Processes of Evolution + change in populations

exam 3

Wallace + Darwin - broad observations about life

many ways for organisms to be suited for their environment (moths camouflage)

many shared characteristics (genetic code within a species - moths scaly wings)

diversity of life is rich (moths is a biodiverse taxon)

James Hutton

Layers!! - sediments are deposited predictably

Plate tectonics and mountains (erosion, weathering, and gravity lead to deposits and form layers)

Charles Lyell

present is key to the past!!! - uniformitarianism (earth is old / continuous processes)

Fossilization

bones were at one point sedimented over, and organic material became replaced with inorganic material, through the process of erosion it is exposed

relative dating - the deeper the fossil, the older it is

radiometric dating - carbon dating (how much C14 is left in a fossil, as they no longer take any in just release it)

Fossilization - Environment and Anatomy

have to be buried to fossilize, soft body won’t fossilize (need bones/hard shell)

Georges Cuvier

older fossils have less in common with current animals

the closer fossils are in the stratigraphic record the more similar they are

Jean Baptiste Lamarck

Species come from other species through time

Believed this was due to use/disuse and the inner want (was wrong) - giraffe offspring have longer necks because the parents wanted to reach higher

Darwin and his 3 ideas

Variations exists everywhere, heritable traits are passed to offspring, and more offspring are born than can survive and thrive

Variation is the raw material of evolution

some phenotypes are better in certain distinct environments

descent with modification

more variation in each generation as heritable traits get passed down - common ancestry

Natural selection

having better traits in an environment means that individual is more likely to survive and pass down those traits than others

artificial selection (breeding for specific traits)

Evolution by natural selection

1) variation in traits

2) heritability

3) beneficial trait means a survival advantage

4)survival advantage means more reproductive opportunity

5) more reproductive opportunity means a greater proportion of offspring in the next generation with said beneficial trait

Example - exploiting sand and mud substrates of Nebraska with mouse pens

Sand pen environment or Mud pen environment - variation of fur color in each (half sand half mud in each)

selection against non local mice was observed - sand mice survived in the sand pen while a majority of the mud mice died off (same was seen in the mud pen)

Evolutionary theory’s finer points

cladogenesis, population, microevolution, macroevolution, behavioral traits/physical traits, speed of evolution, and phenotypic plasticity

Cladogenesis

no goal or set endpoint in evolution

Populations / generations / offspring

smallest unit of evolution

evolutionary time (individuals don’t evolve)

currency of evolution (more offspring live to reproductive age)

Microevolution

change in allele frequencies between generations

Macroevolution

small genetic changes lead to morphological changes (selection acting on phenotype)

Behavioral traits / Physical traits

equally visible to selection

domestication (behavioral) - selection for a behavior (wild foxes) can change genes → domestication syndrome

Speed of evolution

can vary greatly (usually slow but not always)

rates determined by : selective pressure, generation times, standing variation(options to evolve), and mutation rates

soft selective sweep

variation existed, but now in a new environment

selective pressure driving the evolution of bees - rapid spread of beneficial trait

Hard selective sweep

new variation present in an environment - new mutation for less melanin in skin color

protection hypothesis, folic acid hypothesis, vitamin D hypothesis

Phenotypic plasticity

an individual acclimating to their environment and expressing a certain phenotype with no change in genes - based on environmental cues

impede evolution - disrupting the genotype phenotype link results in lowered rates of evolution

promote evolution - allow colonization of new habitats increasing the rates of evolution due to novel/plastic traits