Every vertebrate and invertebrate has a body suited to its way of life. A duck can paddle, a hawk can grip, a polar bear stays warm. These suited traits are called adaptations.
Key idea
An adaptation is an inherited trait that helps an organism survive where it lives, such as a duck's webbed feet, a hawk's hooked beak and talons, or camouflage. Adaptations become common over many generations.
| Organism | Adaptation | How it helps |
|---|---|---|
| Duck | Webbed feet | Paddling through water |
| Hawk | Hooked beak, sharp talons | Catching and tearing prey |
| Hummingbird | Long, thin beak | Sipping nectar deep in flowers |
| Polar bear | Thick fur and fat | Staying warm in the Arctic |
| Cactus | Thick stem, spines | Storing water; less water lost |
| Snowshoe hare | White winter fur | Hiding against the snow |
Why it works
In any population, individuals differ a little, and many differences are inherited. Those whose traits suit the place best tend to survive and have more young, and the young inherit those traits. Over many generations the helpful trait becomes common. No animal grows a trait because it needs one; the trait was already in the population.
Worked examples
Worked example: Match it
How does a heron's long legs help it?
- Herons hunt fish in shallow water.
- Long legs let them wade without getting their bodies wet.
Answer: They let it wade in to hunt.
Worked example: Explain it
How did giraffes come to have long necks?
- Giraffes varied in neck length.
- Those with longer necks reached more leaves, survived better and had more young.
- Over many generations long necks became common.
Answer: Through inherited differences and survival over many generations.
Common mistake
Thinking an animal grows an adaptation because it needs it ("the giraffe stretched its neck, so its young had longer necks"). Changes made during one life are not inherited. Adaptations are inherited traits that were already in the population and became common.