Geography Reference
In-Depth Information
plates for over 200 million years prevented any connecting land
from joining. The islands to the north of the trench were formed
from the Asian continent and the islands to the south were
originally part of the Australian continent. The role of plate tec-
tonics is of fundamental importance to explaining many spatial
differences in plant and animal distributions. Other geological
factors include soils, which are important for controlling available
water for plants and provision of nutrients, and topography,
which influences receipt of the Sun's energy, local climate,
hydrology and soils.
Biotic factors
Competition for light, nutrients, water and living space, the ability
to adapt and migrate and the presence or absence of predators and
prey are important components that may result in differences
within the biosphere. Competition arises in situations such as at a
drinking hole in a semi-arid area. Herbivores and other species
may need to wait until the carnivores have left before getting a
drink of water. Another type of competition occurs when there is
a limited amount of food for the individuals of one species and
this may lead to exclusion of weaker individuals and the survival
of the fittest, who are able to gather enough food. The
ecological
niche
is the basis of most ecological patterns in the biosphere.
Where there are no competitors for any of the resources required
by an individual or species, the organism can occupy the ideal
conditions to which it is adapted. However, because of competi-
tion, species usually have to occupy a
niche that is the result of
competitive interaction between several species attracted to the
resources. Competition tends to be strongest between similar
species, since their ecological niches are likely to overlap. The
species able to survive on the lowest amount of the limiting
resource will be better off.
Another biotic factor that produces geographical patterns is the
isolation of groups of organisms, perhaps through plate tectonics.
The biotic component of this isolation is the lack of breeding of
the species with the larger population. This means that a wider
mixing of genes does not occur and so adaptations or changes to a
species can more quickly develop. This can lead to the evolution
