CBSE Class 12 Biology 2024-25: Chapter 6 Evolution Competency-Based Questions with Answers; Download Free PDF

Get ready for your CBSE Class 12 Biology exams with our easy guide on Chapter 6: Evolution. This chapter is very important, especially with the new exam pattern starting in the 2024-25 school year. The CBSE will include 50% more competency-based questions. These questions ask you to use what you've learned in real-life situations.

In this article, we focus on key questions from Chapter 6: Evolution. These questions help you think and solve problems. You’ll find different types of questions, such as multiple-choice, true-false, gap-filling, and short-answer questions. Each question has clear answers to help you understand the concepts better.

To help you study, you can download a free PDF that has all the competency-based questions from Chapter 6: Evolution along with their answer keys.

CBSE 12 Biology Chapter 6 : Evolution Competency-Based Questions

Q.1 A group of students are trying to replicate the famous Miller-Urey experiment using a different set of molecules compared to those employed in the original study.

Their experiment will be deemed supportive and aligning with the Miller-Urey experiment solely on the condition that the molecular weight of -

A. reactants ≥ products
B. reactants < products
C. reactants = products
D. reactants > products

Answer. B. reactants < products

Q.2 Some herbivorous organisms such as giraffes and brachiosaurus are known to have evolved long necks which helps them access food that is not available to other shorter herbivores.

Which of the following type of evolution do the statements shown above describe?

A. co-evolution
B. microevolution
C. divergent evolution
D. convergent evolution

Answer. D. convergent evolution

Q.3 Billions of years ago, when Earth had a reducing atmosphere containing methane and ammonia along with high temperatures, the organisms that came to existence would have been -

A. aerobic and chemo-autotrophic
B. anaerobic and chemo-heterotrophic
C. aerobic and chemo-heterotrophic
D. anaerobic and chemo-autotrophic

Answer. B. anaerobic and chemo-heterotrophic

Q.4 Ginkgo biloba is also known as a living fossil as it has changed very little over time. It is resistant to disease and pests, is tolerant of a wide range of environmental conditions and is the last-standing member of its botanical family.

The above is an example of which of the following phenomena?

A. speciation
B. fossilization
C. adaptive radiation
D. survival of the fittest

Answer. D. survival of the fittest

Download PDF
CBSE Class 12 Biology Chapter 1 Sexual Reproduction in Flowering Plants: Important Competency-Based Questions 2024-25	Click Here
CBSE Class 12 Biology Chapter 2 Human Reproduction: Important Competency-Based Questions 2024-25	Click Here
CBSE Class 12 Biology Chapter 3 Reproductive Health: Important Competency-Based Questions 2024-25	Click Here
CBSE Class 12 Biology Chapter 4 Principles Of Inheritance And Variation: Important Competency-Based Questions 2024-25	Click Here
CBSE Class 12 Biology Chapter 5 Molecular Basis Of Inheritance: Important Competency-Based Questions 2024-25	Click Here
CBSE Class 12 Biology Chapter 6 Evolution: Important Competency-Based Questions 2024-25	Click Here

Q.5 Which of the following phenomena significantly contributes to speciation?

P) Natural Selection

Q) Genetic Drift

R) Gene flow S) Geographic Isolation

T) Stabilizing Selection

A. only Q and S
B. only R and T
C. only P, Q and S
D. only Q, R and T

Answer. C. only P, Q and S

Q.6 Two statements are given below - one labelled Assertion (A) and the other labelled Reason (R).

Assertion (A): Genetic makeup serves as the primary factor in shaping the phenotype of a species and not vice versa.

Reason (R): Adaptation involves the phenotype's interaction with the environment, leading to changes in genetic makeup over generations.

Which of the following is correct?

A. Both A and R are true, and R is a correct explanation for A.
B. Both A and R are true, but R is not a correct explanation for A.
C. A is true, but R is false.
D. A is false, but R is true.

Answer. B. Both A and R are true, but R is not a correct explanation for A.

Q.7 A large population of a species of fish in a lake has been relatively genetically unchanged for a long time. A small bird species from an island migrate to the forest around the lake and prey on the smaller-sized fish.

Would the population of the fish species adhere to the Hardy-Weinberg law? Justify your answer.

Answer. [1 mark for each of the following]

- No

- The scenario violates the rule of 'no gene flow/migration' from the Hardy-Weinberg law.

Q.8 Arrange the following evolutionary phenomenon with respect to their contribution to evolution (from most significant to least significant). Justify your answer with respect to each phenomenon.

(A) Vegetative propagation
(B) Natural selection
(C) Hybridisation
(D) Genetic drift

Answer. [1 mark for the following]

[Appropriate marks to be deducted even if anyone is incorrect]

Natural selection >Hybridisation >Genetic drift >Vegetative propagation

[1 mark for each of the following justifications]

- Natural selection - It acts by favouring the variations and traits that increase an organism's fitness in its environment and leads to their accumulation over time. Hence, natural selection is considered the most significant factor driving evolution.

- Hybridisation - It involves the interbreeding of different variants, leading to the mixing of genetic material. This can enhance the genetic diversity that might contribute to the creation of new species making it an important factor in evolution.

- Genetic drift - occurs due to random changes in gene frequencies in small populations due to chance events. It could be less significant than natural selection and hybridisation as its effects are less predictable and may not always lead to adaptive changes.

- Vegetative propagation - is a form of asexual reproduction that produces genetically identical individuals. Thus, it contributes the least to overall genetic diversity and is the least significant factor in terms of evolution.

Q.9 Lake Tanganyika harbours a wide variety of cichlid fish. These fish have minor modifications in the jaw shape, number of teeth, and intestine length amongst various other features, and have evolved to feed on algae, plankton, plants, insects, and other fish of various sizes also residing in the lake.

(a) Which of the following evolutionary phenomenon does the above scenario describe?
(b) Based on (a), mention any FOUR advantages of this phenomenon.

Amnswer. (a) Adaptive radiation

(b) This diversification allows the fish in the lake to

- exploit different food sources
- exploit different habitats
- reduce competition
- maximizing their chances of survival
- increase beneficial traits and specialization
- creates a more stable ecosystem

[0.5 marks each for any four of the above]

[Accept any other valid answer]

Q.10 Over the course of human evolution, the size of the brain has consistently grown larger.

(a) Mention any TWO factors that could be responsible for this continual expansion.
(b) Which category of evolution does this pattern align with - stabilising, directional, or disruptive? Justify your answer.

Answer. (a) [1 mark each for any two of the following points]

The human brain evolved to occupy a larger volume and become complex because of the following reasons -

- development and use of tools by early humans required higher cognitive abilities.

- need to adapt, innovate, and exploit resources.

- need for complex interactions, cooperation, and communication within social groups.

- need for problem-solving capabilities.

- need for enhanced memory and learning capabilities

- transmission of knowledge through generations

[Accept any other valid answers]

(b) [0.5 marks each for any two of the following points]

- Directional selection

- The increase in brain size over time suggests a consistent directional shift toward larger brains due to the adaptive advantages conferred by cognitive enhancements.

[Accept any other valid answers.]

Q.11 What is the frequency of heterozygous genotype (Aa) in a randomly mating population in which the frequency of all dominant phenotypes is 0.36?

Answer. [1 mark for the detailed calculation and 1 mark for the answer] According to the Hardy-Weinberg equilibrium,

p² + 2pq + q² = 1

The dominant phenotype (AA and Aa) can be represented by p² + 2pq is equal to 0.36.

q² = 1 - (p² + 2pq) = 1- 0.36 = 0.64

q = 0.8

p = 1- 0.8 = 0.2

2pq = 2*0.2*0.8 = 0.32

Therefore, the frequency of the heterozygous genotype is 0.32.

Q.12 Prokaryotic and eukaryotic cells have distinct flagella with differences in structure and mechanism. Prokaryotic flagella are helical and driven by a rotary motor powered by ion flow. Eukaryotic flagella feature a 9+2 microtubule arrangement, propelled by microtubule sliding via dynein motor proteins.

Identify if the above can be classified as homologous or analogous structures. Justify your answer

Answer. [1 mark for each of the following points]

- Analogous structures

- The prokaryotic and eukaryotic flagella, though they have a similar function, differ in structure and mechanism, due to independent evolution, and hence are analogous structures.

Q.13 Among plants, angiosperms, or flowering plants, stand out as the most diverse and numerous group of plants on Earth today, a reflection of their evolutionary triumph.

Mark this statement as TRUE/FALSE and give any FOUR reasons for your answer using the characteristic features of angiosperms.

Answer. [1 mark for the following]

- True

[1 mark each for any FOUR of the following points]

- Angiosperms adapt widely, spanning deserts to rainforests, and high altitudes to aquatic habitats, driving global diversity and distribution.

- Angiosperms' flower and fruit evolution enables efficient reproduction by luring diverse pollinators, promoting successful pollination and genetic variety.

- Angiosperms use varied strategies — self and cross-pollination — to thrive in diverse conditions, leading to their evolutionary triumph.

- They co-evolve with pollinators, developing traits that attract specific species, and enhancing pollination efficiency. This symbiotic bond boosts both plant and pollinator success.

- Many angiosperms have relatively short life cycles, allowing them to reproduce and spread rapidly. This quick turnaround time increases their evolutionary potential.

[Accept any other valid answers]

Q.14 In a population of birds, individuals with intermediate beak sizes can effectively feed on a range of available seeds while birds with either small or large beak sizes find it difficult to access certain seeds.

(a) Which birds are more likely to be naturally selected?
(b) Based on (a), which type of natural selection does this phenomenon exemplify?

Answer. 1 mark for each of the following:

- The mutated population of amphibians are likely to exploit unique ecological niches in the archipelago.

- This may eventually lead to the formation of different species.

[Accept any other valid answer]

Q.15 Genetic drift will lead to speciation in very large populations.

Explain why this statement is false in TWO points.

Answer. 1 mark for each of the following:

- Genetic drift is the change in frequency of an existing gene variant in the population due to random chance.

- This effect is negligible when population sizes are very large and speciation may not occur.

👉 CBSE Class 12 Study Materials

CBSE Class 12 Syllabus 2024-25	CBSE Class 12 Previous Year Papers
NCERT Books For Class 12 Books	NCERT Class 12 Solutions
CBSE Class 12 Full Study Material	CBSE Class 12 Sample Paper 2024-25