SCIENCE & TECHNOLOGY (Class-10)
(all questions in cbse) Chapter 9 : Heredity and Evolution
1. Who proposed the theory of inheritance of acquired characters.Answer: J.B. Lamarck . cbse class 10 heredity and evolution notes
2. State one of the evolutionary forces leading to the origin of a new species according to the synthetic theory of evolution.Answer: Origin of new species is based on natural selection acting on genetic variations that appear among the members of a population.
3. Give an example of a vestigial organ present in human body.Answer: Vermiform appendix.
4. What is the evolutionary significance of the fossil Archaeopteryx?Answer: Archaeopteryx is the connecting link between reptiles and birds. It has both reptilian on features and avian(bird-like) features.
5. Who proposed the double helical model of DNA?Answer: Watson and Crick.
6. Who proposed the theory of natural selection?Answer: Charles Darwin.
7. What is retro virus?Answer: A virus with RNA as the genetic material eg: HIV is a retro virus.
8. What is a genetically modified organism (GMO)?Answer: The organism that contains a segment of foreign DNA.
9. Name any two genetic diseases.Answer: Hemophilia and colour blindness.
10. One of the examples of two analogous organs can be the wing of parrot anda) Flippers of whale. c)Foreleg of horse b) Front leg of frog d)Wing of houseflyAnswer: Wing of housefly
SHORT ANSWER QUESTIONS (2 marks)
1. What are transgenic organisms? Which property of DNA is used as a tool in genetic engineering?Answer: The organisms that contain a segment of foreign DNA are known as transgenic organisms.The complimentary property of the nucleotides of DNA.is the most powerful tool in genetic engineering.
2. Explain how the sex of the child is determined at the time of conception in human beings.Answer: Male human beings have XY sex-chromosomes and female human beings have XX sex-chromosomes. If a sperm carrying x-chromosome fertilizes with the ovum, then sex of the baby will be female. If a sperm carrying y-chromosome fuses with the ovum, the sex of the baby will be male.
3. By comparing the similarity of nucleotide sequences in DNA of different kinds of organisms, evolutionary relationships can be established.a) Arrange the following according to their evolutionary closeness (You may use your knowledge of classification also) Cockroach, mango tree, gorilla, fish. b) Whose DNA among the following do you think is most similar to that of humans. Answer: (a) cockroach – fish – gorilla( b) Gorilla
4. Mention the ways by which variant genotypes are produced in organism? Answer: a) gene mutation b) Crossing over c) Hybridization
5. In human beings blue eye colour is recessive to brown eye colour . If a brown eyed man has a blue eyed mother then finda) What are the possible genotypes of his father?b) What is the genotype of the man and his mother? Answer: BB , Bb B. Man: Bb, mother: bb
6. What are fossils? Of what interest are fossils to the evolutionary biologists? Answer: A fossil is the remnant or impression of an organism that lived in the Remote past. Use of Fossils a) Phylogeny, the evolutionary history can be reconstructed from the fossils.b) The fossil record has helped in building the broad historical sequence of biological evolution.
SHORT ANSWER QUESTION (3 marks)
1. a) Who isolated DNA for the first time from pus cells?b) Why is DNA called polynucleotide?c) Name two purine nitrogenous bases found in a DNA molecule. Answer: a) F.Meishcer, named it nuclein. b)DNA is called polynucleolide because it is a polymer or long chain of nucleolide. c)Purine:- Adenine and Guanine.
2. a) Who put forward the double helical model of DNA?b) What are the three chemically essential parts of nucleotides constituting a DNA? Answer: a) Watson and Crick. b)Nucleotide constituting –DNA Nitrogen bases (Purines and Pyrimidines), Pentose sugar(Deoxyribose sugar) and a phosphate molecule.
3.Guinea pig having black colour when crossed with guinea pig having same colour produced 80 offspring, out of which 60 were black and 20 were white. Now,find out:a)What is the possible genotype of the guinea pigs?b)Which trait is dominant and which trait is recessive? c)What is this cross called as and what is its phenotypic ratio? Answer: a) Bb x Bb b)Black is dominant and white is recessive. c) Monohybrid cross, phenotypic ratio=3:1
4. Write a brief account on . Who disproved this theory? Answer: salient points of Lamarck‘s theory:1.The use and disuse of an organ leads to acquiring of change in the features of that organ. 2. These changes are inherited by the offspring.3. Favourable variations result in evolution of new species. August Weisman disproved this theory.
5. Distinguish between acquired and inherited traits giving one example of each. Answer: Acquired traits1) A trait (or characteristic) of a organism which is not inherited‘ but develops in response to the environment is called an acquired trait.(2) The acquired traits of an organism cannot be passed on to its future generations. e.g. low weight‘ of beetle, cut tail‘ of a mouse.Inherited traits1) A trait (or characteristic) of an organism which is caused by a change in its genes (or DNA) is called an inherited trait.2) The inherited traits of an organism are passed on to its future generations. e.g. red colour of beetles, fur coat of guinea pigs.
6. Why did Mendel chosen pea plant for his experiments? T-II 2015Answer: Mendel chose pea plant for his experiments because it is:(a) Easy to grow (b) Short lifespan(c) Easily distinguishable characters (d) Larger size of flower (e) Self-pollinated.
Q.1 Explain Heredity?
Transmission of characters from parents to offspring’s is known as heredity.• Fertilized egg or zygote carries hereditary information.• The zygote develops into a particular type of offspring only.• Thus, eggs laid by a sparrow hatch into sparrows and a dog reproduce to give birth to pups only.
Q.2 What is the study of heredity and variation called?
The study of heredity and variation is called Genetics.
Q.3 Explain Variation?
Variation means some individual diversity in the organism of one generation from that of the parental generation.• Variation passes from generation to generation.• In sexual reproduction, both similarities and variation are clearly observed among the offspring’s of same parents.• Due to variation, any two persons rarely show complete similarity.Accumulation of Variation During Reproduction : - Q.4 Why is asexual reproduction not ideal for variations?Asexual reproduction involves a single parent and is hence not ideal for facilitating variations. Organisms raised are exact copies of their parents and are known as clones. Due to their identical set of chromosomes, they exhibit no or very little variations. These variations may be either due to some environmental factors like light, scarcity of food, abundance of food, temperature etc or due to small inaccuracies in DNA copying (mutation). Out of these two factors, only mutations are heritable. But the quantum of variations would be too little and would take too many years to show effect.
Q.5 What is the source of genetic variation in asexually reproducing organisms?
The source of genetic variation in asexually reproducing organisms is mutation(inaccuracies in DNA replication).
Q.6 Variation useful for the survival of a species. Justify?
Variation is useful for the survival of species over time. If a population of reproducing organisms were suited to a particular niche and if the niche were drastically altered, the population could be wiped out. However, if some variations were to be present in a few individuals in these populations, there may be some chance of their survival.E.g. : If the temperature of water increases by global warming, most bacteria would die. But a population of heat resistant bacteria could survive here. These few variants would be resistant to the heat and would survive and grow further.
Q.7 Why is sexual reproduction ideal for variations?
Sexual reproduction is ideal for facilitating variations because two parents are involved in it and there is formation and fusion of gametes. Due to crossing over and exchange of gene segments, off-springs show variations from their parents. They are not carbon copies of their parents. Due to recombination of parental genes, variations occur which are heritable.Heredity
Q.8 What is meant by inherited traits?The characteristics or traits which are transmitted from the parents to the offspring’s are known as inherited traits. E.g. Height, skin colour, ability to roll tongue, haemophilia.
Q.9 What did Mendel propose?
Mendel proposed that for regulation of every character (in an organism) there is a pair of factors.
Q.10 What is a gene? How does it work?
Gene is a small segment of DNA on a chromosome occupying specific position in which is a hereditary determinant or unit of a biological function. Genes are passed from parents to offspring’s via chromosomes present in the nuclei of the parents’ gametes.Genes function through the formation of specific proteins that serve as a structural or functional component required for expression of a character.
Q.11 Why did Mendel select pea plant in his experiment?
Mendel selected the pea plant for his experiments because -• Pea can be termed as biennial plant, i.e. two generations of a pea plant can grow in a given year. This means that mendel could get enough time to observe a larger number of generations.• Many easily identifiable and contrasting characters are present in pea plants.• Self fertilizing in nature and also cross bred experimentally.• Produce large number of offspring.
Q.12 Who was gregor Mendel?
Gregor mendel is considered the father of Genetics. He was a monk, biologist and botanist born in Austria in 1822 and who died in 1884. His experiments consisted of crossing pea plants of distinct characteristics (size, color of the seeds, etc.), cataloging the results and interpreting them. The experiments led him to enunciate his laws, results published in 1886 with no scientific repercussion at that time. Only at the beginning of the 20th century, in 1902, 18 years after his death, were his merits broadly recognized.
Q.13 What is mono hybridism?Mono hybridism is the study of only one characteristic in the crossing of two pure individuals (hybridization) for that characteristic.
Q.14 What is the condition for Mendel’s second law to be valid?Mendel’s second law is only valid for genes located in different chromosomes. For genes situated in the same chromosome, i.e., linked genes (genes in linkage) the law is not valid since the segregation of these genes is not independent.
Q.15 What is the difference between dominant trait and recessive traits?Dominant traits refers for the alternative of a character that expresses itself in the F1generation. For example, Yy shows the dominant trait for yellow colour of seed. Seed is yellow even when single copy of dominant allele i.e., Y is presentRecessive trait means the trait, which is unable to express itself in the presence of the dominant trait. For example, shows the recessive trait for green colour of the seed. It is expressed only when both the alleles are recessive i.e., y
Q.16 What constitutes the link between one generation and the next?The hereditary information is transferred from parents to offspring through the gametes. So, gametes constitute the link between one generation and the next and pass on the paternal and maternal characters to the offspring.
Q.17 What is meant by alleles?Alleles are pair unit factors that control the expression of a character.
Q.18 What is mono hybrid cross?When only a single pair of contrasting or differentiating traits is considered in a cross (or inheritance of only one pair of contrasting traits is studied in a cross), it is called monohybrid cross, e.g ; When only a single pair of contrasting or differentiating traits is considered in a cross (or inheritance of only one pair of contrasting traits is studied in a cross), it is called mono hybrid cross.e.g.
The two forms of the trait appear in F2 generation in ratio of three dominant to one recessive, 3 : 1. It is also called mono hybrid ratio.
Q.19 (a) What is genetics?(b) Give the common name of plant on which Mendel performed his experiments.(c) What for did Mendel use the term factors and what are these factors called now.(d) What are genes? Where are the genes located?(a) Genetics is the branch of biology that deals with the study of heredity and variation.(b) Garden pea – Pisum sativum.(c) The units of inheritance of characters. These factors are now called as genes.(d) Gene is a hereditary unit, a segment of DNA. It is located on a chromosome at a particular locus or position.
Q.20 What are the components of chromosome?Each chromosome is double or replicated and consists of two thread like structures called chromatids attached to each other at centro mere.Each chromatid has a number of dense areas arranged linearly which are known as chromomeres. They represent the areas of active genes.Internally each chromosome has two spirally coiled threads called chromonemataembedded in matrix. These are DNA molecules.
Q.21 What is sex chromosome?A chromosome which is associated with sex determination is called sex chromosome.There are 2 types of sex chromosomes- the X- chromosome and the Y- chromosome.Males possess one X and one Y chromosomes while females possess 2 X chromosomes.Therefore, the sex of a child is determined by the inheritance of X or Y chromosome from the fatherParents Male FemaleGametes X Y XProgeny XX XYFemale (50%) Male (50%)
Q.22 "The sex of the children is determined by what they inherit from their father and not from the mother." Justify.The children inherit similar chromosomes (22 + X) from the mother but the sex of the children will depend on the chromosome they inherit from the father. If a child inherits (22 + X) chromosomes from the father that the child will be a girl but when a child inherits (22 + Y) chromosomes from the father then the child will be a boy.
Q.23 Difference between Genotype and Phenotype:
Q.24 What do you mean by sex determination?The phenomenon determining whether the developing embryo will be a male or a female is known as sex determination.
Q.25 Describe the role of environmental factors in sex determination. • In some species, the sex determination is regulated by environmental factors.• For example, in turtle Chrysema Picta, high incubation temperature results into development of a female.• In a lizard, Agama agama, high incubation temperature results into development of a male.
Q.26 State Mendel’s Laws of InheritanceMendel on the basis of his observations of mono hybrid and dihybrid crosses in pea plants gave the following principles of inheritance-(i) Law of Unit Characters- According to this law, all the traits are separate entities or units by themselves. Their inheritance is controlled by 'factors', now known as genes.(ii) Law of Dominance - Each gene has more than one form of expression. These forms of expressions are called alleles or allelomorphs. Each pair of alleles will have a dominant allele and a recessive allele. In the presence of the dominant gene, the recessive gene will never express itself. Only if both the alleles are recessive, the recessive trait will be exhibited.(iii) Law of Segregation - This is also called the law of purity of gametes. According to this law, the gametes are pure for a particular trait. This is because the alleles of a pair separate during gamete formation and again come together after fertilization. Therefore, in each gamete only either of the two alleles is present and it is pure for that trait..(iv) Law of Independent Assortment - This law explains how more than one trait is inherited. According to this law, when there are two pairs of alleles, all four alleles assert themselves independently and are inherited independently.
Q.27 What is retro virus?A virus with RNA as the genetic material instead of DNA. E.g., HIV is a retro virus.
Q.28 Explain the result of mono hybrid cross?(i) Only one of the parental trait is observed in F1 progeny when two contrasting character of a trait is considered.(ii) The trait which is seen in F1 hybrid is dominant one.(iii) When F1 hybrid is self pollinated both the characteristics appear in ratio of 3:1 which shows that F1 hybrid has the traits of both characteristics.
Q.29 What is dihybrid cross? Mendel crossed the round and green seeded pea plants with the wrinkled and yellow seeded pea plants. Give the phenotypic ratio of F2 generation.A dihybrid cross is one in which two pairs of contrasting characters are taken at a time in this cross.
Q.30 How do traits get expressed?(i) Chromosomes present in nucleus contain hereditary information.(ii) Chromosomes are made up of DNA and protein. It’s important component is DNA.(iii) Chromosomes occur in pair, one comes from mother and others from father.(iv) Part of DNA responsible for a trait is called gene.(v) A gene is expressed in the form of proteins. E.g. for tallness of a plant if proteins work efficiently a lot of hormone will be produced and the plant will be tall
Q.31 List the contrasting characters which were taken for experiments by mendel?Mendel selected varieties that differed with respect to seven traits with easily distinguishable contrasting forms, i.e., he selected fourteen varieties as shown in the table given below
Q.32 How was it established that genes are located on the chromosomes?In all the organisms, the number of chromosomes is fewer than the number of characteristic features, which are many. If 'genes' are responsible for a characteristic feature, they have to be certainly many more than the number of chromosomes. For example, in human beings, the total number of chromosomes is 23 pairs, but the total number of characters (genes) has been estimated to be between 30,000 to 40,000. This suggests that genes are located on the chromosomes
Q.33 Give example of animals in which sex is not genetically determined.(i) snail-can change sex.(ii) turtle-High incubation temperature leads to develop female offspring.(iii) Lizard-High incubation temperature leads to develop male offspring
Q.34 What are auto somes and how are they different from sex chromosomes?
Q.35 What is a factor and who coined the term ?The carriers of hereditary information were called factors. The term ‘factor’ was coined by Mendel.
Q.36 How did the Mendelian 'factors' acquire a change in the terminology? Who changed it?The carriers of hereditary information were called 'factors' by Mendel. Wilhelm Johansson later called these factors genes.
Q.37 Explain the law of segregation by taking an example.Law of segregation :Paired factors responsible for a character segregate into gametes and are recombined at the time of fertilisation.When a yellow seeded and green seeded plants are crossed, the F1 progeny are all yellow seeded. It indicates that yellow colour is dominant over green seed colour. When F1 plants are self pollinated, we get yellow and green seeded plants in the ratio of 3 :1
Q.38 What is the reason that a male is called 'hetero gametic'?A male is called hetero gametic because he forms two different types of gametes. One containing 'X' chromosome and the other containing 'Y' chromosome.
Q.39 Give an example of a plant showing sex determination.Coccinia indica is a plant showing sex determination.
Evolution Q.40 Define evolution:Evolution is a gradual and orderly process of change in the forms of life from simple to complex during the course of time that has given rise to the existing diversity of life.
Q.41 Who gave the concept of evolution?Charles Darwin, a British naturalist gave the concept of evolution.
Q.42 What do you understand by natural selection?Natural selection refers to increase in the frequency of genes, which results in evolution of populations that are better adapted to existing environment.
Q.43 What is meant by genetic drift?Change in the frequency of some gene creating diversity without any adaptations caused by chance factor alone is called genetic drift.
Q.44 What are the two basic factors of evolution ?Variation and heredity are the two basic factors of evolution.
Q.46 Explain Darwin’s theory of evolution?According to Darwin’s theory of evolution:(i) There is natural variation within any population and some individuals have more favourable variations than others.(ii) Population remains fairly constant even though all species produce a large number of off springs.(iii) This is due to ‘competition’ or struggle for existence between same and different species.(iv) The struggle for survival within population eliminates the unfit individuals and those with ‘favourable variations’ survive and pass on these variations to their progeny to continue. This is called natural selection.(v) The favourable variations are accumulated over a long time period leading to the origin of a new species.
Q.47 Describe the contribution of Lamarck?Contribution of Lamarck :(i) Lamarck proposed a theory called “The Theory of inheritance of Acquired Characters” to explain the origin and evolution of species.(ii) The theory was explained in his book ‘Philosophic Zoologique.
Q.48 How do homologous organs provide evidence in support of evolution?Homologous organs support evolution :(i) The similarities of structure and origin of organs indicate that all vertebrates had common ancestors. For example, the forelimbs of humans, whale and bat show structural similarities but functional dissimilarities. Forelimbs in humans used for grasping or holding the things, in whale for swimming and in bat for flying.(ii) All the organs and systems of the vertebrates show fundamental similarities i.e. homology, which indicate towards common ancestry. Thus, homologous point that organic evolution has taken place.
Q.49 Describe briefly four ways in which individuals with a particular trait may increase in a population.The individuals with a particular trait may increase in a population in the following ways–(i) Sufficient Food : By obtaining more food the individuals can increase in growth and reproduction.(ii) Differential Reproduction : It gives an advantage to the individuals to survive and reproduce.(iii) Variations : The useful variations help the individuals to adopt the environmental condition(iv) Genetic Drift : The random change in the frequency of alleles in a population over successive generations due to error during DNA copying on the gametes
Q.50 Who explained the mechanism of origin of new species for the first time? How does new species arise according to his theory? What was his second observation?Charles Darwin. New species arise by the slow accumulation of advantageous variations over a period of time. His second observation says that over population results in competition for food and shelter, ultimately leading to a struggle for existence among the members of a species.
Q.52 Differentiate between inherited and acquired traits.
Q.53 Which theory of evolution did Darwin give? Mention the limitation of Darwinism.Darwin gave the Theory of Natural Selection.Darwinism explains evolution with the help of variation but it does not explain how variation occurs.
Q.54 The chromosomal number of the sexually producing parents and their offspring is the same." Justify this statement.The first step in sexual reproduction is gamete formation. In this step, the number of chromosomes gets halved. Thus, each gamete receives half the number of chromosomes to that of somatic cells. During fertilisation, the fusion of male and female gametes takes place, which results in the number of chromosomes in the zygote to be equal to that of somatic cells. Thus, the chromosomal number of the sexually producing parents and their offspring is the same.
Q.55 “Evolution cannot be equated with progress”. Justify this statement.Evolution cannot always be equated to progress because• Evolution does not always lead to the formation of a new species.• The newly formed species as a result of evolution may have complex organisation but cannot be considered 'better' to the earlier species.• Evolution simply leads to diversification.Speciation Q.56 What is speciation? What are the different ways in which it can occur?The formation of a new species by evolution or any genetic modification of the previously existing species in a population is called speciation.Few factors that affect speciation are(a) Geographical isolation : - Geographical isolation is one of the factors which may lead to speciation. In this a group of individuals of a species may become geographically isolated from other members or species. So, both these groups grow in different environment and hence evolve to form a new species. Various factors which play an important role in this type of speciation are -(i) Natural selection (ii) Genetic drift(b) Hybridization : - Hybridization is a process by which new types of species come into existence as a result of mating of two distinct species. This process may lead to the existence of new species which is different from the parents. Hence, hybridization may result in speciation.
Q.57 What are the factors that give rise to a new species?New species are produced as a result of• Mutations giving rise to new genetic variations• Genetic recombination during sexual reproduction provides wider variability for natural selection to operate.• Natural selection of variants better adapted to the existing environment.• Genetic drift - random increase in the number of variants not having any selective advantage due to the change factor• Reproductive isolation of populations with different characters due to geographic or behavioural patterns.
Q.58 Define the term ‘species’:A species can be defined as a group of similar organisms that can interbreed and produce fertile off springs.
Q.59 Define population:Population is the group individuals of species living in a particular area.
Q.60 When a pesticide is sprayed on a population of insects, all insects do not get killed but few of them survive. Give reason. When a pesticide is sprayed on a field most of the insects are killed because they are sensitive to the pesticide. A few of the insects survive because they have variations which made them resistant against the pesticide, such that the pesticide has no effect on these insects.
Evolution and Classification Q.61 What is meant by characteristics? Give an example:Characteristics are details of appearance or behaviour, i.e., a particular form or particular function in the body of an organism. For example, ability of plants to carry out photosynthesis.
Q.62 How do embryological studies provide evidence for evolution?The similarities in embryonic development reinforce the idea of evolution from common ancestors. The sequence of embryonic development in different vertebrates shows striking similarities. Note chord and gill clefts appear in the embryos of all vertebrates.
Q.63 Difference between homologous and analogous organs with example
Q.64 Define Vestigial organs?Vestigial organs are those organs, which are rudimentary and functionless in the evolved forms but are well developed and functional in the ancestral forms. Eg: Vermiform appendix in human beings.
Q.65 What are the basic characteristics for separation of major groups of organisms?The basic characteristics for separation of major groups of organisms are -1. Organisms of the cell, if it is prokaryotic or eukaryotic.2. Organisation of the body(cell design), whether it is unicellular or multicellular.3. If there is division of labour in the multicellular body.4. Whether they can produce their own food by photosynthesis.5. The way the organs of the body develop and become specialised.
Q.66 What is meant by hierarchy?Hierarchy is the framework of classification in which the groups are arranged in the order of increasing or decreasing levels of similarities.
Q.67 Define Primitive and advanced organism:Organisms that originated first and have not changed much during the course of evolution are called primitive or lower organisms. Primitive organisms have a simple body structure and ancient body design Eg., bacteria.Organisms that originated later and have changed much during the course of evolution are called advanced organisms or higher organism. Advanced organisms have a complex body structure and organization. E.g., Primates.
Q.68 How has the method of artificial selection by humans helped in the evolution of different vegetables? Explain in brief giving an example.Humans have developed different varieties of vegetables from a single wild cabbage by artificial selection some of these are as follows —(i) Some farmers have wanted to select very short distances between the leaves and developed the present day cabbage.(ii) Some farmers selected immature green flowers and developed the broccoli.(iii)Some have selected the sterile flowers and developed the cauliflowers.(iv) Some farmers selected the swollen part of the wild cabbage and developed the kohlrabi.(v) Some of them have selected the larger leaves and developed Kale.So, all these vegetables are descended from a common ancestor.
Q.69 What are fossils? What do they tell about the process of evolution?The preserved traces or impressions of the body parts of living organisms are calledfossils.Since fossils reveal evolutionary relationships among different organisms, they are the proof of organic evolution.
Q.70 What is palaeontology? What is its importance?Palaeontology is a branch of biology that deals with the study of fossils. It provides a direct evidence of evolution and is called a written document of evolution
Q.71 What is meant by molecular phylogeny?Molecular phylogeny is the study of evolutionary relationship by comparing the DNA of different species.
Q.72 How the study of fossil is considered significant?The study of fossil is considered significant because-(i) Fossils provide direct evidence of past life.(ii) These provide convincing proof of organic evolution.
Q.73 How do we know how old a fossil is?The age of fossils can be determined by two ways-(i) If we dig into the earth and start finding fossils, it can be assumed that the fissils closer to the surface are more recent to those found in deeper layers.(ii) By detecting the ratio of different isotopes of the same element in the fossil materials
Q.74 Name the tools that are used to study human evolution:The tools that are used to study human evolution are excavations, time dating and study of fossils, determining DNA sequences.
Q.75 Explain the importance of fossils in deciding evolutionary relationships:Age of fossils can be found out by estimation of the depth of the layer of the rocks in which it is found. It can be found out by the ratio of the isotopes in the fossil containing rocks. Thus, we can find out the types of organisms (plants, animals and microbes) that existed at a particular geological time and reconstruct the evolutionary process.
Q.76 Give the evidence that the birds have evolved from reptiles.Fossils provide evidence of evolution. A fossil bird called Archaeopteryx, which lived in the Late Jurassic Period around 148–150 million years ago, had feathered wings like that of birds and a long bony tail, jaws with sharp teeth and various skeletal features like that of reptiles. Thus, Archaeopteryx is considered a connecting link between reptiles and birds.Some dinosaurs had feathers that provide them insulation in cold weather; however, they could not fly using those feathers. Birds seem to have later used feathers to fly. This, of course, means that birds are very closely related to reptiles because dinosaurs were reptiles. Hence, it suggests that birds have evolved from reptiles.
Q.77 Insects, octopus, planaria and vertebrates possess eyes. Can we group these animals together on the basis of eyes that they possess ? Justify your answer giving reason.While making groups, we need to decide the characteristics that are responsible for the more fundamental differences among organisms. The characteristics that account for the broadest divisions among living organisms should be independent of any other characteristics in their effects on the forms and structural functions of organisms like cellularity, mode of nutrition and nature of cell.Insects, octopus and planaria are invertebrates. They cannot be grouped together with vertebrates, as they lack an internal skeleton with a backbone. Also, all of them belong to different phyla on the basis of different characteristics they possess. Just on the basis of one characteristic, i.e., presence of eyes, these organisms cannot be grouped together.
Evolution Should Not Be Equated with Progress
Q.78 Describe the human evolution.The modern humans are called Homo sapiens. Many scientific investigations have shown that the modern humans evolved in Africa. Few thousand years ago some ancestors left Africa while other stayed back. The residents spread across Africa and the migrants spread across the planet from Africa to West Asia, Central Asia, Eurasia, South Asia, Indonesia, Australia and America. They went forwards and backwards with groups separating from each other, or sometime coming together. Like all other species, they were also living their lives to the best of their ability.
Q.79 A blue colour flower plant denoted by BB is crossbred with that of white colour flower plant denoted by bb.(a) State the colour of flower you would expect in their F1 generation plants.(b) What must be the percentage of white flower plants in F2 generation if flowers of F1 plants are self-pollinated?(c) State the expected ratio of the genotypes BB and Bb in the F2 progeny.Blue colour flower plant:- BBWhite colour flower plant:- bbThe cross involved is as follows:
(a) In F1 generation, all plants will have blue flower.(b) In the F2 generation, 25% of flowers are white in color.(c) The ratio of the genotypes BB and Bb in the F2 generation would be 1(BB) : 2(Bb).
Q.80 If we 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 F1 generation but appeared in F2 generation, mentioning the reason for the same.When a pure breeding tall pea plant is crossed with a pure breeding dwarf pea plant(a) All the plants in the F1 generation appear tall.(b) The ratio of tall pea plant to dwarf pea plants is 3 (tall) : 1 (dwarf).(c) The dwarf plant does not appear in the F1 generation but appears in the F2 generation because the progeny produced in the F1 generation were heterozygous (Tt). Hence, when they were selfed for obtaining the F2 generation, dwarf plants were also formed in the progeny. The cross involved in as follows
Value Based Question:
Q.1 A village recorded highest cases of atrocities against women the health officer of the village organised a skit to convey the fact that women should not be punished for the birth of a girl child. They should be given due respect in society. The villagers were greatly motivated.(i) What is the method of sex determination in humans? (ii) What are the sex chromosomes in males? (iii) What value was the officer trying to highlight through the skit? 1. Sex is determined at the time of fertilisation and the two sexes are produced in approximately equal numbers. A human male has XY sex-chromosomes and produces two types of sperms (heterogametic). Either with X-chromosome or with Y-chromosome.A human female has XX sex-chromosomes and produce ova of one type (homogametic) all with X-chromosomes.Parents Male FemaleGametes X Y XProgeny XX XY Female (50%) Male (50%)
2. The sex chromosomes in male is a X and a Y chromosome.
3. (i) Awareness (ii) Social Responsibility (iii) Concern for women
Q.2 Anita had a huge scar on her cheek after she met with an accident during her school days. She is worried if her baby would inherit the scar she had acquired. Her doctor, a sincere medical practitioner explained and successfully convinced Anita.(i) What are acquired traits?(ii) How is it different from inherited traits?(iii) Mention the values the doctor exhibits.
1. Traits which are acquired due to interaction with the environment are called acquired traits. Acquired traits are not inheritable. For example; if a boxer develops bulging biceps, it does not mean that his son would be borne with bulging biceps.
2. 
3. (i) Awareness (ii) Social responsibility (iii) Professional ethics
Q.3 Mita observed that her grandmother was preparing a family tree. On enquiring why it was done, she explained that it was necessary to know our roots as we have inherited many traits from our ancestors. She also mentioned that many family values and traditions are no longer followed as joint families had disappeared?(i) Who are the earliest members of human species? (ii) Where have the earliest members emerged?(iii) What values do you think children would learn in a joint family?(i) The earliest documented members of the genus Homo are Homo habilis, which evolved around 2.3 million years ago(ii) Africa(iii) 1. Sharing and caring 2. Respect for elders 3. Concern for others 4. Knowledge of any genetic disorders in the family
Multiple Choice Questions :Q.1 Exchange of genetic material takes place in(a) Vegetative reproduction(b) Asexual reproduction(c) Sexual reproduction(d) BuddingSol. (c)
Q.2 Two pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower progeny. The nature of the cross will be(a) Double fertilisation(b) Self pollination(c) Cross fertilisation(d) No fertilisationSol.(b)
Q.3 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’Sol. (a)
Q.4 Which of the following statement is incorrect?(a) For every hormone there is a gene.(b) For every protein there is a gene.(c) For production of every enzyme there is a gene.(d) For every molecule of fat there is a geneSol. (d)
Q.5 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 yellowSol. (a
Q.6 In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosome is/are(i) Large chromosome(ii) Small chromosome(iii) Y-chromosome(iv) X-chromosome(a) (i) and (ii)(b) (iii) only(c) (iii) and (iv)(d) (ii) and (iv)Sol. (c)
Q.7 The maleness of a child is determined by(a) The X chromosome in the zygote(b) The Y chromosome in zygote(c) The cytoplasm of germ cell which determines the sex(d) Sex is determined by chanceSol. (b)
Q.8 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 girlSol. (b)
Q.9 Select the incorrect statement(a) Frequency of certain genes in a population change over several generations resulting in evolution(b) Reduction in weight of the 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 evolutionSol. (b)
Q.10 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)Sol. (a)
Q.11 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 F1plants 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)Sol. (b)
Q.12 A basket of vegetables contains carrot, potato, radish and tomato. Which of them represent the correct homologous structures?(a) Carrot and potato(b) Carrot and tomato(c) Radish and carrot(d) Radish and potatoSol. (c)
Q.13 Select the correct statement(a) Tendril of a pea plant and phylloclade of Opuntia are homologous(b) Tendril of a pea plant and phylloclade of Opuntia are analogous(c) Wings of birds and limbs of lizards are analogous(d) Wings of birds and wings of bat are homologousSol. (a)
Q.14 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 determinedSol. (b)
Q.15 Which of the following statements is not true with respect to variation?(a) All variations in a species have equal chance of survival(b) Change in genetic composition results in variation(c) Selection of variants by environmental factors forms the basis of evolutionary processes.(d) Variation is minimum in asexual reproductionSol. (a)
Q.16 A trait in an organism is influenced by(a) Paternal DNA only(b) Maternal DNA only(c) Both maternal and paternal DNA(d) Neither by paternal nor by maternal DNASol. (c)
Q.17 Select the group which shares maximum number of common characters(a) Two individuals of a species(b) Two species of a genus(c) Two genera of a family(d) Two genera of two familiesSol. (a)
Q.18 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 anotherSol. (b)
Q.19 From the list given below, select the character which can be acquired but not inherited(a) Colour of eye(b) Colour of skin(c) Size of body(d) Nature of hairSol. (c)
Q.20 The two versions of a trait (character) which are brought in by the male and female gametes are situated on(a) Copies of the same chromosome(b) Two different chromosomes(c) Sex chromosomes(d) Any chromosomeSol. (a)
Q.21 Select the statements that describe characteristics of genes(i) Genes are specific sequence of bases in a DNA molecule(ii) A gene does not code for proteins(iii) In individuals of a given species, a specific gene is located on a particular chromosome(iv) Each chromosome has only one gene(a) (i) and (ii)(b) (i) and (iii)(c) (i) and (iv)(d) (ii) and (iv)Sol. (b)
Q.22 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 : 1Sol. (c)
Q.23 The number of pair (s) of sex chromosomes in the zygote of humans is(a) One(b) Two(c) three(d) fourSol. (a)
Q.24 The theory of evolution of species by natural selection was given by(a) Mendel(b) Darwin(c) Morgan(d) LamarckSol. (b)
Q.25 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 reptilesSol. (d)
Short Answer Questions
Q.26 How is the sex of a newborn determined in humans?Genes inherited from parents decide whether the new born will be a boy or a girl. Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY).If a child inherits (22 + X) chromosomes from the father then the child will be a girl but when a child inherits (22 + Y) chromosomes from the father then the child will be a boy. Therefore, the sex of a child is determined by the inheritance of X or Y chromosome from the father Parents Male FemaleGametes X Y XProgeny XX XY Female (50%) Male (50%)
Q.27 Do genetic combination of mothers play a significant role in determining the sex of a new born?No. The sex of a human baby is determined by the composition of its sex chromosomes (a single distinct pair among humans' 23 pairs of chromosomes). As females possess two copies of the same chromosome (referred to as the 'X' chromosome) and all children will inherit an ‘X’ chromosome from their mother regardless of whether it is a boy or girl. But, the sex of the children will depend on the chromosome they inherit from the father i.e.,. males. Males have one copy of the X chromosome and one copy Y chromosome. Therefore, the genetic combination of mothers do not play a significant role in determining the sex of a new born.
Q.28 Mention three important features of fossils which help in the study of evolution.(a)We can study about extinct species from their fossils.(b) They help us to know which organisms evolved earlier and which of them evolved later.(c) Fossils represent modes of preservation of ancient species.
Q.29 Why do all the gametes formed in human females have an X chromosome?In human sexual reproduction, two distinct gametes fuse to form a zygote. Gametes are reproductive cells produced by a type of cell division called meiosis. Gametes are also called sex cells. They contain only one set of chromosomes and are said to be haploid.The female gametes or eggs however, contain only the X sex chromosome and are homogametic. The females are XX and produce egg cells that contain an X chromosome. Therefore, during meiosis, at the time of gamete formation, one X chromosome enters each gamete. Hence all the gametes possess an X chromosome.
Q.30 In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation.A chromosome which is associated with sex determination is called sex chromosome. There are 2 types of sex chromosomes- the X- chromosome and the Y- chromosome. Males possess one X and one Y chromosomes while females possess 2 X chromosomes.The sex of a child is determined by type of sex chromosome contributed by the male gamete. A child will inherit similar chromosomes namely ‘X’ chromosome from the mother but if a child inherits ‘X’ chromosomes from the father also, then the child born will be a girl but when a child inherits ‘ Y’ chromosomes from the father then the child born will be a boy. Since the ratio of male gametes containing X chromosome and those containing Y chromosome is 50:50, therefore, the statistical probability of getting either a male or female child is 50 : 50
Q.31 A very small population of a species faces a greater threat of extinction than a larger population. Provide a suitable genetic explanationA population with a small number of individuals are under threat of extinction as there are very less individuals which can reproduce successfully. A population with a large number of individuals is better in producing new individuals hence continuing the species preventing themselves from extinction.
Q.32 What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor?(a)Homologous structures: The structures which are similar in basic structure and embryonic origin but perform different functions in different species are called homologous organs. For example, the forelimbs of a human, a bird, a lizard and a frog show similarity in basic structure but perform different functions.(b) Yes, homologous structures have common ancestor but structures are variously modified to carry out different activities.
Q.33 Does the occurrence of diversity of animals on earth suggest their diverse ancestry also? Discuss this point in the light of evolution.Though animals have a vast diversity in structures they probably do not have a common ancestry, because common ancestry may greatly limit the extent of diversity. Two species have the same trait because the common ancestor of the two species had the trait. For example, all vertebrate embryos look very similar during the earlier stages of development, including having gill pouches and tails. Thus, a reptilian embryo, a bird embryo and a human embryo look very similar, even though they develop into very different adult organisms. The best explanation for this similarity in embryos is a shared history of vertebrates—all vertebrates share a common ancestor that had a tailed embryo with gill pouches. In this way, we can built small groups of species with recent ancestors, then super groups with distant ancestors and so on. We can thus keep going backwards until we come to the notion of a single species at the head of the beginning of the evolutionary time.As many of these diverse animals inhabit the same habitat, their evolution by geographical isolation and speciation is also not likely. Thus, a common ancestry for all the animals is not the likely theory.
Q.34 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(i) yellow — dominantGreen — recessive(ii) Round — dominantWrinkled — recessive
Q.35 Why did Mendel choose pea plant for his experiments?Mendel selected the pea plant for his experiments because-• Pea can be termed as biennial plant, i.e. two generations of a pea plant can grow in a given year. This means that Mendel could get enough time to observe a larger number of generations.• Many easily identifiable and contrasting characters are present in pea plants.• Self fertilizing in nature and also cross bred experimentally.• Produce large number of offspring
Q.36 A woman has only daughters. Analyse the situation genetically and provide a suitable explanation.The sex of a child is determined by type of sex chromosome contributed by the male gamete because males possess one X and one Y chromosomes while females possess two ‘X’ chromosomes.A child will therefore, inherit similar chromosomes namely ‘X’ chromosome from the mother but if a child inherits ‘X’ chromosomes from the father also, then the child born will be a girl but when a child inherits ‘ Y’ chromosomes from the father then the child born will be a boy. Therefore, in the above given situation, since the woman has only daughters, it is evident that every time the male ‘X’ chromosome has fused with the female ‘X’ chromosome thereby leading to the birth of daughters.Long Answer QuestionsQ.37 Does geographical isolation of individuals of a species lead to formation of a new species? Provide a suitable explanation.Yes. Geographical isolation gradually leads to genetic drift. In sexually reproducing species, geographic isolation can generate a barrier to gene flow that can result in genetic drift and/or local adaptation and differentiation. This may impose limitations to sexual reproduction of the separated population. Therefore, The separated individuals start breeding among themselves leading to the generation of new variations. These changes can accumulate to a point that speciation occurs.
Q.38 Bacteria have a simpler body plan when compared with human beings. Does it mean that human beings are more evolved than bacteria? Provide a suitable explanationBacteria and human beings have indeed been evolving for the same amount of time and they both perform all the activities of life. But, human beings are far more complex organisation and differentiation than bacteria. Being multicellular, they require division of tasks, detailed regulation of gene expression, complex body design etc. The regulatory networks are more complex than in bacteria. As complex organisation and differentiation develop through evolution, humans are concerned to be far more evolved than bacteria.
Q.39 All the human races like Africans, Asians, Europeans, Americans and others might have evolved from a common ancestor. Provide a few evidences in support of this view.Studies regarding human origins and migrations reveal the fact that all people are truly part of the same human family, separated only by time and distance. Molecular biology (genetics), archaeology, geology etc all point to the conclusion that human beings belong to a single ancestral species of Homo sapiens sapiens and have originated in Africa about 100-200,000 years ago, migrating outside the African continent around 80,000 years ago. Therefore, we can say that all the human races like Africans, Asians, Europeans, Americans and others might have evolved from a common ancestor.Few evidences in support of this view are -(i) All of them have a common body plan, structure, physiology and metabolism.(ii) They all have constant chromosome number and common genetic blue print.(iii) All races of human beings have a common gene pool and can freely inter-breed among themselves to produce fertile offspring’s.
Q.40 Differentiate between inherited and acquired characters. Give one example for each type
Q.41 Give reasons why acquired characters are not inherited.Acquired traits are traits of an organism which are not inherited but develop in response to the environment. These traits can influence only the somatic cells .i.e., non-reproductive cells. Somatic cells cannot transfer traits from parents to offspring’s unlike germ cells. So, there is no influence on the DNA of the germ cell; therefore, the traits are not coded in the genes of the chromosomes. Thus, there is no scope of inheritance. The trait acquired during the lifetime of an organism dies with the death of the organism. Hence, we can say that acquired characters are not inherited.
Q.42 Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinionMorphology, is the study of the size, shape, and structure of animals, plants, and microorganisms and of the relationships of the parts comprising them. There is immense diversity in size, form, structure and morphological features in the living world. But at the molecular level these, diverse types of organisms exhibit unbelievable similarity. The most complex molecules built up in living organisms are chains of smaller molecules. The various kinds of small molecules are much the same in all life forms, but the specific sequences of components that make up the very complex molecules are characteristic of a given species. For instance, the basic bio molecules like DNA, RNA, carbohydrates, proteins etc. exhibit remarkable similarity in all organisms.
Q.43 In the following crosses write the characteristics of the progeny
Q.44 Study the following cross and showing self pollination in F1, fill in the blank and answer the question that followsParents RRYY × rryy Round, yellow wrinkled, greenF1 – Rr Yy × ? Round, yellow Rr Yy Round, yellow
Q.45 In question 44, what are the combinations of character in the F2 progeny? What are their ratios?(i) Round yellow — 9(ii) Round green — 3(iii) Wrinkled yellow — 3(iv) Wrinkled green — 1Ratios- 9 : 3 : 3 : 1
Q.46 Give the basic features of the mechanism of inheritance(i) Characters are controlled by genes.(ii) Each gene controls called allele one character(iii) There may be two or more forms of the gene. One form may be dominant while the other is recessive.(iv) Genes are present on chromosomes. Each parent possesses a pair of genes for each characteristic on a chromosome.(v)An individual has two forms of the gene whether similar or dissimilar(vi) When a male gamete fuses with the female gamete during fertilization, they make a new cell called zygote with a full set of genes.(vii)The two forms separate at the time of gamete formation.(viii) The two forms are brought together in the zygote.(ix) The zygote carries characteristics of both the parents which are inherited through the genes. The offspring inherits each trait from its parent characters. The trait shown by the first generation is dominant.
Q.47 Give reasons for the appearance of new combinations of characters in the F2progeny.The reason for the appearance of new combination in the F2 generation is given by the law of independent assortment. According to this law, allele pairs separate independently during the formation of gametes. This means that traits are transmitted to offspring independently of one another. Mendel formulated this principle after performing dihybrid crosses between plants that differed in two traits, such as seed color and pod color. After these plants were allowed to self pollinate, he noticed that the same ratio of 9:3:3:1 appeared among the offspring. Mendel concluded that traits are transmitted to offspring independentlyFor example,In a dihybrid cross between two plants having round yellow (RRYY) and wrinkled green seeds(rryy), four types of gametes (RY, Ry, rY, ry) are produced. Each of these segregate independent to each other, each having a 25% of the total gametes produced. Heredity and Evolution : NCERT Intext Questions
Q.1 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?Sol. Trait B is likely to have arisen earlier because it is present in a larger portion of the population.
Q.2 How does the creation of variations in a species promote survival?Sol.Variations take place in response to the changes in the environment. Such variations enable a species to cope with the new changes. Thus, variations help a species in survival.
Q.3 How do Mendel’s experiments show that the traits may be dominant or recessive?Sol. During monohybrid cross by Mendel, one of the pair of traits did not appear in the F1 generation. But that trait appeared in the F2 generation. Based on this observation, Mendel concluded that a trait could be dominant or recessive.
Q.4 How do Mendel’s experiments show that traits are inherited independently?Sol.During dihybrid cross by Mendel, it was observed that when two pairs of traits were considered; each trait expressed independent of the other. Thus, Mendel was able to propose the Law of Independent Assortment which says about independent inheritance of traits.
Q.5 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 trait – blood group A or O – is dominant? Why or why not?Sol.This information is not sufficient. For considering a trait as dominant or recessive, we need data of at least three generations. This data is about only two generations.
Question – 6 - How is the sex of a child determined in human beings?Sol.Somatic cells in human beings contain 23 pairs of chromosomes. Out of them the 23rd pair is composed of different types of chromosomes which are named as X and Y chromosomes. The 23rd pair contains one X and one Y chromosome in a male. On the other hand, the 23rd pair in a female contains X chromosomes. This means that all the eggs would have X chromosome as the 23rd chromosome, while a sperm may have either X or Y chromosome as the 23rd chromosome. When a sperm with X chromosome fertilizes the egg, the resulting zygote would develop into a female child. When a sperm with Y chromosome fertilizes the egg, the resulting zygote would develop into a male child.
Q.7 What are the different ways in which individuals with a particular trait may increase in a population?Sol.When a beneficial trait appears, it can increase in a population. The example of blue beetles in the chapter shows this. Since blue beetles could not be spotted by the crows hence more blue beetles could survive. Sometimes, an accident can also lead to proliferation of a new trait in a population, as happened in the example of trampling of bushes by elephants. It can be said that sudden or gradual changes in the environment or some mutation in a species can lead to a particular trait being passed on through generations.
Q.8 Why are traits acquired during the lifetime of an individual not inherited?Sol. Acquired traits do not bring any change in the genotype of an individual. Hence, acquired traits do not get inherited.
Q.9 Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?Sol.Small numbers of surviving tigers means that a small gene pool of tigers is left. A smaller population reduces the chances of variations. A time may come when lack of useful variations may result in extinction of tigers. Hence, a small number of surviving tigers is a cause of worry from the point of view of genetics.
Q.10 What factors could lead to the rise of a new species?Sol.Speciation can happen if two groups of the same species are somehow prevented from interbreeding for several generations. This can happen because of geographical segregation or because of some genetic changes.
Q.11 Will geographical isolation be a major factor in the speciation of a self-pollinating plant species? Why or why not?Sol.In a self-pollinating plant species, geographical segregation cannot be a major factor in speciation, because no new trait can become a part of the genotype in self-pollination plant species. However, there are some chances of some environmental changes which can lead to some variations.
Q.12 Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not ?Sol.In case of an asexually reproducing organism, geographical isolation cannot be a major factory in speciation because meiosis does not take place during asexual reproduction.
Q.13 Give an example of characteristics being used to determine how close two species are in evolutionary terms.Sol. Let us take the example of humans and apes. Both of them have similar body design. Body hair and mammary glands are present in both the animals. Hence, these two animals are closely related in evolutionary term. Now take some common characters between a fish and a man. Vertebral column, brain box and jaws are present in both of them. But fish and man look entirely different from each other. Hence, they are not very closely related in evolutionary term; rather are like distant relatives.
Q.14 Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?Sol.Wings of a butterfly are composed of chitinous membrane, while wings of a bat are composed of bony skeleton. Hence, these are not homologous organs rather analogous organs.
Q.15 What are fossils? What do they tell us about the process of evolution?Sol. The preserved remains of animals or plants or other organisms from the distant past are called fossils. These fossils tell us about many extinct animals and also give insights into how the evolution could have taken place.
Q.16 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?Sol. In spite of wide differences in size, colour and looks, human beings can interbreed. Hence, all of them are kept under one species.
Q.17 In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better’ body design? Why or why not?Sol. It depends on our perception of ‘better’ design. If complexity of body design is the criterion, then chimpanzee is obviously better than bacteria. But if ability of survival in almost all kinds of habitat is a criterion then bacteria are far ahead than any other group of organisms.Heredity and Evolution : NCERT Exercise Questions
Q.1 A Mendelian experiment consisted of breeding tall pea plant 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 makeup of the tall parent can be depicted as? (a) TTWW (b) TTww (c) TtWW (d) TtWwSol. (c) TtWW
Q.2 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 a grass (d) All of the aboveSol. (d) All of the above
Q.3 In evolutionary terms, we have more in common with (a) A Chinese boy (b) A chimpanzee (c) A spider (d) A bacteriumSol. (a) A Chinese boy
Q.4 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?Sol.This information is not sufficient. For considering a trait as dominant or recessive, we need data of at least three generations. This data is about only two generations.
Q.5 How are the areas of study; evolution and classification interlinked?Sol. The modern system of classification is also called phylogenetic classification; which means it is based on evolutionary relationships. Hence, evolution and classification are closely related.
Q.6 Explain the term analogous and homologous organs with examples.Sol. Homologous Organs: Organs which have common design but serve different functions in different animals are called homologous organs. For example; the forelimbs of all tetrapods are composed of humerus, radio-ulna, tarsals and metatarsals. Yet, the forelimbs of frogs are adapted to a jumping movement, those of birds are used for flying and those of humans are used for handling tools. This shows that frogs, birds and humans have evolved from a common ancestor.Analogous Organs: Organs which have different design but serve a common function in different animals are called analogous organs. Wings of birds and wings of bat are good examples of a pair of analogous organs. Wings of birds are composed of all the bones of forelimb and are covered with feathers. Wings of bats are mainly composed of the digital bones and a thin membrane covering the structure. Yet wings in both the organisms are used for flying.
Q.7 Outline a project which aims to find the dominant coat colour in dogs.Sol.For this, take a male dog with brown coat and bitch with white coat. Cross them to get the F1 generation. After that, allow the F2 generation to come into being. Tabulate data from two generations and find out the dominant coat colour.
Q.8 Explain the importance of fossils in deciding evolutionary relationships.Sol.There are certain animals which became extinct millions of years ago. Fossils of many of such animals give important clues about missing links in the evolutionary relationship. The fossil of archaeopteryx is a good example of missing link. The fossil of archaeopteryx shows characters of birds and reptiles; which suggests that birds have evolved from reptiles. This example shows the importance of fossils in deciding evolutionary relationships.
Q.9 What evidence do we have for the origin of life from inanimate matter?Sol.The famous experiment by Miller and Urey could establish that life originated from inanimate matter. These scientists replicated the conditions which may have existed during the early years of origin of the earth. In that experiment, inorganic substances gave rise to amino acids. Amino acid; we know are the bases of various biomolecules.
Q.10 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?Sol. During sexual reproduction, genotype of the progeny is contributed by two different individuals. This opens up scope for various permutations and combinations. Moreover, the crossing over during meiosis is another means for producing variations. Hence, there are more chances of variations during sexual reproduction than during asexual reproduction.
Q.11 How is the equal genetic contribution of male and female parents ensured in the progeny?Sol. Gametogenesis involves meiosis which leads to haploidy in the gametes. A zygote thus gets 50% of genes from each parent. Thus, equal genetic contribution is ensured from male and female parents.
Q.12 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?Sol. This statement is true to some extent. There are many apparent variations which help an individual in survival. But there are certain variations which may not be beneficial, yet they are inherited through subsequent generations. The colourful plumage of peacock is a good example. The colourful plumage of a peacock helps it in finding a suitable mate but it also makes it conspicuous for its predators.
Q1)Define evolution.
Ans-It a slow gradual process which occurs due to cumulative effects of adaptations and helps it to survive in a better way.
Q2)How are fossils helpful in developing evolutionary relationships?Ans: Fossils forms a connecting link between groups of organisms.Q3)Cat’s paw ,human hand and horse’s legs-are these organs homologous or analogous? Give reason
Ans- They are homologous organs as they are of same origin performing different functions.origin is forearm modified.Q4)Wings of bird and wings of insect-are these organs homologous or analogous?give one suitable season to support your answer.
Ans-They are analogous organs as both have developed from different origin and perform same function of flying.
Q5)Give one difference between eyes and eye spot.Which animal possesses eye spots?Ans-eyes are well developed organs helping to form an image, but eye spots just enable the animalto distinguish between day light and darkness.e.g. planaria and euglena possess eye spots
Q6) Give one difference between artificial selection and natural selection.Ans-Artificial selection is that in which man selects the beneficial gene and modifies it according to his requirement whereas in natural selection nature selects the advantageous gene and helps it to multiply.
Q7) What is true- humans have evolved from chimpanzees or humans and chimpanzees both have evolved from a common ancestor?Ans- Both have evolved from a common ancestor because both are existing today .man has not replaced chimpanzees.
Ans - The mechanism behind the expression of trait is the presence of a functional gene.When gene is functional it is capable of producing a hormone or enzyme which helps in expression of that trait.But sometimes genes get altered and become non-functional,then the enzyme is not produced and the trait does not get expressed.
Q9) What will happen to the expression of a particular trait if agene get altered?Ans - When gene gets altered the corresponding enzyme is not produced,hence the hormone related to it is not produced and the particular trait does not expressed.there are chances that instead a disease maybe seen due to altered gene
Q10)What are various ways by which genes can enter a population?Ans. The various way area) GENE MIGRATION is gene flow which occurs when some members of main population migrate to other areas and may not come back .this is geographical isolation.b) GENETIC DRIFT -is change in gene frequency due to chance or accident and not by natural selection.c) NATURAL SELECTION-is a process in which better quality genes sekected by nature areallowed to multiply.d) MUTATIONS arise suddenly- they are sudden changes in the gene inherited by offsprings for atleast 4-6 generations.
Q11) How will new species arise in case:a) Two sub-populations are separated due to a huge mountain in between them?b) A small population of individuals gets drifted away from the main land due to sea?Ans. New species will arise;a) The huge mountain acts as a geographical barrier and the members of the two sub-population will not be able to mate with one another due to this mountain .this will keep mating within the members of their own sub-population and hence two new species will arise.b) when the small population gets drifted away from main land by sea,here also chances are that there may be some kind of gene flow between the partly separated populations,but if the two populations do not meet, chances are that two new species would arise.
Q12) Only advantageous variations help in the evolution of an organism giving rise to a new species.expalin with the help of an example.Ans.This is because the advantageous variations are selected by nature and allowed to multiply or propogate fast to increase their members.because such variations help an individual to survive in a better manner in changing environment the population increases.this can be explained as underA- EVOLUTION OF EYE which has occurred bit bt bit and not in one step.even the rudimentary eye was advantageous to Planaria or Octopus even though a clear image was not formed as in humans still it gave a fitness advantage.B-EVOLUTION OF WING-earlier feathers were formed to provide warmth to the body,later these feathers helped in flying.
Type-II SHORT ANSWER QUESTIONS (2 marks)
1. What are transgenic organisms? Which property of DNA is used as a tool in genetic engineering?Ans. The organisms that contain a segment of foreign DNA are known as transgenic organisms.The complimentary property of the nucleotides of DNA.is the most powerful tool in genetic engineering.
2. Explain how the sex of the child is determined at the time of conception in human beings.Ans. Male human beings have XY sex-chromosomes and female human beings have XX sex-chromosomes. If a sperm carrying x-chromosome fertilizes with the ovum, then sex of the baby will be female. If a sperm carrying y-chromosome fuses with the ovum, the sex of the baby will be male.
3. By comparing the similarity of nucleotide sequences in DNA of different kinds of organisms, evolutionary relationships can be established.a) Arrange the following according to their evolutionary closeness (You may use your knowledge of classification also) Cockroach, mango tree, gorilla, fish. b) Whose DNA among the following do you think is most similar to that of humans. Ans. a) cockroach – fish – gorilla b) Gorilla
4. Mention the ways by which variant genotypes are produced in organism?Ans. a) gene mutation b) Crossing over c) Hybridization
5. In human beings blue eye colour is recessive to brown eye colour . If a brown eyed man has a blue eyed mother then find a) What are the possible genotypes of his father? b) What is the genotype of the man and his mother?Ans. BB , Bb B. Man: Bb, mother: bb
6. What are fossils? Of what interest are fossils to the evolutionary biologists?Ans. A fossil is the remnant or impression of an organism that lived in the Remote past. Use of Fossilsa)Phylogeny , the evolutionary history can be reconstructed from the fossils.b) The fossil record has helped in building the broad historical sequence of biological evolution.
SHORT ANSWER QUESTION (3 marks)
1. a) Who isolated DNA for the first time from pus cells? b) Why is DNA called polynucleotide? c) Name two purine nitrogenous bases found in a DNA molecule.Ans. a) F.Meishcer, named it nuclein. b)DNA is called polynucleolide because it is a polymer or long chain of nucleolide. c)Purine:- Adenine and Guanine.
2. a) Who put forward the double helical model of DNA? b) What are the three chemically essential parts of nucleotides constituting a DNA?Ans. a) Watson and Crick.b) Nucleotide constituting –DNA Nitrogen bases (Purines and Pyrimidines), Pentose sugar(Deoxyribose sugar) and a phosphate molecule.
3.Guinea pig having black colour when crossed with guinea pig having same colour produced 80 offspring, out of which 60 were black and 20 were white. Now,find out:a)What is the possible genotype of the guinea pigs?b)Which trait is dominant and which trait is recessive?c)What is this cross called as and what is its phenotypic ratio?Ans.a) Bb x Bb b)Black is dominant and white is recessive. c)Monohybrid cross, phenotypic ratio=3:1
4.Write a brief account on salient points of Lamarck‘s theory. Who disproved this theory?A. Lamarckism1.The use and disuse of an organ leads to acquiring of change in the features of that organ.2. These changes are inherited by the offspring.3. Favourable variations result in evolution of new species. August Weisman.
5. Distinguish between acquired and inherited traits giving one example of each.Ans .Acquired traits1) A trait (or characteristic) of a organism which is ‗not inherited‘ but develops in response to the environment is called an acquired trait.(2) The acquired traits of an organism can not be passed on to its future generations. e.g. low weight‘ of beetle, cut tail‘ of a mouse.Inherited traits1) A trait (or characteristic) of an organism which is caused by a change in its genes (or DNA) is called an inherited trait.2) The inherited traits of an organism are passed on to its future generations. e.g. red colour of beetles, fur coat of guinea pigs.
LONG ANSWER QUESTIONS – (5marks)
1. a. What is genetics?b. Give the common name of plant on which Mendel performed his experiments.c. What for did Mendel use the term factors and what are these factors called now.d. What are genes? Where are the genes located?Ans. A. The branch of biology that deals with the study of heredity and variation.b. Garden pea – Pisum sativum.c. The units of inheritance of characters. These factors are now called as genes.d.Gene is a hereditary unit, a segment of DNA. It is located on a chromosome at a particular locus or position.
1. Define heredity. (1 mark)
2. What is speciation? (1 mark)
3. Define variation? (1 mark)
4. Differentiate between homologous organs and analogous organs. (2 marks)
5. If a trait A exist 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? (2 marks)
6. Why are the small numbers of surviving tigers a cause of worry from the points of view of
genetics? (2 marks)
7. Will geographical isolation be a major factor in the speciation of a self-pollinating plant
species? Why or why not? (2 marks)
8. Explain the mechanism of sex determination in human beings. (2 marks)
9. Define fossils. Explain briefly any two ways in which the study of fossils helps in
understanding about the base life. (3 marks)
10. In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a
better body design? Why or why not? (3 marks)
11. Explain with example how characteristics of a population changes over the year for the
following situations:
(i) To gain survival advantages
(ii)Due to accidental survival
(iii) Temporary change of characteristics. (5 marks)
2. What is a gene? (1 mark)
3. Write the scientific term used for ‘science of heredity and variation’? (1 mark)
4. Explain why evolution cannot be said to progress from lower forms to higher forms. (2 marks)
5. How does the creation of variations in a species promote survival? (2 marks)
6. What are the different ways in which individuals with a particular trait may increase in a
population? (2 marks)
7. Give an example of characteristics being used to determine how close two species are in
evolutionary terms. (2 marks)
8. 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? (2 marks)
9. How is the sex of the child determined in human beings? (3 marks)
10. What are fossils? What do they tell us about the process of evolution? (3 marks)
11. Define the term ‘evolution’. Why are traits acquired during the life-time of an individual not
inherited? (3 marks)
12. Define ‘evolution’? State Darwin’s theory of evolution. (5marks)
1. State one advantage of variation of a species. [2009]
Ans. The variation of a species increases the chance of its survival in a changing environment.
2. What is the effect of DNA copying which is not perfectly accurate on the reproduction process? [2008]
Ans. DNA copies generated will be similar but it will not necessarily be identical to the original.
3. What decides that humans give rise to humans? (Imp.)
Ans. It is the heredity that decides that humans give rise to humans.
4. What are hereditary characteristics?
Ans. The characteristics which can be passed from parents to the children are called hereditary characteristics.
5. Are the variations created by sexual reproduction heritable or non-heritable? (Imp.)
Ans. The variations created in sexual reproduction are heritable.
6. What are the components of a chromosome? (Imp.)
Ans. Two chromatids attached at a centromere, together form a chromosome.
7. What is a retrovirus?
Ans. A virus that has RNA as its genetic material is known as a retrovirus, e.g., AIDS virus.
8. What is a sex chromosome?
Ans. A chromosome that helps in determining the sex of an individual is known as a sex
chromosome.
9. How many chromosomes are there in a human ovum?
Ans. 23 chromosomes.
10. Who coined the term ‘factor’? (Imp.)
Ans. The term ‘factor’ was coined by Mendel.
11. Give the monohybrid ratio.
Ans. Monohybrid ratio = 3 : 1.
12. Write the dihybrid ratio.
Ans. Dihybrid ratio = 9 : 3 : 3 : 1.
13. Define the term ‘speciation’.
Ans. Speciation is the formation of new species from pre-existing species. Speciation depends on distribution of
population, mutation, micro-evolution and macro-evolution.
14. What is a factor?
Ans. The carriers of hereditary information were called factors by Mendel.
15. Name the most accepted theory of evolution.
Ans. Synthetic theory of evolution.
16. Define the term ‘evolution’.
Ans. Evolution can be defined as the gradual unfolding of the organisms from pre-existing
organisms through change since the beginning of life.
17. Whose theory influenced Darwin? What did Darwin fail to explain? (Imp.)
Ans. The theory of Malthus inspired Darwin. Darwin failed to explain how variations arise.
18. Define ‘recessive characteristic’.
Ans. Any characteristic present in the parental generation that does not appear in F1 generation but reappear in F2
generation is known as recessive character.
19. What is the basis of sex determination in most plants and animals? (Imp.)
Ans. In most plants and animals genetic basis of sex determination is gamete (chromosome).
20. What are fossils? What do they tell about the process of evolution? [2008]
Ans. The preserved traces or impressions of the body parts of living organisms are called fossils. Since fossils reveal
evolutionary relationships among different organisms, they are the proof of organic evolution.
Two marks
1. 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
species, which trait is likely to have arisen earlier?
Ans. In asexual reproduction there very small variation in trait due to small inaccuracies in DNA copying . Therefore,
trait B which exists in 60% of population must have arisen earlier than trait A which occurs in 10% of the population.
2. How does creation of variations in a species promote survival?
Ans. The variations generated in offspring do not have equal chances to survive and get inherited in the next
generation as number of environment factors as well as on the nature of variation.For example, in a heat wave most
of the bacteria will die but a few having pre-adaptation or variation to tolerate heat wave, will survive and multiply.
3. ‘Variations that confer an advantage to an individual organism only will survive in a population.’ Justify.
Ans. Useful variations give advantage to individuals in obtaining more food, reproduction, adaptation to
environmental changes and higher success in the struggle for existence. They give benefit in survival and increasing
the population. Differential reproduction increases the useful variations in the populations. Other individuals with
harmful variations will be destroyed. For example, some bacteria have ability to tolerate high temperature. But other
non-resistant bacteria will be killed.
4. What do you understand by the term heredity? [2008]
Ans. The transmission of recognisable traits or characters like height, complexion, eye-colour, shape of nose, shape
of chin, etc. from the parents to their offspring is called heredity.
5. What constitutes the link between one generation and the next? [2008]
Ans. The hereditary information is transferred from parents to offspring through the gametes. So, gametes
constitute the link between one generation and the next and pass on the paternal and maternal characters to the
offspring.
6. "The sex of the children is determined by the what they inherit from their father and not from the mother."
Justify. [2008]
Ans. The children inhert similar chromosomes (22 + X) from the mother but the sex of the children will depend on
the chromosome they inherit from the father. If a child inherits (22 + X) chromosomes from the father that will be a
girl but when a child inherits (22 + Y) chromosomes from the father that will be a boy. Therefore, the sex of a child is
determined by the inheritance of X or Y chromosome from the father.
7. Explain the terms analogous and homologous organs with one example of each. [2008]
Ans. Analogous organs : — The organs which look alike and perform same functions but are quite different in basic
structure and embryonic origin in different species are called analogous organs. For example, the wing of a bat and
the wing of a bird are analogous organs.
Homologous organs : — The organs which are similar in basic structure but perform different functions in different
species are called homologous organs. For example, the
forelimbs of a human, a birds, a lizard and a frog show
similarity in basic structures.
8. 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? [2008]
Ans. Yes, the given information is enough. Blood group O is
dominant. It is because the F1 progeny, i.e. daughter has blood
group O which is dominant over blood group A.
9. Define variation in relation to a species. Why is variation beneficial to the species? [2008]
Ans. The differences among the individuals of a plant or animal of a species are called variations. All the variations in
a species do not equally survive in the environment where they are found. Depending on the nature of variation,
different individuals have different types of advantages. For example – bacteria can survive in very high temperature
also.
10. Describe briefly four ways in which individuals with a particular trait may increase in a population. [2008]
Ans. The individuals with a particular trait may increase in a population in the following ways–
(i) Sufficient Food :- By obtaining more food the individuals can increase in growth and reproduction.
(ii) Differential Reproduction :- It gives an advantage to the individuals to survive and reproduce.
(iii) Variations : The useful variations help the individuals to adopt the environmental condition.
(iv) Genetic Drift :- The random change in the frequency of alleles in a population over successive generations due to
error during DNA copying on the gametes.
11. What are acquired characteristics? (Imp.)
Ans. Characteristics which people acquire during their lives, like knowledge and skills are called acquired
characteristics. Development of muscles in an athlete is an acquired characteristic.
12. What is variation?
Ans. Variation is the difference or dissimilarity between parents and children as individuals of a species. It can be
defined as the occurrence of difference among the individuals of a species.
13. Why is variation less common in asexually reproducing organisms?
Ans. Asexual reproduction tends to preserve the similarities among all the individuals belonging to a given line of
descent. Therefore, asexually reproducing organisms show more hereditary features.
14. Clarify the term heredity and variation. (Imp.)
Ans. Heredity means continuity of features from one generation to another whereas variation is the occurrence of
differences among the individuals.
15. Define variation in relation to a species. Why is variation beneficial to the species? (Imp.)
Ans. The differences or dissimilarities between the parents and the children as individuals of the same species are
called variations.
Variation is beneficial to the species as
(i) they enable the organisms to adapt themselves in the changing environment.
(ii) variations form the basis of heredity.
(iii) they form raw materials for evolution and development of new species.
16. What are autosomes?
Ans. In females two copies of an unpaired chromosome are present along with paired chromosomes. These are
known as sex chromosomes. The rest of the chromosomes are known as autosomes.
7. What is the reason that a male is called 'heterogametic'? (Imp.)
Ans. A male is called heterogametic because he forms two different types of gametes. One containing 'X'
chromosome and the other containing 'Y' chromosome.
8. What was the basic study material of Mendel? How did he bring in the term 'factor'?
Ans. The basic study material of Mendel were the contrasting characters in various generations of garden pea. He
said that these characters are controlled by units known as factors.
9. Why can the wings of a bird and the wings of a bat not be considered analogous? (Imp.)
Ans. Wings of a bird and a bat are modified forelimbs and hence, show structural similarity. Hence, they cannot be
considered as analogous structures.
10. How did the Mendelian 'factors' acquire a change in the terminology? Who changed it?
Ans. The carriers of hereditary information were called 'factors' by Mendel. Johanssen later called these factors
genes.
1. What is palaeontology? What is its importance? (Imp.)
Ans. Palaeontology is a branch of biology that deals with the study of fossils. It provides a direct evidence of
evolution and is called a written document of evolution.
3 marks
1. The genotype of green stemmed tomato plants is denoted as GG and that of purple stemmed tomato plants is
denoted as gg. When these two are crossed with each other :
(a) What colour of stem would you expect in the F1 progeny?
(b) Give the percentage of purple stemmed plants if F1 plants are self pollinated.
(c) In what ratio would you find the genotypes GG and gg in the progeny?
Draw flow chart in support of your answer. [2011 (T-II)]
Ans. (a) Green stemmed tomato plant Purple stemmed tomato plant (b) If F1 plants are self pollinated 25% purple
stemmed plants
(c) We would find the genotypes GG and gg in 1 : 1 ratio.
2. (a) Name the plant used by Mendel to carry out his experiments.
(b) Study the following cross and answer the questions that follow :
Parents Green and Wrinkled seed × Yellow and Round seed
F1 Generation All Green and Round seeds
F2 Generation Green and Round (9) Green and Wrinkled (3)
Yellow and Round (3) Yellow and Wrinkled (1)
(i) List the dominant and recessive characters.
(ii) Are the characters linked or independent? [2011 (T-II)]
Ans. (a) Garden Pea (Pisum sativum)
(b) (i) Dominant characters are Green and Round seeds.
Recessive characters are yellow and wrinkled seeds.
(ii) The characters are independent.
3. Acquired characters are not inherited. Justify the statement with an example. The wings of
bat and the wings of insects are considered analogous organs. Why? [2011 (T-II)]
Ans. The acquired changes during a lifetime are not inherited by the progeny. It can be understood with the help of
some examples such as —
If a group of mice having tail will breed, their progeny will also have the same type of tail but if the tail of all the
mice is removed by surgery in each generation, no tailless mouse will be produced even after a few generations. It is
because the removal of tail is a physical change which could not make a change in the gene responsible for the
presence of tail in mice.
The wings of birds and the wings of insects are considered as analogous organs because they have different
structures but perform the same function.
4. How has the method of artificial selection by humans helped in the evolution of different vegetables? Explain in
brief giving an example. [2011 (T-II)]
www.jsuniltutorial.weebly.com/ Page 6
Ans. Humans have developed different varieties of vegetables from a single wild cabbage by artificial selection some
of these are as follows —
(i) Some farmers have wanted to select very short distances between the leaves and developed the present day
cabbage.
(ii) Some farmers selected immature green flowers and developed the broccoli.
(iii) Some have selected the sterile flowers and developed the cauliflowers.
(iv) Some farmers selected the swollen part of the wild cabbage and developed the kohlrabi.
(v) Some of them have selected the larger leaves and developed Kale.
So all these vegetables are descended from a common ancestor.
5. (a) Write two factors which could lead to the rise of a new species.
(b) (i) What is the scientific term of the organs shown below? (ii) How do these organs provide evidence in support
of evolution? [2011 (T-II)]
Ans. (a) Following factors could lead to the rise of a
new species :
(i) Physical barrier : Absence of gene flow amongst
sub-populations due to the presence of physical
barriers lead to the rise of a new species.
(ii) Gene Mutation : A large mutation can make same
members reproductively isolated from the rest. It
leads to the rise of a new species.
(b) (i) The organs shown above are homologous organs.
(ii) These organs are similar in basic structure and embryonic origin but perform different functions in different
species.
6. (a) Name the type of sex chromosome present in human male and human female.
(b) With the help of a flow chart determine genetically in human beings the sex of the offspring if a sperm carrying Xchromosome
fertilizes the egg? [2011 (T-II)]
Ans. (a) The type of sex chromosome present in human male and female is known as Chrosome.
(b) Male Female
If a sperm carrying X-chromosome fertilizes the egg, the offspring would be girl.
7. In pea plant round seed is dominant over the wrinkled. If a cross is carried between these two plants, give answer
to the following questions. (a) Mention the genes for the traits of parents. (b) State the trait of F1 hybrids.
(c) Write the ratio of F2 progeny obtained from this cross. What is the name of the cross? [2011]
The cross is monohybrid because in it only one pair of character is
taken into consideration.
8. Guinea pig having black colour when crossed
with guinea pig having same colour produced
100 offsprings out of which 75 were black and
25 were white. Now find out.
(a) What is the possible genotype of the guinea
pig?
(b) Which trait is dominant and which trait is
recessive?
(c) What is this cross called as and what is the
ratio of F2 progeny obtained from these cross?
[2011 (T-II)]
Ans. (a) The possible genotype of the guinea
pig is Bb.
(b) Black colour is dominant and white colour is
recessive.
(c) This cross is called monohybrid cross.
Phenotypic ratio of F2 progeny is 3 : 1
Genotypic ratio of F2 progeny is 1 : 2 : 1
9. Give appropriate terms for the following :
(a) The trait which can express itself in next generation.
(b) The trait an organism have due to inheritance.
(c) Origin of a new species from pre-existing one. [2011 (T-II)]
Ans. (a) Inherited trait (b) Inherited trait (c) Speciation
10. If a pure tall pea plant is crossed with a pure dwarf plant, then in the first generation only tall plants appear.
(a) What happens to the traits of the dwarf plant?
(b) In the second generation, the dwarf trait reappears. Why? [2011 (T-II)]
Ans. (a) According to law of dominance, ‘‘when a pair of contrasting characters are present together, only one is able
to express itself in the F1 generation while others remain suppressed’’. Dwarf trait is recessive trait which does not
express itself in the hybrid (First generation).
(b) Both the characteristics (tall and dwarf) were inherited from the parents to F1 progeny. In F1 progeny only
tallness character was expressed. However, the second generation progeny (F2 progeny) expressed both characters
in a particular ratio i.e. 3 : 1 (three tall and 1 dwarf).
11. How was it established that genes are located on the chromosomes? (Imp.)
Ans. In all the organisms, the number of chromosomes is fewer than the number of characteristic features, which
are many. If 'genes' are responsible for a characteristic feature, they have to be certainly many more than the
number of chromosomes. For example, in human beings, the total number of chromosomes is 23 pairs, but the total
number of characters (genes) have been estimated to be between 30,000 to 40,000. This suggests that genes are
located on the chromosomes.
12. Clarify the terms 'haploid' and 'diploid'. What is the relation between the two terms? (Imp.)
Ans. The paired condition of chromosomes is known as diploid whereas a set of unpaired chromosomes is said to be
haploid.
During gamete formation, the diploid chromosomes segregate and haploid conditions achieved. After fertilisation,
the diploid condition is again restored.
13. Explain the law of segregation by taking an example.
Ans. Law of segregation : Paired factors responsible for a character segregate into gametes and are recombined at
the time of fertilisation.
yellow colour is dominant over green seed colour. When F1 plants are selfed we get yellow and green seeded plants
in the ratio of 3 :1.
14. Suggest three similarities between Mendel's 'factors' and 'chromosomes'.
Ans. Similarities between Mendel's factors and chromosomes are as follows :
(1) Both Mendel's factors as well as chromosomes are present in pairs.
(2) Both segregate during meiotic cell division to form gametes in which they remain unpaired.
(3) After fertilisation the paired feature is again restored in the zygote which develops into an offspring.
15. Justify logically that many genes are present on one chromosome.
Ans. In all organisms the number of chromosomes is fewer than the number of characteristic features which are
many. If 'genes' are responsible for characteristic features, they have to be certainly many more than the number of
chromosomes.
16. Why are the traits acquired during lifetime of an individual not inherited? [2009]
Ans: This is because Acquired traits develop due to the effects of environmental factors, use and disuse of organs
and special (conscious) efforts for example Learning of dance, music, etc.
Differences between Acquired and Inherited Traits :
Acquired Traits Inherited Traits
� These are somatic variations. � These are genetic variations.
� Acquired traits develop due to the effects of
environmental factors, use and disuse of organs and
special (conscious) efforts..
� Inherited traits develop due to reshuffling of genetic
material and mutations
� These traits develop throughout the lifetime of an
individual and die with the death of that individual.
� These traits are transferred (inherited) by the parents
to their offspring. These do not die but are passed on to
the next generation.
� Example—Learning of dance, music, etc, and muscular
body of a wrestler..
� Example—Attached or free earlobe and curly hair
Q.1.What is heredity?
Ans : Heredity refers to the transmission of characters or traits from the parents to their
offspring.
Q.2. Name the plant on which Mendel performed his experiments?
Ans:- Garden Pea (Pisum sativum.)
Q.3. Define variation?
Ans :Variation refers to the differences in the characters or traits about the individuals of a
species.
Q.4. Define a gene?
Ans: Gene is a small segment of DNA on a chromosome occupying specific position in which is a
hereditary determinant or unit of a biological function.
Q.5. Write the expanded form of DNA?
Ans: DNA - Deoxyribonucleic Acid.
Q.6. what are the components of chromosome?
Ans: Each chromosome is double or replicated and consists of two threads like structures called
chromatids attached to each other at centromere.
.Each chromatid has a number of dense areas arranged linearly which are known as
chromomeres. They represent the areas of active genes.
.Internally each chromosome has two spirally coiled threads called chromonemata embedded in
matrix. These are DNA molecules.
Q.7. What is a retrovirus?
Ans : A virus having RNA (Ribonucleic acid) as genetic (heredity) material is called Retrovirus. For
example, Human immunodeficiency virus (HIV) is a retrovirus.
Q.8. What is sex chromosome?
Ans : A chromosome which is associated with sex determination is called sex chromosome.
Q.9. How is sex determined in human beings?
Ans :Sex is determined at the time of fertilization and the two sexes are produced in
approximately equal numbers. A human male has XY sex-chromosomes and produces two types
of sperms (heterogametic). Either with X-chromosome or with Y-chromosome.
A human female has XX sex-chromosomes and produce ova of one type (homogametic) all with
X-chromosomes.
Q.10. What do you understand by evolution?
Ans :Evolution is the sequence of gradual changes which takes place in the primitive organisms
over million of years in which new species are produced.
Q.11. Define homologous organs?
Ans : Homologous organs are those organs which have the same basic structure and
developmental origin but have different functions and appearance. e.g., the forelimb of a frog, a
bird and a man seem to be built from the same basic design of bones, but they perform
different functions.
Q.12. Explain Darwin’s theory of evolution?
Ans :According to Darwin’s theory of evolution:
(i) There is natural variation within any population and some individuals have more favourable
variations than others..
(ii) Population remains fairly constant even though all species produce a large number of off
springs.
(iii) This is due to ‘competition’ or struggle for existence between same and different species.
(iv) The struggle for survival within population eliminates the unfit individuals and those with
‘favourable variations’ survive and pass on these variations to their progeny to continue. This is
called natural selection.
(v) The favourable variations are accumulated over a long time period leading to the origin of a
new species.
Q13. Define genetics. What is the contribution of Mendel in this branch of biology?
Ans :Genetics is the branch of biology which deals with the study of heredity and variation.
Contribution of Mendel : Mendel done his experiments on garden pea(pisum sativum) and
discovered the scientific principles which govern patterns of inheritance i.e. the principle of
inheritance. He explained the contrasting characters are controlled by units which he
called Factors. Today these factors are called genes.
Q14. Where are the genes located? What is the chemical nature of gene?
Ans : Genes are located on chromosomes. Chemically, genes are made of DNA(deoxy ribonucleic
acid).
Q15. During which stage of cell division can chromosome be seen? Write the features of
prokaryotic and eukaryotic chromosome.
Ans : Chromosomes can be seen during the metaphase stage of the cell division.
FEATURES OF PROKARYOTIC CHROMOSOME:
Prokaryotes (bacteria) have a single chromosome. The chromosome is circular and made up of a
DNA molecule associated with a few proteins.
EUKARYOTIC CHROMOSOME:
Eukaryotes contain many chromosomes. Each is made up of a DNA molecule andmore number
of basic proteins. The chromosomes are not circular but rod shaped.
Q 16. Who provided the evidence of DNA as a genetic material? Write the names of components
of DNA?
Ans :Griffith, Avery , McLeod and McCarty established that DNA is the genetic material.
Components of DNA : A DNA molecule consists of two polynucleotide chains. Each nucleotide
consists of (a) nitrogenous base (Adenine/guanine/Thymine or Cytosine) ,a pentose
sugar(deoxyribose) and a phosphate group.
Q17 .What do you understand by the double helical structure of DNA? Who proposed this
structure?
Ans : J.D.Watson & F.H.C.Crick proposed the double helical structure of DNA.
The important features of the model are:
(i) DNA molecule consists of two polynucleotide strands forming a double helix.
Each helical turn has a length of 3.4nm in which ten nucleotides present.
(ii) Each polynucleotide stand has a backbone of sugar and phosphate. The nitrogenous base is
attached to the sugar.
(iii) The nitrogenous bases of the two stands of a double helix form a pair with the help of
hydrogen bonds. Adenine pairs with Thymine , whereas the guanine pairs with Cytosine. Such a
specific pairing of the bases is called complimentarypairing.
A and T are complimentary to each other and G is complimentary to C. The hydrogen bonding
between the nitrogenous bases holds the two strands together as a result of which the base
pairs remains stacked between the two strands.
This structure can be compared with the steps of a spiral staircase.
Q18.Describe the different types of chromosomes.
Ans:- depending on the position of the centromere,a chromosome may have either equal arms,
or one long and one short arm. Accordingly, four types of chromosomes are known :
Metacentric:It is a chromosome with the centromere near the middle and the two arms are
almost equal in length.
Sub-metacentric:In this type of chromosome the centromere is situated closer to one end. As a
result , one arm of the chromosome is long and one is slightly short.
Acrocentric:It is the type of the chromosome which has the centromere near the end. In this case
one arm is very long and the other one is very short.
Telocentric:In this type of the chromosome, the Centromere is situated at the tip of the
chromosome.
Q19. How many types of nitrogenous bases are present in DNA? Name them.
Ans:-In DNA two types of nitrogenous bases are present. These are (i) PURINES which
are adenine and guanine (ii)PYRIMIDINES which are Thymine and cytosine.
Q.20.How do embryological studies provide evidence for evolution?
Ans:- The similarities in embryonic development reinforce the idea of evolution from common
ancestors. The sequence of embryonic development in different vertebrates shows striking
similarities. Notochord and gill clefts appear in the embryos of all vertebrates.
Q.21. Define evolution. And Describe the contribution of Lamarck?
Ans:- Evolution is the sequence of gradual changes which takes place in the primitive organisms
over millions of years in which new species are produced.
Contribution of Lamarck:
(i) Lamarck proposed a theory called “The Theory of inheritance of Acquired Characters” to
explain the origin and evolution of species.
(ii) The theory was explained in his book ‘Philosophic Zoologique.
Q.22. What are homologous organs? How do they provide evidence in support of evolution?
Ans:- Homologous organs are those organs which have the same basic structure and
developmental origin but have different functions and appearance.
Homologous organs support evolution:
(i) The similarities of structure and origin of organs indicate that all vertebrates had common
ancestors. For example, the forelimbs of humans, whale and bat show structural similarities but
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functional dissimilarities. Forelimbs in humans used for grasping or holding the things, in whale
for swimming and in bat for flying.
(ii) All the organs and systems of the vertebrates show fundamental similarities i.e. homology,
which indicate towards common ancestry. Thus, homologous point that organic evolution has
taken place.
Q.23. Define the following terms?
Ans:- (i) Vestigial organs: Vestigial organs are those organs, which are rudimentary and
functionless in the evolved forms but are well developed and functional in the ancestral forms.
Eg: Vermiform appendix in human beings.
(ii) Analogous organs : Are those organs which have different basic structure and developmental
origin but have similar appearance and perform similar functions. Eg: The wings of and insect
and a bird have different structures, but they perform the same function of flying.
Q.24. 1. What are transgenic organisms? Which property of DNA is used as a tool in genetic
engineering?
Ans:-The organisms that contain a segment of foreign DNA are known as transgenic
organisms.The complimentary property of the nucleotides of DNA.is the most powerful tool in
genetic engineering.
Q.25. Explain how the sex of the child is determined at the time of conception in human beings.
Ans:- Male human beings have XY sex-chromosomes and female human beings have XX sexchromosomes.
If a sperm carrying x-chromosome fertilizes with the ovum, then sex of the baby
will be female. If a sperm carrying y-chromosome fuses with the ovum, the sex of the baby will
be male.
1. Q. Why did Mendel chosen pea plant for his experiments?
Answer: Mendel chose pea plant for his experiments because it is:
(a) Easy to grow (b) Short lifespan (c) Easily distinguishable characters (d) Larger size of flower
(e) Self-pollinated.
2. Q. What do you understand by evolution?
Ans:-Evolution is the sequence of gradual changes which takes place in the primitive organisms
over million of years in which new species are produced.
3. Q. What is a gene?
Ans :Gene is a small segment of DNA on a chromosome occupying specific position in which is a
hereditary determinant or unit of a biological function.
4. Q. With the help of suitable examples, explain why certain traits cannot be passed on to the
next generation. What are such traits called?
Solution: The traits which are acquired during the lifetime of a person are called acquired traits.
These traits involve changes in non reproductive cells (somatic cells) which are not transferred to
germ cells. So, these traits cannot be passed on to the next generation. For example: Learning
skills like swimming, dancing, cooking, body building, etc are acquired traits and cannot be
passed on to the next generation.
5. Q. A trait may be inherited, but may not be expressed." Justify this statement with the help of
a suitable example.
Ans: When a tall plant was crossed with a short plant, the first (F1) generation plants were all
tall. But when the F1 generation plants were crossed, the second (F2) generation plants were not
all tall: there were both tall and short plants.
This shows that the F1 plants had inherited their trait from the short plants but did not express
it in the presence of the tallness, and had transferred it to the next generation.
6. Q. 'It is a matter of chance whether a couple will give birth to a male child or a female child."
Justify this statement with the help of a flow chart showing the fusion of sex chromosomes.
Ans: Sex is determined at the time of fertilization and the two sexes are produced in
approximately equal numbers. A human male has XY sex-chromosomes and produces two types
of sperms (heterogametic). Either with X-chromosome or with Y-chromosome.
A human female has XX sex-chromosomes and produce ova of one type (homogametic) all with
7. Q. What are homologous organs? How do they provide evidence in support of evolution?
Ans: Homologous organs are those organs which have the same basic structure and
developmental origin but have different functions and appearance.
Homologous organs support evolution:
(i) The similarities of structure and origin of organs indicate that all vertebrates had common
ancestors. For example, the forelimbs of humans, whale and bat show structural similarities but
functional dissimilarities. Forelimbs in humans used for grasping or holding the things, in whale
for swimming and in bat for flying.
(ii) All the organs and systems of the vertebrates show fundamental similarities i.e. homology,
which indicate towards common ancestry. Thus, homologous point that organic evolution has
taken place.
8. Q. What is a retrovirus?
Ans:A virus having RNA (Ribonucleic acid) as genetic (heredity) material is called Retrovirus. For
example, Human immunodeficiency virus (HIV) is a retrovirus.
9. Q. Who provided the evidence of DNA as a genetic material? Write the names of components
of DNA?
Ans:Griffith, Avery , McLeod and McCarty established that DNA is the genetic material.
Components of DNA: A DNA molecule consists of two polynucleotide chains. Each nucleotide
consists of (a) nitrogenous base (Adenine/guanine/Thymine or Cytosine) ,a pentose
sugar(deoxyribose) and a phosphate group.
10 Q. How many types of nitrogenous bases are present in DNA? Name them.
Ans:-In DNA two types of nitrogenous bases are present. These are
(i) PURINES which are adenine and guanine (ii) PYRIMIDINES which are Thymine and cytosine.
11.Q. How do embryological studies provide evidence for evolution?
Ans: The similarities in embryonic development reinforce the idea of evolution from common
ancestors. The sequence of embryonic development in different vertebrates shows striking
similarities. Notochord and gill clefts appear in the embryos of all vertebrates.
11. Q. Define evolution. And Describe the contribution of Lamarck?
An s: Evolution is the sequence of gradual changes which takes place in the primitive organisms
over millions of years in which new species are produced.
Contribution of Lamarck:
(i) Lamarck proposed a theory called “The Theory of inheritance of Acquired Characters” to
explain the origin and evolution of species.
(ii) The theory was explained in his book ‘Philosophic Zoologique.
12. Q. What are transgenic organisms? Which property of DNA is used as a tool in genetic
engineering?
Ans: The organisms that contain a segment of foreign DNA are known as transgenic organisms.
The complimentary property of the nucleotides of DNA.is the most powerful tool in genetic
engineering.
13. Q.Name the two homologous structures in vertebrates. Why are they so called? How do such
organs help in understanding an evolutionary relationship?
Ans: Limbs of birds, reptiles and humans are all the examples of homologous structures in the
vertebrates. They are called so as the basic structure of the limbs is similar. Though it has been
modified to perform different functions in various vertebrates.
These are organs which are inherited from a common ancestor. Such a homologous
characteristic helps to identify an evolutionary relationship between apparently different species.
14.Q. What are the different ways in which individuals with a particular trait may increase in a
population?
Ans :The different ways in which individuals with a particular trait may increase in a population,
are :
Genetic drift ; Geographical isolation ; Natural selection and Artificial selection
15. Q. Why are the small numbers of surviving tigers a cause of worry from the point of view of
genetics?
Ans : If they all die out became extinct, tiger gene will be lost forever and the coming generation
will not be able to see tiger at all.
CHAPTER-9
Heredity and Evolution
Multiple Choice Questions
1. Exchange of genetic material takes place in
(a) vegetative reproduction
(b) asexual reproduction
(c) sexual reproduction
(d) budding
2. Two pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower progeny. The nature of the cross will be
(a) double fertilisation
(b) self pollination
(c) cross fertilisation
(d) no fertilisation
3. 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’
4. Which of the following statement is incorrect?
(a) For every hormone there is a gene.
(b) For every protein there is a gene.
(c) For production of every enzyme there is a gene.
(d) For every molecule of fat there is a gene
5. 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
6. In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosome is/are
(i) large chromosome
(ii) small chromosome
(iii) Y-chromosome
(iv) X-chromosome
(a) (i) and (ii) (b) (iii) only
(c) (iii) and (iv) (d) (ii) and (iv)
7. The maleness of a child is determined by
(a) the X chromosome in the zygote
(b) the Y chromosome in zygote
(c) the cytoplasm of germ cell which determines the sex
(d) sex is determined by chance
8. 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
9. Select the incorrect statement
(a) Frequency of certain genes in a population change over several generations resulting in evolution
(b) Reduction in weight of the 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
10. 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)
11. 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)
12. A basket of vegetables contains carrot, potato, radish and tomato. Which of them represent the correct homologous structures?
(a) Carrot and potato
(b) Carrot and tomato
(c) Radish and carrot
(d) Radish and potato
13. Select the correct statement
(a) Tendril of a pea plant and phylloclade of Opuntia are homologous
(b) Tendril of a pea plant and phylloclade of Opuntia are analogous
(c) Wings of birds and limbs of lizards are analogous
(d) Wings of birds and wings of bat are homologous
14. 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
15. Which of the following statements is not true with respect to variation?
(a) All variations in a species have equal chance of survival
(b) Change in genetic composition results in variation
(c) Selection of variants by environmental factors forms the basis of evolutionary processes.
(d) Variation is minimum in asexual reproduction
16. A trait in an organism is influenced by
(a) paternal DNA only
(b) maternal DNA only
(c) both maternal and paternal DNa
(d) neither by paternal nor by maternal DNA
1. Which of the following is a working copy
(a) RNA (b) Protein (c) Fats (d) DNA
2. Which of the following is the blue print of body design & body function
(a) RNA (b) Protein (c) DNA (d) Amino acid
3. Spore formation occurs in
(a) Yeast (b) Hydra (c) Amoeba (d) Rhizopus
4. Which of the following can undergo regeneration
(a) Flat worm (b) Round worm (c) Rhizopus (d) Amoeba
5. Rose is multiplied by
(a) tissue culture (b) cutting (c) Layering (d) seeds
6. Pollen grains are produced by
(a) ovary (b) anther (c) filament (d) stigma
7. The male sex organ of a flower is
(a) stamen (b) sepal (c) petal (d) carpel
8. Which one of the following is a unisexual flower
(a) china rose (b) cucumber (c) rose (d) jasmine
9. Male gametes are produced by
(a)pollen grains (b) embryo sac (c) sigma (d) ovary
10. Receptive part of carpel is
(a) ovary (b) Stigma (c) placenta (d) style
11. On germination each pollen grain produces
(a)one male gamete (b) 3 male gametes (c) four male gametes (d)2 male gametes
12. Gonads form
(a) sex organs (b) sex hormones (c)gametes (d) both b & c
13. In man fertilization takes place in
(a)ovary (b) vagina (c) fallopian tube (d) uterus
14. Which of the following is a machanical barrier to conception
(a) condom (b) abortion (c) Cu T (d) oral pill
15. Development of an ovum from an unfertilized ovum is called
(a)vegetative propagation (b) Parthenogenesis (c) asexual reproduction (d) tissue culture
16. Fertilization in plants occurs in
(a) embryo sac (b) Pollen tube (c) stigma (d) style
17. Name the fusion product of male & female gametes
(a) ovum (b) zygote (c) PEN (d) sperm
18. Which part of the flower forms the fruit
(a) stamen (b) ovary (c) petals (d) ovule
19. The normal duration of menstrual cycle is
(a) one day (b) 14 days (c) 28 days (d) 7-8 days
20. Arrest of reproductive capacity in woman in the age of 45-55 years is known as
(a) menopause (b) Puberty (c) menarch (d) gestation
21. Vital connection between mother and foetus is called
(a)uterus (b) Placenta (c) vagina (d) embryo sac
22. The process of attachment of embryo in the uterus is called
(a) placentation (b)implantation (c) gestation (d) ovulation
23. Which of the following is not an STD
(a) AIDS (b) syphilis (c) typhoid (d) gonorrhoea
24. Which of the following is an IUCD
(a) Cu T (b) Diaphragm (c) tubectomy (d) oral pills
25. Which of the following is a sexually transmitted viral disease
(a)genital warts (b) syphilis (c) typhoid (d) gonorrhoea
very useful for exams.really we can score full marks by reading this
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