Individuals of the same species are not all the same. Some animals are larger, hairier, or louder than others, even if they are the same species. These differences are largely determined by an individual’s genes, which are like instructions that are passed from parent to child. Some differences provide advantages like speed, strength, or attractiveness. Those advantages help animals survive and reproduce. Over generations those traits, or adaptations, will be passed on to more individuals until the trait becomes common in that species.

Structural and Behavioral Adaptations

An adaptation can be structural, meaning it is a physical part of the organism. An adaptation can also be behavioral, affecting the way an organism acts.

An example of a structural adaptation is the way some plants have adapted to life in dry, hot deserts. Plants called succulents have adapted to this climate by storing water in their short, thick stems and leaves.

Migration is an example of a behavioral adaptation. Gray whales (Eschrichtius robustus) migrate thousands of kilometers every year. They swim from the cold Arctic Ocean to the warm waters off the coast of Mexico. Grey whale calves are born in the warm southern water, and then travel north in groups to feed.

Adaptations that help with one challenge are sometimes used to help with other problems. Such traits are called exaptations. For example, feathers were probably first adaptations for managing temperature. Later, feathers became longer and helped some species glide or fly.

Some adaptations, on the other hand, lose their function. Whales and dolphins have vestigial leg bones, the remains of an adaptation (legs) that their ancestors used to walk.

Habitat

Adaptations usually develop in response to a change in an organism's habitat.

England's peppered moth (Biston betularia) is a famous example. Before the 1800s, the most common type of this moth was cream-colored with darker spots. Few peppered moths were grey or black.

As the rise of factories changed the environment, the colors of the peppered moth changed. The darker-colored moths became more common. Their sooty color blended in with the trees stained by industrial pollution. Birds couldn't see the dark moths, so they ate the cream-colored moths instead.

Speciation

Sometimes, an adaptation or set of adaptations develops that splits one species into two. This is called speciation.

One way this can happen is through the physical isolation of a species.

A good example is the wide variety of marsupials in Oceania, the area that includes Australia and New Zealand. Long ago, this region was part of Asia. Before it broke away, marsupials arrived. Marsupials are mammals that carry their young in pouches. Marsupials are now the main type of mammal in Oceania. Meanwhile, placental mammals are the main type on every other continent.

Koalas (Phascolarctos cinereus) are one of the most famous marsupials. They adapted to feed on eucalyptus trees, which are native to Australia. The extinct Tasmanian tiger (Thylacinus cynocephalus) was a meat-eating marsupial. It adapted to fill the role played by big cats, like tigers, on other continents. Marsupials in Oceania are an example of adaptive radiation. This is a type of speciation where species develop to fill empty roles in their environment.

Coadaptation

Organisms sometimes adapt to and with other organisms. This is called coadaptation. Certain flowers have adapted their nectar to appeal to hummingbirds. Hummingbirds have adapted long, thin beaks to collect nectar from certain flowers. When a hummingbird drinks nectar from a flower, it accidentally picks up pollen. It then carries that pollen to other flowers. In this relationship, the hummingbird gets food, and the plant's pollen gets distributed. The coadaptation helps both organisms.

Mimicry is another type of coadaptation. With mimicry, one organism has adapted to resemble another. For example, the harmless king snake has developed a color pattern that resembles the deadly coral snake. This mimicry keeps predators away from the king snake.