Download Conditions Required for Natural Selection

CONDITIONS REQUIRED FOR
NATURAL SELECTION
SC.912.L.15.13
VARIATIONS IN A
POPULATION
 Darwin’s
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2 observations:
Variation
Overproduction
 Overproduction-
species tend to produce
excessive numbers of offspring, but in
nature resources are limited
 Variation: difference among members
of a species
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Just as no two people in a human
population are alike, individual variation is
widespread in all species
Variation is heritable
-individuals that
function best tend to
leave the most offspring
- each new generation
has a higher proportion
of individuals with the
advantageous traits
- natural selection could
eventually cause two
isolated populations of
the same species to
become separate species
as they adapted to their
different environments
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Summary:
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Within any population, there are going to be genetic
variations
A variation can lead to differential reproductive success
(some organisms will leave more offspring than others)
Within any population, there may be over production of
offspring
Resources in an environment are often limited, and
therefore not all of the offspring that are produced will
survive
The offspring that can survive have an advantageous
variation that leads to their survival(struggle for
existence)
Survival usually means future reproductive success
(over time, that advantageous variation is kept within
the gene pool, and the others will not)