Closely related to irritability is the capacity of living things for adaptation. You might have noticed that whenever you go outside in the bright sun after having been in a dark room for some time, you feel uncomfortable and the light too intense. However, within a short time you cease to feel so and become quite at home in the sun. You have adjusted or 'adapted' to the new environment. Establishment of this sort of harmony between the organism and its environment is called adaptation. The ability of the plants and animals to adapt to their surrounding enables them to survive the vagaries of the ever-changing environment. For instance, the fish like body of the whale is an adaptation for living in the sea water. The long beak of the nectar-sucking birds is an adaptation for sucking nectar from the flowers.
Figure: The patterns on the feathers of female bittern bird look like reeds. This hides her while she incubates her eggs.