CBSE Class 12 Biology Question Bank 2026: Master Hardy-Weinberg & Evolution
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If you are preparing for the upcoming board exams, the Evolution chapter often stands as a significant hurdle due to its conceptual depth and numerical applications. Specifically, the Hardy-Weinberg Principle is a cornerstone of population genetics that frequently appears in Section C and D of the board papers. This CBSE Class 12 Biology Question Bank 2026 is designed to streamline your revision by focusing on high-yield topics and official exam patterns.
Understanding the equilibrium of a population isn't just about memorizing a definition; it is about analyzing how life changes over generations. For medical aspirants, this topic is equally vital as it forms the basis of understanding genetic disorders and population health in the NEET and FMGE landscapes.
Understanding the Hardy-Weinberg Principle
The Hardy-Weinberg Principle states that allele frequencies in a population remain constant and stable from generation to generation in the absence of evolutionary influences. This state of "genetic equilibrium" suggests that the gene pool—the total genes and their alleles in a population—remains unchanged.
In a diploid organism, if p represents the frequency of the dominant allele and q represents the frequency of the recessive allele, the sum of these frequencies is always equal to 1. When this equilibrium is disturbed, it provides measurable evidence that evolution is occurring.
Core Mathematical Models
To solve the numerical questions in the CBSE Class 12 Biology Question Bank 2026, you must be familiar with two primary mathematical expressions:
The Allele Frequency Equation: Used to determine the individual frequency of dominant and recessive alleles.
The Binomial Expansion Equation: Used to calculate the frequency of homozygous dominant, heterozygous, and homozygous recessive genotypes in a population.
5 Factors Disrupting Genetic Equilibrium
The board frequently asks about the factors that "disturb" the Hardy-Weinberg equilibrium. If any of these five factors occur, the allele frequencies will change, leading to evolutionary progress:
Gene Migration or Gene Flow: Movement of individuals into or out of a population.
Genetic Drift: Random changes in allele frequency occurring by chance, especially significant in small populations (includes Founder Effect and Bottleneck Effect).
Mutation: Random changes in the DNA sequence that introduce new alleles.
Genetic Recombination: Occurs during crossing over in meiosis, leading to new combinations of genes.
Natural Selection: The process where certain heritable traits make it easier for an organism to survive and reproduce.
CBSE Class 12 Biology Question Bank 2026: Important Questions
Very Short Answer Questions (1 Mark)
What is the sum total of all the allelic frequencies in a stable population?
Define 'Gene Pool'.
Which evolutionary agent is responsible for the "Founder Effect"?
Short Answer Questions (2-3 Marks)
Numerical Challenge: In a population, the frequency of the recessive allele (q) is 0.4. Calculate the percentage of heterozygous individuals.
State the three types of Natural Selection with the help of a diagram (Stabilizing, Directional, and Disruptive).
How does the Hardy-Weinberg Principle explain that "evolution is a change in the allele frequencies in a population"?
Long Answer & Case-Based Questions (5 Marks)
Explain the five factors that affect genetic equilibrium. How does a deviation from this equilibrium lead to speciation?
Case Study: A specific population of 1000 individuals has 360 individuals with the genotype AA, 480 with Aa, and 160 with aa. Based on this data, find the frequency of allele A and allele a. Is this population in equilibrium?
Preparation Strategy for 2026 Exams
To excel in the Biology paper, students should follow a structured approach. Based on the analysis of previous years' papers and the latest 2026 competency-based trends:
Master the Numericals: Do not skip the math. The Hardy-Weinberg equations are scoring. Practice at least 10 different variations of allele frequency problems.
Official Resources: Always refer to the official question banks provided by the board. These contain the "Competency Based Questions" that are now 30-40% of the paper.
Diagrammatic Accuracy: For Evolution, practice drawing the graphs for Natural Selection. Labels carry half the marks.
Official Links for CBSE & Board Resources
CBSE Academic Website: Access Question Banks Here
Official Question Bank (Direct): Class 12 Materials
Conclusion
The Hardy-Weinberg Principle is more than just a formula; it is a lens through which we view the stability of life. By utilizing this CBSE Class 12 Biology Question Bank 2026, you are not just preparing for an exam but building a foundation for future medical studies. Focus on the conceptual shifts, practice the official board questions, and ensure your diagrams are precise.
Frequently Asked Questions (FAQs)
Q1: Where can I find the official CBSE Class 12 Biology Question Bank 2026?
Answer: The official question banks are released by the CBSE academic wing. You can access the CBSE Class 12 Biology Question Bank 2026 through the official portal at cbseacademic.nic.in. Navigate to the 'Question Bank' section to find subject-specific PDFs.
Q2: Is the Hardy-Weinberg Principle important for NEET 2026?
Answer: Absolutely. Every year, at least 1-2 questions from population genetics and the Hardy-Weinberg Principle appear in medical entrance exams. Mastering the numericals in your Class 12 prep will give you a significant edge.
Q3: What happens if p^2 + 2pq + q^2 does not equal 1?
Answer: If the sum of genotype frequencies deviates from 1 (or the expected value), it indicates that the population is currently undergoing evolutionary change due to factors like natural selection or mutation.
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