CBSE Important Questions Class 12 Biology Chapter 7

Important Questions Class 12 Biology Chapter 7

Important Questions for CBSE Class 12 Biology Chapter 7 – Evolution

At Extramarks, the set of Important Questions Class 12 Biology Chapter 7 are prepared by subject matter experts. Students can quickly review the chapter’s important topics with this set of questionnaires. These questions explain the marks distribution of important questions, exam patterns, and concepts related to Evolution. Chapter 7 Class 12 Biology Important Questions will help students focus on their exam preparation and improve their answers with accurate solutions to get a 100% score. 

These questions are set in accordance with the revised CBSE syllabus. Class 12 Biology Chapter 7 Important Questions are presented with step-by-step explanations. Students can access these Important Questions from the Extramarks’ website. 

CBSE Class 12 Biology Chapter 7 Important Questions

Study Important Questions for Class 12 Biology Chapter 7 – Evolution

Given below are some of the important questions of  Class 12 Biology Chapter 7. Students can access the link provided to get access to a  set of important questionnaires. 

Very Short Answer Questions                                                                                                            
(1 Mark)

Q1. State the process to determine the age of a fossil.

Ans. Carbon dating is the process that determines the age of a fossil.

Q2. Explain natural selection.

Ans. The process in which out of the entire population the survival and reproductive rate of people possessing specific characteristics are larger than that of the other people is known as Natural selection. The organisms that easily adapt to varying environmental conditions are selected by the environment. 

Q3. What does the “Founder’s effect” mean?

Ans: A phenomenon that influences the genetic diversity of a population is the “Founder’s effect”. A group of human beings splits  from a huge population to create a new group. This is considered to be the founder’s effect. The new group largely varies from its original population.

Q4. Which period is referred to as the “Age of Reptiles”?

Ans: The Jurassic period is referred to as the “Age of Reptiles”.

Q5. How can the age of rock be discovered by using the absolute dating method?

Ans. The age of the rock or fossil can be discovered by measuring the amount of radioactive decay in certain elements present in the rock through the process of absolute dating.

Q6. Which period is referred to as the “Age of amphibians”?

Ans: “Age of amphibians” belongs to the Carboniferous period.

Q7. If the abiotic origin of life is in progress on a planet other than earth, what conditions should be fulfilled there?

Ans: Few climatic conditions like volcanic storms, extremely high temperatures, reducing atmosphere consisting of CH4, NH3, H2, and water vapours are the conditions that need to be fulfilled there if the abiotic origin of life is in progress on a planet other than the Earth.

Q8. State the characteristics of fossils.

Ans. The characteristics of fossils are noted as follows:

  • Fossils act as links between distinct species.
  • They help in discovering the time period in which they existed.
  • They display modes of preservation of various ancient species.
  • They provide aid in discovering the evolutionary characteristics or traits of living beings and their ancestors.

Short Answer  Questions                                                                                                       
(2 Marks)

Q1. What is the study of fossils also known as? State any three points on how the fossils depict past life.

Ans: Palaeontology is known for the study of fossils. It has been considered that fossils depict to us our past life as

  • A cross-section of the Earth’s crust presents the placement of sediments  one on top of another. 
  • During the formation of a specific sediment, each sediment consisting of distinct life forms almost perished.
  • Missing links or connecting links consisted of characters of distinct groups.

Q2. What is natural selection? Who other than Charles Darwin suggested it as the mechanism of evolution?

Ans: There are certain organisms that go through several genetic changes due to significant alterations in their surroundings and adapt to the changes, there they are selected by nature and others are eliminated. Alfred Wallace also suggested a similar mechanism of evolution and it was known as “survival of fittest”.

Q3. What is adaptive radiation? State a suitable example.

Ans. Adaptive radiation takes place due to changes in the environment. The process in which a living organism expands from a single ancestor into numerous new forms is called  adaptive radiation. For example, the finches of the Galapagos island are witnessed with several distinct beaks based on the food consumed by them. This single species adapted to the environmental and nutritional conditions  as well as evolved respective beak types over a long period.

Q4. Why do aerobic living organisms find nascent oxygen toxic?

Ans. Nascent oxygen is highly reactive and can form chemical reactions when it comes in contact with all types of biomolecules existent in living organisms like proteins, DNA, and enzymes. It can lead to variation in DNA and degeneration of proteins and enzymes in reactions, therefore, harmful to aerobic life forms.

Q5. Write a note on genetic drift.

Ans. A mechanism of evolution wherein the allele frequencies transform over generations as a matter of chance is known as Genetic drift. It usually has the maximum effect on a small population. Genetic drift is noticed either when there is a bottleneck effect or a founder effect. Genetic drift does not consider whether the allele is beneficial or toxic to the individual carrying it. There is a probability that a beneficial allele is lost and a harmful allele is carried over.

Q6. Life originated from the earth’s inorganic atmosphere in the past, but this no longer happens today. State two suitable reasons.

Ans: Life cannot be originated from the earth’s inorganic atmosphere due to the following reasons: 

(i) Temperature in the current-day atmosphere is comparatively lesser than that of the primitive atmosphere.

(ii) Due to the presence of oxygen, the current-day atmosphere is oxidising and not diminishing in nature.

Q7. Explain the evolution of birds from reptiles and give one piece of evidence.

Ans: The most prominent evidence that proves that birds have developed from reptiles is the missing link between birds and reptiles. “Birds evolved from reptiles” is displayed by  the species named Archaeopteryx. These are organisms that display both the  characteristics of birds and of reptiles.

Q8. Write down the differences between De Vries mutations and Darwinian Variations.

Ans: The difference between De Vries mutations and Darwinian variations are:

De Vries mutations Darwinian Variations
Mutations are heritable alterations in the characteristics of a population that originate instantaneously and cause speciation. Darwinian variations are steady and happen due to variations over many generations.
Mutations are random and directionless. Variations are small and directional.

 Long Answer  Questions                                                                                              
(3 Marks)

Q1. State the facts that assist Darwin’s Theory of Natural selection.

Ans: The following facts support Darwin’s Theory of Natural selection

  1. Overproduction: – All organisms do not survive even though they multiply at a high rate.
  2. Struggle for survival: – As there are limitations of space and food, all the newborn organisms result in an overproduction that will not survive and fight with one another to evolve. This leads to struggle among the individuals of the same species as well as distinct species for existence.

iii. Variations:  Two individuals of a similar species are not exactly alike even if they come out from the same parental stock.

  1. Survival of fittest: The individuals with potential variation will live during the struggle for survival while those with inefficient variation would die.

Q2. What does Biogeography mean? Explain how Darwin’s finches give biogeographical evidence in favour of evolution.

Ans: Biogeography is the branch of geography that handles the study of the pattern of spreading of plants and animals.

Example: In the Galapagos islands, during Charles Darwin’s voyage, he discovered that the animals of these islands are similar to those in South American islands. Similarly, the birds of Galapagos Island also referred to as Darwin’s finches are not identical to the birds of South America, further, he stated that finches were from ancestral stock that had relocated from the mainland to the island and went through several changes due to distinct environmental conditions. 

Q3. Chemical insecticides remain useful only for a limited time. Explain the process of evolution with an example.

Ans: Several pests and insects that cause damage to the crops in the agricultural fields can be eliminated by the use of chemical pesticides. It is possible to completely get rid of these pests as  chemical insecticides affect some of the pest’s metabolic characteristics, resulting in the pest’s death. Over time, pests  can build resistance to these insecticides which are a result of mutations and they will end up being  useless. Therefore, there is no point in using these insecticides.

Q4. State the types of evolution.

Ans. The various types of evolution are as follows:

  1. Convergent evolution– The process in which evolution takes place independently, under identical selection pressures is known as convergent evolution. A few examples of convergent evolution are  birds, flying insects, and other flying species that have all developed the ability to fly but are independent of each other.
  2. Coevolution – The process in which evolution takes place in tandem when two or more species exert selection pressures on each other is known as coevolution evolution. A few examples of coevolution evolution are predators and prey, host and parasites, flowering plants and pollinating insects, and mutualistic or symbiotic interactions.
  3. Adaptive radiation– The process in which evolution takes place when a species breaks down into numerous new forms when an alteration  in the environment makes new resources accessible or forms new environmental threats is known as Adaptive radiation. One example of adaptive radiation is finches on the Galapagos Islands, they have evolved distinctly shaped beaks.

Q5. Mention some examples that display evolution by anthropogenic action.

Ans: The selection of resistant variation on a minor time scale is caused due to extreme usage of  herbicides, pesticides, etc. This applies  to antibiotic or drug-resistant microbes as well.

A few examples of pesticides are Methomyl, and Aldrin, while examples of herbicides are Dinosep and Acetochlor.

FAQs (Frequently Asked Questions)

1. ention the significant events or stages of human development.

The primate Dryopithecus is the common ancestor of apes and man that survived about 15 million years ago. The stages of human development are as follows: 

  1. Australopithecus: They were 4ft tall with a brain capacity between 500 to 650 cc. They had bipedal locomotion, were  omnivorous, had an erect posture, and used stone weapons for hunting and surviving in caves.
  2. Homo Erectus: They displayed an increase  in brain size, were good hunters, domesticated animals, ate meat, and discovered fire.

iii. Netherlands man: They were short with heavy brows, large jaws, retreating foreheads, and stooped postures. They were good hunters and made tools.

  1. Cro-magnon man: They were wholly erect and 6 ft tall. Bones were used as tools and they were cave dwellers. 

v. Homo sapiens: Currently, humans are referred to as Homo sapiens. They have a brain capacity of 1450cc along with a skull that is  very thick. The intelligence they have has helped them to adapt and control the environment.

2. Enumerate the key concepts in the evolution theory of Darwin.

Darwin’s Theory of Evolution contains two main concepts that are:

  • Branching Descent
  • Natural Selection

Branching Descent- The process in which original species arise from a single ancestor is known as Branching Descent. They could adapt to the new environment with the help of reproductive isolation. For instance, Darwin’s finches emerged from a single-grain eater species.

Natural Selection- The process in which the changes in an individual improve the survival instincts of species is known as Natural Selection. Many variations are carried forward to successive generations which aided them to live in the altering environmental conditions. For instance, some giraffes have long necks whereas others have necks that are short. If the low-lying shrubs are disposed of for a few reasons, the giraffes with necks that are short would be exchanged for giraffes with long necks.

3. Mention what ways Stanley Miller simulated the condition of: i) Primitive atmosphere on earth. ii) Energy source at the time of origin of life. iii) Formation of organic molecules of life.

  1. i) A mixture of ammonia, methane, hydrogen, and water vapour of a fluid in a closed flask. 
  2. ii) Sun was the source of energy during the origin of life. This energy is provided by electric discharge using electrodes in this experiment.

iii) Throughout the experiment, the organic molecules generated are amino acids.