CBSE Class 12 Biology Evolution Worksheet Set A

Evolution MCQ Questions with Answers Class 12 Biology

Question : Which of the following had huge fearsome dagger like teeth?
(1) Dryopithecus
(2) Tyrannosaurus
(3) Ichthyosaur
(4) Homo erectus
Answer (2)

Question : Hardy-Weinberg equilibrium is not affected by which of the following factors?
(1) Random mating
(2) Genetic recombination during gametogenesis
(3) Natural selection
(4) Variations due to mutation
Answer (1)

Question :The Darwinian variations are
(1) Small and directionless
(2) Random and directional
(3) Small and directional
(4) Random and directionless
Answer (3)

Question : The homologous organs are
(1) Wings of pigeon and housefly
(2) Wings of housefly and bat
(3) Wings of pigeon and forelimbs of man
(4) Wings of butterfly, bat and housefly
Answer (3)

Question : The fish-like giant reptile which existed 200 mya was
(1) Pteranodon
(2) Ichthyosaur
(3) Triceratops
(4) Tyrannosaurus
Answer (2)

Question : The first organisms that invaded land were
(1) Plants
(2) Fishes
(3) Insects(4
) Bacteria
Answer (1)

Question : Organs which have similar origin and developmental plan, but different functions are called
(1) Vestigial organs
(2) Analogous organs
(3) Homologous organs
(4) Physiological organs

Answer (3)

Question : Australopithecines probably lived in the
(1) East African grasslands
(2) West African grasslands
(3) North American grasslands
(4) South American grasslands
Answer (1)

Question : Which among the following are called the Darwin’s finches?
(1) Archaeopteryx
(2) Pteranodon
(3) Pavo cristatus
(4) Small black birds
Answer (4)

Question :  Which of the following evolved into the first amphibians?
(1) Lobefins
(2) Shrews
(3) Salamanders
(4) Turtles
Answer (1)

Question : The wrongly matched pair w.r.t. the organisms and their probable time of evolution is
(1) Jawless fish – around 350 mya
(2) Lobefins – around 350 mya
(3) Fish-like giant reptiles – around 320 mya
(4) Sea weeds – around 320 mya
Answer (3)

Question :  Find the odd one out
(1) Trunk of an elephant and hand of a chimpanzee
(2) Ginger and sweet potato
(3) Wings of bat and insect
(4) Nails of human beings and claws of a cat
Answer (4)

Question : Seed ferns originated in
(1) Carboniferous period
(2) Devonian period
(3) Silurian period
(4) Cretaceous period
Answer (1)

Question : The convergent evolution of two species is usually associated with
(1) A recent common ancestor
(2) Analogous organ
(3) Homologous organ
(4) Different habitat
Answer (2)

Question : Which one of the following are analogous structures? 
(1) Wings of Bat and Wings of Pigeon
(2) Gills of Prawn and Lungs of Man
(3) Thorns of Bougainvillea and Tendrils of Cucurbita
(4) Flippers of Dolphin and Legs of Horse
Answer (2)

Question : The chronological order of human evolution from early to the recent is 
(1) Australopithecus → Ramapithecus → Homo habilis → Homo erectus
(2) Ramapithecus →Australopithecus → Homo habilis → Homo erectus
(3) Ramapithecus → Homo habilis → Australopithecus → Homo erectus
(4) Australopithecus → Homo habilis → Ramapithecus → Homo erectus
Answer (2)

Question : A molecule that can act as a genetic material must fulfill the traits given below, except
(1) It should be able to express itself in the form of 'Mendelian characters'
(2) It should be able to generate its replica
(3) It should be unstable structurally and chemically
(4) It should provide the scope for slow changes that are required for evolution
Answer (3)

Question :  The process by which organisms with different evolutionary history evolve similar phenotypic adaptations in response to a common environmental challenge, is called 
(1) Convergent evolution
(2) Non-random evolution
(3) Adaptive radiation
(4) Natural selection
Answer (1)

Question : Variation in gene frequencies within populations can occur by chance rather than by natural selection. This is referred to as 
(1) Genetic drift
(2) Random mating
(3) Genetic load
(4) Genetic flow
Answer (1)

Question : Which of the following structures is homologus to the wing of a bird? 
(1) Flipper of Whale
(2) Dorsal fin of a Shark
(3) Wing of a Moth
(4) Hind limb of Rabbit
Answer (1)

Question : 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.On the above statements which one of the following options is correct?
(1) Both (a) & (b) are false
(2) (a) is correct but (b) is false
(3) (b) is correct but (a) is false
(4) Both (a) & (b) are correct
Answer (4)

Question :  Which is the most common mechanism of genetic variation in the population of a sexually-reproducing organism? 
(1) Recombination
(2) Transduction
(3) Chromosomal aberrations
(4) Genetic drift
Answer (1)

Question :  A population will not exist in Hardy-Weinberg equilibrium if 
(1) The population is large
(2) Individuals mate selectively
(3) There are no mutations
(4) There is no migration
Answer (2)

Question : Forelimbs of cat, lizard used in walking; forelimbs of whale used in swimming and forelimbs of bats used in flying are an example of 
(1) Analogous organs
(2) Adaptive radiation
(3) Homologous organs
(4) Convergent evolution
Answer (3)

Question : Analogous structures are a result of 
(1) Stabilizing selection
(2) Divergent evolution
(3) Convergent evolution
(4) Shared ancestry
Answer (3)

Question : The eye of octopus and eye of cat show different patterns of structure, yet they perform similar function. This is an example of 
(1) Homologous organs that have evolved due to divergent evolution
(2) Analogous organs that have evolved due to convergent evolution
(3) Analogous organs that have evolved due to divergent evolution
(4) Homologous organs that have evolved due to convergent evolution
Answer (2)

Question : The wings of a bird and the wings of an insect are: 
(1) Homologous structures and represent convergent evolution
(2) Homologous structures and represent divergent evolution
(3) Analogous structures and represent convergent evolution
(4) Phylogenetic structures and represent divergent evolution.
Answer (3)

Question : Genetic drift operates in 
(1) Small isolated population
(2) Large isolated population
(3) Non-reproductive population
(4) Slow reproductive population
Answer (1)

Question : Which of the following had the smallest brain capacity?
(1) Homo habilis
(2) Homo erectus
(3) Homo sapiens
(4) Homo neanderthalensis
Answer (1)

Question :  The tendency of population to remain in genetic equilibrium may be disturbed by 
(1) Lack of migration
(2) Lack of mutations
(3) Lack of random mating
(4) Random mating
Answer (3)

Question : In Hardy-Weinberg equation, the frequency of heterozygous individual is represented by
(1) p²
(2) 2pq
(3) pq
(4) q²
Answer (2)

Question : According to Darwin, the organic evolution is due to 
(1) Interspecific competition
(2) Competition within closely related species
(3) Reduced feeding efficiency in one species due to the presence of interfering species
(4) Intraspecific competition
Answer (1)

Question : Industrial melanism is an example of 
(1) Neo Lamarckism
(2) Neo Darwinism
(3) Natural selection
(4) Mutation
Answer (3)

Very Short Answer Type Questions

Question. What were the characteristics of life forms that had been fossilised?
Answer : The organisms with hard parts are likely to be fossilised, than those who do not have such parts. The harder the material, better it would be preserved soft parts fossils occur rarely, e.g., birds and pterosaurs have very light bones, hollowed out and specialised for flight. So, they have sparser fossil record as compared to mammals, whose bones are partially mineralised during life.

Question. Did aquatic life forms get fossilised? If, yes where do we come across such fossils?
Answer  Yes, aquatic forms of life do get fossilised, infact, there are more aquatic than terrestrial fossil organisms. Such fossils of sea creatures are found in mountains as opposed to deep sea beds. This is because the rocks in which the fossils are found used to be at the bottom of oceans Due to the changes in the crustal plates over time, the ocean sediments were pushed up to form mountains.

Question. What are we referring to when we say ‘simple organisms’ or ‘complex organisms’?
Answer  These terms are used to classify organisms according to their evolutionary history. Simple organisms refer to those organisms that have simple structural and functional organisation and are considered primitive, whereas Complex organisms refer to those organisms that have higher and complex levels of structural and functional organisation. These are more advanced and said to have arisen from simple organisms.

Question. How do we compute the age of a living tree?
Answer  To estimate the age of a living tree, following steps are required (i) Measure the circumference of the tree trunk (at about 4.5 feet above the ground). (ii) Calculate the diameter of the trunk. This is done by dividing the circumference by 3.14. Divide this (i.e., diameter) by 2 to get the radius. (iii) Determine the growth factor. A tree’s growth factor is the measurement of the width it gains annually. The trees’s growth factor can be seen from the data available or by measuring the rings of a dead tree from the same species. (iv) Multiply the diameter and the tree species average growth factor and the so done calculating suggest the approximate age of the tree in years.

Question. Give an example for convergent evolution and identify the features towards which they are converging.
Answer  When unrelated animals converging to the same form or structure, that is very adaptive in their common environment. It is called convergent evolution, e.g., Australian marsupials and placental mammals. Such as (placental wolf and Tasmanian wolf). These two sub-classes of mammals have adapted in similar ways to a particular food supply, locomotor skill or climate. Their resemblances in overall shape, locomotor mode and feeding and foraging are superimposed upon different modes of reproduction, the feature that accurately reflects their distinct evolutionary relationships.

Question. How do we compute the age of a fossil?
Answer The age of a fossil can be computed by radioactive dating (also called radiometric dating). It is a technique based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. Among the best known techniques are radiocarbon dating, potassium-argon dating and uranium lead dating.

Question. Rearrange the human activities mentioned below as per the order in which they developed after the modern Homo sapiens came into existence during ice age:
(i) Human settlement
(ii) Prehistoric cave art
(iii) Agriculture 
Answer. The order of activities is as follows:
(i) Pre-historic cave art
(ii) Agriculture
(iii) Human Settlement

Question. Coelacanth was caught in South Africa. State the significance of discovery of Coelacanth in the evolutionary history of vertebrates. 
Answer. Coelacanth evolved as first amphibian (lived on both land and water). It is an ancestor of modern day frogs and salamanders.

Question. Name the scientist who disproved spontaneous generation theory. 
Answer. Louis Pasteur disproved the theory of spontaneous generation.

Question. What did Louis Pasteur’s experiment on ‘killed yeast’ demonstrate? Name the theory that got disproved on the basis of his experiment. 
Answer. Louis Pasteur demonstrated that life comes only from pre-existing life. The theory of spontaneous generation was disproved on the basis of his experiment.

Question. When does a species become founders to cause founder effect?
Answer. When the change in the alleles frequency is so different in the new sample of population that they become a different species, the original drifted population becomes founder.

Question. Write the hypothetical proposals put forth by Oparin and Haldane. 
OR
State two postulates of Oparin and Haldane with reference to origin of life. 
Answer. Oparin and Haldane proposed that life originated from pre-existing non-organic molecules and the diverse organic molecules were formed from these inorganic constituents by chemical evolution i.e., formation of life was preceded by chemical evolution.

Question. According to Hardy-Weinberg’s principle, the allele frequency of a population remains constant. How do you interpret the change of frequency of alleles in a population? 
Answer. Change of frequency of alleles in a population will result in natural selection leading to the evolution.

Question. If the frequency of one allele is ‘p’ and for another, it is ‘q’ for one gene, what will be the formula to calculate allele frequency in future generations according to Hardy–Weinberg genetic equilibrium? 
Answer. (p+q)² = p² + 2pq + q² = 1

Question. What does Hardy-Weinberg equation p2 + 2pq + q2 = 1 convey?
Answer. Hardy–Weinberg equation conveys genetic equilibrium, i.e., sum total of all allelic frequencies is 1.

Question. What is founder effect? 
Answer. Sometimes the change in allele frequency is so different in the new sample of population that they become a different species. The original drifted population becomes founder and the effect is called founder effect.

Question. By what Latin name the first hominid was known?
Answer. Homo habilis

Question. Among Ramapithecus, Australopithecous and Homo habilis, who probably did not eat meat?
Answer. Homo habilis

Short Answer Type Questions

Question. Louis Pasteur’s experiments, if you recall, proved that life can arise from only pre-existing life. Can we correct this as life evolves from pre-existent life or otherwise we will never answer the question as to how the first forms of life arose? Comment.
Answer  Yes, we can correct this as life evolves from pre-existent life. The first life that appeared on earth was apparently the result of chemical evolution, i.e., the life originated from inorganic molecules which formed organic molecules, further forming complex compounds. This finally resulted into simple cells and then simple organisms, wherein complexity development with time. However, once life originated, abiogenesis could not follow, and hence, life evolved further only through biogenesis, i.e., pre-existent life gave rise to new life.

Question. The scientists believe that evolution is gradual. But extinction, part of evolutionary story, are ‘sudden’ and ‘abrupt’ and also group-specific. Comment whether a natural disaster can be the cause for extinction of species.
Answer  Yes, a natural disaster can be the cause for extinction of species. As new species evolve to fit ever changing ecological niches, older species fade away. But, the rate of extincition is far from constant. In last 500 million years, 50 - 90% or more of all species on earth have disappeared in a geological blink of the eye. Many times, these mass extinctions had been the consequence of a natural disaster. The most studied mass extinction between the Cretaceous and Palaeocene periods about 65 million years ago, killed off the dinosaurs and made room for mammals to rapidly diversify and evolve. The cause is suspected to be volcanic eruptions and impact of large asteroids or comets striking the earth.

Question. Why is nascent oxygen supposed to be toxic to aerobic life forms?
Answer  Nascent oxygen is very reactive and can react with different biomolecules. Nascent oxygen is a permanent oxidising agent. It is highly reactive and can react readily with different kind of molecules including DNA, proteins present in the cells of aerobic life forms. It is thus, considered toxic if it reacts with DNA, it can lead to mutations and defective proteins, both structural and functional. Similarly if it reacts with proteins and enzymes, they are degraded and many metabolic pathways may hence be impaired.

Question. While creation and presence of variation is directionless, natural selection is directional as it is in the context of adaptation. Comment.
Answer  The creation and presence of variations is directionless in regard that they occur randomly and spontaneously. The variations which are helpful in the adaptations of an organism towards its surroundings would be passed on to next generations. Natural selection is the most critical evolutionary process, which can be considered directional as it leads to only one path that is selection and perpetuation of better adapted individuals. Natural selection leads to survival of the fittest and disappearance of all those organisms which do not all fit in the preveling environmental conditions.

Question. The evolutionary story of moths in England during industrialisation reveals, that ‘evolution is apparently reversible’. Clarify this statement.
Answer  During the last century in the industrial regions of England, a light coloured peppered moth Biston betularia was found on the bark of trees. The tree bark was covered by whitish lichens, so light coloured moths escaped unnoticed from predatory birds. After industrialisation, barks got covered by smoke, so the white moths were selectively picked up by birds. However, the black coloured moths escaped unnoticed against a dark background and became abundant. However, in recent years, reduced industrial pollution has led to the growth of lichens again and thus, the population of light coloured moths is again increasing. This evolutionary story of moths in England, thus reveals, that ‘evolution is apparently reversible’

Question. Comment on the statement that ‘evolution and natural selection are end result or consequence of some other processes, but themselves are not processes’.
Answer  Evolution helps us to understand the history of life. We can view evolution as a pattern of evolutionary change and as a process as well. The world we see, all the inanimate and animate, is only the success stories of evolution. When we describe the story of this world, we describe evolution as a process. On the other hand, when we describe the story of life an earth, we treat evolution as a consequence of a process called natural selection. Natural selection is the outcome of favourable variations among organisms and environmental conditions. Thus, we are still not very clear whether to regard evolution and natural selection as processes or end result of processes. 

Question. Branching descent and natural selection are the two key concepts of Darwinian theory of evolution. Explain each concept with the help of a suitable example. 
Answer. Branching descent: Different species descending from the common ancestor get adapted in different habitats, e.g., Darwin’s finches—varieties of finches arose from grain eaters; Australian marsupials evolved from common marsupial.
Natural selection: It is a process in which heritable variations enable better survival of the species to reproduce in large number, e.g., white moth surviving before the industrial revolution and black moth surviving after industrial revolution; long-necked giraffe survived the evolution process; DDT-resistant mosquitoes survive. (Any suitable example)

Question. While creation and presence of variation is directionless, natural selection is directional as it is in the context of adaptation. Comment. 
Answer. Creation and variation occur in a sexually reproducing population as a result of crossing-over during meiosis and random fusion of gametes and independent assortment of genes. It is however the organisms that are selected over a period of time which are determined by the environmental conditions. In other words, the environment provides the direction with respect to adaptations so that the organisms are more and more fit in terms of survival.

Question. Explain adaptive radiation with the help of a suitable example. 
Answer. It is the process of evolution of different species in a given geographical area starting from a common point and radiating to other geographical areas (habitats). Examples:
(i) Darwin’s finches
- Darwin travelled to Galapages Islands and observed many varieties of finches on the same island.
- All varieties had evolved from original seed-eating finches.
- With alteration in beaks some became insectivorous and some vegetarian.

Question. Why are the wings of butterfly and birds said to be analogous organs? Name the type of evolution of which the analogous organs are a result of. 
Answer. Wings of butterfly and birds are not anatomically similar structures though they perform similar functions. Hence, they are called analogous structures. Analogous organs result from convergent evolution.

Question. What do you infer from the resemblance between flying squirrel and flying phalanger with reference to their evolution? 
Answer. Evolution of marsupial mammals has resulted in flying phalanger through adaptive radiation.
Evolution of placental mammals has led to the evolution of a flying squirrel (independently). The resemblance between the two proves convergent evolution.

Question. “Post-industrialisation, the population of melanised moth increased in England at the expense of white-winged moths.” Provide explanations.
OR
Explain the increase in the numbers of melanic (dark winged) moths in the urban areas of post-industrialisation period in England. 
OR
In England, during the post-industrialised period, the count of melanic moths increased in urban areas but remained low in rural areas. Explain. 
Answer. Pre-industrialisation period had more white winged moth against grey lichens on tree trunks.During industrialisation large amount of soot and smoke deposited on tree trunks, making the bark dark. Against the dark background white moths could easily be preyed upon.Melanised moth could camouflage against dark bark. This natural selection increased their number.

Question. Explain the interpretation of Charles Darwin when he observed a variety of small black birds on Galapagos Islands. 
Answer. In Galapagos Islands, the small black birds amazed Darwin and he later called them finches. He realised that there were many varieties of finches in the same island. All the varieties evolved on the island itself. This process of evolution was called adaptive radiation, According to Darwin this evolution was based on available resources, food and space. There is survival of the fittest.

Question. Anthropogenic action can hasten the evolution. Explain with the help of a suitable example.
Answer. Excessive use of herbicides, pesticides, etc., has only resulted in selection of resistant varieties in a much lesser time scale which is equally true for microbes against which we employ antibiotics or drugs against eukaryotic organisms/cells. As a result of which resistant organisms/cells are appearing in a time scale of months or years and not centuries. For example, when DDT was used for the first time, maximum mosquitoes died but few survived due to variation in the population. These mosquitoes showed resistance to DDT and survived to reproduce successfully in the presence of DDT and gradually such mosquito population became DDT resistant, following natural selection.

Question. Identify the following pairs as homologous or analogous organs:
(i) Sweet potato and potato
(ii) Eye of octopus and eye of mammals
(iii) Thorns of Bougainvillea and tendrils of Cucurbits
(iv) Forelimbs of Bat and Whale 
Answer. (i) and (ii) are analogous organs.
(iii) and (iv) are homologous organs.

Question. In a certain population, the frequency of three genotypes is as follows.
Genotypes: BB       Bb     bb
Frequency: 22%   62%  16%
What is the likely frequency of B and b alleles? 
Answer. Frequency of B allele = all of BB + ½ of Bb = 22 + 31 = 53%
Frequency of b allele = all of bb + ½ of Bb = 16 + 31 = 47%.

Long Answer Questions

Question. State the theory of Biogenesis. How does Miller’s experiment support this theory?
Answer. The theory of biogenesis states that a living organism arises from another living organism.
For Miller’s experiment: 
- Experiment was performed by S.L. Miller and H.C. Urey in 1953.
- Experimental set-up: In a closed flask containing CH₄, H₂, NH₃ and water vapour at 800°C, electric discharge was created. The conditions were similar to those in primitive atmosphere.
 Observations: After a week, they observed presence of amino acids and complex molecules like sugars, nitrogen bases, pigments and fats in the flask

Conclusions:
(i) It provides experimental evidence for the theory of chemical origin.
(ii) It showed that the first non-cellular form of life was created about 3 billion years ago.
(iii) It showed that non-cellular biomolecules exist in the form of DNA, RNA, polysaccharides and protein.

Question. State the contribution of Louis Pasteur in understanding the origin of life on earth. Explain the procedure that he followed to arrive at his conclusion. 
Answer. Louis Pasteur dismissed the theory of spontaneous generation and demonstrated that life came from pre-existing life. He took two long-necked flasks. He left one flask with a straight neck and the other was bent to from an ‘S’ shape. He put sterile broths in both the flasks. He placed killed yeast in pre-sterilised bent flask and the other flask was left open to air.
After several weeks he observed that the straight neck flask was discoloured and cloudy, while the curved flask had not changed. Thus he concluded that the germs in air were able to fall unobstructed down the straight necked flask while they got trapped in the curved flask.

Question. Differentiate between the explanations given by Darwin and de vries respectively on the mechanism of evolution.
Answer. Differences between Darwin’s and de Vries’ theory of evolution

Question. p² + 2pq + q² = 1. Explain this algebraic equation on the basis of Hardy Weinberg’s principle.
Answer. In a diploid if p represents the frequency of allele A and q represents the allele frequency of a, then frequency of AA individuals in a population is p². Similarly of aa is q² and of Aa is 2pq. Hence p² + 2pq + q² = 1. This is abinomial expansion of (p+q)².
According to Hardy–Weinberg principle, total genes and their alleles in a population or gene pool remains constant. This is called genetic equilibrium. Sum total of all the allelic frequencies is 1 [p+q = 1/(p+q)² = 1].

Question. (a) How does the Hardy–Weinberg’s expression (p² + 2pq + q² = 1) explain that genetic equilibrium is maintained in a population?
(b) List any two factors that can disturb the genetic equilibrium. 
Answer. (a) (i) Sum total of all the allele frequencies is 1: Let there be two alleles A and a in a population. The frequencies of alleles A and a are p and q, respectively. The frequency of AA individual in a population is  p² and it can be explained that the probability that an allele A with a frequency of P appear on both the chromosomes of a diploid individual is simply the product of the probabilities, i.e., p². Similarly, the frequency aa is q² and that of Aa is 2pq.
p² + 2pq + q² = 1, where  p² represents the frequency of homozygous dominant genotype, 2pq represents the frequency of the heterozygous genotype and represents the frequency of the homozygous recessive.
(ii) Genetic equilibrium states the status of evolution. If there is some fluctuation or disturbance in genetic equilibrium or Hardy–Weinberg equilibrium, i.e., change of frequencies of alleles in a population then it can predicted that evolution is in progress.
(b) Factors that affect Hardy–Weinberg equilibrium:
(i) Gene migration or gene flow
(ii) Genetic drift
(iii) Mutation (Any two)

Question. What is disturbance in Hardy-Weinberg genetic equilibrium indicative of? Explain how it is caused. 
Answer. Disturbance in Hardy-Weinberg equilibrium is an indicator of change of frequency of allele in a population, resulting in evolution.
It is caused by any of the following factors:
(i) Genetic drift
(ii) Gene flow or gene migration
(iii) Mutation
(iv) Genetic recombinations
(v) Natural selection

Question. (a) Differentiate between analogous and homologous structures.
(b) Select and write analogous structures from the list given below:
(i) Wings of butterfly and birds
(ii) Vertebrate hearts
(iii) Tendrils of Bougainvillea and Cucurbita
(iv) Tubers of sweet potato and potato 
Answer. (a) Differences between analogous and homologous structures

(b) Wings of butterfly and birds.
Tubers of sweet potato and potato.

Question. What is natural selection? How is artificial selection different from natural selection? Give one example each from plants and animals where artificial selection has operated.
Answer. The nature builds some pressure on the population of a species and as a result few individuals are eliminated and few adapt to adjust with changes and become fit. This biological phenomenon is called natural selection.

Differences between natural selection and artificial selection
 Natural selection                                               Artificial selection
It is a natural phenomenon.                               It is the practice done by man.
As a result only fit individuals increase in a       As a result commercially high yielding and
population.                                                        disease resistance varieties increase.

Question. How do fossils help us in understanding the evolutionary history? 
Answer.  Paleontological evidences
- The study of fossil is called paleontology.
- Fossils are the remains or impressions of past organisms preserved in sedimentary rocks or other media.
- Different-aged rock sediments in earth’s crust indicate the presence of fossils of different life forms which died during the sediment formation.
- A variety of fossils ranging from the modern organisms to extinct organisms can be observed.
-By studying the different sedimentary layers, the geological time period in which the organism existed can be predicted, e.g., Dinosaurs.

ONE MARK QUESTIONS
1.What causes speciation according to Hugo de Vries?
2.Mention the type of evolution that has brought the similarity as seen in potato tuber and sweet potato.

TWO MARK QUESTION
3.How do Darwin’s finches illustrate adaptive radiation?
4.How is Darwin’s concept of evolution different from de Vries?
5.What is divergent evolution? Explain taking an example of plants.
6.Why are the wings of butterfly and birds said to be analogous organs? Name the type of evolution of which the analogous organs are a result of.