CBSE Class 12 Biology Evolution Assignment Set 02

Artificial Selection : It is the process carried out by man to select better breeds of plants and aminals.
Bio-geography : The study of patterns of distribution of plants and aminals in different parts of earth.
Founders Effect : A genetic drift in human population where a population in a new settlement have different gene frequency from that of the parent population. The original drifted population said to be founder.
Gene Pool : Sum total of all the genes in a population.
Genetic Drift : Chance elimination of genes of certain traits from a population due to migration or death.
Panspermia : Units of life in the form of so called spores, which were transferred to earth from outer space (as believed by some scientists).
Saltation : Single step large mutations.
Speciation : It is the formation of new species from the pre-existing ones. Organic (Biological) Evolution : Changes in the characteristics/features of organisms or groups of such populations over a number of generations.
Homologous organs : These have same basic structure and embryonic origin but perform different functions in different species.
Analogous organs : These organs are different in their basic structure and embryonic origin but perform similar functions.
Human Evolution : Ramapithecus ® Australopithecus ® Homo habilis ® Homo erectus ® Homo sapiens ® Homo sapiens sapiens. The Theories of Origin of Life
Theory of Special Creation : According to this theory God has created life within 6 days.

Long Answer Type Questions

Question. Name the law that states that the sum of allelic frequencies in a population remains constant. What are the five factors that influence these values? 
Answer : Hardy-Weinberg Principle states that the sum of allelic frequencies in a population is stable and is constant from generation to generation, i.e., the gene pool (total genes and their alleles in a population remains constant. This is called genetic equilibrium. The sum total of all the allelic frequencies is Five factors that influence these values are
(i) Gene Migration or Gene Flow When migration of a section of population to another place occurs, gene frequencies change in the original as well as in the new population. New genes/alleles are added to the new population and these are lost from the old population. There would be gene flow if this gene migration, happens multiple times.
(ii) Genetic Drift It refers to the elimination of the genes of certain traits when a section of population migrates or dies of natural calamity. It is an evolutionary force operating in small populations whereby gene frequency changes by chance leadings to loss of some genes or gain of others irrespective of their selective advantages or disadvantages.
(iii) Mutation The sudden heritable change which is directionless in gene is called mutation. It alters the genetic frequency or genetic make up of an individual.
(iv) Genetic Recombination This phenomenon occurs during gamete formation when chromosomes pass from parents to offsprings which show new combination of characteristics.
(v) Natural Selection It is a phenomenon by which some members of population having traits that enable them to grow and reproduce at higher rater are favoured. Hence, they leave more surviving offspring in the next generation than others.

Question. Explain divergent evolution in detail. What is the driving force behind it?
Answer : Divergent evolution is the evolution of a number of different forms of animals or plants froms of a common ancestral form. The driving force behind, it is adaptations to newly involved habitat and the prevailing environmental conditions there. As the original population increases in size, it spreads out from its centre of origin to exploit new habitas and food resources. In time this results in a number of populations each adapted to its particular habitat, eventually these populations will differ from each other sufficiently to become new species. A good example of this process is the evolution of the Australian marsupials into species adapted as carnivores, herbivores, burrowers, fliers, etc. Another example is that of peritadactyl limb in mammals. The flipper of a seal, wing of a bat, forelimb of a male, front legs of horse and the arm of a man perform different functions, but exhibit the same structural plan including same pentadactyl pattern of bones.

Question. You have studied the story of peppered moths in England. Had the industries been removed, what impact could it have on the moth population? Discuss. 
Answer : In the population of pepper moth two variants exist the dark and the light coloured. Before industrialisation, the light coloured moths were prevalent because they blended well with the lichen covered bark of the trees. The predators were unable to spot them and hence, their population were more in number. With industrialisation, the barks got covered with soot. The growth of lichens reduced, the light coloured moths were thus, spotted by the predators and their number decreased. However, the black variants were camouflased better on soot covered barks and their number increased drastically. If the industries were removed, the population of black moths would have declined because as stated before, they would not be able to camouflage against a light background (no black soot). Also the growth of lichens would increase. Therefore, the dark variants would be spotted better by predators and be eaten more frequently.

Question. What are the key concepts in the evolution theory of Darwin? 
Answer : Key concepts of Darwin’s theory of evolution are as follows
(i) Over Production Living beings have an innate ability of producing own kind for the continuity of race. It has been observed that more individuals of each kind are produced than could possibly survive.
(ii) Struggle for Existence Individuals multiply in geometric ratio, whereas space and food remain almost limited.
(iii) Variations Members of a population vary is size, form and other characteristics even though they look superficially similar, no two individuals are alike. These variations are gradual and those with adaptive value are passed on to next generation.
(iv) Survival of the Fittest and Natural Selection During struggle for existence only those individuals could survive which exhibit beneficial variations and adapt better to changing environment. This is known as natural selection.
(v) Origin of Species Natural Selection results in modification of traits within a lineage, which over a period of long time can bring about evolution of original species into new one.

Question. Two organisms occupying a particular geographical area (say desert) show similar adaptive strategies. Taking examples, describe the phenomenon.
Answer : This phenomenon indicated in the question is convergent evolution where by organisms, not closely related, evolve similar traits independently as a result of adaptation to similar environment. e.g.,
(i) Streamlined shape of sharks and dolphins. The former is a fish, while dolphin is a mammal, but both of them depend on swift movement through the water, so a streamlined shape is essential. Thus, it is the similar habitat that resulted in selection of similar adaptive features in different groups of organisms, but toward the same function.
(ii) Spines (modified leaves) and thorns (modified stems), both look similar and provide protection to the plant, but the plants to which they belong are distantly related.

Question. We are told that evolution is a continuing phenomenon for all living things. Are humans also evolving? Justify your answer. 
Answer : New research suggests that despite modern technology and industrialisation, ‘humans continue to evolve’. In the last 10,000 years or so, the pace of our evolution has speeded up 100 times creating more mutations in our genes and hence, greater natural selection.
Some clues that show humans are evolving are
(i) Lactose Tolerance Historically the gene that regulated human’s ability to digest lactose was shut down as infants are weaned off of their mother’s breast milk. However, adult human in regions of Africa and Northern Europe developed the ability to tolerate lactose in their diets as recent as 5,000 or 6,000 years ago due to mutations.
(ii) Wisdom Teeth Our ancestors had much bigger jaws than we do to lactose their eating habits. Today our jaws are much smaller and wisdom teeth are often impacted estimates say that they will disappear in the coming population.

Question. Had Darwin been aware of Mendel’s work would he been able to explain the origin of variations. Discuss. 
Answer : Yes, had Darwin been aware of Mendel’s work, he would have been able to explain the origin of variations. Darwins observation of different forms of an individual in a population could be related to the presence of different forms of alleles of a gene. The gene express as the most adaptive traits are selected naturally and become more abundant than those that are expressed as less adaptive traits. Over the time, the accumulation of these traits might change the species to an extent that it develops into a new one and adapted to the specific environment.

Important Questions for NCERT Class 12 Biology Evolution

Question. Mutations are :
(a) Random
(b) Directionless
(c) Both 1 and 2
(d) Always small
Answer : C

Question. Stanley Miller performed his experiment for explanation of origin of life, in which year ?
(a) 1953
(b) 1970
(c) 1870
(d) 1960
 Answer : A

Question. In some animals, the same structures developed along different directions due to adaptions to different needs this is called as :
(a) Divergent evolution
(b) Convergent evolution
(c) Parallel evolution
(d) None of these
 Answer : A

Question. Conventional religious literature tells us about the theory of special creation. Which of the following is/are included in the theory ?
(a) All living organisms that we see today were created as such
(b) The diversity was always the same since creation  and will be the same in future.
(c) Earth is about 4000 year old.
(d) All of these
 Answer : D

Question. Cranial capacity of homo erectus was about :
(a) 650-800 cc
(b) 1400 cc
(c) 900 cc
(d) 1600 cc
Answer : C

Question. Out of the following the theory of natural selection is based on certain observations, which are :
(A) Natural resources are limited
(B) Populations are stable in size except for seasonal fluctuations.
(C) Members of a population vary in characteristics even though they look superficially similar
(D) Most of variations are inherited
(a) A, C and D
(b) A, B, C and D
(c) B and C
(d) A, B and C
Answer : B

Question. The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas is called as :
(a) Convergent evolution
(b) Adaptive radiation
(c) Parallel evolution
(d) Continental drift
 Answer : B

Question. Why, pouched mammals survived in Australia?
(a) Divergent evolution
(b) Continental drift
(c) Adaptive radiation
(d) Convergent evolution.
Answer : B

Question. Dinosours disappeared around :
(a) 200 million years ago
(b) 20 million years ago
(c) 65 million years ago
(d) 65 billion years ago
 Answer : C

Question. The animals which evolved into the first amphibian that lived on both land and water, were :
(a) Jawless fish
(b) Lobefins
(c) Ichthyosours
(d) Shrew
 Answer : B

Question. Darwin worked on, which island for explanation of natural selection ?
(a) Malay archipelago
(b) Galapagos
(c) Sumatra
(d) Port Blaier
 Answer : B

Ques. From his experiments, S.L. Miller produced amino acids by mixing the following in a closed flask.
(a) CH₄, H₂, NH₃ and water vapor at 800°C
(b) CH₃, H₂, NH₄ and water vapor at 800°C
(c) CH₄, H2, NH₃ and water vapor at 600°C
(d) CH₃, H₂, NH₃ and water vapor at 600°C
Answer: A

Ques. Which of the following is the correct sequence of events in the origin of life?
I. Formation of protobionts
II. Synthesis of organic monomers
III. Synthesis of organic polymers
IV. Formation of DNA-based genetic systems
(a) I, II, III, IV (b) I, III, II, IV
(c) II, III, I, IV (d) II, III, IV, I
Answer: C

Ques. Following are the two statements regarding the origin of life.
(A) The earliest organisms that appeared on the earth were non-green and presumably anaerobes.
(B) The first autotrophic organisms were the chemoautotrophs that never released oxygen.
Of the above statements which one of the following options is correct?
(a) Both (A) and (B) are correct.
(b) Both (A) and (B) are false.
(c) (A) is correct but (B) is false.
(d) (B) is correct but (A) is false. 
Answer: A

Ques. Which one of the following is incorrect about the characteristics of protobionts (coacervates and microspheres) as envisaged in the abiogenic origin of life?
(a) They were partially isolated from the surroundings.
(b) They could maintain an internal environment.
(c) They were able to reproduce.
(d) They could separate combinations of molecules from the surroundings. 
Answer: C

Ques. The concept of chemical evolution is based on
(a) interaction of water, air and clay under intense heat
(b) effect of solar radiation on chemicals
(c) possible origin of life by combination of chemicals under suitable environmental conditions
(d) crystallisation of chemicals. 
Answer: C

Ques. Which of the following amino acids was not found to be synthesised in Miller’s experiment?
(a) Alanine
(b) Glycine
(c) Aspartic acid
(d) Glutamic acid
Answer: D

Ques. Which one of the following experiments suggests that simplest living organisms could not have originated spontaneously from non-living matter?
(a) Larvae could appear in decaying organic matter.
(b) Microbes did not appear in stored meat.
(c) Microbes appeared from unsterilised organic matter.
(d) Meat was not spoiled, when heated and kept sealed in a vessel. 
Answer: D

Ques. According to Oparin, which one of the following was not present in the primitive atmosphere of the earth?
(a) Methane
(b) Oxygen
(c) Hydrogen
(d) Water vapour
Answer: B

Ques. There is no life on moon due to the absence of
(a) O2
(b) water
(c) light
(d) temperature. 
Answer: B

Ques. Most abundant organic compound on earth is
(a) protein
(b) cellulose
(c) lipids
(d) steroids. 
Answer: B

Ques. 1st life on earth was
(a) cyanobacteria
(b) chemoheterotrophs
(c) autotrophs
(d) photoautotrophs.
Answer: B

Ques. The correct sequence for the manufacture of molecules/organic compounds on the primitive earth is
(a) NH3, nucleic acid, protein and carbohydrate
(b) protein, carbohydrate, water and nucleic acid
(c) NH3, protein, carbohydrate and nucleic acid
(d) NH3, water, nucleic acid and protein.
Answer: D

Ques. The first organisms were
(a) chemoautotrophs
(b) chemoheterotrophs
(c) autotrophs
(d) eukaryotes. 
Answer: B

Ques. Which was absent in the atmosphere at the time of origin of life?
(a) NH3
(b) H2
(c) O2
(d) CH4
Answer: C

Ques. Which one of the following sequences was proposed by Darwin and Wallace for organic evolution ?
(a) Overproduction, variations, constancy of population size, natural selection
(b) Variations, constancy of population size, overproduction, natural selection
(c) Overproduction, constancy of population size, variations, natural selection
(d) Variations, natural selection, overproduction, constancy of population size 
Answer: C

Ques. Darwin’s theory of pangenesis shows similarity with theory of inheritance of acquired characters then what shall be correct according to it?
(a) Useful organs becomes strong and developed while useless organs become extinct.
(b) Size of organs increase with aging.
(c) Development of organs is due to will power.
(d) There should be some physical basis of inheritance. 
Answer: D

Ques. Which of the following refer to correct example(s) of organisms which have evolved due to changes in environment brought about by anthropogenic action?
(1) Darwin’s Finches of Galapagos islands.
(2) Herbicide resistant weeds.
(3) Drug resistant eukaryotes.
(4) Man-created breeds of domesticated animals like dogs.
(a) only (1) (b) (1) and (3)
(c) (2), (3) and (4) (d) only (4) 
Answer: C

Ques. Embryological support for evolution was disapproved by
(a) Karl Ernst von Baer
(b) Alfred Wallace
(c) Charles Darwin
(d) Oparin. 
Answer: A

Ques. Flippers of penguins and dolphins are examples of
(a) adaptive radiation
(b) convergent evolution
(c) industrial melanism
(d) natural selection.
Answer: B

Ques. The similarity of bone structure in the forelimbs of many vertebrates is an example of
(a) homology
(b) analogy
(c) convergent evolution
(d) adaptive radiation.
Answer: A

Ques. Among the following sets of examples for divergent evolution, select the incorrect option.
(a) Forelimbs of man, bat and cheetah
(b) Heart of bat, man and cheetah
(c) Brain of bat, man and cheetah
(d) Eye of octopus, bat and man 
Answer: D

Question. Viviparity is considered to be more evolved because
(a) the young ones are left on their own
(b) the young ones are protected by a thick shell
(c) the young ones are protected inside the mother’s body and are looked after they are born leading to more chances of survival
(d) the embryo takes a long time to develop
Answer : C

Question. Evolution of different species in a given area starting from a point and spreading to other geographical areas is known as
(a) adaptive radiation
(b) natural selection
(c) migration
(d) divergent evolution.
Answer : A

Question. When two species of different genealogy come to resemble each other as a result of adaptation, the phenomenon is termed as
(a) microevolution
(b) co-evolution
(c) convergent evolution
(d) divergent evolution.
Answer : C

Question. For the MN-blood group system, the frequencies of M and N alleles are 0.7 and 0.3, respectively
The expected frequency of MN-blood group bearing organisms is likely to be
(a) 42%
(b) 49%
(c) 9%
(d) 58%
Answer : A

Question. Which of the following is an example for link species? 
(a) Lobe fish
(b) Dodo bird
(c) Sea weed
(d) Chimpanzee
Answer : D

Question. The concept of chemical evolution is based on
(a) interaction of water, air and clay under intense heat
(b) effect of solar radiation on chemicals
(c) possible origin of life by combination of chemicals under suitable environmental condition.
(d) crystallization of chemicals.
Answer : C

Question. The phenomenon of “Industrial melanism” demonstrates
(a) natural selection
(b) induced mutation
(c) genetic drift
(d) geographical isolation
Answer : A

Question. In 1953, S. L. Miller created primitive earth conditions in the laboratory and gave experimental evidence for origin of first form of life from pre-existing non-living organic molecules. The primitive earth conditions created include 
(a) low temperature, volcanic storms, atmosphere rich in oxygen
(b) low temperature, volcanic storms, reducing atmosphere
(c) high temperature, volcanic storms, non-reducing atmosphere
(d) high temperature, volcanic storms, reducing atmosphere containing CH₄, NH₃, etc.
Answer : D

Question. Which is correct formula of Hardy-Weinberg’s law?
(a) p² + pq + q² = 0
(b) p² + pq + q2 = 1
(c) p² + pq + q² = infinity
(d) p² + 2pq + q² = 1
Answer : D

Question. Which type of selection explains industrial melanism observed in moth, Biston bitularia?
(a) Stabilising
(b) Directional
(c) Disruptive
(d) Artificial
Answer : B

Question. Fossils are generally found in 
(a) sedimentary rocks
(b) igneous rocks
(c) metamorphic rocks
(d) any type of rock
Answer : A

Question. According to Hugo de Vries, speciation is due to
(a) accumulation of small variations
(b) intraspecific breeding
(c) inter specific breeding
(d) saltation
Answer : D

Question. Match the scientists listed under column ‘I’ with ideas listed column ‘II’.
Column I                     Column II
A. Darwin              (i) Abiogenesis
B. Oparin              (ii) Use and disuse of organs
C. Lamarck           (iii) Continental drift theory
D. Wagner            (iv) Evolution by natural selection
(a) A-(i); B-(iv); C-(ii); D-(iii)
(b) A-(iv); B-(i); C-(ii); D-(iii)
(c) A-(ii); B-(iv); C-(iii); D-(i)
(d) A-(iv); B-(iii); C-(ii); D-(i)
Answer : B

Very Short Answer Questions

Question: According to deVries what is saltation?
Answer: According to de Vries, saltation is single step (large) mutation.

Question: Name the common ancestor of the great apes and man.
Answer:Dryopithecus/Ramapithecus

Question: State the significance of biochemical similarities amongst diverse organism in evolution.
Answer: Biochemical similarities indicate evolution from common or shared ancestry.

Question:  State the significance of Coelacanth in evolution. 
Answer: It is an ancestor of amphibians.

Question:  Write the probable differences in eating habits of Homo habilis and Homo erectus.
Answer: Homo habilis did not eat meat. They were vegetarian.
Homo erectus ate meat. They were meat eater.

Question: Write the names of the following:
(a) A 15 mya primate that was ape-like
(b) A 2 mya primate that lived in East African grasslands 
Answer: (a) Dryopithecus
(b) Australopithecine/Homo habilis.

Short Answer Questions

Question: With the help of any two suitable examples explain the effect of anthropogenic actions on organic evolution. 
Answer: Charles Darwin, based on his observations during a sea voyage around the world in the ship H.M.S. Beagle, concluded the following:
- Varying degrees of similarities can be observed between existing life forms and those that existed millions of years ago.
-There has been gradual evolution of life forms with new forms arising at different periods of history.
- Any population has built-in variations in characteristics which adapt it better to environment.
- The characteristics which enable some populations or individuals to survive better in natural conditions (climate, food, physical factors) would out-breed others (Survival of the fittest).
- Those populations which are better fit (reproductively fit) in an environment will be selected by nature and will survive more (Natural selection).
- Adaptability is inherited and fitness is the end result of ability to adapt and get selected by nature.
Examples of natural selection.
(a) Industrial melanism:
- In England, before industrialisation in 1850’s, white-winged moths were more in number than dark-winged moths.
- But after industrialisation in 1920’s, dark-winged moths became more in number than whitewinged moths.
- This is because during industrialisation, the tree trunks covered by white lichens became dark due to deposition of dust and coal particles (soot and smoke).
- As a result, white-winged moths could be easily picked up by predators from the dark background and dark-winged moths survived.
- In mixed population, those that can better adapt, survived and there was increase in their population size.
(b) Chemical resistance:
- Excessive use of herbicides and pesticides has resulted in evolution of resistant varieties of microbes in much lesser time scale.
- Microbes are also becoming resistant to antibiotics and drugs because of same reason.
- As a result, pathogenic bacteria are appearing in very short period.
(c) Man has bred selected plants and animals and thus created new breeds with in short period of times.

Question: According to the Darwinian theory, the rate of appearance of new forms is linked to their life cycles. Explain. 
Answer: Microbes have a very short life cycle and divide fast. They can produce millions of organisms within few hours. Thus, it is easy to see variant population in less span of time. On the other hand, higher organisms have a long time span and the variations are not visible in a short time.

Question: What does the following equation represent? Explain.
p² +2pq+q² = 1
Answer: The equation represents Hardy-Weinberg’s Principle which states that allele frequencies in a population are stable and are constant from generation to generation. 1 represents stable allelic frequency indicating no evolution occurring. p represents frequency of homozygous dominant (AA), 2 pq represents frequency of heterozygous (Aa) and q represents frequency of homozygous recessive (aa).

Question: Gene flow occurs through generations and can occur across language barriers in humans. If we have a technique of measuring specific allele frequencies in different population of the world, can we not predict human migratory patterns in pre-history and history? Do you agree or disagree? Provide explanation to your answer. 
Answer: Yes, I agree. Gene flow occurs through generations. By studying specific allele frequencies, we can predict the human migratory patterns in pre-history and history. Studies have used specific genes/chromosomes/mitochondrial DNA to trace the evolutionary history and migratory patterns of humans (The project is known as the Human Genographics Project).

Question: What are we referring to when we say ‘simple organisms’ or ‘complex organisms’?
Answer: These are the terms to classify organisms according to their evolutionary history. Simple organisms have simple structural and functional organisation and are considered primitive,whereas complex organisms have complex structural and functional organisation and are said to have arise from simple organisms.

Question: How can you say the lobefin fish were the ancestors of amphibian? 
Answer: Lobefins fish have stout and strong fins, so they can move on land and swim in water to maintain a dual lives like amphibians

Question: Fill in the blank (i), (ii), (iii), (iv) with name of the mammals of Australia. 
Placental mammal           Marsupial mammal
Anteater                                     (i)
(ii)                                    Spotted cuscus
Bob cat                                     (iii)
(iv)                                  Tasmanian wolf
Answer: (i) Numbat
(ii) Lemur
(iii) Tasmanian tiger cat
(iv) Wolf

Question: According to one of the most widely accepted theories, earth’s atmosphere before origin of life consisted of a mixture of
(a) O₃, CH₄, O₂ and H₂O
(b) O₃, NH₃, CH₄ and H₂O
(c) H₂, CO₂, NH₃ and CH₄
(d) CH₄, NH₃, H₂ and H₂O vapours

Answer: d

Question: The chronological order of human evolution from early to the recent stages is
(a) Ramapithecus → Australopithecus → Homo habilis → Homo erectus
(b) Australopithecus → Ramapithecus → Homo habilis → Homo erectus
(c) Pithecanthropus pekinensis → Homo habilis → Homo erectus
(d) Australopithecus → Ramapithecus →  Pithecanthropus pekinensis → Homo erectus

Answer: a

Question: For a long time, it was believed that life came out of decaying and rotting matter like straw, mud, etc. This was the theory of
(a) catastrophism
(b) spontaneous generation
(c) panspermia
(d) chemogeny

Answer: b

Question: Who proposed that the first form of life could have come from pre-existing non-living organic molecules and it precedes chemical evolution?
(a) SL Miller
(b) Oparin and Haldane
(c) Charles Darwin
(d) Alfred Wallace

Answer: b

Question: According to Charles Darwin’s observations
(a) existing life forms share similarities to the life forms that existed million of years ago
(b) life forms evolve gradually
(c) any population has built in variations which enable them to survive in natural conditions
(d) All of the above

Answer: d

Question: Fossils are useful in
(a) studying extinct organisms
(b) studying history of organisms
(c) Both (a) and (b)
(d) None of the above

Answer: c

Question: First human like hominid is known as
(a) Neanderthal man
(b) Homo habilis
(c) Dryopithecus
(d) Homo erectus

Answer: b

8. Embryological support for evolution given by Ernst Haeckel includes the
(a) presence of hair all over the body in adult human
(b) absence of tail bone and presence of wisdom tooth
(c) absence of vestigial gill slits in human’s embryo
(d) presence of row of vestigial gill slits in embryo of all vertebrates

Answer: d

Question: Tendrils of Cucurbita and thorns of Bougainvillea are examples of
(a) vestigial organs
(b) analogous organs
(c) homologous organs
(d) homoplasy

Answer: c

Question: Change of lighter coloured variety of peppered moths (Biston betularia) to darker variety in the industrial era occurred due to
(a) selection of darker variety for survival
(b) deletion of gene
(c) industrial carbon deposited on the wings
(d) translocation of gene

Answer: a

Question: Development of different functional structures from a common ancestral form is called
(a) differential evolution
(b) adaptive radiation
(c) non-adaptive radiation
(d) regressive evolution

Answer: b

Question: Evidence that evolution of life forms has indeed taken place on earth has come from
(a) fossil studies (palaeontological evidences)
(b) morphological and comparative anatomical studies
(c) biochemical studies
(d) All of the above

Answer: d

Question: The process by which different type of finches were evolved in Galapagos islands is a consequence of
(a) adaptive radiation
(b) geographic similarity
(c) geographic dissimilarity
(d) adaptive convergence

Answer: a

Question: The diversity in the type of finches and adaptation to different feeding habits on the Galapagos islands, as observed by Darwin, provides an evidence of
(a) origin of species by natural selection
(b) intraspecific variation
(c) intraspecific competition
(d) interspecific competition

Answer: a

Question: ‘XX’ is a type of selection process in evolution that promotes population changes in one particular direction. ‘XX’ favours small or large sized individuals mean size of population changes. Identify ‘XX’.
(a) Stabilising selection
(b) Directional selection
(c) Disruptive selection
(d) None of the above

Answer: b

Question: Australian marsupials are the example of
(a) homologous radiation
(b) analogous radiation
(c) adaptive radiation
(d) convergent radiation

Answer: c

Question: Survival of the fittest is possible due to the
(a) overproduction
(b) favourable variations
(c) environmental changes
(d) inheritance of acquired characters

Answer: b

Question: Example of anthropogenic evolution is
(a) selection of resistant microbes to pesticides
(b) antibiotic resistant eukaryotic cells
(c) Industrial melanism is Biston betularia
(d) All of the above

Answer: d

Question: Which of the following situations would most likely result in the highest rate of natural selection?
(a) Reproduction by asexual method
(b) Low mutation is an stable environment
(c) Little competition
(d) Reproduction by sexual method

Answer: d

Question: The sequence of origin of life may be
(a) Inorganic materials → Organic materials → Colloidal aggregate → Eobiont → Cell
(b) Organic materials → Inorganic materials → Colloidal aggregate → Eobiont → Cell
(c) Inorganic materials → Organic materials → Eobiont → Cell → Colloidal aggregate
(d) Organic materials → Inorganic materials → Eobiont → Cell → Colloidal aggregate

Answer: a

Question: Darwinian fitness can be estimated by
(a) how long different individual in a population survive
(b) number of offspring produced by different individuals in population
(c) individual have a large size in population
(d) species recover after mass extinction

Answer: b

Question: Which of the following factors was not taken into account by Darwin in his theory of natural selection?
(a) Struggle for existence
(b) Discontinuous variations
(c) Parasites and predators as natural enemies
(d) Survival of the fittest

Answer: b

Question: Hugo de Vries put forth his idea of mutation by his work on
(a) pea plant
(b) Drosophila
(c) evening primrose
(d) maize plant

Answer: c

22. Which of the following are the two key concepts of Darwinian theory of evolution?
(a) Genetic drift and mutation
(b) Adaptive radiation and homology
(c) Mutation and natural selection
(d) Branching descent and natural selection

Answer: d

Question: Genetic equilibrium refers to the phenomenon in which
(a) the trait remains constant in a population
(b) the total genes remain constant in a population
(c) the total genes keeps on varying in a population
(d) traits keeps on varying in a population

Answer: b

Question: Artificial selection to obtain cows yielding high milk output represents
(a) stabilising selection as it stabilises this character in the population
(b) directional as it pushes the mean of the character in one direction
(c) disruptive as it splits the population into two, one yielding higher output and the other lower output
(d) stabilising followed by disruptive as stabilises the population of produce higher yielding cows

Answer: b

Question: Hardy-Weinberg principle can be expressed as
(a) p² - 2pq - q² = 1
(b) p² + 2pq + q² ≥ 1
(c) p² + 2 pq + q² ≤ 1
(d) p² + 2pq + q² = 1

Answer: d

Question: What was the Lamarck’s explanation for long necked giraffes?
(a) Stretching of necks over many generations
(b) Short neck suddenly changed into long one
(c) Natural selection
(d) Mutation

Answer: a

Question: Which of the following conditions represents the extent of evolutionary change in Hardy-Weinberg principle?
(a) Value of (p + q)²
(b) Difference between measured value and expected value
(c) Sum of measured value and expected value
(d) This principle cannot predict the extent of evolutionary change

Answer: b

Question: Choose the incorrect pair.
(a) Invertebrates were formed and active – By 500 mya
(b) Seaweeds existed – Around 320 mya
(c) First organisms that invaded land – Single-celled animals
(d) Fish with stout and strong fins – Around 350 mya

Answer: c

Question: Brain (cranial) capacity of Homo habilis was
(a) 750-850 cc
(b) 750-800 cc
(c) 650-800 cc
(d) 550-700 cc

Answer: c

Question: Giant dinosaurs and reptiles predominated during the Jurassic period. This period was also marked for the evolution of higher insects and angiosperms, conifers, cycads, etc. Jurassic period belongs to which era?
(a) Cenozoic
(b) Palaeozoic
(c) Mesozoic
(d) Proterozoic

Answer: c

Question: In which era Protozoa, sponge and algae originate?
(a) Cenozoic era
(b) Azoic era
(c) Proterozoic era
(d) Mesozoic era

Answer: c

Question: What does presence of homologous organs in different animals indicate?
(a) Different ancestry
(b) Common ancestry
(c) Independent development
(d) Dependent development

Answer: b

Question: The correct order of evolutionary scale is
(a) Palaeozoic → Archaeozoic → Cenozoic
(b) Archaeozoic → Palaeozoic → Proterozoic
(c) Palaeozoic → Mesozoic → Cenozoic
(d) Mesozoic → Archaeozoic → Proterozoic

Answer: c

Question: The difference between Homo sapiens and Homo erectus was
(a) Homo sapiens originated in Africa, while Homo erectus originated in Asia
(b) Homo erectus were much smaller in size than Homo sapiens
(c) Homo erectus stayed in Africa, while Homo sapiens did not
(d) the size of the brain of Homo erectus was smaller than that of Homo sapiens

Answer: d

Question: Which of the following is not an examples of adaptive radiation?
(a) Wombat, numbat, flying phalanger
(b) Darwin’s finches
(c) Different mammals in other parts of world
(d) Lemur and spotted cuscus

Answer: d

Question: Homo sapiens arose during
(a) ice age between 75000-10000 years ago
(b) continental drift between 75000-10000 years ago
(c) continental drift between 75000-5000 years ago
(d) ice age between 50000-10000 years ago

Answer: a

QUESTIONS

VSA (1 MARK)

Question 1. Name one fish like reptile that evolved from land reptile about 200 million years ago?
Answer: Ichthyosaurs.
In simple words: Ichthyosaurs were aquatic reptiles that evolved from land-dwelling ancestors and lived in the oceans around 200 million years ago.

Exam Tip: Remember specific fossil examples like Ichthyosaurs when studying vertebrate adaptation to aquatic life.

Question 2. For a long time, it was believed that life originated from decaying matter. What is this theory known as? Name the scientist who experimentally disproved this theory.
Answer: The theory is known as the Theory of Spontaneous Generation (Abiogenesis). It was experimentally disproved by Louis Pasteur.
In simple words: People once thought life could spring from non-living things like mud and straw, but Louis Pasteur proved living things only come from pre-existing life using swan-necked flasks.

Exam Tip: Associate Louis Pasteur with the swan-neck flask experiment that conclusively debunked spontaneous generation.

Question 3. If abiotic origin of life is in progress on a planet other than earth, what should be the conditions there?
Answer: The required conditions are very high temperature, volcanic storms, and a strongly reducing atmosphere containing methane (\(\text{CH}_4\)), ammonia (\(\text{NH}_3\)), hydrogen (\(\text{H}_2\)), and water vapor, but devoid of free oxygen.
In simple words: A planet must have intense heat, volcanic activity, and an atmosphere rich in reducing gases like methane and ammonia to synthesize the first organic molecules.

Exam Tip: Note that a reducing atmosphere (without free oxygen) is crucial for chemical evolution and the synthesis of early organic compounds.

Question 4. Name the person who proposed that population tends to increase geometrically while food production increases arithmetically.
Answer: Thomas Malthus.
In simple words: Thomas Malthus observed that populations grow faster than the food supply, leading to a struggle for existence.

Exam Tip: Malthus's essay on population strongly influenced both Charles Darwin and Alfred Russel Wallace in formulating natural selection.

Question 5. Name the scientist who had also come to similar conclusion as that of Darwin about natural selection as a mechanism of evolution. Which place did he visit to come to conclusions?
Answer: Alfred Russel Wallace. He visited the Malay Archipelago (Malay Peninsula and surrounding islands).
In simple words: Alfred Wallace independently arrived at the theory of natural selection after studying flora and fauna in the Malay Archipelago.

Question 6. Explain Oparin-Haldane theory of chemical evolution of life.
Answer: According to the Oparin-Haldane theory, life originated spontaneously from non-living organic molecules through chemical evolution. Primitive Earth had high temperatures, volcanic activity, and a reducing atmosphere containing methane, ammonia, hydrogen, and water vapor. As Earth cooled, water vapor condensed to form oceans. Energy from electrical discharges (lightning) and UV radiation caused simple inorganic molecules to combine into simple organic compounds (amino acids, sugars), which further polymerized to form complex macromolecules (proteins, nucleic acids) that eventually led to the first primitive forms of life.
In simple words: Life started step-by-step from chemicals on early Earth, where lightning and heat converted simple gases in the atmosphere into organic building blocks in the oceans.

Exam Tip: Clearly mention the sequence: Inorganic molecules -\(\gt\) Organic monomers -\(\gt\) Macromolecules -\(\gt\) First cellular life form.

Question 7. Distinguish between convergent and divergent evolution giving one example of each.
Answer:
1. Divergent Evolution: It is the evolutionary process where species originating from a common ancestor develop different structures and functions to adapt to different environments. It represents homology. Example: Forelimbs of mammals (such as whale flippers, horse forelimbs, and human hands) share a common anatomical structure but perform different functions.
2. Convergent Evolution: It is the evolutionary process where unrelated species living in similar ecological niches independently evolve similar functional structures due to similar adaptation pressures. It represents analogy. Example: Wings of insects and wings of birds.
In simple words: Divergent evolution means same origin but different functions (homology), while convergent evolution means different origin but similar functions (analogy).

Exam Tip: Use the golden rule: Homology = Divergent Evolution = Common Ancestry; Analogy = Convergent Evolution = Similar Function/Different Ancestry.

Question 8. What is adaptive radiation? Explain with an example.
Answer: Adaptive radiation is the evolutionary process in which different species diverge from a single point of origin in a given geographical area and radiate to other distinct ecological habitats. Example: Darwin's finches found on the Galapagos Islands. A single ancestral seed-eating bird species migrated to different islands and evolved into various distinct species with specialized beaks adapted for insect-eating, seed-crushing, and cactus-feeding depending on available food sources.
In simple words: Adaptive radiation is when one ancestral species quickly diversifies into many new species to fill different ecological roles in a new area.

Exam Tip: Mention Darwin's finches or Australian marsupials as standard textbook examples when explaining adaptive radiation.

Question 9. How did Louis Pasteur disprove spontaneous generation theory?
Answer: Louis Pasteur used pre-sterilized swan-necked flasks in his famous experiment. He placed killed yeast broth in flasks where the neck was drawn out into a long, S-shaped curve (swan neck) which allowed air to enter but trapped dust particles and microbes. No life appeared in this flask as long as it remained undisturbed because airborne microorganisms were trapped in the bend. However, when the flask was broken or tilted so that microbes reached the broth, new organisms rapidly grew. This proved that life originates only from pre-existing life (biogenesis) and not spontaneously from non-living matter.
In simple words: Pasteur showed that nutrient broth stays sterile in a swan-necked flask because dust and germs get trapped in the curved neck, proving microbes come from the air, not out of nothing.

Exam Tip: Emphasize the role of the swan-neck in trapping airborne dust particles while allowing air exchange.

SA-1 (3 MARKS)

Question 10. (i) State the Hardy-Weinberg principle.
(ii) When there is a disturbance in the Hardy-Weinberg equilibrium, what would it result in?
(iii) According to this principle, what is the sum total of all allelic frequencies?
Answer:
(i) The Hardy-Weinberg principle states that allele frequencies in a population are stable and remain constant from generation to generation in the absence of evolutionary forces (gene flow, genetic drift, mutation, recombination, and natural selection).
(ii) Disturbance or change in Hardy-Weinberg equilibrium results in evolution or speciation.
(iii) The sum total of all allelic frequencies in a population is equal to 1 (i.e., \(p + q = 1\) or \(p^2 + 2pq + q^2 = 1\)).
In simple words: Gene frequencies stay constant unless disturbed, and any shift in this balance drives evolution, with total allele frequency always adding up to 1.

Exam Tip: Memorize the mathematical formulation \(p^2 + 2pq + q^2 = 1\) along with its components representing genotype frequencies.

Question 11. Classify the following as examples of homology and analogy–
(i) Hearts of fish and crocodile
(ii) Wings of butterfly and birds
(iii) Eyes of Octopus and Mammals
(iv) Tubers of potato and Sweet potato
(v) Thorns of Bougainvillea and spines of Opuntia
(vi) Thorn of Bougainvillea and tendrils of cucurbits.
Answer:
(i) Hearts of fish and crocodile: Homology
(ii) Wings of butterfly and birds: Analogy
(iii) Eyes of Octopus and Mammals: Analogy
(iv) Tubers of potato and Sweet potato: Analogy
(v) Thorns of Bougainvillea and spines of Opuntia: Analogy
(vi) Thorn of Bougainvillea and tendrils of cucurbits: Homology
In simple words: Structures with similar origin are homologous, while those with similar function but different origin are analogous.

Exam Tip: Double-check potato (stem tuber) vs sweet potato (root tuber) - they are analogous structures representing convergent evolution.

Question 12. Stanley Miller and Harold Urey performed an experiment by recreating in the laboratory the probable conditions of the atmosphere of the primitive earth.
(i) What was the aim of the experiment?
(ii) In what forms was the energy supplied for chemical reactions to occur?
(iii) For how long was the experiment run continuously? Name two products formed.
Answer:
(i) The aim of the experiment was to experimentally prove Oparin and Haldane's theory of chemical evolution and the origin of life from non-living organic molecules.
(ii) Energy was supplied in the form of electric discharge using electrodes (simulating lightning) and heat.
(iii) The experiment was run continuously for 1 week (7 days). The products formed included simple amino acids (such as glycine, alanine, and aspartic acid) and sugars.
In simple words: Miller and Urey simulated early Earth conditions with electrical sparks and gases for a week, successfully producing amino acids.

Question 13. 'Industrial Melanism' in peppered moth is an excellent example of 'Natural selection'. Justify the statement.
Answer: Before industrialization in 19th-century England, tree trunks were covered with light-colored lichens, making white-winged moths camouflaged and dark-winged (melanized) moths easily visible to predatory birds. Consequently, white-winged moths survived better and were more abundant. After industrialization, soot covered the tree trunks, killing lichens and turning trees dark. Now, dark-winged moths became camouflaged while white-winged moths were easily spotted and eaten by birds. Thus, nature selected the dark-winged variant for survival, illustrating evolution through natural selection.
In simple words: Peppered moths changed color proportions because polluted dark trees favored dark moths, while clean light trees favored white moths due to bird predation.

Question 14. Fill up the blanks left in the table showing Era, period and organism.
 

Answer:
(a) Quaternary
(b) Cenozoic
(c) Cretaceous
(d) Mesozoic
(e) Carboniferous
(f) Paleozoic
In simple words: The table correctly matches geological eras and periods with the dominant life forms that evolved during those times.

Exam Tip: Memorize the chronological sequence of geological eras: Paleozoic -\(\gt\) Mesozoic -\(\gt\) Cenozoic.

Question 15. (i) In which part of the world, Neanderthal man lived?
(ii) What was his brain's capacity?
(iii) Mention the advancement which Neanderthal man showed over Homo erectus.
Answer:
(i) Near Eastern and Central Asia.
(ii) Around 1400 c.c.
(iii) Neanderthal man had a larger brain capacity, used animal hides to cover and protect their bodies, and buried their dead.
In simple words: Neanderthals lived in central/near-eastern Asia, possessed bigger brains than Homo erectus, and practiced burial rituals and clothing use.

Exam Tip: Remember Neanderthal brain size (1400 cc) is very close to modern human brain size (1350-1450 cc).

Question 16. Figures given below are of Darwin's finches? Variety of beaks of Darwin's finches.
(a) Mention the specific geographical area where these were found.
(b) Name and explain the phenomenon that has resulted in the evolution of such diverse species in the region.
(c) How did Darwin visit the particular geographical area?
Answer:
(a) Galapagos Islands.
(b) Adaptive radiation. It is the process of evolution of different species in a given geographical area starting from a point and radiating to other habitats, adapting to different food habits (e.g., seed-eating, insect-eating).
(c) Through a sea voyage in a sail ship named H.M.S. Beagle.
In simple words: Darwin studied finches in the Galapagos Islands during his voyage on H.M.S. Beagle, observing how their beaks radiated into diverse forms based on their diets.

Exam Tip: Always link Darwin's finches to adaptive radiation and the H.M.S. Beagle expedition.

Question 17. Give examples to show evolution by anthropogenic action.
Answer: Evolution by anthropogenic (human-induced) action refers to evolutionary changes driven by human activities. Examples include:
1. Excess use of herbicides and pesticides resulting in the selection of resistant weed and pest varieties within a short time scale.
2. Extensive use of antibiotics and drugs leading to the emergence of drug-resistant microbes and bacteria.
3. Industrial melanism where human pollution drove the selection of dark-colored peppered moths.
In simple words: Human actions like using pesticides, antibiotics, and pollution rapidly trigger natural selection and resistance in organisms.

Exam Tip: Antibiotic resistance in bacteria and pesticide resistance in insects are classic, high-scoring examples of anthropogenic evolution.

LA (5 MARKS)

Question 18. Is evolution a 'process' or the end result of a 'process'? Discuss. Describe various factors that effect Hardy-Weinberg equilibrium.
Answer:
Is evolution a process or end result?
Evolution can be viewed as both. The changes occurring in organisms across generations due to environmental pressures constitute a dynamic biological process. However, the immense diversity of life forms, adaptations, and complex species we see today is the end result of millions of years of evolutionary processes acting on Earth.
Factors affecting Hardy-Weinberg equilibrium:
1. Gene Migration (Gene Flow): Movement of alleles between populations through immigration or emigration changes allele frequencies.
2. Genetic Drift: Random or chance changes in allele frequencies in a population (such as the founder effect or bottleneck effect).
3. Mutations: Spontaneous, random changes in DNA sequence introduce new alleles into a population.
4. Genetic Recombination: Crossing over and independent assortment during gamete formation generate new genetic combinations.
5. Natural Selection: Differential reproduction of genotypes favored by environmental conditions is the most significant driving force of evolution.
In simple words: Evolution is both the ongoing process of genetic change and the final rich diversity of life, driven by factors like mutation, gene flow, genetic drift, recombination, and natural selection.

Exam Tip: List all five factors affecting Hardy-Weinberg equilibrium clearly with brief descriptions for maximum marks.

Question 19. How do Darwin and Hugo de Vries after regarding Mechanism of Evolution?
Answer:
- Charles Darwin: According to Darwin, evolution is a gradual, slow, and continuous process driven by small, directional variations. He believed that variations are cumulative and natural selection acts on these minor variations to produce new species.
- Hugo de Vries: According to Hugo de Vries, evolution occurs through sudden, large, and random mutations rather than gradual accumulation of small variations. He termed single-step large mutations as saltation and believed these sudden changes drive speciation.
In simple words: Darwin believed evolution happens slowly through small, gradual variations, whereas Hugo de Vries argued it happens suddenly through large, random mutations (saltation).

Exam Tip: Contrast Darwin's gradualism ("small, directional variations") with Hugo de Vries's mutation theory ("single-step large mutations/saltation").

Question 20. With the help of suitable diagram, represent the operation of natural selection on different traits.
Answer: Natural selection can alter variation in a population through three main ways depending on which traits are favored:
1. Stabilizing Selection: Favors median (intermediate) phenotypes and eliminates extreme variants, narrowing the peak of the bell curve.
2. Directional Selection: Favors one extreme phenotype over the other, causing the peak of the population curve to shift in that direction.
3. Disruptive Selection: Favors both extreme phenotypes at the expense of intermediate forms, splitting the population distribution curve into two separate peaks.
In simple words: Natural selection can either stabilize average traits, push the population toward one extreme, or split it into two extremes.

Exam Tip: Be sure to sketch and label the three graphs (Stabilizing, Directional, and Disruptive selection) clearly when asked in exams.