A. An adaptation is an INHERITED characteristic
set of characteristics which improves the chances of survival of
an organism. A complex adaptation evolves over a long period of
Some inherited characteristics have no apparent adaptive value.
Examples of adaptations:
land plants vs aquatic plants
B. Types of adaptations:
1. Morphological- those which involve the structures of organisms,
or their anatomy. (Most obvious form). (examples: structures
of human foot, beaks of birds or hooves of horses).
Morphological adaptations are important in food-getting.
those which involve the various physical and
chemical needs of organisms, including biochemical characteristics.
(examples: various enzymes needed for digestion, clotting of
blood or muscular contraction).
those which involve reactions to the environment.
(example: migration of birds, courtship behaviors, hiding and
storing nuts by squirrels, and tracking abilities of hunting dogs.)
C. Any one adaptation depends upon all other adaptations. The
behavioral adaptation of bird migration, for example, not only depends
upon nervous coordination, but also upon morphological adaptations such
as feathers, lightweight bones, and strong muscles.
D. Adaptations involving deception and camouflage are widespread in nature:
1. Camouflage- a kind of "disguise" to blend with the environment.
a. cryptic coloration- when the organism's color matches
the color of his environment. This enables the organism to
hide in his environment. An example of this is the peppered
moth, which can be either black or white. The white moth
matches the bark of the tree, whereas, the black moth
matches the bark of the tree when it is covered with soot
from industrial pollution. Another example is the stripes on
tigers which break up the general body outline of the animal
when he is amongst the weeds so that another animal may not
see the tiger approaching. katydid
b. shape- Some animals "hide" by means of their
example, many insects resemble the twigs of plants; pipefishes
can resemble the algae among which they live by swimming in
an upright position. walking stick; noctuid caterpillar;
c. mimicry- In nature, sometimes a tasty organism has a
pattern similar to that of a distasteful organism. The origin of
a mimic's coloration pattern is genetic. By random chance,
variations occur which cause one group of organisms (the
mimics) to resemble another group (the models). Those
organisms which possess the variation are less likely to be
eaten. Therefore, they will survive to reproduce offspring
with the same variation. Eventually, through continued
change and natural selection, the mimic gains a close
resemblance to the model.
Furthermore, mimicry does not have to be total
mimicry. Any little change which improves the chances of
survival and reproduction can be selected by natural selection.
An example of this is the robber fly, who is the mimic of the
bumblebee. The two nsects are not closely related, but their
similarity in coloration deceives possible predators.
Consequently, predators gnore the mimic just as they do
the Monarch butterfly (model) is on the left, and the Viceroy (mimic)
is on the right.
This involves a display of bright colors and
patterns. These color patterns announce rather than conceal the
presence of animals. For example, the yellow and black stripes
of a bumblebee are recognizable to possible predators. See examples below:
E. Industrial Melanism, otherwise known as the
of the Peppered Moth .
Evolution and adaptation do not always require extremely long periods of
time. In England a rapid evolution of the peppered moth has been occurring
for the last 100 years. In the middle of the nineteenth century almost all of the
peppered moths in England were light in color. Black moths possessing a
pigment called melanin were rare. Originally the tree trunks were very light in
color. As a result, the moths blended with their environment. Birds which fed
upon peppered moths had difficulty locating light-colored moths. However,
dark moths were easily seen. As the industrialization in England increased,
the tree trunks became covered with soot and smoke. Eventually they
turned black. Then the mutant, black forms of the peppered moth, had a
distinct advantage. When the black moths rested on the soot covered tree
trunks they were invisible to the birds. Light-colored moths, however,
became easy prey. During the last 100 years, the gene pool has evolved to
such an extent that over 90% of the peppered moths are black. This
particular phenomenon is called industrial melanism.
This story of industrial melanism is important for two reasons:
A. It shows that evolution is truly an interaction of organism and
B. It points out that evolution and natural selection operate on the
basis of genetic change within a population.
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