Download Phenotype Genotype and the Environment

Unit 6
Phenotype,
Genotype and the
Environment
What are
the
Main
Definitions
Regarding
Evolution
1 Evolution: A change in
allele frequency(genes)
over time.
2 Descent with
Modification: All life
on earth descended
from a common
ancestor over millions
of years.
3 Microevolution vs.
Macroevolution:
Microevolution: Shorter
periods of time. Changes
are within a species.
Macroevolution:
speciation (formation of
new species) occurs.
4 Cladogram or phylogenetic
tree: Illustrates descent with
modification.
5
6
7
Species: A group of
organisms that
interbreed.
Natural selection: Those
with advantageous traits
survive and reproduce.
Bell Curve: It is a graph
of normal-distribution.
In any normal population this would be the
distribution of traits that you would expect
34%
2%
14%
34%
14% 2%
Bell Curve for Height on A Football Team
Important
Points
About
Evolution
1
Microevolution leads
to macroevolution
(descent with
modification).
2
Natural selection
does not have a
direction, scheme,
or a grand plan.
3
Natural selection is
the driving force
behind evolution.
4
Selection occurs due
to an organisms
phenotype, not
genotype. Why?
The phenotype is
exposed to the
environment not
the genotype.
Color, size,
strength, eye-sight,
etc.
The environment doesn’t “see” recessive alleles.
They are hidden, but still passed on.
The 3
Types of
Natural
Selection
1. Stabilizing Selection:
Favors the average
and eliminates the
extremes.
Babies that are
too small are
not strong
enough, but if
too large,
complications
in delivery.
Stabilizing Selection
2. Directional Selection.
Favors one of the extreme
variations of a trait.
3. Disruptive Selection:
Favors both extreme
variations of a trait.
Gene Flow - The loss or gain of alleles in a
population due to the migration of fertile
individuals or between gamete populations.
When an organism moves from one area to
another, it takes its alleles with it.
• Founder Effect:
• Population Bottleneck:
– A small group branches – A large population is
off or colonizes a new
dramatically reduced to a
area.
few individuals.
. Genetic Drift = change in the gene pool that takes
place as a result of chance