VBQs Evolution Class 12 Biology

VBQs for Class 12

VBQs Evolution Class 12 Biology with solutions has been provided below for standard students. We have provided chapter wise VBQ for Class 12 Biology with solutions. The following Evolution Class 12 Biology value based questions with answers will come in your exams. Students should understand the concepts and learn the solved cased based VBQs provided below. This will help you to get better marks in class 12 examinations.

Evolution VBQs Class 12 Biology

Very Short Answer Type Questions

Question. Write the probable differences in eating habits of Homo habilis and Homo erectus.
Answer :
Homo habilis did not eat meat, were vegetarian while Homo erectus were probably meat eaters.

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 :
(i) Pre-historic cave art.
(ii) Agriculture / Human Settlement. 

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

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 :
The formula to calculate allele frequency is :
(p + q)2 = p2 + 2pq + q2 = 1 

Question. List the two characteristics of mutation that help in explaining evolution.
Answer :
(i) Mutation are random and inheritable.
(ii) Same type of mutations may occur in a number of individuals of same species. 

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


VBQs Evolution Class 12 Biology

Study the ladder of human evolution given above and answer the following questions.
(i) Where did Australopithecus evolve?
(ii) Write scientific name of Java man.
Answer :
(i) East Africa.
(ii) Homo erectus. 

Short Answer Type Questions

Question. Mention the evolutionary significance of the following organisms : 
(i) Shrews
(ii) Lobefins
(iii) Homo habilis
(iv) Homo erectus
Answer :
(i) First mammals 
(ii) First amphibians (lived both on land and in water) / fish with stout and strong fins which could move on land and go back to water. 
(iii) First human like being / hominid / brain capacity from 650 – 800 cc / did not eat meat.
(iv) Large brain around 900 cc / eat meat. 

Question. Compare and contrast the theories of evolution proposed by Darwin and Hugo De Vries.
Answer :

S.No.Drawin’s Theory of Natural SelectionDe Vries Theory of Mutation
1. Minor variations cause evolution.Mutation are random and directionless.
2.Darwinian variations are small and directional.Mutations are random and directionless.
3.Evolution is gradual.Sudden mutations cause evolution.

Question. Explain the interpretation of Charles Darwin when he observed a variety of small black birds on Galapagos Island.
Answer :
Charles Darwin observed an amazing variety of small black birds called Darwin’s finches in the same island. All the varieties evolved on the island itself from ancestral stock and have radiated to different habitats where they have undergone adaptive changes. Darwin interpreted the formation of a number of divergent species from a common ancestral stock with new species adapting different habitats as adaptive radiation resulting into the divergent evolution.
According to Darwin this evolution was also based on available resources of food and space and on this basis therefore by observing their characteristics on the Galapagos islands, he proposed his famous theory known as the ‘theory of natural selection’. The main postulates of this theory are as follows :
(i) All organisms possess an enormous power of fertility.
(ii) There is a struggle for the existence within a species as well as between two different species for food, space and resources.
(iii) Nature will favour the survival of the fittest.
(iv) Darwin believed that variations ultimately lead to the formation of new species.

Question. Describe the three different ways by which Natural selection can affect the frequency of a heritable traits in population.
Answer :
(i) Stabilization, in which more individual acquire average character value i.e., medium sized individuals. 
(ii) Directional, more individuals acquire value other than the average character value.
(iii) Disruptive, more individuals acquire peripheral character value at both ends of distribution curve. Consequently the original population is disrupted into two or more separate groups that later evolved into new species.
Detailed Answer :
Natural selection can affect the frequency of a heritable trait in a population in the following ways:
(i) It can lead to stabilization (in which more individual acquire mean character value i.e. medium-sized individuals).
(ii) It may result in directional change (more individuals acquire value other than the mean character value).
(iii) It may result in disruption (more individuals acquire peripheral character value at both ends of the distribution curve). 

Question. Write in what context did Darwin use that terms ‘fitness‘, ‘survival‘ and ‘selection‘ while elaborating the mechanism of evolution.
Answer :
Fitness refers to reproductive fitness (will leave more progeny) – more survival and hence selected by nature – natural selection. 

Question. Fitness is the end result of the ability to adapt and get selected by nature. Explain with suitable example.
Answer :
Industrial Melanism : Before industrialisation started in England it was observed, there were more white – winged peppered moth on trees than dark winged moth but after industrialisation, there were more dark – winged moths in the same area, predators spot a moth against a contrasting background, post industrialisation the tree trunk became dark due to industrial smoke and soot, Under this condition the white- winged moth did not survive due to predators, but the dark-winged moth managed to survive.
Detailed Answer :
Fitness is based on certain characteristics which are inherited and the ability to adapt to the changing environment. It is the end result of adaptation because a fit individual survives and unfit individuals are eliminated from the population.
Individuals continuously compete with each other in a population for food, space and light. The one which is better adapted and naturally selected by nature survives and reproduces.
For example, industrial melanism : It is a case of natural selection. In England, it was observed before industrialisation that whitewinged moth were more than dark-winged moths. But the situation became reversed after industrialisation. It was found that predators would spot and pick a moth against a contrasting background. During pre-industrialisation, the tree trunks were covered with white lichens and on white-background dark coloured moth could be picked up.
During post industrialisation, the tree trunks were covered by dark, dust, coal particles and became dark on which white moth could easily be picked up. Thus, it was found that industrial melanism supports evolution by natural selection. 

Question. (i) How does the Hardy – Weinberg’s expression (p2 + 2pq + q2 = 1) explain that genetic equilibrium is maintained in a population ?
(ii) List any two factors that can disturb the genetic equilibrium. 
Answer :
(i) The gene pool i.e. the total genes and their alleles in a population tend to remain constant, this is called genetic equilibrium.
Sum total of all allelic frequencies is 1.
Individual frequencies can be named p, q, etc.
In a diploid, p and q represent the frequency of allele A and allele a. The frequency of AA individuals in a population is simply p2.
This is simply stated in another way i.e., 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 of aa is q2, of Aa 2pq. Hence, p2 + 2pq + q2 = 1. When frequency measured, differs from expected
values, the difference (direction) indicates the extent of evolutionary change. Disturbance in genetic equilibrium or Hardy – Weinberg equilibrium i.e. change of frequency of alleles in a population would then be interpreted as resulting in evolution.
(ii) Gene migration / gene flow / gene drift / mutation / genetic recombination / natural selection.

Question. With the help of an algebraic equation, how did Hardy-Weinberg explain that in a given population the frequency of occurrence of alleles of a gene is supposed to remain the same through generations ?
Answer :
In a population of diploid organisms If frequency of allele A = p and frequency of allele a = q ½
Genotype frequency under random mating are
AA = p2 (for the AA homozygotes)
aa = q2 (for the aa homozygotes)
Aa = 2pq (for the Aa heterozygotes)
(In absence of selection, mutation, genetic drift or other forces, allelic frequency p and q are constant through generation).
Therefore, p2 + 2pq + q2 = 1
Detailed Answer:
The Hardy-Weinberg model enables us to compare a population’s actual genetic structure over time with the genetic structure we would except if the population were in Hardy-Weinberg equilibrium (i.e, not evolving). If genotype frequencies differ from those we would except under equilibrium, we can assume that one or more of the model’s assumptions are being violated and attempt to determine which one(s). 
Hardy and Weinberg assigned the letter p to the frequency of the dominant allele A and the letter q to the frequency of the recessive allele a.
Since the sum of all the alleles must equal 100%, then p + q = 1. They then reasoned that all the random possible combinations of the members of a population would be equal (p + q)2 or p2 + 2pq + q2 = 1.
The overall equation for the Hardy-Weinberg equilibrium is expressed in this way: p2 + 2pq + q2 = 1 [binomial expansion of (p + q)2].

Question. (i) Rearrange the following in an ascending order of evolutionary tree : reptiles, salamander, lobfins, frogs.
(ii) Name two reproductive characters that probably make reptiles more successful than amphibians.
Answer :
(i) Lobefins, frogs, salamanders and reptile.
(ii) Two reproductive characters that made reptiles more successful than amphibians are :
(a) Reptiles lay eggs on land.
(b) Reptiles lay thick shelled egg which do not get dry up in sun shine unlike those of amphibians.

Long Answer Type Questions

Question. (i) How did Darwin explain adaptive radiation ?
Give another example exhibiting adaptive radiation.
(ii) Name the scientist who influenced Darwin and how ? 
Answer :
Darwin explained the phenomenon of adaptive radiation on the basis of his investigation on fauna of Galapogas islands. Finches of Galapogas island offer the best example of adaptive radiation.
(i) During his journey, Darwin went to Galapogas island and observed that there were many varieties of finches in the same island. They varied from normal seed-eating ones to those that ate insects. 
Another example of adaptive radiation is evolution of the Australian marsupials from a single ancestor. 
(ii) Work of Thomas Malthus influenced Darwin.
He gave an idea about population growth and food availability. He said that present growth of human population is more than what food and other resources can sustain. This means that many people would die of starvation to level out the population. His views gave the Darwin the idea about “survival of fittest”.

Question. (i) How did Darwin explain adaptive radiation by taking an example of finches ?
(ii) How did Darwin’s view on evolution differ from that of de-Vries ?
Answer :
(i) Darwin conjectured that the Darwin’s finches evolved on the island itself. 
There were seed-eating finches and other finches with altered beaks arose allowing different types of food eating habits like insectivorous and vegetarian finches. 
This process of evolution of different species in a given geographical area starting from a point and radiating to other areas of (geographical) habitats is called adaptive radiation. 

VBQs Evolution Class 12 Biology

Question. (i) Describe Hardy – Weinberg Principle.
(ii) List any four factors which affect genetic equilibrium.
(iii) Describe founder effect. 
Answer :
(i) Allele frequencies in a population are stable and constant / gene pool, total genes and their alleles in a population remain constant from generation to generation and maintain genetic equilibrium. 
(ii) Factors affecting genetic equilibrium are —
(a) Gene migration / gene flow.
(b) Genetic drift.
(c) Mutation.
(d) Genetic recombination.
(e) Natural selection. 
(iii) (a) Change in allele frequency.
(b) New genes develop, old genes are lost.
(c) Migration.
(d) Drift.
(e) New species. 
When section of population gets separated due to migration or genetic drift, gene frequencies changes, sometimes this change in allele frequency is different in the new population so that they becomes new species, this is called founder effect. 

Question. How does the process of natural selection affect Hardy–Weinberg equilibrium ? Explain. List the other four factors that disturb the equilibrium.
(i) Write Hardy–Weinberg principle.
(ii) Explain the three different ways the natural selection can affect the frequency of a heritable trait in a population shown in the graph given below.

VBQs Evolution Class 12 Biology

Answer : (i) Hardy–Weinberg’s principle says that allele frequencies in a population are stable and constant from generation to generation. The gene pool remains constant. This is called genetic equilibrium. Sum total of all the allelic frequencies is 1. Individual frequencies e.g. can be named p, q etc. Natural selection disturbs the allelic frequencies. Through natural selection either the frequency of p increases or the frequency of q it disturbs the natural frequency. In a diploid, p and q represent the frequency of allele A and allele a. The frequency of AA individuals in a population is simply p2.
This is simply stated in another ways i.e. the probability that an allele A with a frequency of p appear on both the chromosomes of a diploid individual is the product of the probabilities.
Hence, p2 + 2pq + p2 = 1.
The factors that affect the Hardy–weinberg’s equilibrium are : Migration, Gene flow, Genetic drift, mutation and genetic recombination.
(ii) Variation due to mutation or recombination during gametogenesis or due to gene flow or genetic drift results in changed frequency of genes and alleles in future generation. Natural selection can lead to stabilization (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).