1. Phenotype, Genotype and the Environment
Unit 6
Phenotype, Genotype and the Environment

2. Definitions Regarding
Evolution: A change in
allele frequency(genes)
over time. 1
What are
the
Main
Definitions Regarding
Evolution
Descent with
Modification: All life
on earth descended
from a common
ancestor over millions
of years. 2

3. 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. 4

5. Natural selection: Those with advantageous traits
Species: A group of
organisms that
interbreed. 5
Natural selection: Those
with advantageous traits
survive and reproduce. 6
Bell Curve: It is a graph
of normal-distribution.
In any normal population this would be the
distribution of traits that you would expect 7
34%
14% 2%

6. Bell Curve for Height on A Football Team

7. Important
Points
About Evolution 1
Microevolution leads to macroevolution
(descent with modification).
Natural selection
does not have a direction, scheme,
or a grand plan. 2
Natural selection is the driving force behind evolution. 3

8. 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.

9. Stabilizing Selection:
Favors the average
and eliminates the
extremes.
The 3 Types of
Natural Selection
Babies that are too small are
not strong enough, but if too large,
complications
in delivery.

10. Stabilizing Selection

11. 2. Directional Selection.
Favors one of the extreme variations of a trait.

12. 3. Disruptive Selection:
Favors both extreme variations of a trait.

13. 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.

14. Founder Effect:
A small group branches off or colonizes a new area.
Population Bottleneck:
A large population is dramatically reduced to a few individuals.
. Genetic Drift = change in the gene pool that takes place as a result of chance