NCERT Questions for Class 12 Biology Chapter 6 – Evolution

Important Questions with Solutions of Class 12 Biology Chapter 6 – Evolution

1) Elaborate on the chemical evolution of life through the Oparin-Haldane theory.

Ans – The pre-existing, non-living organic molecules (like RNA and proteins) bring the first life into existence and lead on with chemical evolution. According to this theory, life is a substantial emergence from the inorganic molecules where amino acids work as the building blocks. The next step is to give a mix & make it into complex polymers followed by structures with the quality to sustain and replicate themselves. Gathered proteins to balance out metabolism is the thought portrayed by Oparin. However, macromolecules surrounded with membranes to frame cell-like structures were Haldane’s idea.

2) Differentiate between convergent & divergent evolution with examples.

Ans – The differences between convergent & divergent evolution are:

Divergent evolution	Convergent evolution
A common ancestral form helps in the evolution of various functional structures. This kind of development is viewed in homologous organs.	The evolution of similar adaptive functional structures occurs in an unrelated group of organisms. This kind of development is viewed in analogous organs.
Darwin’s Finches is an example.	Aquatic vertebrates and wings of insects, birds, and bats can be examined.

3) In evolution, why variation is vital?

Ans – A very significant part of survival in any environment is variation. Setting a particular niche can wipe out the whole population of reproducing organisms in a swipe while some variations in their lifestyle can save their lives.

4) Birds have evolved from reptiles. Justify it.

Ans – Birds and reptiles pertain a perplexed link which proves that birds have evolved from reptiles and is also further shown by the archaeopteryx, which further was detailed into organisms that pertain to features of birds and reptiles with feathers in their body and jaws with identical twins.

5) Explain the statement with two strong reasons – Life originated from the earth’s inorganic atmosphere in the post, but this no longer happens today.

Ans – The reasons behind the above statement are,

1. The temperature in the present-day has decreased compared to the ancient atmosphere.
2. Due to oxygen in the air, the present-day atmosphere is much more oxidizing.

6) Distinguish between convergent & divergent evolution.

Ans – The similarities & variations between convergent & divergent evolution are:

Divergent evolution	Convergent evolution
It is a process in which new species are evolved from a single ancestral form.	In this process of evolution which happens in an isolated geographical area, more than one adaptive radiation occurs.
Australian marsupials are a perfect example of it.	Camels in Asia and Llmas in South America seem to be good examples.

7) Elaborate on the concept of natural selection and evolution considering industrial melanism.

Ans – The process of accepting changes with the cause of survival in living creatures is a mechanism known as Natural selection. According to it, survival of the fittest is the reason for the ultimate growth in evolution. Very few remaining differences are kept untouched and some are transmitted, with the aim of new forms to rise over time.

In 1850, a mother collection was found where white-winged moths were dominant towards the black-winged moths (which rose through industrialization). As a reason, it is claimed that the trunk got a shade darker as an effect of the smoke during the post-industrial period which caused the racism within the moths as a weapon to survive. Before industrialization, the white-winged moths were advantaged due to trees coated with thick growth of off-white-coloured lichens. Throughout this time, the black-winged moths could be recognized by the traitors. Thus, nature chooses the best species for the job.

8) Define Biogenetic law. Explain how comparative embryology provides evidence for evolution.

Ans – The presence of the developmental pattern has come to evidence by embryological studies. The unicellular structure is from where our lives begin. Some embryos are hard to differentiate due to their vast physical resemblance, which includes fish, frogs, turtles, birds & man.

During the evolution of an organism known as ontogeny, a mammalian embryo goes through fish-like, amphibian-like, reptile & bird-like stages. In different groups of organisms, different evolutionary steps (phylogeny) are repeated. This confused state made Ernst Haeckel generate a famous theory called – Recapitulation Theory or Biogenetic Law stating “Ontogeny recapitulates phylogeny”. The pattern and steps of embryonic development show great similarities. It includes the outer look of the gill cleft and notochord in the embryonic development of all vertebrates, starting from fish and ending at man.

9) State the facts supporting Darwin’s theory of Natural selection.

Ans – The factors supporting Darwin’s theory of Natural selection are:

1. Overproduction: All organisms reproducing frequently cannot survive.
2. Struggle for Existence: The progeny will be in prolonged competition for survival due to the limited amount of space to live and food to eat. This develops a sense of struggle in all kinds of species.
3. Variations: No two individuals can be alike, irrespective of them being twins.
4. Survival of fittest: Individuals appreciating variations and adjusting accordingly will only be the ones surviving.

10) Define chemogeny.

Ans – Ancient ways of livelihood are inspired by inorganic matter as a cause of the action of special external forces is called chemogeny. For example: electric charge, UV light & more.

1. Temperature being 900 Celsius or below, saturated and unsaturated hydrocarbons were feasted.
2. Later this hydrocarbon condensed to sugar, forming small chain compounds of carbon, hydrogen, and oxygen.
3. Fatty acids are formed by condensation and polymerization of Ketones and aldehydes.
4. Amino acids are formed by reacting with ammonia, hydrocarbon & water.
5. Nucleotides are formed and react with warm seawater rich in primary organic compounds.

Class 12 Biology Chapter 6 Evolution – Topics Covered

Evolution is the fundamental concept of biology; it explains how species evolve through time. It holds the view that every living organism is linked and has a single ancestor. Evolutionary changes in populations occur due to the actions of natural selection, genetic drift, and others that cause changes in the genetic composition over generations.

What is Natural Selection?

Natural selection is one of the major mechanisms of evolution as suggested by Charles Darwin. It refers to how organisms that are better adapted in their environment tend to survive and reproduce more than those that are not. This means that, gradually over time, it leads to the accumulation of favorable characteristics in a population.

How does Genetic Drift contribute to Evolution?

Genetic drift is another very important factor of evolution. Random changes in the frequency of alleles within the population define genetic drift. It leads to a loss of variation, taking place in most cases in smaller populations, contributing to the formation of new species.

Evidence for Evolution

Scientific evidence supports evolution from many fields, from the fossil record to comparative anatomy, embryology, molecular biology, and biogeography.

Fossil Records

The fossil record shows gradual changes in species through time, making it a chronological record of the history of life. Transitional fossils—such as Tiktaalik—fill in gaps in our understanding of how different groups of organisms are related.

Comparative Anatomy

Comparative anatomy studies the similarities and dissimilarities found in the anatomies of several species. For instance, forelimbs of vertebrates are homologous structures that provide evidence regarding common descent and the evolutionary process.

Molecular Biology

Advances in molecular biology have changed our perception of evolution. The comparison of different species’ DNA sequences allows for making inferences about evolutionary relationships and the reconstruction of the tree of life.

Evolutionary Patterns

Evolutionary patterns refer to the different ways by which species change over time. Common patterns in evolution include convergent evolution, divergent evolution, adaptive radiation, and coevolution.

Convergent Evolution

Convergent evolution is the process by which unrelated species develop similar traits because of similar environmental pressure. For instance, the wings of birds and bats have evolved independently to serve in flight.

Divergent Evolution

Divergent evolution occurs when closely-related species evolve different traits because of different environmental pressure. It can cause the formation of new species over time.

Adaptive Radiation

Adaptive radiation means the very fast diversification of a single ancestral species into several forms. It very often occurs by opening up new ecological niches in which species can exploit quite different resources.