Define the term population from an ecological perspective.Describe various relationships between plants and animals in terms of of how natural...

Population is the members of a given species of animal in
a defined geographical area.  This can be at the local level and at the regional level. 
Populations tend to have fuzzy boundaries, with the traits marking a particular
population being more marked in the middle of the population and more transitional along
the boundaries.  Biologically, humans are best thought of in terms of populations rather
than as races, as races are sociological rather than biological
constructs.

The initial colonization of an area by a spcies
is known as a pioneer population, depending on the degree of isolation of that
population, this can lead to significant genetic drift, as well as adaptation to new
ecological challenges.  As populations spread you frequently can have interbreeding of
populations along boundaries, but inability of more remote specimens to
interbreed.

Populations are shaped by birth, deaths and
migration (including immigration and emigration). They are shaped by natural events such
as disease and natural disasters.

Populations will
frequently achieve a balance or equilibrium for long periods leading to stability, but
new competition, environmental change such as climate change, natural disasters, or
increased predation can lead to dynamism that can knock the population out of
equilibrium.