Any environmental stress, like temperature range, rainfall, availability of food
and water source, competition and predation cause an organism to develop and change over time
in response to them. For example, many species were wiped out in the successive Ice Ages over
the last million years. Thier habitats were changing and only those generalized enough would
survive.
A selected trait which is shared by one (or two, rarely) species.
Human's ability to speak is an apomorphous character. No other animal has the ability for
conceptual language other than Homo sapiens (humans).
Occurs when an organism is cut off from others of same species (parental species)
for long enough to prevent interbreeding when and if the two groups are reunited. Geographic
isolation results in the formation of new species, often quite quickly.
Characteristics shared by non-related groups and species,
i.e. wings of bats, birds and insects. The groups are not recently related,
i.e. birds, mammals, arthropods are completely different taxa, however each has responded
to some enironmental stress which resulted in adaptations for flight.
A process by which an organism retains characteristics of an earlier form of development,
often embryonic. In early stages of development may species share primitive
characteristics, thus neotony offers a sort of guideline as to how much groups of organisms have
diverged from one another. It can be a powerful mechanism for evolutionary change. A good
example is that of a mexican salamander when conditions are unfavourable remains in it's tadpole
like larvae stage through its whole life. It reproduces and dies without ever attaining
the adult form and leaving the water.
While not really a true type of fat,
this terms describes the fatty layer which clings to the underside of the skin. Other apes do not have
this, in the wild, their fat is in between organs in the body cavitity. In the case of humans
this layer develops not only in and around the organs in the torso, but also spreads under the skin all
over the body. It gives aquatic and semi-aquatic mammals their streamlined shapes. It gives us
also a stream-lined shape!
A "line", in the East Indian archipelago, named and placed by Victorian biologist Alfred Russel Wallace which separates the Asiatic
fauna from the Australian fauna. The line is a deep ocean channel which has not had a land bridge even
in the lowest sea stands.
