Organisms rarely live in a constant environment. They
experience times of feast and times of famine, changing
numbers of predators, prey and pathogens, and changing
physical and chemical environmental conditions.
To put it simply,
life is change. To survive, an organism has to be able
to maintain itself in response to perturbation (homeostasis)
and changing environmental factors (adaptation). This is a
constant process, since as the various process of life leads to changes
in the environment.
Take yourself as an example, when the temperature rises you
sweat and you even decide to remove some clothes; when
the temperature drops you shiver and get unbundled up - both the
these are adaptive responses. One type
is physiological (sweating
and shivering) – such responses are generally unconscious,
you do not decide to shiver, your body does. The
other is behavioral (putting on and taking off clothing) and requires
conscious thought.
There are also slower types of
adaptation, such as the ability to grow thick and more insulating
fur for the winter, and the shedding of fur in preparation
for the summer.
Very rapid
(seconds) adaptive responses depend primarily upon changes
in the activity of proteins,
somewhat slower responses (minutes to hours, days, and months)
begin with changes in protein activity, but then involve
changes in gene
expression.
The types of adaptation an organism can perform
are the result of evolution.
|
