Biology Reference
In-Depth Information
Adaptation
One feature of the natural world that much impressed Charles Darwin is how well
organisms are adapted by their form and behaviour to survive and reproduce in
their natural environment. I will describe here one animal example and one plant
example. There is another animal example illustrated in the Frontispiece.
Figure 3.3 shows a woodpecker as an example of a bird adapted to its particular
environment.
Fig. 3.3
Darwin was interested in those features of woodpeckers that suit this type of bird
to its lifestyle. They have powerful beaks that act as both hammers and chisels, and
enable the bird to make holes in trees to use as nests and to find insects living in the
wood and bark. The beak contains a long tongue to extract insects from inside the
wood. The skull is thick and has a cushion of spongy bone at its base to absorb the
shock of hammering. Unlike most birds that have three toes pointing forwards and
one backwards, woodpeckers have two toes pointing each way. This arrangement
of toes helps the woodpecker to grip rough vertical surfaces. The tail feathers are
strong and stiff, providing a brace to help the woodpecker maintain its grip with
short legs while making holes in trees. These adaptations all help woodpeckers to
survive and reproduce.
