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Evolution
History of the theory
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Jean-Baptiste Lamarck  one of the first to
recognize organisms have changed
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Published ideas in 1809
Proposed that through selective use or disuse of
organs, organisms could acquire or lose certain traits
during their lifetime
He did not understand how traits were inherited, but
he realized that organisms adapt
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Thomas Malthus  1798 published a book
that said the human population was growing
faster that the earth could supply
He was afraid that the growing population
would result in not enough living space or
resources
Darwin's observations
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Darwin sailed around the world on the
H.M.S. Beagle in 1831 took 5 years
He noticed that the same type of animals had
noticeable differences
On each island, he would see different traits
unique to that particular island
Published observations in On the Origin of
Species
Natural Selection
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Darwin’s evolution explanation
Struggle for existence – all organisms
compete for resources
Survival of the fittest – each organism has an
environmental fitness
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This fitness is the result of adaptations
Whoever is the most fit for the environment will
survive
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Certain traits are beneficial and enable the
organism to survive
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These will be passed on to future offspring's
He also proposed that “bad” traits will not be
passed on
Evidence for evolution
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Structural Adaptations
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Physiological adaptations
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Changes in metabolic activities
Fossils
Biochemistry
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Mimicry
camouflage
Nearly all organisms share DNA, ATP, and enzymes
Embryology
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At one point, all embryos look similar
Mimicry
Camouflage
Bacterial Adaptations
Anatomy
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Homologous structures
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Analogous structures
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Similar in arrangement and function
Forelimbs in crocodiles, whales, birds
Similar function, different structure
wings
Vestigial structures
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No modern-day purpose
Ostrich wings, pelvic bones in whales
Vestigial Structures
Homologous structures
Mechanisms of Evolution
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Populations, not individuals, evolve
Gene pool – all of the population’s genes put
together into 1 pool
Allelic frequency - percentage of a specific
allele within the population
If alleles stay the same  genetic equilibrium
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Anything that changes the alleles results in
evolution
Natural selection and variation
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Some variations may increase or decrease
chances of survival
Stabilizing – favors the average individuals
Directional – favors one of the extreme
variations of a trait
Disruptive – both extremes are favored
Evolution of Species
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Speciation  process that produces two
species from one
Reasons:
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Geographical isolation
Reproductive isolation
Changes in the gene pool
Ecological competition
Continued evolution
Patterns of Evolution
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Adaptive radiation  species evolve to fit
habitats
Divergent radiation  members of a species
become less alike (adapt to environment)
Convergent evolution  unrelated species
become more alike