Question

a population of pigs lives on an island together with burrowing termites. pigs that have the longest snouts tend to survive more frequently than those with shorter snouts. over time, most of the pig population is made up of individuals that have very long snouts. this is an example of which type of selection?
directional selection
disruptive selection
stabilizing selection
ecosystem selection

Explanation:

• Directional selection: Favors one extreme phenotype (long snouts in pigs here). Over time, population shifts towards this extreme as it confers survival advantage (pigs with long snouts survive more).
• Disruptive selection: Favors two or more extreme phenotypes over intermediate. Not the case here as only long - snout (one extreme) is favored.
• Stabilizing selection: Favors intermediate phenotype. Opposite of what's described (intermediate snout length not favored).
• Ecosystem selection: Not a standard term in evolutionary biology selection types.

Answer:

directional selection