Overview of Evolutionary Biology
Darwin’s idea of evolution caused a “paradigm shift” – a new
way of looking at and understanding living things – a natural
explanation for the commonalities and diversity of living things
Presented two major ideas
• common descent
• natural selection
Common descent explains common features of organisms –
anatomy, biochemistry, behavior, …
Natural selection explains the “fit” between organisms and their
environment
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2
3
Natural selection – due to the interaction of organisms and their
environment and results in organisms that have increased
abilities to survive or reproduce in their environment
Artificial selection – due to intentional human control of the survival
and reproduction of organisms and results in organisms that suit
a human desire – also know as “selective breeding”
Natural selection produces “descent with modification”
Natural selection operating in different populations of the same
species produces divergence of lineages and potentially different
- speciation
species
p
p
Extinction – the
failure of a lineage
to persist
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Continued divergence
multiplies lineages and
sometimes produces “major
transitions” in form and
function.
Descent with modification
appears to have produced the
full range of biological
diversity – the “tree of life”
Evolutionary biology is a scientific endeavor that studies the
patterns and processes of evolution
Two general approaches are used by evolutionary biologists
• empirical
• theoretical
h
i l
Empirical studies
• observational
• fossils provide information on past evolution
• comparative anatomy and molecular studies – similarities
provide information relationships of lineages and
can provide evidence of past selection
• behavioral and ecological studies document factors that
influence past and future evolution
• manipulative experimental studies
•…
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Read:
• Mikkelsen’s studies of human and chimp molecular evolution
• Khatovich’s studies of differences in gene expression in
humans and chimps
A manipulative experiment
Pizzari’s sperm competition experiment in chickens
• used existing mating system in chickens
• made predictions about how male chickens should respond
to change in amount of sperm competition
• manipulated amount of sperm competition and compared
results with expectations
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100
Offspring Number (N)
Offspring Number (N)
Theoretical approaches
• mathematical models or logical reasoning allow predictions
about the outcome of environmental change
• e.g. sex ratio selection and evolution (later)
• e.g. parental investment theory
80
60
40
20
0
0
5
10
15
Parental Investment (size)
20
80
60
40
20
0
25
05
0.5
0
5
10
15
Parental Investment (size)
20
25
0
5
10
15
Parental Investment (size)
20
25
0
5
10
15
Parental Investment (size)
20
25
0.5
0.4
Offspring Fitness
Offspring Fitness
100
0.3
0.2
0.1
0.4
0.3
0.2
0.1
0
0
0
5
10
15
Parental Investment (size)
20
25
1.6
3
1.4
Parental Fitnesss
Parental Fitness
2.5
2
1.5
1
0.5
12
1.2
1
0.8
0.6
0.4
0.2
0
0
0
5
10
15
Parental Investment (size)
20
25
7
8