CBSE Class 12 Biology Evolution NCERT Solutions

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NCERT Solutions PDF Class 12 PDF

CBSE Class 12 Biology, Chapter 7: Evolution, introduces the fascinating journey of life's development. This chapter delves into the core theories explaining how organisms change over time, supported by compelling evidence. You'll explore the significance of fossils as historical records and understand how comparative anatomy, looking at similarities and differences in body structures, reveals evolutionary relationships. The chapter also introduces the fundamental principles of population genetics, which explain the genetic changes within populations that drive evolution. Key concepts like natural selection, the driving force behind adaptation, and artificial selection, where humans influence traits, are explained in detail. Furthermore, you'll learn about homologous organs, which share a common ancestry, and analogous organs, which serve similar functions but evolved independently. The Hardy-Weinberg principle, a cornerstone of population genetics, is also discussed, providing a baseline for understanding evolutionary change. These solutions aim to clarify these intricate evolutionary mechanisms, offering clear explanations and practical examples to solidify your understanding for exams.

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Quick info

BoardCBSE
ClassClass 12
SubjectBiology Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 7

Chapter summary

Chapter 7 of the CBSE Class 12 Biology Exemplar focuses on Evolution. These NCERT Solutions break down the core concepts, including the historical theories of evolution, the evidence supporting evolutionary processes (like palaeontology and comparative anatomy), and the mechanisms driving evolution, such as natural and artificial selection. The solutions also touch upon population genetics and the Hardy-Weinberg principle, providing a solid foundation for understanding how life on Earth has diversified.

Learning outcomes

  • Understand the concept of evolution and its historical theories.
  • Identify and explain the evidence for evolution from fossils and comparative anatomy.
  • Differentiate between homologous and analogous organs.
  • Explain the mechanisms of natural selection and artificial selection.
  • Understand the principles of population genetics and the Hardy-Weinberg equilibrium.
  • Recognize examples of evolution in action, such as antibiotic resistance.

Topics covered

Paper topics

  • Origin of Life
  • Theories of Evolution
  • Evidence for Evolution
  • Palaeontological Evidence (Fossils)
  • Comparative Anatomy and Morphology
  • Homologous Organs
  • Analogous Organs
  • Embryological Evidence
  • Mechanisms of Evolution
  • Natural Selection
  • Artificial Selection
  • Population Genetics (Hardy-Weinberg Principle)

Important topics

  • Evidence for Evolution (Fossils, Homologous & Analogous Organs)
  • Natural Selection vs. Artificial Selection
  • Hardy-Weinberg Principle
  • Adaptive Radiation
  • Convergent and Divergent Evolution
  • Origin of Life

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Questions and Solutions

Multiple Choice Questions (MCQs) - Q.1

Q.1 Which of the following is used as an atmospheric pollution indicator?
  1. Lepidoptera
  2. Lichens
  3. Lycopersicon
  4. Lycopodium
Solution: The correct option is (b) Lichens. Lichens are sensitive to air pollutants, particularly sulfur dioxide and nitrogen oxides. They cannot survive or grow well in areas with high levels of these pollutants because the pollutants interfere with their ability to photosynthesize. Therefore, their presence or absence, and the health of their thalli, serve as a reliable indicator of air quality. Lepidoptera refers to an order of insects (butterflies and moths). Lycopersicon is the genus for tomato plants. Lycopodium is a genus of clubmosses, a type of pteridophyte.

Multiple Choice Questions (MCQs) - Q.2

Q.2 The theory of spontaneous generation stated that
  1. life arose from living forms only
  2. life can arise from both living and non-living
  3. life can arise from non-living things only
  4. life arises spontaneously, neither from living nor from the non-living.
Solution: The correct option is (c) life can arise from non-living things only. This concept, also known as abiogenesis, proposed that living organisms could originate directly from non-living matter. However, this theory was scientifically disproven by experiments, most notably by Louis Pasteur, who demonstrated that life arises from pre-existing life (biogenesis).

Multiple Choice Questions (MCQs) - Q.3

Q.3 Animal husbandry and plant breeding programmes are the examples of
  1. reverse evolution
  2. artificial selection
  3. mutation
  4. natural selection
Solution: The correct option is (b) artificial selection. Animal husbandry and plant breeding involve humans deliberately selecting organisms with specific desirable traits and breeding them to enhance those characteristics in subsequent generations. This is a form of artificial selection. Mutation is a change in DNA. Natural selection is the process driven by environmental pressures. Reverse evolution is a hypothetical concept of species reverting to more primitive forms.

Multiple Choice Questions (MCQs) - Q.4

Q.4 Palaeontological evidences for evolution refer to the
  1. development of embryo
  2. homologous organs
  3. fossils
  4. analogous organs
Solution: The correct option is (c) fossils. Palaeontology is the scientific study of fossils, which are the preserved remains or traces of organisms from past geological ages. The examination of fossils provides crucial evidence for evolutionary history, showing the progression of life forms over time and transitional stages between different groups.

Multiple Choice Questions (MCQs) - Q.5

Q.5 The bones of forelimbs of whale, bat, cheetah and man are similar in structure, because
  1. one organism has given rise to another
  2. they share a common ancestor
  3. they perform the same function
  4. they have biochemical similarities
Solution: The correct option is (b) they share a common ancestor. The similarity in the bone structure of the forelimbs of these diverse animals (whale, bat, cheetah, man) is a classic example of homologous organs. These organs have the same fundamental structure and developmental origin, inherited from a common ancestor, but have been modified through divergent evolution to perform different functions.

Multiple Choice Questions (MCQs) - Q.6

Q.6 Analogous organs arise due to
  1. divergent evolution
  2. artificial selection
  3. genetic drift
  4. convergent evolution
Solution: The correct option is (d) convergent evolution. Analogous organs are structures that have similar functions but different evolutionary origins and underlying structures (e.g., wings of insects and birds). They arise when unrelated organisms independently evolve similar adaptations to cope with similar environmental challenges or to perform similar functions. This process is known as convergent evolution.

Multiple Choice Questions (MCQs) - Q.7

Q.7 (p+q)^2 = p^2 + 2pq + q^2 = 1, represents an equation used in
  1. population genetics
  2. Mendelian genetics
  3. biometrics
  4. molecular genetics
Solution: The correct option is (a) population genetics. The equation (p + q)^2 = p^2 + 2pq + q^2 = 1 is the mathematical expression of the Hardy-Weinberg principle. This principle is fundamental to population genetics as it describes the conditions under which allele and genotype frequencies remain constant in a population from one generation to the next, serving as a baseline for detecting evolutionary change.

Multiple Choice Questions (MCQs) - Q.8

Q.8 Appearance of antibiotic-resistant bacteria is an example of
  1. adaptive radiation
  2. transduction
  3. pre-existing variation in the population
  4. divergent evolution
Solution: The correct option is (c) pre-existing variation in the population. When a population of bacteria is exposed to an antibiotic, individuals that already possess genes conferring resistance (due to random mutations or gene transfer) are more likely to survive and reproduce. This leads to an increase in the frequency of resistant bacteria in the population over time, demonstrating natural selection acting on existing variations.

Common mistakes

  • Confusing homologous and analogous organs.
  • Misunderstanding the difference between natural and artificial selection.
  • Incorrectly applying the Hardy-Weinberg principle.
  • Not recognizing the significance of fossils as evidence for evolution.

Revision tips

  • Focus on understanding the definitions and examples of homologous and analogous organs.
  • Clearly distinguish between the processes of natural and artificial selection.
  • Practice applying the Hardy-Weinberg equation to population genetics problems.
  • Review the various lines of evidence for evolution, especially fossils and comparative anatomy.

Practice MCQs

Q1. Which of the following organisms is commonly used as an indicator of atmospheric pollution?

Q2. The theory of spontaneous generation, also known as abiogenesis, proposed that:

Q3. Animal husbandry and plant breeding programs are practical applications of:

Q4. Palaeontological evidence for evolution is derived from:

Q5. The structural similarity in the forelimbs of a whale, bat, cheetah, and human, despite their different functions, indicates:

Q6. Analogous organs, such as the wings of insects and birds, are a result of:

Q7. The equation <math>(p + q)^2 = p^2 + 2pq + q^2 = 1</math> is fundamental in:

Q8. The emergence of antibiotic-resistant bacteria is a classic example of:

Frequently asked questions

What is the main focus of the Evolution chapter in CBSE Class 12 Biology?

The chapter focuses on the scientific understanding of how life on Earth has changed over millions of years, covering theories, evidence like fossils and comparative anatomy, and the mechanisms driving evolution such as natural selection.

How do NCERT Solutions for Evolution help students?

These solutions provide clear, step-by-step explanations for complex concepts, helping students understand evolutionary processes, evidence, and genetic principles like the Hardy-Weinberg equilibrium, which is crucial for exam preparation.

What is the significance of homologous and analogous organs in evolution?

Homologous organs (like forelimbs of vertebrates) indicate a common ancestry (divergent evolution), while analogous organs (like wings of birds and insects) show adaptation to similar functions from different ancestors (convergent evolution).

What does the Hardy-Weinberg principle represent?

The Hardy-Weinberg principle is a mathematical model in population genetics that states allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.

Can you explain 'artificial selection' in the context of evolution?

Artificial selection is a process where humans intentionally select and breed organisms for specific desirable traits, leading to significant changes in populations over time, as seen in domestic animals and crops.

What is the role of fossils in understanding evolution?

Fossils are preserved remains of ancient organisms that provide direct evidence of past life forms, their structures, and how they have changed over geological time, helping to reconstruct evolutionary history.

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