An adaptation is “the appearance or behaviour or structure or mode of life of an organism that allows it to survive in a particular environment”.
Some adaptations are structural. Structural adaptations are physical features of an organism like the bill on a bird or the fur on a bear. Other adaptations are behavioral. Behavioral adaptations are the things organisms do to survive. For example, bird calls and migration are behavioral adaptations.

Examples of Adaptations
a) Webbed feet
In most aquatic animals, swimming is a must. To aid swimming, many animals have adapted and evolved with webbed feet. Webbed feet help animals propel themselves through the water with ease. This can help the animal swim faster to catch prey or escape a predator. Also, if an animal has to swim long distances, webbed feet can help it save energy so it can swim farther

b) Sharp Claws
Sharp claws can be used for many different purposes. For instance, many herbivores use their sharp claws for digging for berries, roots, and herbs or burrowing for shelter. Animals that eat meat may use their claws for killing their prey or tearing meat from their kills. Also, claws can be used to increase traction to run faster, as in the case of the cheetah. Other times, sharp claws have evolved for use in defense.

c) Sharp Teeth
Sharp teeth help an animal eat meat. Found primarily on meat-eating animals, or carnivores, sharp teeth are used mainly for the tearing and chewing of an animal’s prey. Rather than developing the dull teeth of plant-eaters, or herbivores, carnivores rely on their sharp teeth to allow them to eat and survive. Sharp teeth can serve another purpose: defense.

d) Large beaks
The large beak of the macaw has been adapted to help it crack open large nuts to reach the sweet fruit and pulp inside. On other birds however, the large beak is used to tear meat, as in the case of the rhinoceros hornbill. The rhinoceros hornbill uses its large beak to tear meat off of an animal it scavenges — usually the result of another animal’s kill.

e) Striped Fur
Striped fur is one variation of a special adaptation called camouflage. Striped fur, in most cases, helps animals blend into their environment. This helps the animal in one of several ways, including hiding from predators and sneaking up on prey. Striped fur, as in the case of a tiger’s vertical stripes, serves the animal by helping it match the surrounding vegetation, thus making it nearly invisible to other animals.

f) Brightly Colored Feathers
Brightly colored feathers can serve several purposes, including camouflage, defense, and mating. In some parts of the rain forest, the macaw and its brightly colored feathers can hide amid similarly brightly colored plants and flowers. The male peacock uses its bright feathers for another purpose: attracting a mate.

Other examples:
a) Desert animals prevent water loss from their body by reducing surface area, making skin impermeable through its thickening and hardening, as well as through the presence of scales and spines (Phrynosoma, Moloch), reducing the number of sweat glands in mammals, avoiding day heat by seeking the shadows of rocks and becoming active at night (nocturnal), and excreting wastes as solid dry pellets.

b) Some desert animals store water in their body and use it economically; the camel stores water in the tissues all over the body, whereas the desert lizard (Uromastix) stores it in the large intestine.

c) Mimicry is defined as the imitation of one organism by another for the purpose of concealment, protection, or other advantages. The species that imitates is called a mimic and the one which is copied a model. Depending on the purposes of mimicry, it can be protective or aggressive.

d) In Tundra climate most of the plants are small, grow close together and close to the ground. This protects them from the cold temperatures and the strong winds. The animals in these regions are usually white or light colored, e.g., polar bear, penguin. This adaptation helps them in maintaining their body temperature, and in camouflaging. These animals can store fat in their body as they eat a lot during the summer. In hibernation, their metabolic activity is reduced to a great extent. In this state, their heartbeat, breathing rate and temperature become very low.