) Round, green (iii) Wrinkled, yellow (iv) Wrinkled, green
(a) (i) and (ii) (b) (i) and (iv) (c) (ii) and (iii) (d) (i) and (iii)

Answer: (c) (ii) and (iii).

[ In the F1 generation, the plants have the genotype RrYy (round, yellow). When these F1 plants are selfed, the F2 generation shows four types of seeds:

Round, yellow (parental combination)

Round, green (new combination)

Wrinkled, yellow (new combination)

Wrinkled, green (parental combination)

The new combinations that were not present in the parents are round, green (ii) and wrinkled, yellow (iii). ]

Question: During the course of evolution, the process by which the characteristic features of the members of a species modify due to the influence of various factors and thus give rise to the organisms with new characteristic features is called : [SEBA2019]

(a) speciation (b) evolution (c) inheritance (d) variation

Answer: (b) evolution.

[ Evolution is the process by which the characteristic features of a population of organisms change over successive generations. ]

Question: If a cross is made between the plants having TT(tall) and tt (dwarf) genetic composition, which types of plants we will obtain in the next generation ? [SEBA 2020]

(a) Tall (TT) and Dwarf (tt) both (b) Only tall (c) Only dwarf (d) None of the above

Answer: (a) Tall (TT) and Dwarf (tt) both .

[ If a cross is made between plants with the genetic composition TT (tall) and tt (dwarf), the resulting plants in the next generation will be Tall (TT) and Dwarf (tt) both. ]

Question: When two pea plants , one with yellow and round seeds and the other with green and wrinkled seeds are crossed, the plants of the F2 generation will be obtained in the ratio of : [SEBA 2021]

(a) 1:1 (b) 3:1 (c) 9:3:3:1 (d) 1:1:1:1

Answer: (c) 9:3:3:1

[ When two pea plants, one with yellow and round seeds (genotype YYRR) and the other with green and wrinkled seeds , are crossed, the plants of the generation will exhibit a phenotypic ratio of (c) 9:3:3:1. ]

Question: An example of homologous organs are [SEBA 2023]

(a) Wings of a birds and a bat (b) Wings of a butterfly and a bat

Answer: (a) Wings of a bird and a bat.

[ Homologous organs are structures in different species that have a common evolutionary origin but may have different appearances and functions.]

Question: Which of the following chromosome sets will determine the male sex in a human infant ? [SEBA 2023]

(a) XX (b) XY (c) XO (d) YO

Answer: (b) XY.

[ In humans, sex determination is controlled by the presence of sex chromosomes. The typical sex chromosome combination for males is XY, and for females, it is XX. ]

Question: In peas, a pure tall plant (TT) is crossed with a short plant (tt). The ratio of pure tall plants to short plants in F2 is
(a) 1 : 3 (b) 3 : 1 (c) 1 : 1 (d) 2 : 1

Answer : (c) 1 : 1.

[ When a pure tall plant (TT) is crossed with a short plant (tt), the F1 generation produces all tall plants (Tt). When these F1 plants are self-pollinated, the F2 generation gives a genotypic ratio of 1 TT : 2 Tt : 1 tt. Here, TT is pure tall and tt is short. So, the ratio of pure tall plants (TT) to short plants (tt) is 1 : 1.]

Question: The example of homologous organ are [2025]

(a) potato and runners grass (b) our arm and a dog’s foreleg

Answer: (d) All of the above.

Question: In evolutionary terms, we have more in common with [2025]

(a) a Chinese schoolboy (b) a spider (c) a chimpanzee (d) a bacterium

Answer: (a) A Chinese schoolboy

Question: Our genetic footprints can be traced back to our [2025]

(a) Asian roots (b) African roots (c) European roots (d) American roots

Answer: (b) African roots.

Question: The wings of a bat and the wings of a birds are [2025]

(a) homologous organs (b) analogous organs (c) invertebrate (d) hormone

Answer: (b) analogous organs.

[ Analogous organs are structures that have different evolutionary origins but perform similar functions.]

Question: In evolutionary terms, which among the following has better body design [2025]

(a) Bacteria (b) Spider (c) Fish (d) Chimpanzee

Answer: (a) Bacteria .

Question : 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

Answer : (c) TtWW

[ The given information indicates a typical Mendelian dihybrid cross involving two traits: plant height (tall or short) and flower color (violet or white). The fact that almost half of the progeny were short suggests that the tall parent must be heterozygous for the trait of plant height. The resulting progeny would have a genotype of Tt (heterozygous for height) and WW (heterozygous for flower color).]

Very Short Question and Answer :

Question: What is a dominant character ? [1M 2019]

Answer: A dominant character is a trait that expresses itself in an organism even when only one copy of the corresponding allele is present.

Short Question and Answer :

Question: What are fossils? What do they tell us about the process of evolution?

Answer: Fossils are the preserved remains or impressions of dead plants and animals that lived in the past.

They provide evidence for the process of evolution by showing how organisms have changed over millions of years. By studying fossils found in different layers of rocks, we can understand the evolutionary relationships between organisms and learn about the history of life on Earth.

Question: If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier? [2M]

Answer: Trait B is likely to have arisen earlier. In asexually reproducing species, new traits appear due to mutations and spread only through reproduction. A trait present in 60% of the population has had more time to pass from parent to offspring. Hence, it probably originated earlier than trait A (10%).

Question: How does the creation of variations in a species promote survival? [2M]

Answer: The creation of variations helps a species to survive in changing environmental conditions. If climate, food availability, or diseases change, some individuals with useful variations can adjust better. They survive and reproduce, passing those traits to the next generation. Thus, variations increase the chances of survival of the species.

Question: How do Mendel’s experiments show that traits may be dominant or recessive? [2M]

Answer: Mendel crossed pure tall pea plants with pure short pea plants. In the generation, all plants were tall, showing that tallness is the dominant trait. When these plants were self-pollinated, the generation produced both tall and short plants in a 3:1 ratio. The reappearance of short plants proved that shortness is a recessive trait that remained hidden in the generation.

Question: 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? [2M]

Answer: No, this information alone is not enough to decide which trait is dominant. The daughter has blood group O, which means she received one O allele from each parent. The mother is O, so her genotype is OO. The father, though showing blood group A, must be AO. This shows A is dominant over O, but we already know that from genetics, not just from this single case.

Question: How is the sex of the child determined in human beings? [2M]

Answer: In human beings, the sex in a human child is determined by the father. The mother always contributes an X chromosome, while the father contributes either an X or a Y chromosome. If the child receives X from father, it is a girl (XX); if it receives Y from father, it is a boy (XY). Thus, the father's chromosome decides the sex of the child.

Question: What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor?

Answer: Homologous structures are organs that have the same basic structure and origin but perform different functions. For example, the forelimbs of humans, whales and bats have a similar basic bone structure but perform different functions.

Yes, homologous structures indicate that the organisms have evolved from a common ancestor.

Question: Give the pair of contrasting traits of the following characters in pea plant and mention which is dominant and recessive
(i) yellow seed (ii) round seed
Answer: The pair of contrasting traits for the given characters in the pea plant are:

Character	Dominant Trait	Recessive Trait
(i) Yellow seed	Yellow seed	Green seed
(ii) Round seed	Round seed	Wrinkled seed

Long Question and Answer :

Question: How do Mendel’s experiments show that traits are inherited independently?

Answer: Mendel's experiments show that traits are inherited independently through his work with dihybrid crosses. He crossed pea plants that differed in two traits, such as seed shape and seed colour. Surprisingly, the generation produced not only the expected combinations but also new combinations like round-green and wrinkled-yellow seeds. This proved that the two traits were inherited independently of each other, meaning the inheritance of one trait did not affect the inheritance of the other .

Question: Differentiate between inherited and acquired characters. Give one example for each type.
Answer: The difference between inherited and acquired characters are :

Inherited characters	Acquired characters
(i) These are traits passed from parents to offspring through genes.	(i) These are traits developed during an individual’s lifetime.
(ii) They are present since birth.	(ii) They are not present at birth.
(iii) They can be transferred to the next generation.	(iii) They cannot be transferred to the next generation
Example: Blood group in humans.	Example: Muscular body developed by exercise.

Question: Explain the relation between evolution and classification. [SEBA 2019]

Answer: Evolution and classification are closely related because classification helps us understand the evolutionary relationships among organisms. Organisms with more similarities are generally more closely related and share a more recent common ancestor. Classification is based on similarities and differences among organisms, which help us trace their evolutionary history.

Question: How may pairs of sex chromosomes are contained by the human beings ? Explain how is sex determined in a human child . [2019]

Answer: Human beings have one pair of sex chromosomes. Females have two X chromosomes (XX), whereas males have one X chromosome and one Y chromosome (XY).

The sex in a human child is determined by the father. The mother always contributes an X chromosome, while the father contributes either an X or a Y chromosome. If the child receives X from father, it is a girl (XX); if it receives Y from father, it is a boy (XY). Thus, the father's chromosome decides the sex of the child.

Question: What is a dominant character ? How did Mendel Prove through his experiments that the inherited characters are transmitted independently from one generation to the next ? [3M 2018]

Answer: A dominant character is a trait that gets expressed in an organism even when the two copies of the gene for that trait are not identical.

Mendel performed a dihybrid cross between pea plants with round, yellow seeds and wrinkled, green seeds. In the F₁ generation, all the plants produced round, yellow seeds. When these plants were self-pollinated, the F₂ generation showed four types of seeds in the ratio 9 : 3 : 3 : 1. The appearance of new combinations, such as round green and wrinkled yellow seeds, proved that different pairs of traits are inherited independently of each other.

Question: Define homologous organs and analogous organs. Can the wings of a bird and that of a bat be considered as homologous organs ?Justify your answer . [3M 2018]

Answer: Homologous organs: Organs which have the same basic structure (origin) but perform different functions are called homologous organs. Example: Forelimbs of humans, whales and bats.

Analogous organs: Organs which have different basic structure (origin) but perform similar functions are called analogous organs. Example: Wings of insects and birds.

No, the wings of a bird and a bat are not homologous organs; they are analogous organs. Both perform the same function, but differ in structure. Bird wings have feathers, while bat wings consist of skin folds supported by elongated fingers. Thus, they perform the same function but have different structural modifications for flight.

Question: What factors could lead to the rise of a new species ? Explain. [3M 2020]

Answer: The factors that could lead to the rise of a new species are geographical isolation, genetic drift, natural selection, and reproductive isolation. When a population gets separated by physical barriers, variations accumulate over generations. Genetic drift and natural selection act differently on separated groups. Eventually, they become so different that they cannot interbreed, leading to the formation of a new species.

Question: What do you understand by geographical isolation ? Will this be a major factor in the speciation of a self pollinating plant species ? Why or why not ? [3M 2020]

Answer: Geographical isolation occurs when populations of a species are separated by physical barriers, such as rivers, mountains or seas, which prevent them from interbreeding.

No, geographical isolation will not be a major factor in the speciation of a self-pollinating plant species because it can reproduce using its own pollen. Therefore, geographical isolation does not significantly affect its reproduction, unlike in cross-pollinating plant species.

Question: 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?

Answer: No, we cannot determine whether light eye colour is dominant or recessive from this information alone. The fact that children with light-coloured eyes are likely to have parents with light-coloured eyes only shows that the trait may be inherited from their parents. To determine whether it is dominant or recessive, we need more information about the inheritance pattern of eye colour across different generations.

Question: In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation.

Answer: In human beings, females have XX sex chromosomes, while males have XY sex chromosomes. The mother’s egg always carries an X chromosome, whereas the father’s sperm carries either an X or a Y chromosome with an equal probability. If an X-bearing sperm fertilises the egg, a female child (XX) is born and if a Y-bearing sperm fertilises the egg, a male child (XY) is born. Therefore, the probability of having either a male or a female child is 50% each .

Question: Explain the importance of fossils in deciding evolutionary relationships.

Answer: Fossils help us to study the evolutionary relationships between different organisms. They provide evidence of the organisms that lived in the past. By comparing fossils with present-day organisms, we can understand how organisms have evolved over time. Fossils found in deeper rock layers are generally older than those found in upper layers. Thus, fossils help us trace the evolutionary history of organisms and understand their relationships with one another.

Question: What evidence do we have for the origin of life from inanimate matter?

Answer: The experiment conducted by Stanley Miller and Harold Urey in 1953 provided evidence for the origin of life from inanimate matter. They created conditions similar to those believed to exist on the early Earth by using a mixture of gases such as methane, ammonia, hydrogen and water vapour. When electric sparks were passed through the mixture, amino acids were formed. This supported the idea that organic molecules necessary for life could have originated from non-living substances.

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9. Heredity and Evolution SEBA/ASSEB Class 10 Science– Important Questions and Answers | Assam HSLC

SEBA/ASSEB Class 10 Science Chapter 9: Heredity and Evolution Important Questions and Answers | HSLC Assam

Chapter 9: Heredity and Evolution

Multiple Choose Question and Answer :

Very Short Question and Answer :

Question: What is a dominant character ? [1M 2019]

Short Question and Answer :

Long Question and Answer :

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