Mechanism of Evolution — Part 2: Hardy–Weinberg principle and human evolution: visual lesson, ISC Class 12 Biology

Lesson

Measuring evolution and tracing our own

Part 2 — how to tell whether a population is evolving, and the story of human evolution.

In this lesson you will

State the Hardy–Weinberg principle and calculate allele and genotype frequencies
List the factors that disturb Hardy–Weinberg equilibrium
Give the features of human ancestors in sequence

Concept

The Hardy–Weinberg principle

In a large, randomly mating population with no mutation, migration, drift or selection, allele and genotype frequencies stay constant from generation to generation. For two alleles with frequencies p and q: p + q = 1 and p² + 2pq + q² = 1.

Table of Hardy–Weinberg terms
Term	Meaning
p	Frequency of allele A
q	Frequency of allele a
p²	Frequency of AA
2pq	Frequency of Aa
q²	Frequency of aa

Diagram

The Hardy–Weinberg square

Random union of gametes is like a Punnett square of the gene pool: the areas give the genotype frequencies.

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