EVOLUTIONARY THEORY
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Transcript of EVOLUTIONARY THEORY
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JEAN BAPTISTE LAMARCK
EVOLUTIONARY THEORY
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JEAN BAPTISTE LAMARCK
B:1774 D:18292 theories of how organisms changed over
time1. Acquired characteristics2. Law of use and disuseTheories were determined to be incorrect
BUT he was the first to publicly state that evolution of organisms occurs
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CHARLES DARWIN
EVOLUTIONARY THEORY
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CHARLES DARWIN
B:1809 D:1882Man most famously credited for
“discovering” evolution5 basic principles of natural selection1. Individuals of species vary2. Some variations heritable3. More born than can survive4. Competition for resources5. Most fit individuals survive to reproduce
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NATURAL SELECTION
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NATURAL SELECTION
Darwin’s explanation for how changes in organisms occur
Nature is acting upon the phenotype of each individual organism; a favorable phenotype increases survival in the environment
Organisms must adapt, migrate or dieDarwin’s theory revolves around the
reproductive success of organisms with favorable phenotypes
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MUTATIONS
VARIATION
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MUTATIONS
Driving force for evolutionOrigin source for new alleles in a populationRandom changes in the genotypes of
members of a populationFavorable/useful mutations increase
organism’s chances for survivalMutations are rare so the effects are rarely
seen in a specific populationCumulatively, mutations are why we are
humans and not house plants
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VARIATION FROM RECOMBINATION
VARIATION
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VARIATION FROM RECOMBINATION
Genetic variation by mutation alone tends to be a slow process (unless you are a bacteria)
Genetic recombination through sexual reproduction speeds up this process dramatically
Mechanisms:1. Crossing-over: exchange of genes between
homologous chromosomes2. Independent assortment: genes segregate
independently of each other
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VARIATION FROM MIGRATION
VARIATION
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VARIATION FROM MIGRATION
Members of different populations of the same species are able to interbreed and produce fertile offspring
As members migrate from one population to another, they take their specific genotypes with them
Over time, this causes changes in the gene frequencies of the gene pools of each population
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VARIATION FROM MIGRATION
Examples of variations in populations:1. Morphological: differences in body shapes
and colors 2. Chromosomal: in some species, there can
be a difference in chromosome number and shape; common in plants and insects
3. Protein: amino acid substitutions that do not affect protein structure