Ncert Books Class 12 Biology Chapter 7 Free Download

To score high marks, students should focus on understanding key concepts such as the origin of life, Darwin's theory of natural selection, speciation, molecular evolution, Hardy-Weinberg equilibrium, genetic drift, and evolution of humans. Exam preparation should also include practicing application-based questions and diagrams, as these are often assigned for 3- and 5-mark questions.

HOTS questions in this chapter usually require students to analyze scenarios, interpret data, or compare evolutionary processes. Examples include:

• Explaining how antibiotic resistance demonstrates evolution in action
• Predicting outcomes if Hardy-Weinberg equilibrium is disturbed
• Justifying the difference between convergent and divergent evolution through new examples
• Analyzing phylogenetic trees and their implications on human evolution

Based on recent CBSE trends, Evolution typically carries 7–9 marks in the Class 12 Biology paper. Expect a mix of 1-mark objective questions, 3-mark short answers, and at least one 5-mark long answer covering evolutionary mechanisms or theories. Core concepts such as Darwin’s theory, Hardy-Weinberg principle, and application of evolutionary concepts are often targeted for higher marks.

The Hardy-Weinberg principle is used to predict allele and genotype frequencies in a population that is not evolving. It helps in detecting when evolution has occurred by comparing expected and observed genetic frequencies. Real-world applications include studies on antimicrobial resistance and conservation genetics. This question is frequently asked as it tests both conceptual understanding and application ability, fulfilling CBSE’s objectives for higher-order cognitive skills.

Students often confuse convergent and divergent evolution. Remember:

• Convergent evolution leads to similar features in unrelated species due to similar environments (e.g., wings of bats and insects).
• Divergent evolution produces different features in species from a common ancestor (e.g., Darwin’s finches’ beaks).

For maximum marks, diagrams such as evolutionary trees, flowcharts of speciation events, and illustrations of homologous and analogous organs should be:

• Neat and well-labeled
• Directly relevant to the question
• Accompanied by brief explanatory notes

Application-based questions often present a real or hypothetical situation, asking students to explain evolutionary principles such as adaptive radiation, natural selection in action, or the consequence of genetic mutations. For example, questions might describe a pest’s resistance to pesticides and ask students to explain the evolutionary mechanisms behind this change.

The study of human evolution provides context for understanding biological diversity and links with genetics, anthropology, and natural selection. Board questions often require explanations of key fossil evidence, the significance of evolutionary milestones, and comparisons between humans and primates, testing both factual recall and synthesis of multi-topic understanding.

Concept-based questions directly ask for explanations of theories, definitions, or differences (e.g., explain Darwin’s theory, compare homologous and analogous organs), while application-based questions involve scenarios or case studies requiring the practical use of evolutionary principles (e.g., explaining an observed phenomenon using Hardy-Weinberg law). Look for trigger words like "explain with an example", "analyze", or "justify" to identify application focus.