2.6 Adaptations

What is an adaptation?

An adaptation is an inherited trait that increases an organism's fitness — its ability to survive and reproduce — in a given environment. Adaptations arise through natural selection: individuals with favorable traits leave more offspring, so those traits become more common over generations. Adaptations can be structural, physiological, or behavioral.

Environmental change and extinction risk

When environments change quickly (climate shifts, habitat loss, pollution), species with narrow tolerance ranges or slow reproduction may not adapt fast enough and face extinction. Species with high genetic diversity, short generation times, and broad tolerance are more likely to adapt or survive change. Human activity accelerates environmental change, outpacing many species' ability to adapt.

Examples of adaptations

Structural: thick fur in arctic mammals for insulation. Physiological: antifreeze proteins in fish blood; antibiotic resistance in bacteria from mutation and selection. Behavioral: migration to follow food or favorable climate, hibernation to conserve energy. These traits result from generations of selective pressure matching organisms to their environment.

Key terms

Adaptation

An inherited trait that increases an organism's fitness (survival/reproduction) in its environment.

Natural selection

The process by which individuals with favorable heritable traits survive and reproduce more, increasing those traits' frequency over generations.

Structural adaptation

A physical trait, like thick fur, that helps an organism survive its environment.

Physiological adaptation

An internal biochemical trait, like antifreeze proteins or antibiotic resistance, that improves survival.

Why rapid environmental change increases extinction risk

Adaptation through natural selection takes many generations; if change happens faster than species can adapt, populations decline or go extinct.

Try an AP-style question

Why do bacteria adapt to antibiotics faster than elephants adapt to habitat change?

1. They reproduce much faster
2. They are smarter than elephants
3. Elephants don't have any genes
4. Antibiotics cause helpful mutations