Experimental Ensembles with the LM/LMK Past and Future Work Susanne Theis.
Bio 163 patterns of evolution and genes lmk 2013
Transcript of Bio 163 patterns of evolution and genes lmk 2013
Patterns and Processes of Evolution
Macroevolutionary Patterns Large-scale (more than a single species) Occurs over long periods of time
Microevolution Small-scale (within a single species) Forms variations in populations
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Speciation – Isolating MechanismSpecies – group of organisms that interbreed to
produce fertile offspring under normal conditions –
share a common gene poolSpeciation – formation of a new species
Requires reproductive isolation – organisms do not interbreed; gene pools become separateBehavioralGeographicTemporal
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Patterns of Extinction
Background Extinction – “business as usual” extinction – slow and steady
Mass Extinction – many species become extinct over a short period of timeCauses:AsteroidVolcanic eruptionsMoving continentsChanging sea levels
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Rates of Evolution
Gradualism – change in species is slow and steady
Punctuated Equilibrium – long periods of stability followed by short periods of rapid change
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Patterns of Macroevolution:
Adaptive RadiationA single species evolves into many speciesOften occurs when a niche opens up
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Organisms come to resemble one another but evolved differently
Source of analogous structures!
Examples: Dolphins and sharks Marsupials and
mammals
Patterns of Macroevolution:
Convergent Evolution
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Coevolution
Organisms with close ecological relationships evolve togetherPollinators and flowers
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The Role of Genes in Evolution
In terms of genetics, evolution is the change in the frequency of alleles in a population’s gene pool
Natural selection leads to that change
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Genetic DriftRandom change in allele frequency –
changes in the gene pool of a small population due to chance
Types of Genetic Drift: Bottleneck Effect – change in allele
frequency following dramatic reduction in population size
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Genetic Drift Founder Effect – small group colonizes a
new habitat
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Molecular Evolution
Molecular Clocks – use mutation rates in DNA to estimate time two species have been evolving independently
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Molecular Evolution: Hox Genes
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Genes which control an organism’s basic body plan Anterior/posterior ends Limbs, wings
small sequence changes during embryological development can cause large changes in adults