Quammen, 199x

1
Process of Evolution Ch. 11
2
Darwin, Galapagos, and finches.
3
Gene Pool Concept Gene Pool sum total of all
alleles in a population. Population all
individuals interacting at a specific place and
time.
4
Gene Pool Concept Individual the phenotypic
expression of the alleles, the place-holder. Fitn
ess the ability to pass on your alleles to the
next generation.
5
Evolution change in allele frequencies of gene
pool through natural selection. (descent with
modification) Natural Selection differential
reproduction of genotypes based upon their
genetic constitution. Those individuals most
adapted to environment survive, whereas those
less adapted do not.
6
Natural Selection Postulates 1) genetic
variation. 2) traits can be inherited by the next
generation. 3) more individuals are produced in
the population than can survive. 4) survival and
reproduction are not random.
7
Natural Selection -Acts on the population not
the individual. -Response to external forces,
i.e. the environment.
8
Mowed lawn
Moist meadow
Natural Selection in Action ex. Self-heal
(Prunella vulgaris)
9
Artificial Selection e.g., Brassica oleracea
If man can by patience select variations useful
to him, why, under changing conditions of life,
should not variations useful to natures living
products often arise, and be preserved and
selected? (C. Darwin)
10
Evolution / Natural Selection does not imply
purpose, intention, planning, or voluntary
decision-making.
Bent grass (Agrostis tenuis) on lead mine
tailings, Wales.
11
Natural Selection Results of Natural
Selection -adaptation - adjusting to
environment, becoming more competitive, more
resistant. -loss of alleles from the population
can result in a reduction of alleles, or
complete elimination.
12
Hardy-Weinberg Principle p2 2pq q2 1 p
proportion of alleles A q proportion of
alleles a Hardy-Weinberg provides a tool for
detecting evolutionary forces and changes.
13
Hardy-Weinberg Principle Assumptions of
Hardy-Weinberg equilibrium -no genetic mutation
is occurring. -the population is isolated and
there is no migration. -the population is large,
probability laws apply. -mating is
random. -natural selection is not occurring.
14
Agents of Change In order for evolution to
occur allele frequencies in a population must
deviate from equilibrium. There are five agents
of evolutionary change. 1) Natural Selection we
already know how that works.
15
Agents of Change 2) Mutation -introduces new
alleles, new variation. -raw material for change
upon which evolutionary forces can act. -rates
are generally very slow.
16
Agents of Change 3) Gene Flow -movement of
alleles into or out of a population. -in other
words, migration. -introduction of new
mutations. -changes in allele frequencies.
17
Agents of Change 4) Genetic Drift -random
changes in the gene pool. -has a greater impact
on small populations. -Bottleneck
effect. -Founder effect.
18
Agents of Change 5) Non-Random Mating -mating
is often with those in close proximity. -inbreedin
g. -self-pollination is the extreme case. -tends
to increase the homozygous condition.
19
Species different kinds of organisms
20
Speciation when a population undergoes
sufficient genetic change to be considered a
different species. Biological Species Concept
capacity to produce fertile offspring when
crossed Morphological Species Concept
distinction made on morphological / anatomical
similaritiesare populations sufficiently
different?
Isolated for 50 million years
21
Sympatric Speciation Usually due to biotic
reproductive barriers. Polyploidy increase in
chromosomes beyond typical 2n condition Mutations
inhibiting gene flow
22
Allopatric Speciation Usually due to abiotic
reproductive barriers.
23
Alfred Who??
1848
1913
Alfred Wallace
Aru