CBSE Class 10 Biology Heredity And Evolution Worksheet Set B

Objective Questions

Question. If the fossil of an organism is found in the deeper layers of earth, then we can predict that :
(a) the extinction of organism has occurred recently
(b) the extinction of organism has occurred thousands of years ago
(c) the fossil position in the layers of earth is not related to its time of extinction
(d) time of extinction cannot be determined.
Answer : B

Question. Which of the following statement is incorrect with respect to variations ?
(a) all variations in a species have equal chance of survival
(b) change in genetic composition results in variations
(c) selection of variations by environmental factors forms the basis of evolutionary process
(d) variations are the minimum in asexual reproduction
Answer : A

Question. One of the following traits of the parents cannot be passed on to their future generations. This trait is :
(a) cleft chin
(b) pointed chin
(c) scarred chin
(d) broad chin
Answer : C

Question. Some dinosaurs had feathers although they could not fly but birds have feathers that help them to fly. In the context of evolution, this means that :
(a) reptiles have evolved from birds
(b) there is no evolutionary connection between reptiles and birds
(c) feathers are homologous structures in both the organisms
(d) birds have evolved from reptiles
Answer : D

Question. Select the incorrect statement from the following :
(a) frequency of certain genes in a population changes over several generations resulting in evolution
(b) reduction in the weight of an organism due to starvation is genetically controlled
(c) low weight parents can have heavy weight progeny
(d) traits which are not inherited over generations do not cause evolution.
Answer : B

Question. New species may be formed if :
(i) DNA undergoes significant changes in germ cells
(ii) chromosome number changes in the gamete
(iii) there is no change in the genetic material
(iv) mating does not take place
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii), (iii) and (iv)
(d) (i), (ii) and (iii)
Answer : A

Question. According to the evolutionary theory, formation of a new species is generally due to :
(a) sudden creation by nature
(b) accumulation of variations over several generations
(c) clones formed during asexual reproduction
(d) movement of individuals from one habitat to another.
Answer : B

Question. The presence of which of the following types of organs in two animals indicates that they are not derived from a common ancestor ?
(a) homologous organs
(b) excretory organs
(c) analogous organs
(d) reproductive organs
Answer : C

Question. The presence of which of the following types of organs in two organisms indicates that they are derived from the same ancestor ?
(a) analogous organs
(b) respiratory organs
(c) digestive organs
(d) homologous organs
Answer : D

Question. One of the following has not been produced from wild cabbage by the process of artificial selection. This one is :
(a) kohlrabi
(b) cabbage
(c) spinach
(d) kale
Answer : C

Question. The fossil trilobite was originally :
(a) an arthropod
(b) an invertebrate
(c) a reptile
(d) an ave
Answer : A

Question. One pair of organs in the following animals are not homologous. This is :
(a) forelimbs in humans and lizard
(b) forelimbs in lizard and frog
(c) wings in butterfly and bat
(d) wings in bat and bird
Answer : C

Question. Amongst which of the following animals, sex of the offsprings not genetically determined?
(a) Humans
(b) Snails
(c) Birds
(d) Dogs
Answer : B

Question. The inheritance of color trait in flower is as shown. R and r denotes two different genes for color. Which law of Mendel can be explained using the image?
(a) Law of segregation and law of independent assortment
(b) Only law of segregation
(c) Law of segregation and law of dominance
(d) Only law of independent assortment.
Answer : C

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 : B

Question. The maleness of a child is determined by ___.
(a) X chromosome in zygote
(b) Y chromosome in zygote
(c) The cytoplasm of germ cells which determines the sex
(d) Sex is determined by chance
Answer : B

Question. The wings of a housefly and the wings of a sparrow are an example of :
(a) analogous organs
(b) vestigial organs
(c) respiratory organs
(d) homologous organs 
Answer : A

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  

Question : A Mendelian experiment consisted of breeding pea plants bearing violet flowers with pea plants bearing white flowers. What will be the result in F1 progeny?
a. Heterozygous plant with violet flowers.
b. Homozygous plant with violet flowers
c. Heterozygous plant with white flowers
d. Homozygous plant with white flowers
Answer :  A 

Question : Who is called father of genetics? 

Answer : Father of genetics: Gregor Mendel. 

 

Question : Which other term can be used for natural selection? 

Answer :  Better adaptability can be used for natural selection

 

Question : Mendel took tall pea plants and short pea plants and produced F₁ progeny through cross-fertilisation. What did Mendel observe in the F1 progeny? 
Answer : When Mendel cross fertilized tall pea plants and short pea plants, he observed that all plants in the F₁ progeny were tall.

Question : Mendel crossed the round and green seeded pea plants with the wrinkled and yellow seeded pea plants. Give the phenotypic ratio of F₂ generation.
Answer :  The phenotypic ratio of F₂ generation when round and green seeded pea plants were crossed with the wrinkled and yellow seeded pea plants is: Round Yellow : Round Green : Wrinkled Yellow : wrinkled Green = 9 : 3 : 3 : 1.

Question : Are there any organisms where sex of the newborn is not genetically determined? Give example.
Answer :  Yes, there are organisms in which sex of the newborn is not genetically determined. An example is snail, which can change its sex.

Question : Give reason: Phenotypic and genotypic ratios are different.
Answer :  The phenotypic ratio in F₂ generation when F₁ tall plants are crossed with each other is Tall : Dwarf = 3 : 1 Whereas, the genotype ratio will be TT : Tt : tt = 1 : 2 : 1 . Here, both TT and Tt refer to tall plants, they have the same phenotype but different genotype.

Question : Define heredity.
Answer : Heredity deals with the inheritance of characters from one generation to the next.

Question : How does the creation of variations in a species promote survival?
Answer : Variations increases the adaptability of an organism to its changing environmental conditions.

Question : Name two human traits that show variations.
Answer : Colours of eyes and shape of external ears.

Question : Which of the two sperm or egg–decides the sex of the child?
Answer : The sperm decides the sex of the child.

Question : What is microevolutions?
Answer : Microevolutions is the evolution that takes place on a relatively small scale at the population level and can change the common characteristics of particular species.

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

Question : What is evolution?
Answer : Evolution is the sequence of gradual changes which take place in living organisms over millions of years to give rise to new species.

Question : What are fossils?
Answer : Fossils are preserved traces or remains of living organisms of geological past.

Question : Name the scientist who put forth the theory of natural selection.
Answer : Charles Darwin.

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, because it exist in larger fraction of the population.

Question : Give an example of characteristics being used to determine how close two species are in evolutionary terms.
Answer : Homologous characteristics are being used to determine how close two species are in evolutionary terms. For example, the forelimbs of human and bird have similar basic structure though they are modified to perform different functions in them. The basic structure or anatomical similarity points to the existence of a common ancestor from these have evolved.

Question : What are fossils? What do they tell us about the process of evolution?
Answer : Fossils are the remains of organisms that once existed on earth. They represent the ancestors of plants and animals that are alive today. They provide evidences of evolution by revealing the characteristics of the past organism and the changes that have occurred in these organisms to give rise to the present organisms

Question : What are the different ways in which individuals with a particular trait may increase in a population?
Answer : (a) Natural selection
(b) Genetic drift
(c) Geographical isolation.

Question : Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?
Answer : No, because they have different basic designs though they are used for the same purpose of flying.
They are analogous organs.

Question : Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?
Answer : As the number of surviving tigers is small, the sets of genes will be limited. This results in limited variation in characters during sexual reproduction, thereby causing danger for their survival in changing conditions.

Question : Will geographical isolation be a major factor in the speciation of a self-pollinating plant species? Why or why not?
Answer : In a self-pollinating plant species, geographical isolation cannot be a major factor in speciation. This is because in self-pollinating plants, pollination is occurring in the same plant. So a natural barrier cannot cause hindrance.

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.

Question : In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better’ body design? Why or why not?
Answer : No, we can't say there's a better body design as these organisms evolved to survive in the environment according to their needs. If a chimpanzee has strong limbs capable of multiple actions, the bacteria can survive in extreme conditions where it is impossible for other organisms. Therefore there is no better design of the body.

Question : Will geographical isolation be a major factor in the speciation of a self-pollinating plant species. Why or why not?
Answer : No, geographical isolation cannot be a major factor in the speciation of self-pollinating plant species.
It is because such plants do not depend on other plants for its further reproduction to be carried out.

Question : How do Mendel’s experiments show that traits may be dominant or recessive?
Answer : Mendel took pea plants of two different characters i.e., tall plants and short plants. The first generation of F₁ progeny formed were all tall. This shows that traits may be either dominant or recessive, there is no way in between traits obtained.

Question : What are fossils? What do they tell us about the process of evolution?
Answer : Preserved traces of living or dead organisms on solid hard surface is called fossil. 
Fossils help us to know the evolution.If a fossil is found closer to the surface of earth, then it is more recent in origin than the fossils we find in deeper layers. Fossils, like Archaeopteryx, help us to find evolutionary relation between organisms.

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?
Answer : The given information is not enough to tell us which of the traits-blood group A or O – is dominant. In blood heredity, bood type A is always dominant and blood type O is always recessive. Here, father’s Blood group can be IAIA (homozygous) or IAi (heterozygous) genotypically, whereas that of mother is ii. For daughter to be born with blood group O, she must receive i type gene one each from father and mother.
For this father must have heterozygous IAi blood group and mother must have homozygous blood group ii.

Question : What are the different ways in which individuals with a particular trait may increase in a population?
Answer : The ways in which individual with a particular trait may be increased in a population are:
(a) If it can survive in the adverse condition i.e., naturally selected.
(b) It can also be increased by the inheritance.

 

Short Answer

Question : Show by simple sketches how and what type of beetles survive due to variations in a population. 

Answer :  Variations in a population of beetles

 

Question : Genes controls traits '. Explain this statement with an example. 10.What is DNA copying? State its importance
Answer : Genes controls traits by synthesizing the specific enzyme. Plant height depends on the amount of a particular plant hormone. The amount of plant hormone made will depends on enzyme. If enzyme work efficiently the plant will be tall. if the gene for that enzyme has an alteration that makes enzyme less efficient, the amount of hormone will be less and plant will be short.

Question : How do Mendel’s experiments show that traits are inherited independently?
Answer : Mendel performed an experiments in which he took a tall plant with round seeds and a short plant with wrinkled-seeds. In F1, They were all tall and had round seeds. Tallness and round seeds were thus dominant traits. When, he used these F1 progeny to generate F2 progeny by self-pollination, he found that some F2 progeny were tall plants with round seeds, and some were short plants with wrinkled seeds. At the same time there tall plants, but had wrinkled seeds, while others were short, but had round seeds. Thus,Mendel’s experiments show that the tall/short trait and the round seed/wrinkled seed trait are independently inherited.

Question : The chromosome number of the sexually reproducing parents and their offspring issame."" Justify the statement.
Answer : In sexually reproducing organisms, male and female gametes / reproductive cells with only half the number of chromosomes (as in the parent cell) are produced. during fertilization, when male and female gametes fuse to give to a zygote, original number of chromosomes are restored.

Question : What is variation? How is variation created in a population? What is the importance of variation for survival of a species?
Answer : The differences in the traits shown by the individuals of a species and also by the offsprings (siblings) of the same parents are referred to as variation. New variation may arise during the
process of DNA copying that already has variations accumulated from previous generations. Species having suitable variations have more chance of survival if there is change in environmental conditions.

Question : A green stemmed rose plant denoted by GG and a brown stemmed rose plant denoted by gg are allowed to undergo a cross with each other.
(a) List your observations regarding:
(i) Colour of stem in their F1 progeny
(ii) Percentage of brown stemmed plants in F2 progeny if F1 plants are self pollinated.
(iii) Ratio of GG and Gg in the F2 progeny.
(b) Based on the finding of this cross, what conclusion can be drawn?
Answer : (a) (i) Colour of the stem in F1 progeny: All green
(ii) Percentage of brown stem: 25 %
(iii) GG: Gg is 1: 2
Parent: GG X gg
Gametes: G g
F1: Gg Green stem
Parents : Gg X Gg
Gametes: G g G g
F2: GG Gg Gg gg
(b) Based on the above cross, it can be concluded that green colour is dominant and get expressed in F1 generation. The brown stem, which does not get express itself in the F1 generation, is the recessive character.

Question : With the help of a flow chart explain in brief how the sex of a newborn is genetically determined in human beings. Which of the two parents, the mother or the father, is responsible for determination of sex of a child?
Answer : In human beings, the sex of the individual is genetically determined. Sex chromosome of
male is XY and of female is XX. Sex of a child depends on what happens at fertilisation. The woman produces eggs having X chromosome while the man produces 50% sperms having X chromosome and 50% sperms having Y chromosome. Man therefore, actually determines the sex of the new born baby

Question : How is the equal genetic contribution of male and female parents ensured in the progeny? Explain
Answer : Equal genetic contribution of male and female parents in the progeny is ensured by the equal inheritance of chromosome from each parent.Human possesses 23 pairs of chromosomes, of which 22 pairs are autosomes and 1 pair is the sex chromosomes. The two sex chromosomes in human are X and Y. Females have 2 X chromosomes and males have a X and Y chromosome. During the process of fertilization, a haploid sperm fuses with a haploid ovum to produce a diploid zygote. Zygote receives equal amount of genetic material from each parent and thus, retains the diploid nature on fertilization.

Question : Define the following terms.
a. Heredity , b. Gene , c. Alleles
Answer : Heredity – Transmission of characters from one generation to another or from parents to offspring.
Gene – It is the basic unit of inheritance. It consists of a sequence of DNA, which is the genetic material. Genes can mutate and can take two or more alternative forms.
Alleles – The alternative forms of genes. They affect the same characteristics or traits in alternate forms. They are located on the same place of the

Question : How do Mendel’s experiments show that traits may be dominant or recessive?
Answer : Mendel selected true breeding tall (TT) and dwarf (tt) pea plants.When a tall pea plant is crossed with a short (dwarf) pea plant, all the F1 hybrids are tall. (i.e., in this case, the gene causing tallness is dominant while the gene causing dwarfness is recessive.).The trait expressing itself in the hybrid is the dominant one.
(Mendel’s first law of inheritance states that when a pair of contrasting factors is brought in a hybrid, one factor inhibits the appearance of the other. The one which inhibits is the dominant one and which is inhibited is recessive.)

Question : How do Mendel’s experiments show that traits may be dominant or recessive?
Answer : Mendel selected true breeding tall (TT) and dwarf (tt) pea plants. Then, he crossed these two plants.
The seeds formed after fertilization were grown and these plants that were formed represent the first filial or F1 generation. All the F1 plants obtained were tall.
Then, Mendel self-pollinated the F1 plants and observed that all plants obtained in the F2 generation were not tall. Instead, one-fourth of the F2 plants were short.
From this experiment, Mendel concluded that the F1 tall plants were not true breeding. They were carrying traits of both short height and tall height. They appeared tall only because the tall trait is dominant over the dwarf trait.

Question : a) Why did Mendel choose garden pea for his experiments? Write two reasons.
b) ‘Different species use different strategies to determine sex of a newborn individual. It can be environmental cues or genetically determined.’ Explain the statement by giving example for each strategy.
Answer : (a) Reasons:
(i) Pea plant is small and easy to grow.
(ii) A large number of true breeding varieties of pea plant are available.
(iii) Both self and cross-pollination can be made possible. Because this plant has a short life cycle, the results may be gathered and evaluated more quickly.
(iv) The garden pea possesses a number of features that are diametrically opposed to one another.
b) Environmental Cue: (i) In some animals, the temperature at which fertilised eggs are kept determines whether the developing animal in egg is male or female.
(ii) In some animals like snail, individual can change sex.
Genetical Cue: A child who inherits an X-chromosome from her father will be a girl and one who inherits a Y- chromosome from the father will be a boy.

Question : If we cross pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plants of F1 generation. If we now self- cross the pea plant of F1 generation, then we obtain pea plants of F2 generation.
(a) What do the plants of F2 generation look like? (b) State the ratio of tall plants to dwarf plants in F2 generation. (c) State the type of plants not found in F2 generation but appeared in F2 generation, mentioning the reason for the same.
(d) State Mendel's laws of inheritance.
Answer : a) All plants of F1 generation will be tall plants.
(b) 3:1
(c) Dwarf trait is recessive trait which was not expressed in the F1 generation, the recessive trait gets expressed in the F2 generation after self pollination.
(d) Laws of Mendel
• Law of Dominance says that a gene has two contrasting alleles and one always expresses itself in the organism.
• Law of Segregation says that traits get segregated completely during the formation of gametes without any mixing of alleles.
• Law of Independent Assortment says that the traits can segregate independently of different characters during gamete formation 

Question : Name the following: 

i) Who proposed the theory of inheritance of acquired characters?

ii) Who first suggested organism never originate spontaneously from non-living?

iii) Who wrote the book "Origin of Species"?

Answer : i) Lamarck

ii) Louis Pasteur

iii) Charles Darwin

 

Question : How are the areas of study − evolution and classification − interlinked?
Answer : Classification involves grouping of organism into a formal system based on similarities in internal and external structure or evolutionary history.Two species are more closely related if they have more characteristics in common. And if two species are more closely related, then it means they have a more recent ancestor.

 

Question : How has the method of 'artificial selection' by humans helped in the evolution of different vegetables? 

Answer :  A wild variety of a plant species may exhibit different variations. In due course of time, humans had selected some of these variants and had grown them for generations and that they had become totally different species. For example, variants in wild cabbage were selected on the basis of certain features
i. Short distances between leaves, led to the formation of green leaf buds-the common cabbage.

ii. Arrested flower development has bred broccoli.

iii. The variant with sterile flowers has made the cauliflower.

iv. Variant with swollen leaf parts-kohlrabi.

v. Variant with larger leaves-kale. 

Question : Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?
Answer :  Geographical isolation prevents gene flow between populations of a species whereas asexual reproduction generally involves only one individual. In an asexually reproducing organism, variations can occur only when the copying of DNA is not accurate. Therefore, geographical isolation cannot prevent the formation of new species in an asexually reproducing organism.

Question : 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?
Answer : A species is a group of organisms that are capable of interbreeding to produce a fertile offspring. Skin colour, looks, and size are all variety of features present in human beings. These features are generally environmentally controlled. Various human races are formed based on these features. However, there is no biological basis to this concept of races. Therefore, all human beings are a single species as humans of different colour, size, and looks are capable of reproduction and can produce a fertile offspring.

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 : In species, variations that offer survival advantages are naturally selected. Individuals adjust to their environments with the help of these selected variations and consequently these variations are passed on to their progeny. Evolution of organisms occurs as a result of this natural selection.
However, there can be some other variations, which do not offer any survival advantage and arise only accidentally. Such variations in small populations can change the frequency of some genes even if they are not important for survival.
This accidental change in the frequency of genes in small populations is referred to as genetic drift.
Thus, genetic drift provides diversity (variations) without any survival advantage.

Question : A group of grass hoppers - some green and some brown-lived in 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 grasshoppers would be normally picked up by predatory birds because they can be easily seen in dry bushes and grasses as compared to brown grasshoppers.
(B) As brown grasshoppers would be eaten less, their population will increase.
(C) This phenomenon is called ‘Natural Selection’. It is based on the ‘Theory of Evolution’ proposed by Charles Darwin

Question : How can we trace evolutionary relationships?
Answer : Evolutionary relationships can be traced by studying fossils, by studying homologous and analogous organs, by comparing the embryos of different animals and by comparing the DNA’s of different species.

Question : Why evolution should not be equated with progress?
Answer : Evolution cannot be equated with progress because it seems to have just given rise to more complex body designs. For example bacteria still flourish in spite of a very simple body design while dinosaurs did not survive in spite of complex design. Thus evolution is simply the generation of diversity and shaping of diversity by environmental selection.

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

Question : What are homologous organs? Explain with an example.
Answer : Homologous organs are those organs in different plants or animals which have the same basic structural design and origin but may have different functions.
Example., hand of human and fore-limb of frog.

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

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

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

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

Question : What is classification?
Answer : It is the arrangement of organism into series of groups based on the similarity of characters on physiology, anatomy, morphology and other relationships.

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

More Important Questions For How Do Organisms Reproduce

Very Short Answer Questions

Question. “Each organism has its own identity” Explain.
Answer : (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 to chromosomes genes.

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

Question. What is the genetic constitution of human sperm?
Answer :The genetic constitution of sperm is 22+ X chromosome or 22 + Y chromosome.

Question. What is genetics?
Answer : Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.

Question. What is the probability that a human progeny wiil be a boy?
Answer : 50% probability

Short Answer

Question. List two differences in tabular form between dominant trait and recessive traits.
Answer : Differences in tabular form between dominant trait and recessive traits.
Dominant trait                                                             Recessive trait
(i) It is the trait controlled by dominant allele.        It is the trait controlled by recessive allele.
(ii) It is the trait which is expressed in                   It is the trait which remains suppressed in
F1 generation.                                                     F1 generation and appears in F2 generation.

Question. What are genes? Where are these located?
Answer : The basic functional unit of heredity are called genes. They are also the structural unit of heredity.
They are located on chromosomes and their locations are called loci (singular-locus). Genes could be the sequence of DNA in some organisms and those of RNA in some others.

Question. An elephant learns a trick at the circus. Will his offspring’s also know the trick by birth? Support your answer with reasons.
Answer : Learning a trick at the circus is not an inherited trait. It is an acquired trait which cannot be transferred into the progeny. So, his offspring’s will not know the trick by birth.

Question. Why we humans are not exact copy of one of the parents?
Answer : Some of the people resemble one of their parents because of genes. Every person has two copies of each gene inherited from each parent. The dominant gene form is expressed in their body.

Question. Traits acquired during lifetime of an individual are not inherite(D)
Answer : These are acquired traits that do not make any change to the DNA of an organism.

Question. What indication do we get by reappearance of dwarf plant in F2 generation?
Answer : After obtaining progeny in F2 generation in a di hybrid cross, Mendal concluded that when two pairs of traits are combined in a hybrid, one pair of character segregates independently of the other pair of character.

Question. Give an example where sex is determined by the environmental factors.
Answer : In some snails and turtles sex is determined by the environmental factors like temperature of water.

Question. Why did Mendal choose garden pea for his experiments? Write two reasons.
Answer :  Mendal choose garden pea for his experiments because
(1)Pea plant is a small and easy to grow
(2)Short life cycle

Question. How do Mendel’s experiment show that traits are inherited independently?
Answer : If a body builder builds his muscles, this trait is acquired trait and restricted to muscles only these changes don’t affect the DNA of germs cells hence don’t pass on to next generation.

Question. How the genes, chromosomes and DNA are inter related to each other?
Answer : Genes are segments of DNA , which is wound compactly into chromosomes.DNA is genetic material of an organism, genes are the functional part of this material and chromosomes are the vehicles of heredity as they carry genes.

Question. A body builder builds his muscles. Will his child will born with strong muscles? If not, why strength of muscles didn’t pass on next generation?
Answer : If a body builder builds his muscles, this trait is acquired trait and restricted to muscles only these changes don’t affect the DNA of germs cells hence don’t pass on to next generation.

Question. How is the equal genetic contribution of male and female parents ensured in the progeny?
Answer : Equal genetic contribution of male and female parents in the progeny is ensured by the equal inheritance of chromosome from each parent. Human possesses 23 pairs of chromosomes, of which 22 pairs are autosomes and 1 pair is the sex chromosomes. The two sex chromosomes in human are X and Y. Females have 2 X chromosomes and males have a X and Y chromosome. During the process of fertilization, a haploid sperm fuses with a haploid ovum to produce a diploid zygote. Zygote receives equal amount of genetic material from each parent and thus, retains the diploid nature on fertilization.

Question. (A) Why did Mendel carry out an experiment to study inheritance of two traits in garden pea?
(B) What were his findings with respect to inheritance of traits in F1 and F2 generation?
(C) State the ratio obtained in the F2 generation in the above mentioned experiment.
Answer : (A) Mendel carried out crosses with two traits to see the interaction and basis of inheritance between them. In a dihybrid cross given by Mendel, it was observed that when two pairs of characters were considered each trait expressed independent of the other.
(B) For example, a cross between round yellow and wrinkled green parents.

Question :Tabulate two distinguishing features between acquired traits and inherited traits with one example of each.
Answer :  

Question :

(i) Define Genetics.
(ii)Who is regarded as the ‘Father of Genetics’? Name the plant on which he performed his experiment.
(iii)Why did he select that specific plant for his experiments?
Answer :

(i)Genetics is the branch of biology that deals with the study of heredity and variations.
(ii)Gregor Johann Mendel is regarded as the Father of Genetics. He performed his experiment on garden pea.
(iii)He selects garden pea plant for his experiment for following reasons
* Garden pea plants were easily available
* They grow in one season
* Fertilization was easy

Question. When a cell reproduces, what happens to its DNA?
Answer :  When a cell reproduces, its DNA is copied and passed on to the offspring.

Case based study questions

1. Reproduction results in variation from one generation to the next. The variation produced in the organisms during the successive generation gets accumulated over a long period of time in an organism. After several generation these variations comes up in the organisms and the organisms starts showing up different characteristics and hence leads to the appearance of new species. The main advantage of variation in a species is that it increases the chance of its survival in a changing environment. The organisms which shows positive variation, survives. Those who do not showvariations get extinct.

Question. What are variations?
Answer : The difference in the characteristics of individual in a population is called variation.

Question. Why the variations are accumulated over generations?
Answer : Due to their inheritance

Question. What are the positive variations?
Answer : Variations that provides survival advantage to an organism

2. The following picture shows the inheritance of gene forms (alleles) for blood group in humans

Question. If blood group of father is A and of mother is B, what are the possible blood groups of their offspring?
Answer : A, B, AB, O

Question. What will the blood group of child if both parents have “O” blood group?
Answer : O

Question. Which allele is recessive in the above case?
Answer : O

More Question

Q1) Do all variations in a particular species have equal chances of survival in an environment?
Q2) Give scientific terms for;
a) the similarities with parents present in an offspring.
b) the differences with parents present in an offspring.
Q3) When is a recessive trait capable of expressing itself?write its expression with respect to height of plant(genotype).
Q4)  When a pesticide is sprayed on a population of insects,all insects do not get killed but few of them survive.give reason.
Q5) In a mendeliancross,tall plants and purple flowers were crossed with dwarf plant and white flowers.How would you denote------------
a) the genotype pf the two parents.
b) the genotype and phenotype of F1 progeny.
c) the results obtained by selfing F1 progeny to get F2 progeny.give the ratio obtained in F2 generation.