This week we are going to continue our on
evolution and we are going to be focusing
on Natural Selection. Evolution is any change
in the relative freq. of alleles in a populations
over a period of time. Fitness is an organisms
ability to successfully pass on its genes
to its offspring. So this is not the same
as physical fitness. A more fit individual
is one that survives and reproduces. A mechanism
for evolution is a process that will result
in evolution. Four examples include, Natural
Selection, Genetic Drift, Sexual Selection
and Artificial Selection. We are going to
focus on Natural Selection. Natural Selection
is the process whereby organisms better adapted
to their environment tend to survive and produce
more offspring. Natural Selection does not
act on a gene it acts on the phenotype of
the individual. So for example an organism
with longer wings will survive it doesn't
mater if the genotype is big W little w or
big W big W, just that it has that phenotype
of longer wings. There are 4 key factors to
natural selection. The first factor is genetic
variation exists between members of a species
this variation has to be passed down from
generation to generation. Our 2nd key factor
is overproduction of offspring. More offspring
are produced then can survive. Our 3rd key
factor is struggle for existence. Organisms
are going to compete for limited resources
such as food, water, space, and mates. Organisms
that are better at getting those limited resources
are favored in nature. And our 4th key factor
is differential survival and reproduction.
So those with the most advantageous are more
likely to survive and reproduce. Adaptations
are physical or behavioral traits that make
organisms better suited to their environment.
These are small changes that happen in every
generation.
