Please see Chapter 7 Evolution Exam Questions Class 12 Biology below. These important questions with solutions have been prepared based on the latest examination guidelines and syllabus issued by CBSE, NCERT, and KVS. We have provided Class 12 Biology Questions and answers for all chapters in your NCERT Book for Class 12 Biology. These solved problems for Evolution in Class 12 Biology will help you to score more marks in upcoming examinations.
Exam Questions Chapter 7 Evolution Class 12 Biology
Objective Type Questions
Question. When migration of a section of population takes place gene frequencies change
(a) At the place where the new population migrated
(b) At the place from where the population have migrated
(c) Both (a) and (b)
(d) Remains same at both the places
Question. Which of the following factors do not affect the Hardy–Weinberg Principle?
(a) Gene flow
(b) Use and disuse of organs
(c) Genetic drift
(d) Natural selection
Question. If natural selection leads to stabilizations this means
(a) More individuals acquire mean character value
(b) More individuals acquire value other than mean character value
(c) More individuals acquire peripheral character value at both the ends of distribution curve
(d) None of these
Question. Narrowing and increasing height of peak in a population distribution curve indicates
(a) More individuals acquire value other than mean character value
(b) More individuals acquire mean character value
(c) More individuals acquire peripheral character value at both the ends of distribution curve
(d) None of these
Question. The first cellular form of life appeared on earth
(a) 3000 mya
(b) 2000 mya
(c) 4000 mya
(d) 4500 mya
Question. First organism that invaded land were
(c) Both together
(d) None of these
Question. In 1938, an extinct fish (Coelacanth) was caught in which continent
(a) South America
(b) South Africa
(d) South asia
Question. Reptiles evolved from
Question. The giant ferns belong to
Question. Coal deposits were formed by felling of
(b) Sea weeds
Very Short Answer Questions
Question. Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
Answer. A recent study of fossil revealed a small terrestrial dinosaur with feathers covering the limb and body. This finding established that feathers evolved earlier than wing and may be functioning as thermoregulator to face adverse conditions. These newly developed feathers earlier helped in gliding and then flying.
Question. Attempt giving a clear definition of the term species.
Answer. Species can be defined as a group of reproductively isolated population which can interbreed among each other.
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. Among Ramapithecus, Australopithecous and Homo habilis, who probably did not eat meat?
Answer. Homo habilis
Question. Find out through internet and popular science articles whether animals other than man has self-consciousness.
Answer. Many animals other than humans have self consciousness. For example, dolphins and chimpanzees are considered highly intelligent. They have a sense of self and they also recognise others among themselves and others. They communicate with each other by whistles, tail-slapping, and more body movements.
Question. List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
|Modern day animals
|Corresponding ancient fossil
|Homo sapiens neanderthalensis
Question. Practice drawing various animals and plants.
Answer. Draw labelled diagrams of various animal and plants from your text book.
Question. Describe one example of adaptive radiation.
Answer. Darwin’s finches in the Galapagos Island once had a common ancestor but with evolution they modified into different types according to their food habitat.
Question. State the significance of Coelacanth in evolution.
Answer. It is an ancestor of amphibians.
Question. Using various resources such as your school library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal, say horse.
Answer. The evolution of horse is represented as
(i) Eohippus: This stage is characterised by a short head and neck. It had four functional toes and a splint of 1 and 5 on each hind limb and a splint of 1 and 3 in each forelimb. The molars were short crowned that were adapted for grinding the plant diet.
(ii) Mesohippus: It was slightly taller than Eohippus. It had three toes in each foot.
(iii) Merychippus: It had the size of approximately 100 cm.
Although it still had three toes in each foot, but it could run on one toe. The side toe did not touch the ground.
The molars were adapted for chewing the grass.
(iv) Pliohippus: It resembled the modern horse and was around 108 cm tall. It had a single functional toe with splint of second and fourth in each limb.
(v) Equus: Pliohippus gave rise to Equus or the modern horse with one toe in each foot. They have incisors for cutting grass and molars for grinding food.
Question. Can we call human evolution as adaptive radiation?
Answer. No, human evolution cannot be called as adaptive radiation because parent species of Homo sapiens have evolved by progressive evolution from Homo habilis to Homo erectus lineage.
Short Answer Questions
Question. Diagrammatically represent the experimental set up that proves Oparin–Haldane hypothesis.
Question. While creation and presence of variation is directionless, natural selection is directional as it is in the context of adaptation. Comment.
Ans. 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. Protein synthesis machinery revolves around RNA but in the course of evolution it was replaced by DNA. Justify.
Ans. Since RNA was unstable and prone to mutations, DNA evolved from RNA with chemical modifications that makes it more stable.
DNA has double stranded nature and has complementary strands. These further resist changes by evolving a process of repair.
Question. What must have provided energy for the warmth for life to originate on primitive earth? Name the first organism to release oxygen into the atmosphere.
Ans. Energy for life to originate must have been provided by heat, cosmic rays and lightning.
Cyanobacteria was the first organism to release oxygen into the atmosphere.
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?
Ans. 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%.
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.
Ans. 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. Mention the contribution of S.L. Miller’s experiments on Origin of Life.
Ans. S.L. Miller created an environment in laboratory similar to the one that existed before life originated.
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. After a week, they observed presence of amino acids and complex molecules like sugars, nitrogen bases, pigments and fats in the flask.
This provided experimental evidence for the theory of chemical origin.
Question. Convergent evolution and divergent evolution are the two concepts explaining organic evolution. Explain each one with the help of an example.
Differentiate between divergent and convergent evolution. Give one examples of each.
Ans. Convergent evolution: When more than one adaptive radiation appeared to have occurred in an isolated geographical area and two or more groups of unrelated animals resemble each other for similar mode of life or habitat, it is called convergent evolution, e.g., Australian marsupials, placental mammals.
Divergent evolution: In some animals, the same structures developed along different directions due to adaptations to different needs. This is known as divergent evolution. For example,forelimbs of whales, bats, cheetah and human perform different functions but have similar anatomical structure with similar bones arranged in similar segments.
Question. Explain divergent evolution with two examples.
Ans. Some structures developed along different directions due to adaptations to different needs performing different functions. This is called divergent evolution. Examples:
(i) Forelimbs of whales, bat, cheetah and humans have similar pattern of bones.
(ii) Thorns of Bougainvillea and tendrils of Cucurbita are modifications of stem.
Long Answer Questions
Question. State the theory of Biogenesis. How does Miller’s experiment support this theory?
Ans. The theory of biogenesis states that a living organism arises from another living organism.
For Miller’s experiment: • Life appeared 500 million years after formation of earth.
• Different theories were given to explain the origin of life.
(i) Theory of special creation: According to this theory, God created life by his divine act of creation.
(ii) Theory of panspermia/cosmozoic theory: According to early Greek thinkers, units of life called spores or panspermia came from outer space and developed into living forms. This theory was rejected as spores cannot survive extreme cold, dryness or UV rays from Sun, which are required to be crossed to reach earth.
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.
Ans. 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. Evolution is a change in gene frequencies in a population in response to changes in theenvironment in a time scale of years and not centuries. Justify this statement with reference to DDT. How does the theory of Hugo de Vries support this?
Ans. When DDT was used for the first time, maximum mosquitoes died but few survived due to variation in a 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 within a time span of few years.
According to Hugo de Vries, evolution is caused by sudden large differences in the population and not minor variations.
Question. (a) Name the primates that lived about 15 million years ago. List their characteristic features.
(b) (i) Where was the first man-like animal found?
(ii) Write the order in which Neanderthals, Homo habilis and Homo erectus appeared on earth. State the brain capacity of each one of them.
(iii) When did modern Homo sapiens appear on this planet?
Ans. (a) Primates called Dryopithecus and Ramapithecus lived 15 million years ago.
Their characteristic features are:
(i) They were hairy and walked like gorillas and chimpanzees.
(ii) Ramapithecus was more man-like.
(iii) Dryopithecus was more ape-like.
(b) (i) First man-like animal was found in Ethiopia and Tanzania.
(ii) The order of appearance from the earliest to the latest is: Homo habilis, Homo erectus, Neanderthals.
The brain capacity of Homo habilis is 650–800 cc, of Homo erectus is 900 cc and of Neanderthals is 1400 cc.
(iii) Modern Homo sapiens appeared between 75,000–10,000 years ago.
Question. How do fossils help us in understanding the evolutionary history?
Ans. (i) 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.
Question. What are analogous structures? How are they different from homologous structures? Provide one example for each.
Differentiate between homology and analogy. Give one example of each.
|Organisms having the same structure developed along different directions due to adaptations/ different functions.
|Different structures having the same function (in different organisms).
|Result of divergent evolution.
|Result of convergent evolution.
|Indicates common ancestry.
|Does not indicate common ancestry.
|Anatomically same structures.
|Anatomically different structures.
|Example:Forelimbs of whale—bats—cheetah—human/ Thorns of Bougainvillea and tendrils of cucurbits
|Example: Wings of butterfly and birds, Sweet potato and potato
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
Ans. (a) Table 7.4: Differences between analogous and homologous structures
|These are anatomically not similar but perform similar functions.
|These are anatomically similar but perform different functions.
|They are a result of convergent evolution.
|They are a result of divergent evolution.
(b) Wings of butterfly and birds.
Tubers of sweet potato and potato.