What Is Evolution?
Evolution is the change in heritable traits of populations over generations, driven mainly by natural selection acting on genetic variation. The Hardy-Weinberg principle gives biologists a baseline to detect when a population is actually evolving.
Evolution is the process by which populations of organisms change over successive generations through mechanisms like natural selection, genetic drift, mutation and gene flow.
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Step-by-step worked examples
In a population of 1,000 people, the recessive allele frequency is q = 0.3. How many people are expected to be homozygous recessive?
Homozygous recessive frequency = q² q² = 0.3² = 0.09 Expected individuals = 0.09 × 1000 = 90 people
If the recessive allele frequency is q = 0.2, what is the dominant allele frequency p, and what fraction of the population is heterozygous?
p + q = 1 → p = 1 − 0.2 = 0.8 Heterozygous frequency = 2pq = 2 × 0.8 × 0.2 = 0.32 So 32% of the population is heterozygous
A moth population starts with 50% dark-colored moths. After pollution increases predation on light moths over 10 generations, dark moths rise to 90%. What evolutionary mechanism explains this?
Predators selectively remove light moths (lower survival/reproduction) Dark-color allele frequency increases each generation This directional shift in allele frequency due to differential survival is natural selection (industrial melanism)
Flashcards
Quick quiz
Q1.What is the main driving mechanism of adaptive evolution?
Q2.In Hardy-Weinberg equilibrium, if p = 0.6, what is q?
Q3.Which of these is NOT a mechanism of evolution?
Q4.A population in Hardy-Weinberg equilibrium is best described as...
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Common mistakes
Thinking evolution means an individual organism changes during its lifetime. — Correct: Evolution happens at the population level across generations, not within one individual.
Believing evolution has a 'goal' or always makes organisms 'better'. — Correct: Evolution has no goal — it favors whatever traits improve survival/reproduction in the current environment.
Confusing natural selection with genetic drift. — Correct: Natural selection is driven by fitness differences; genetic drift is random chance, strongest in small populations.
Assuming humans no longer evolve. — Correct: Human populations still show measurable allele frequency changes (e.g., lactase persistence) — evolution is ongoing.
FAQ
What is evolution?
Evolution is the change in heritable traits of a population over generations, driven by natural selection, drift, mutation and gene flow.
What is the formula related to evolution and allele frequencies?
The Hardy-Weinberg equation p² + 2pq + q² = 1 predicts genotype frequencies in a non-evolving population.
What are examples of evolution in action?
Antibiotic-resistant bacteria, Darwin's finches' beak shapes, and industrial melanism in peppered moths are classic examples.
How do you calculate allele or genotype frequency in evolution?
Use the Hardy-Weinberg equation: p + q = 1 for alleles, and p² + 2pq + q² = 1 for genotype frequencies.