CBSE Class 10 Biology Heredity Worksheet Set J

Question. 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.

Answer: b

Question. In evolutionary terms, we have more in common with
(a) a Chinese school-boy.
(b) a chimpanzee.
(c) a spider.
(d) a bacterium. 

Answer: a

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

Very Short Answer Type Questions :

Question. “Experience of an individual during its lifetime cannot be passed on its progeny and cannot direct evolution”. Justify this statement giving an example.
Answer : Since acquired characters are not inherited over generations. Change in non-reproductive tissues cannot be passed on to the DNA of the germ cells.

Question. Mendel observed a contrasting trait in relation to position of flowers. Mention the trait.
Answer : Axial flower position (dominant), terminal flower position (recessive).

Question. What is a gene?
Answer : It is a functional piece of DNA that is responsible for expression of a trait in the organisms.

Question. A violet pea plant [VV] was crossed with a white one[vv]. F1 generation was allowed to self pollinate and F₂ generation was also obtained, Answer the following questions:
a. What would be the phenotype of plants in F1 generation?
b. What would be the percentage of plants with white flowers in F2 generation?
c. What would be the ratio of vv: Vv in F2 generation.
Answer :
a. all violet flowers
b. 25%
c. 1 : 2.

Question. A tall pea plant was crossed with a dwarf one. F1 generation was allowed to self pollinate and F2 generation was also obtained. Answer the following questions:
a. What would be the phenotype of plants in F1 generation?
b. What would be the phenotypic ratio in F2 generation?
c. Give reason for your observation in F1 generation.
Answer :
a. all tall
b. 3:1
c. Reason: The tall trait of pea plant is dominant trait over short trait, a recessive trait.

Question. What is F₂ generation?
Answer : The generation produced by the offsprings of F₁ generation i.e., first generation as parent is called F₂ or second generation.

Question. In an area A, the leaf materials available to beetles were very less. What are the two consequences seen in case of beetles?
Answer :
a. Due to poor nutrition, the average weight of adult beetles decreases.
b. The number of beetles (population) decreases due to starvation.

Question. What is micro evolution? Does it explain speciation?
Answer :
a. In micro evolution, the changes are small which occurs in lower categories and change the common characteristics of a particular species.
b. It does not properly explain speciation.

Question. How are characters or traits controlled?
Answer : Characters or traits of an organism are controlled by the genes /DNA.

Question. If YYRR is round yellow, what do the following represent?
yyrr yyRR
Answer :
yyrr - Wrinkled, green seeds
yyRR — Round, green seeds

Question. How are fossil studies important in working out evolutionary relationships. How would the age of fossils be determined?
Answer : Fossils are impressions of the body/ body parts or the remains of organisms living in the past, which got preserved in sediments of earth. Any remains of an organism that has been preserved in the earth’s crust.
Study of fossils helps in working out evolutionary relationships. Age of fossils can be determined by time dating using isotopes of carbon (carbon dating).

Question. What is a gene?
Answer: Gene is the unit of inheritance. Gene is the part of a chromosome which controls the appearance of a set of hereditary characteristics.

Question. What is the importance of DNA copying in reproduction? Why is variation beneficial to the species but not necessary for the individual? Explain.
Answer : DNA copying is essential part of reproduction because it ensures that same blueprint of the body design is maintained. Variation for the species is beneficial for adaptation and better survival. It may result in new species formation.

Question. Give the respective scientific terms used for studying:
a. the mechanism by which variations are created and inherited, and
b. the development of new type of organisms from the existing ones.
Answer :
a. Heredity
b. Species

Question. How did Mendel explain that it is possible that a trait is inherited but not expressed in an organism?
Answer : Yes, it is possible.
Example - When pure tall pea plants are crossed with pure dwarf pea plants, only tall pea plants are obtained in F1 generation.
On selfing tall plants of F₁ both tall and dwarf plants are obtained in F₂ generation in the ratio 3:1.
Reappearance of the dwarf character, a recessive trait in F₂ generation shows that the dwarf trait/ character was present in individuals of F₁ but it did not express (due to the present of tallness, a dominant trait / character)

Short Answer Type Questions :

Question. (a) “Each organism has its own identity”. Explain.
(b) What is speciation?
Answer :
a. (i) The DNA of each organism is different from others.
(ii) The DNA of each organism is specific within the same species with specific number of chromosomes/genes.
b. Emergence of new species from pre-existing forms through natural selection/artificial selection/ genetic drift/evolution, etc.

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

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

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

Question. Fore limbs of amphibians, reptiles, birds and mammals show similarity in their bones but Wings of bat and bird don’t. What conclusion can be drawn from such observation regarding their ancestry?
Answer : The organs which have similar basic structure and mode of origin but perform different functions in different animals are called homologous organs, e.g., forelimbs of amphibians, reptiles, birds and mammals.
Homologous organs give an evidence of common ancestory and evolutionary relationship between apparently different species.
Analogous organ are the organs in different organisms which have different basic structure but have similarity in shape and function, e.g., wings of bat and bird. These organs do not provide an evidence in support with common ancestory.

Question. What are fossils? What do they tell about the process of evolution?
Answer : The fossils can be defined as remains or impressions of the hard parts of the past individuals in the strata of the earth. Fossils helps in working out evolutionary relationships. Fossils provide one of the most acceptable evidences in support of evolution, because we can study the evolutionary past of individuals in the form of their fossils. By studying fossils occurring in different strata of rocks, geologists are able to reconstruct the time course of evolutionary events.
Age of fossils can also be found by time dating using isotopes of carbon (carbon dating).

Question. 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?
Answer : No, depending on the nature of variations different individuals have different kinds of advantages. However, when a drastic change occurs in environment only those organism in the population will survive which have an advantageous variation in that population to survive in changed environment.

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?
Answer : Trait B is likely to have arisen earlier as it occurs in more number.

Question. a. Why traits such as intelligence and knowledge cannot be passed on to the next generation?
b. How can we say that birds are closely related to reptiles and have evolved from them?
Answer :
a. Traits such as intelligence and knowledge are not heritable traits, which do not bring upon any changes in the DNA of the germ cells and, therefore, cannot be passed on to the progeny.
b. This can be said because traits such as feathers were first seen in reptiles like Dinosaurs, which performed the function of providing insulation to them in cold weather although they could not fly using the feathers but later birds adapted the feathers for flight. This means that birds are very closely related to reptiles, as dinosaurs were reptiles.

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 say that the traits is recessive or dominant unless we know the nature of the two variants of a trait.

Question. A group of grasshoppers — some green and some brown lived in a grassland having dry bushes and dry grass.
a. Which one would normally be picked up by predatory birds and why?
b. Population of which grasshopper will increase?
c. Name this phenomenon.
Answer :
a. Green grass hopper, because they stand out, against brown background of dry bushes.
b. Brown
c. Natural selection.

Question. a. State any two factors that could lead to the rise of a new species.
b. How do analogous organs provide evidence in favour of evolution?
Answer :
a. Natural Selection, Genetic drift, Mutations, Variations.
b. The organs which are similar in function but are structurally different suggest that although these two organs may look alike superficially giving an idea of common ancestory but the different in structure and origin suggests that organisms having these organs have a distant ancestor but such organs have developed during the course of evolution as an adaptation to similar mode of life.

Question. (a) Differentiate between:
1. Homologous organs and Analogous organs.
2. Pollination and Fertilization
(b) What do fossils tell us about the process of evolution?
Answer :
a. (i) Organs in different organisms with same origin with different function/ different origin, same function.
(ii) Transfer of pollen from the stamen to the pistil of the flower/fusion of male and female gametes.
b. Help in establishing links and act as evidence of evolution.

Question. (a) Explain why the wing of a bat and the wing of bird are considered to be analogous organs.
(b) List two factors that lead to the formation of a new species.
Answer :
a. Design, structure and components are different.
Origins are not common.
b. Genetic drift and natural selection.

Question. a. Name the scientist who gave the idea of evolution of species by natural selection.
b. What conclusion did Mendel draw from his experiments about traits?
c. Arrange the following according to evolution.
Cockroach, Mango tree, Gorilla, Fish
Answer :
a. Darwin
b. Traits are inherited independently.
c. Mango tree — Cockroach - Fish — Gorilla.

Question. a. What are fossils?
b. Explain the importance of fossils in evolutionary relationship.
Answer :
a. Impressions of the body parts of the organisms and preserved traces of the living organisms are called fossils.
b. The presence of fossilized remains of the organism is the evidence of existence of organisms million years ago which have now become extinct. Fossil also help in determining the connecting links between various groups and their origin from their primitive ones.

Question. Explain the importance of fossils in deciding evolutionary relationships.
Answer : Fossils help us to know the following:
(a) Fossils help to trace the racial history of organisms.
(b) They help to measure the geological time.
(c) Older fossils lie at the depth and young fossils are at the upper surface of the earth. Complex organisms are present at top and simple organisms are present at the bottom.
(d) Fossil like—Archaeopteryx-show the link between two different types of species.

Question. The human beings who look so different from each other in terms of colour, size and looks are said to belong to the same species. Why? 
Answer: Human beings are said to belong to the same species because of the following reasons:
1. DNA studies.
2. Number of chromosome is same,
3. All have a common ancestor.
4. They interbreed among themselves to produce fertile young ones of their own kind.

Question. 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?
Answer : Variations are seen more in sexual reproduction than asexual reproduction because variations occur due to change in DNA coding and due to sexual reproduction in which two genes from two different sexes i.e., male and female genes crossing over takes place and hence cause the variation.

LONG ANSWER TYPE QUESTIONS 

Question. Explain the analogous organs and homologous orgAnswer : Identify the analogous and homologous organ amongst the following: Wings of an insect, wings of a bat, forelimbs of frog, forelimbs of human. 
Answer : Analogous organs are those organs that have same function but have different structural design and origin. E.g., wings of birds and insects. Homologous organs are those organs in different plants or animals which have the same basic structural design and organ but have different appearance and functions. Analogous—Wings of an insect, wings of a bat Homologous–Forelimbs of frog, forelimbs of human and wings of bat.

Question. Green and red coloured seeds are recessive and dominant trait respectively. Out of F1 and F2, in which generation will the green seed appear, if both parents are not hybrid.
Answer : F2 generation.

Question. Dead remains of two species A and B were buried. Later only A’s body was found to be a fossil but not B’s given reason.
Answer : B’s body did not have hard tissues, like bones.

Question. A group of class X students prepared a street play to educate masses on gender disparity to stop sex determination of girl child and abort it. (a) In human being, what is the chance of giving birth to a girl child? (b) Who is responsible for the birth of a female child and why? (c) What value is depicted among the group members of class X?
Answer : (a) The chance of giving birth to a girl child is 50%. (b) Male (father) is responsible for the birth of a female child as only the male individual is a carrier both of X and Y chromosomes which will determine the sex of the foetus. (c) The group members show team work, collaborative leadership, participating citizenship etc.

Question. Define ‘evolution’. State Darwin’s theory of evolution.
Answer : Evolution is a change in the genetic composition of a population. Darwin’s theory

1. The size of population remains the same, constant despite the fact that more offsprings are produced than needed.
2. Variations provide adaptations.
3. The best adapted organism survive in the changing environment (survival of the fittest).
4. Nature selects the best organisms with better adaptations and after many generations new species are formed (natural selection).

Question. What are various evidences in factors of evolution?
Answer : Evidences are:
(a) Homologous organs: Organs which have same structure but different function. E.g., wings of a bat, hands of man and limbs of monkey.
(b) Analogous organ. Organs which perform similar function but are structurally different are called analogous organ. E.g., wings of bat, insects, birds.
(c) Vestigial organs: These organs are those which appear in an organism but are functionless e.g., vermiform appendix, nictitating membrane in eye is present in human beings but has no function.
(d) Embryological evidence: The study of embryos of vertebrates shows that all of them have same origin as their structure at initial stage is same. Embryo of frog, fish, man looks alike. (e) Fossils as evidence: Archaeopteryx fossils shows a link between bird and reptiles as this fossil has some feature of bird and some of reptile.

Question. Species A shares ten characteristics with species B, species C share fifteen characteristics with D which of the two pairs share closer relation.
Answer : C and D.

Question. With the help of an example explain how “Genes control characteristics or traits’’?
Answer : Tallness of a plant is a characteristic. Height of a plant depend on the amount of hormone secreted by the plant responsible for its tallness. The gene has the coding for the amount of hormone released. If the gene for that hormone has an alteration and makes its efficiency low, then the plant will be short. Thus, this shows that traits are controlled by gene.

Question. Why are traits acquired during the life-time of an individual not inherited?
Answer. This happens because an acquired trait involves change in non-reproductive tissues (somatic cells) which cannot be passed on to germ cells or the progeny. Therefore, these traits cannot be inherited.