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Theory of evolution
Many ideas were out there to explain how
species change over time but the first published
was
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Charles Darwin in the H.M.S. Beagle
traveled the world for 5 years and made
observations of living and fossilized plants
and animals.
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Started to notice relationships among species
 Most significant stop- the Galapagos
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Quick Time™a nd a
TIFF ( Unco mpre ssed ) dec ompr esso r
ar e nee ded to see this pictur e.
Found many unique species similar but different
then those of the mainland. IDEA
CAN SPECIES CHANGE OVER TIME?
Now that an idea was formed DARWIN
had to collect evidence
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For two decades Darwin worked and
experimented and read and borrowed
from Thomas Malthus.

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Malthus idea was that human population grows
faster than food supply
Darwin idea was that individuals struggle
to compete in changing environmental
conditions. Which individuals survive?
Natural selection

Mechanism for change in populations.
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In Nature organisms produce more offspring
than can survive
Due to independent assortment in any
population individuals have variations
Individual with useful variations will survive
Over time offspring with certain variations
make up most of the population
and
may look nothing like their
ancestors

In Indonesia Alfred Russell Wallace reached a
similar conclusion but Darwin was the first to
publish.
Interpreting evidence after Darwin

Much data has been gathered but
as Humans have only been here a
short time and what happened
before us is subject to
interpretation.
Evidence for Evolution

Adaptation is variation that aids an organism’s
chance of survival in its environment.
Structural adaptations
 Mimicry
Camouflage
Physiological adaptations
 Fossils
 Anatomy
 Homologous structure
- Analogous structure
 Vestigial structure
 Embryology- viruses
 Biochemistry- Modern approach
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Mechanisms of Evolution
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What was missing from Darwins theory?
Genes
Who evolves Populations or individuals?
Natural selection acts on the range of
phenotypes
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Evolution occurs as a population genes and their
frequencies change over time
Gene pool
How much (percentage) of any specific allele in
the gene pool is called Allelic frequency
Genetic equilibrium
When the frequency of alleles remains
the same over generations
Does it evolve?
Changes in genetic equilibrium
Mutation -most lethal but some…….
Are useful
Genetic drift- change of allelic
frequencies by chance events…
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
can greatly affect small populations making
recessive alleles more common than in the larger
population,
Gene Flow- Can be affected by movement
into and out of a population
Three types of natural selection
that act on variation
Stabilizing-favors
average individual
in a population
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Directional selection

Occurs when Natural selection
favors on of the extreme
variations of the trait
Disruptive selection

Individual with either
extreme of a trait’s
variation are selected for.
Physical barriers can prevent
interbreeding rendering a new
species (speciation) can no longer interbreed
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Geographic isolation
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When a physical barrier divides a population
Reproductive isolation
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Change in chromosome numbers and
speciation
Speciation rates
 Gradualism
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slow change over time
Punctuated equilibrium
rapid change
Patterns of evolution

Adaptative radiation
Divergent evolution- become more dissimilar
over time
Convergent evolution
Unrelated species occupy similar environments which have similar
pressures which make them look similar
Review

http://www.ptpleasantbch.k12.nj.us/bridge/genbio/evoluti
ontaxon.html