Homology
Two species that share a homologous trait are the Porpoise
and Humans. The porpoise is similar to a dolphin however tends to be smaller,
has a rounded head and a blunt jaw and use their extremities to swim. Humans
stand up straight, have two legs and two arms that are used to walk on land,
but can also be used to swim as well. The feature that is important in the
comparison with humans and the porpoise is the fin and hands, which stem from a
common ancestor.
The porpoise flipper can be compared to the arm and hand of
a human. The flipper is shorter with more restricted movements, where as the
arm of a human is long, a little less then half the size of the body. The
motion of the arm is numerous because of the many different joints. The flipper
and arm however do share the number of flanges, which are five. However the
purpose of these traits are quite different. The human use their arms and hands
for tremendous activity, lifting, pushing, climbing, eating, and swimming. All
these activities require different functions from the arm and hands, which is
the cause for the great complexity in this structure on the human body. In the
case of the porpoise, there are less requirements of the flipper. The flipper
of the porpoise is mostly used to swim, and not really anything else due to the
short nature.
The common ancestor between the human and the porpoise came
millions and millions of years ago, but the reason we can tell this common
ancestor gave them this homologous trait is because the similarity of the structure.
Although the functions are not the same, the bone structure evolved and changed
based on an original structure. The differences only formed based on
environmental differences.
Analogy
The two species that I choose for the analogous trait are a
bird and a butterfly. The butterfly is part of the insect family, they are
generally small however to vary in size, as well as shape and color. They’re
look is based on their environment; the color of their wings is best suited for
their environment. A bird also varies in shape, size and color. Birds however
have the ability to be quite a bit larger then that of a butterfly, however
both creators share the analogous trait of the wing.
The trait of the wing in both bird and butterfly allow the
creature flight. In both creatures there are only two wings, on either side of
the body allowing for the body to be the center of balance. Roughly the shape
of the wings are similar, to engage in similar ways of flight. Although the
butterfly is a member of the insect family and the bird is a member of its on
class, the have both evolved using the same analogous trait, the wing.
Both the bird and the butterfly can be traced back to the
time of the dinosaurs, in fact birds are said to be descendants of dinosaurs.
At this time both ancestors had the ability to fly, however the question is if
we go back far enough, does their common ancestor have this analogous trait of
the wing. The answer is no, this trait was developed based on the environment,
and because the structure is so different it is hard to believe that it came
from the common ancestor. The butterfly has no bones in the wing, where as the
bird has many bones. In fact the structure of the creature itself is entirely
different so t
his evolutionary development with the wing was based on
evolving in a similar environment.
