Transcript Document

3 WAYS TO STUDY BEHAVIOR
1. Proximate causal mechanisms
2. Ontogeny (or development)
3. Evolution
Proximate causal mechanisms act over short
time periods
Ontogenetic (or developmental) mechanisms
act over intermediate time periods
Evolution acts over long time periods
ALLELE: Any one of the alternate forms of DNA
that can exist at a given locus.
EVOLUTION: A change in allele frequency
over time.
GENOTYPE: The genes that underlie a
particular structure or behavior
PHENOTYPE: The organism’s outward
appearance or behavior
No.
Of
Subjects
HEIGHT
Vp = Vg + Ve
Phenotypic variation (Vp) is the sum of
Variance due to genetics (Vg) plus
Variance due to the environment (Ve)
Heritability = ______Vg_______
Vg + Ve
Darwin’s theory of evolution
By natural selection
1. Competition. The ability of a population
to grow is infinite, but the ability of any
environment to support it is finite.
Darwin’s theory of evolution
By natural selection
2. Variation makes a difference.
Organisms within a population vary in
morphology and behavior, and this
variation affects their ability to survive
and reproduce.
Darwin’s theory of evolution
By natural selection
3. Variation is inherited. Offspring
resemble their parents more than they
resemble randomly chosen adults
within the same population.
Drought
Seed
Thickness
And
Hardness
1975
1976
1977
1978
Drought
Mean
Beak Depth
1975
1976
1977
1978
Directional Selection
# of
Inds.
Trait
Stabilizing Selection
# of
Inds.
Trait
140
120
100
No. of
clutches
80
60
40
20
0
5
6
7
8
9
10 11 12
Clutch size
_
%
survival
60 _
_
40
20
_
|
|
|
|
2
4
6
8
|
Clutch size
|
_
%
Parents
sur_
ving
_
40
20
_
|
|
|
|
2
4
6
8
|
Clutch size
|
140
120
100
No. of
clutches
80
60
40
20
0
5
6
7
8
9
10 11 12
Clutch size