Evolution Class 12 Biology Exam Questions

Exam Questions Class 12

Please refer to Biology For Evolution Class 12 Biology Exam Questions provided below. These questions and answers for Class 12 Biology have been designed based on the past trend of questions and important topics in your class 12 Biology books. You should go through all Class 12 Biology Important Questions provided by our teachers which will help you to get more marks in upcoming exams.

Class 12 Biology Exam Questions Evolution

Objective Type Questions

Question. The rate of appearance of new forms during change in environment of Habitat is linked to
(a) Eating habits
(b) Life span
(c) Organism size
(d) None of these

Answer

B

Question. Lamarck gave example of which animal for his of use and disuse of organs
(a) Malay Archipelago
(b) Giraffe
(c) Drosophila
(d) None of these

Answer

B

Question. The two key concepts of Darwinian theory of evolution are
A. Branching ascent
B. Natural selection
C. Branching descent
D. Use and disuse of organs
Options :
(a) A, B and D
(b) B and C
(c) C and D
(d) B, C and D

Answer

B

Question. Theoretically population size will grow exponentially if reproduction is maximum but in fact population sizes are limite (D) The reason behind this is
(a) There had been competition for resources
(b) Only some survive due to better adaptation
(c) Both (a) and (b)
(d) None of these

Answer

C

Question. Who worked on mutation?
(a) Lamarck
(b) Charles Darwin
(c) Hugo de Vries
(d) G J Menel

Answer

C

Question. According to Hugo de Vries saltations are
(a) Multistep large mutations
(b) Single step large mutation
(c) Small step large mutation
(d) None of these

Answer

B

Question. The frequency of occurrence of alleles of a gene in a given population is supposed to
(a) Change at a fast rate
(b) Change at a slow rate
(c) Remains fixed
(d) cannot be monitored

Answer

C

Question. Hardy–Weinberg principle state that
(a) The organism with better adaptation to the environment survives
(b) Organism with mutations forms new species
(c) Living forms have evolved from rotten compounds
(d) Allele frequency in a population is stable and constant from generation to generation

Answer

D

Question. Sum total of all the allele frequencies in a population is
(a) >1
(b) <1
(c) Zero
(d) 1

Answer

D

Question. In a diploid organism the probability that an allele ‘A’ with a frequency p and allele ‘a’ with frequency q to appear on a chromosome pair (Aa) will be
(a) pq
(b) p2q2
(c) 2pq
(d) (pq)2

Answer

C

Question. Theory of natural selection was given by
(a) Louis Pasteur
(b) Charles Darwin
(c) Oparin and Haldane
(d) Aristotle

Answer

B

Question. How the ages of fossils are calculated?
(a) Polymerase chain reaction
(b) Radioactive dating
(c) Ultra–centrifugation
(d) Chromatography

Answer

B

Question. Which of the following is an extinct organism?
(a) Whale
(b) Dinosaurs
(c) Tiger
(d) Rhinosaurus

Answer

B

Question. Alfred Wallace worked on which organism
(a) Giraffe
(b) Malay Archipelago
(c) Drosophila
(d) None of these

Answer

B

Question. Which of the following is not a bone of forelimb?
(a) Humerus
(b) Femur
(c) Radius
(d) Ulna

Answer

B

Question. Homology indicates that the ancestors were
(a) Different
(b) Same
(c) Doesn’t tell about ancestors
(d) None of these

Answer

B

Question. Analogy deals with
(a) Similar anatomy different functions
(b) Similar anatomy similar functions
(c) Different anatomy different functions
(d) Different anatomy similar function

Answer

D

Question. Eye of octopus and mammals are the examples of
(a) Homology
(b) Analogy
(c) Both (a) and (b)
(d) None of these

Answer

B

Question. Which of the following is not an example of root modification?
(a) Potato
(b) Carrot
(c) Sweet potato
(d) Turnip

Answer

A

Question. Wings of mosquito, bat, butterfly performing same function of flying but different anatomy is an example of
(a) Analogy
(b) Homology
(c) Both (a) and (b)
(d) None of these

Answer

A

Question. In England during industrialization (1920) moths with dark wing appeared more in number. The reason for change in wing from white to dark colour was?
(a) Environment heat
(b) As part of defense mechanism against predators
(c) Immigration of dark winged moth from other places
(d) Emigration of white moths to other places

Answer

B

Question. Change in moth population in England post industrialization is an example of
(a) Chemical evolution
(b) Evolution by natural selection
(c) Evolution by biogenesis
(d) Evolution by abiogenesis

Answer

B

Question. Darwin found diversity of small black birds called Finches in
(a) India
(b) Africa
(c) Australia
(d) Galapagos island

Answer

D

Question. The process of evolution of different species in a given geographical areas starting from a point and radiating to other geographical areas is called
(a) Homology
(b) Analogy
(c) Adaptive radiation
(d) Convergent evolution

Answer

C

Question. When more than one adaptive radiation appeared to have occurred in an isolated geographical area it can be called as
(a) Divergent evolution
(b) Convergent evolution
(c) Evolution by anthropogenic action
(d) None of these

Answer

B

Very Short Answer Type Questions

Question. What were the characteristics of life forms that had been fossilised?
– Thinking Process
Fossils are formed and preserved over times so, all organisms are not equally likely to fossilis. It is based towards organisms with hard parts such as bones of vertebrates or calcareous exoskeleton of invertebrates.
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?
– Thinking Process
The geological changes that took place over time transformed many water-bodies into solid rocks and mountains, so fossils of aquatic organism are more likely to be found in mountains.
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 oceAnswer.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. What is the most important pre-condition for adaptive radiation?
Answer. Conditions promoting adaptive radiation are much of the diversity of life originated through episodes of adaptive radiation during periods when ecological space became
available for diversification. There are two primary mechanisms through which ecological space can become available.
(i) intrinsic changes in organisms.
(ii) extrinsic effects, including environmental change and colonisation of isolated landmasses.

Question. How do we compute the age of a rock?
Answer. The age of a rock in years is called its absolute age. It is determined by the natural radioactive decay of certain elements, e.g., uranium, when decays turns into lead. The parent atoms of uranium are converted into daughter atoms of lead over a fixed interval of time. This interval is the decay constant.
The ratio of parent-daughter atoms changes in a quantity that can be measured.
The radioactive half-life (the amount of time required for one half of the parent atoms to beonverted to daughter atoms) is used to calculate the age of the rock.

Question. When we talk of functional macromolecules (e.g., proteins as enzymes,hormones, receptors, antibodies etc), towards what are they evolving?
Answer. Functional macromolecules are evolving towards creation of a complex organism. There are various evidences that are common to simple and complex forms of lite indicate common ancestry, e.g., histones protein tend to be well preserved among all eukaryotes, from amoebas to blue whale or to humans, with only one or two amino acids different.
The genetic code is nearly identical for all known life forms, from bacteria to archaea or animals and plants.

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?
– Thinking Process
According to Hardy-Weinberg equilibrium, p2 + 2pq + q2 =1.
Answer. The likely frequency of B = BB + 1 2 Bb

Evolution Class 12 Biology Exam Questions

Question. Among the five factors that are known to affect Hardy-Weinberg equilibrium, three factors are gene flow, genetic drift and genetic recombination. What are the other two factors?
Answer. The other two factors that affect Hardy-Weinberg equilibrium are mutation and natural selection.
Mutation is a sudden heritable change in an organism which is generally due to change in the base sequence of the nucleic acid in the organism’s genome.
Microbial experiments show that pre-existing advantageous mutations when selected will result in formation of new phenotypes. Over few generations, this would result in speciation.
Thus, resulting in changed frequency of genes and alleles.
Natural selection is a phenomenon by which organisms possessing heritable variations enabling their better survival reproduce and leave greater number of progeny than their counterpart.
It can lead to stabilisation (in which more individuals acquire mean character value),directional change (more individuals acquire value other than the mean character value) or disruption (more individuals acquire peripheral character value at both ends of the distribution curve).

Question. What is founder effect?
Answer. Sometimes, a small number of individuals become isolated from a larger population to form a new population at some distance away from their place of origin.
The gene pool of the new population differs from the source population. It is possible that the change in allele frequency is so drastically different in the new sample that they
 become a different species. The original driftted population becomes founders and this effect is called founder effect.

Question. Who among the Dryopithecus and Ramapithecus was more man like?
Answer. Ramapithecus was more man-like. It walked erect on its hind legs, ate hard nuts and seeds like modern man and had jaws and teeth similar to humAnswer. It arose from Dryopithecus,which was considered to be a common ancestor of man and apes.Dryopithecus was more ape-like with same length of arms and legs.

Question. By what Latin name, the first Hominid was known?
Answer. The first hominid was known as Homo habilis. The brain capacities were between 650-800cc. They probably did not eat meat.

Question. Among Ramapithecus, Australopithecines and Homo habilis who probably did not eat meat?
Answer. Homo habilis probably did not eat meat. This creature was the first human like being, with brain capacities between 650-800cc.

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.
– Thinking Process
The peppered moths were initially white coloured, then black coloured due to industrialisation. In recent years, the light coloured moths are increasing in population
again.
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. State and explain any three factors affecting allele frequency in populations.
Answer. Factors affecting allele frequency in populations are as described below
(i) Mutations These are sudden heritable changes which are supposed to be the primary source of genetic variation. They are of following two types
(a) Chromosomal Mutations They arise due to changes in chromosome number and changes in structure.
(b) Gene Mutations These are changes in gene structure and expression due to addition, deletion, substitution or inversion of nucleotides.
(ii) Non-random Mating Repeated mating between individuals of certain selected traits changes the gene frequency, e.g., selection of more brightly coloured male bird by a female bird may increase the gene frequency of bright colour in the next generation.
(iii) Gene Flow (Gene Migration) It is the movement of alleles into and out of a gene pool. Breeding of immigrants with the host population adds new alleles to the gene pool of the host population.

Question. Gene flow occurs through generations. Gene flow can occur across language barriers in humAnswer. 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, we agree. As the gene flow occurs through geographical barriers over generations, by studying specific allelic frequencies in various populations of the world, we can predict the human migratory patterns in pre-historic and historic era.
There have been projects undertaken such as human genographics project. Which uses data from studies on specific genes/chromosomes/mitochondrial DNA to trace the evolutionary history and migratory patterns of humAnswer.

Question. How do you express the meaning of worlds like race, breed, cultivars or variety?
Answer. The meaning of the given words are as given below Race It is a classification system used to categorise humans into large and distinct populations or groups by anatomical, cultural, linguistic, geographical, historical and for relegious relationship.
Breed It is a specific group of domestic animals or plants having homogenous appearance, homogenous behaviour and other characteristics that distinguish it from other animals or plants of the same species and that were arrived at through selective breeding.Cultivar It is a plant or grouping of plants selected for desirable characteristics that can be maintained by propogation. ‘Cultivar’ stands for ‘cultivated variety’.
Variety A variety arises naturally in the plant kingdom and plant grown from its seeds will typically come out true to type.

Question. When we say ‘survival of the fittest’, does it mean that
(a) those which are fit only survive
(b) those that survive are called fit? Comment.
– Thinking Process
Those individuals which survice and reproduce in their respective environment are called fit.
Answer. In the struggle for existence, the individuals which have more favourable variations will enjoy a competitive advantage over others which have less favourable or unfavourable
variations.
They are considered fit and thus, will survive and reproduce. Such individuals produce more progeny (with more fit individuals) than others who are less adapted in that environment.

Question. Enumerate three most characteristic criteria for designating a Mendelian population.
Answer. Characteristic criteria for designating a Mendelian population are
(i) Population must be sufficiently large.
(ii) Population must have potentialities for free flow of genetic material among individuals, through sexual reproduction.
(iii) Migration should either be nil or negligible

Question. ‘Migration may enhance or blurr the effects of selection’ comment.
Answer. The movement of individuals from one place to another is called migration. It can be the movement of individuals to a different populations (i.e., emigration) or movement of
individual into a particular population (i.e., cmmigration) Migration may bring in more such alleles, that bestow upon the individuals, such adaptations or traits which are selected by
nature. Thus, enhancing the effect of selection.
Similarly, emigration may lead to removal of such alleles that confer better adaptations. Immigration may also bring in those alleles which confer the traits that are not selected by nature, i.e., blurr the effects of selection.
Hence, it is justifiable to say that ‘Migration may enhance or blurr the effects of selection.’

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.
– Thinking Process
Prior to industrialisation, the light coloured moths were prevalent and well adapted to lichen covered trunks of trees.
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.