Overview of Evolutionary Biology
Darwin’s idea of evolution caused a “paradigm shift” – a new
wayy of looking
g at and understandingg livingg things
g – 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 –
y, biochemistry,
y, behavior,, …
anatomy,
Natural selection explains the “fit” between organisms and their
environment
Natural selection – due to the interaction of organisms and their
environment
i
t andd results
lt in
i organisms
i
that
th t have
h
increased
i
d
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
p
pproduces divergence
g
of lineages
g and ppotentiallyy different
species
species - speciation
Extinction – the
failure of a lineage
to persist
Continued divergence
multiplies
p
lineages
g and
sometimes produces “major
transitions” in form and
function.
function
Descent with modification
appears to have
h
produced
d d the
h
full range of biological
diversityy – 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
ii l
• theoretical
Empirical studies
• observational
• fossils provide information on past evolution
• comparative anatomy and molecular studies – similarities
provide information relationships of lineages and
can pro
provide
ide evidence
e idence of past selection
• behavioral and ecological studies document factors that
influence past and future evolution
• manipulative experimental studies
•…
Read:
• Mikkelsen’s studies of human and chimp molecular evolution
• Khatovich
Khatovich’ss studies of differences in gene expression in
humans and chimps
A manipulative experiment
Pizzari’ss sperm competition experiment in chickens
Pizzari
• 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
p
Theoretical
h
i l approaches
h
• mathematical models or logical reasoning allow predictions
about the outcome of environmental change
g
• e.g. sex ratio selection and evolution (later)
• e.g. parental investment theory
Offspring Nu
umber (N)
Offspring N
Number (N)
100
80
60
40
20
0
0
5
10
15
Parental Investment ((size))
20
80
60
40
20
0
25
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
Offspringg Fitness
Offspringg 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 F
Fitness
Parental Fiitness
2.5
2
1.5
1
0.5
1.2
1
0.8
0.6
0.4
0.2
0
0
0
5
10
15
Parental Investment (size)
20
25