Which type of breeding is represented by industrial melanism in peppered moths?

Step 1: Analyze the question The question asks what process industrial melanism in peppered moths (Biston betularia) represents. Although it says "type of breeding," the best fit among the options is the evolutionary mechanism involved.

Step 2: Explain the concept

• Natural selection: Organisms with traits that suit their environment survive and reproduce more, passing those traits on. The environment does the "selecting."
• Artificial selection: Humans deliberately choose which organisms breed (e.g., breeding high-yield crops or cattle).
• Inbreeding: Mating between closely related individuals.
• Outbreeding: Mating between unrelated individuals.

Step 3: Apply it to the peppered moth

1. Before the Industrial Revolution, trees in England were covered with light-colored lichens. The light (peppered) moths were camouflaged, while the dark (melanic) ones were easily seen and eaten by birds.
2. Industrial pollution (soot) killed the lichens and darkened the tree trunks.
3. Now the dark moths were camouflaged, and the light ones were easily spotted by birds.
4. Dark moths survived and reproduced more, so the dark-colored allele became more common in the population.

No human chose which moths would mate. The environment (soot-darkened trees plus bird predation) acted as the selecting pressure. That is natural selection.

Step 4: Eliminate the wrong options

• A: Humans did not deliberately select the moths. Pollution was an accidental side effect.
• C and D: These describe mating patterns, not the survival-based change in the population's traits.

Answer: B. Natural selection

Exam tip: Whenever you see "camouflage," "predation," "survival of the fittest," or "environment favors a trait," think natural selection. If a farmer or breeder is choosing, think artificial selection.