Evolution VBQs 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. What role does an individual organism play as per Darwin’s theory of natural selection ?
Answer :
Individual with reproductive fitness passes on the useful gene to the next generation. 

Question. According to De-Vries what is saltation?
OR
What is ‘Saltation’ according to De Vries?
Answer :
Saltation is a single step large mutation which brings major change as speciation. 

Question. Write the basis of origin of variations in organisms as described by Hugo de Vries.
Answer :
Saltations (Mutation), large differences arising out all of a sudden in a population. 

Question. State the significance of coelacanth in evolution.
Answer :
Coelacanth is a special type of fish called lobfin caught in S. Africa in 1938. It is significant in evolution because it is a missing link between fishes and the amphibians. They evolved into the first amphibians that lived on both land & water.
These were the ancestors of modern day frogs and salamanders. The amphibians further evolved into reptiles. 

Question. Write the names of the following:
(a) A 1.5 mya primate that was ape-like.
(b) A 2 mya primate that lived in East African grasslands. 
Answer :
(a) Dryopithecus. 
(b) Australopithecines / Australopithecus / Homo habilis. 

Question. Rearrange the following in increasing order of evolution.
Gnetales, Ferns, Zosterophyllum, Ginkgo.
Answer :
Zosterophyllum → Ferns → Ginkgo → Gnetales. 

Short Answer Type Questions

Question. Name the first human like hominid. Mention his food habit and brain capacity.
Answer :
Homo habilis were first human like hominid. They probably did not eat meat/vegetarian, and their brain capacities were between 650-800 cc. 

Question. Describe the mechanism of evolution as explained by Hugo de Vries.
Answer :
While working on evening primrose, Hugo de Vries put forward the idea of mutation, which he described as the large change arising out all of a sudden in a population. It is believed that evolution is not due to minor heritable continuous variations as proposed by Darwin but this is due to mutation which cause evolution. According to Darwin, the evolution is a gradual and slow process but de- Vries believed that it is due to saltation, single step large change called mutation and is a discontinuous process. It brings about speciation. 

Question. What does Hardy-Weinberg principle of equilibrium indicate? List any two factors that could alter the alteration. What would such an alteration lead to ?
Answer :
(i) Allele frequencies are stable and constant from generation to generation / the gene pool (total genes and their alleles in a population) remains a constant / sum total of all allelic frequencies is one. 
Hence, p2 + 2pq + q2 = 1 (where p and q represent the frequencies of gene A and allele a).
Factors : Gene migration, gene flow, genetic drift, mutation, genetic recombination, natural selection.
(ii) Such an alteration causes variations at the genetic level and thus leads to evolution.

Question. What does the following equation represent ? Explain.
p2 + 2pq + q2 = 1
OR
p2 + 2pq + q2 = 1. Explain this algebraic equation on the basis of Hardy Weinberg’s principle.
Answer :
The equation p2 + 2pq + q2 = 1 represents the genotypic frequencies of a population, when it is in Hardy-Weinberg equilibrium.
According to this law, the frequency of occurrence of alleles of a gene in a population remains constant through generations unless disturbances, such as mutation and non-random mating are introduced.
Individual frequencies are represented as p and q such as in diploid where p and q represent the frequency of allele A and a respectively. The sum total of allelic frequencies is 1.
The frequency of genotypes, AA is p2, that of aa is q2 and that of Aa is 2pq.
Hence p2 + 2pq + q2 = 1 which is expansion of binomial expression (p + q)2. When frequency measured differs from expected values the difference indicates the extent of evolutionary change.

Question. (i) State Hardy-Weinberg principle. Name any two factors which affect it.
(ii) Draw a graph to show that natural selection leads to directional change.
Answer :
(i) Hardy-Weinberg principle states that the total genes and their alleles in a population remains constant i.e. allelic frequencies in a population are stable and constant from generation to generation.
Gene flow, genetic drift, mutation, genetic recombination, natural selection. (Any two) 
(ii)

Evolution VBQs Class 12 Biology


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 finches – varieties of finches arose from grain eaters / Australian marsupials – evolved from common marsupial. 
Natural selection : A process in which heritable variations enable better survival of a 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 / DDT resistant mosquito survive. 

Question. How can Hardy-Weinberg equilibrium be affected? Explain giving three reasons.
Answer :
(i) Gene migration / gene flow : When migration of a section of population occurs to another place and gene frequencies change in the original as well as in the new population.
(ii) Genetic drift : If the same change occurs by chance / new genes / alleles are added to the new population and these are lost from the old population.
(iii) Mutation : Pre existing advantageous mutations when selected will result in new phenotypes.
(iv) Genetic recombination : Variation in characteristics will be there because of genetic recombination during meiosis and also due to random fusion of gametes.
(v) Natural selection : Heritable variations enabling better survival enabled organisms to reproduce and leave greater number of progeny. 

Question. When does a species become founders to cause founder effect ? 
OR
How does a population become founders’ of a new species. 
Answer :
When a few members or a small group of members from a certain population invades a new geographical region, they may have a different type of or changed allele frequencies from that of the original drifted population, they become the founders of new species and the effect is called as the founder’s effects.

Question. Name the ancestors of man based on the features given below—
(i) Human like, meat eater with 900 cc brain, lived in Java.
(ii) More human with brain size 1400 cc, lived in central Asia, used hides & buried their dead.
(iii) Human like, vegetarian, with brain capacity between 650 cc & 800 cc.
(iv) Man like primate, that existed about 15 mya.
Fossils found in Tanzania.
Answer :
(i) Homo erectus
(ii) Homo sapiens neanderthalensis
(iii) Homo habilis
(iv) Australopithecus africans/Ramapithecus

Long Answer Type Questions

Question. (i) Explain Darwinian theory of evolution with the help of one suitable example. State the two key concepts of the theory.
(ii) Mention any three characteristics of Neanderthal man that lived in near east and central Asia.
Answer : (i) Darwinian theory of evolution :
(a) According to Darwin, evolution took place by natural selection.
(b) The number of life forms depends upon the life span of the organisms and their ability to multiply.
(c) Another aspect of natural selection is the survival of the fittest, in which nature selects the individuals that are most fit to adapt to their environment.
(d) Darwin also observed that variations are inheritable and the species that fit to survive the most, leaves more offsprings. Hence, the population’s characteristics change, giving
rise to the evolution of new life forms.
An example of such selection is the antibiotic resistance in bacteria. When a bacterial population was grown on an agar plate containing antibiotic penicillin, the colonies that were sensitive to penicillin died, whereas one or a few bacterial colonies that were resistant to penicillin survived.
This is because these bacteria had undergone chance mutation, which resulted in the evolution of a gene that made them resistant to penicillin drug. Hence the resistant bacteria multiplied quickly compared with the non-resistant (sensitive) bacteria, thereby increasing their number. Hence, the advantage of an organism over the other helps in the struggle for existence.
The two key concepts of the theory are :
(1) Branching descent : According to this concept, various species have come into existence from a common ancestor.
(2) Natural selection : According to this concept, nature selects the individuals that are most fit to adapt to their environment.
(ii) Characteristics of Neanderthal man :
(a) They possess a brain capacity of 1300 – 1600 cc.
(b) They were short but very strong with outward-curved thigh bones.
(c) They used hides to protect their body. They buried the dead. 

Question. (i) How do the observations made during moth collection in pre and post-industrialized era in England support evolution by Natural Selection ?
(ii) Explain the phenomenon that is well represented by Darwin’s finches other than natural selection.
OR
Taking an example of white-winged moths and dark-winged moths of England in pre and post industrialised era, explain evolution by natural selection. 
Answer :
(i) (a) Before industrialisation white coloured lichen covered the trees in which white winged moths camouflaged themselves from predators.
(b) More white winged moths existed on trees than dark winged or melanised moths.
(c) After industrialisation there were more dark winged moths in the same area i.e., proportion was reversed,
(d) Predators would spot a moth easily against a contrasting background.
(e) During post industrialisation tree trunks became dark due to industrial smoke and soot.
(f) White winged moth did not survive due to detection by predators whereas dark winged survived. 
(ii) The process of evolution of different species in a given geographical area starting from a point, radiating to other areas of geography (habitats) is called adaptive radiation, finches evolved in the same island from original seed eating features, many other altered beaks arose enabling them to become insectivorous and vegetarian finches. 
Detailed Answer:
(i) Before industrialization, white winged moths were more in number as compared to dark winged moths. It is because of less pollution.
The trunk of trees were covered with white coloured thick growth of lichens. Hence light coloured moth were not spotted by the predator and their number increased.
After industrialisation, the tree trunks become dark due to increased industrial pollution. So, now white winged moths could be detected easily and their number got decreased due to easy capture by the predator.
So, nature selected only those moths which were better suited.
(ii) The phenomenon well represented by Darwin’s finches other than natural selection is adaptive radiation.
Adaptive radiation is an evolutionary process in which an ancestral species give rise to new species adapted to new habitats and new ways of life. Darwin finches evolved in same
Island from original seed-eating finches. The alternation in beaks enable some of them to become insectivorous and some vegetarian.

Question. (i) Name the primates that lived about 15 million years ago. List their characteristic features.
(ii) (a) Where was the first man-like animal found ?
(b) Write the order in which Neanderthals, Homo habilis and Homo erectus appeared on earth. State the brain capacity of each one of them.
(c) When did modern Homo sapiens appear on this planet ? 
Answer :
(i) Dryopithecus, Ramapithecus. 
They were hairy.
Dryopithecus is ape like Gorillas and Chimpanzees.
Ramapithecus more man like.
(ii) (a) Ethiopia / Tanzania / Eastern Africa. 
(b) Order of appearance from earliest to the latest = Homo habilis, Homo erectus, Neanderthals. 
Cranial capacity = Homo habilis = 650 – 800 cc, Homo erectus = 900 cc, Neanderthals = 1400 cc.
(c) During ice age / 75000 – 10000 years ago. 


Question. Study the schematic representation of evolutionary history of plant forms given below and mention.

Evolution VBQs Class 12 Biology

(i) The plant form ferns and conifers are most related to 
(ii) The nearest ancestors of flowering plants.
(iii) The most primitive group of flowering plants.
(iv) Common ancestry of psilophyton provides to.
(v) Common ancestors of psilophyton and seed ferns.
(vi) Common ancestors of mosses and tracheophytes.
Answer :
(i) Psilophyton.
(ii) Seed ferns.
(iii) Chlorophyte ancestor.
(iv) Ferns, conifers & seed ferns.
(v) Tracheophyte ancestor.
(vi) Chlorophyte ancestor.