evolution

• linnaeus (1735)

• linnaeus (1735)

discovery of a creator's plan through the classification of species (natural theology)

hutton (1785)

profound change is the cumulative product of slow but continuous processes (gradualism)

malthus (1798)

if the population continues to grow unchecked, eventually we will run out of resources (population trends)

• lamarck (1809)

an early explanation of mechanism of evolution; 1st to come up with the idea of evolution (inheritance of acquired characteristics)

cuvier (1810)

the history of earth marked by floods or droughts that resulted in extension (catastrophism)

lyell (1830)

geologic processes have slow, constant rates through time (uniformitarianism)

• wallace (1858)

came up with the theory of evolution via natural section independently of darwin (natural selection & father of biogeography)

darwin's 8 observations

natural variation, overproduction, struggle for existence, unique organisms, survival of the fittest, change over time, decent with modification, and common descent

mechanisms for evolution

natural selection, gene flow, genetic drift, and mutation

genetic drift

rapid changes in the number and kids of genes in a small, isolated population by chance events

founder effect

isolated individuals set up a new population that has different gene frequencies from the parent population

bottleneck effect

reduction in population size affects the gene frequencies in the surviving members; common amongst endangered organisms

gene flow

movement of genes from the population to another (gain or loss alleles in the gene pool)

stabilizing natural selection

the average trait is favored so the curve narrows (birth weight, height)

directional natural selection

bell curve shifts in one direction, either left or right, as one extreme trait is favored

diversifying/disruptive natural selection

both extreme traits are favored over the average to create a curve with two peaks and a trough in the middle (lobsters)

choice sexual selection

competition for attention of the opposite sex; ex: bird calls and dances, roaring, matting displays

contest sexual selection

competition between members of the same sex for access to the other sex; ex: direct combat between males (fights determine hierarchy)

allopatric speciation

gene flow is prevented by geographic isolation due to the environment changing or a subset of the population

sympatric speciation

occurs when new species evolve while still in the same area; not very common, results from sexual selection and polypoloidy

reproductive isolation

the inability to exchange genes among species

artificial selection

humans choose the traits they determine to be advantageous or preferable (domesticating animals)

pre-

zygotic barriers

impede mating or hinder fertilization if mating does occur

1. habitat isolation

2. temporal isolation

3. behavioral isolation mating attempt

4. mechanical isolation

5. gametic isolation

post-

zygotic barriers

prevents a hybrid from passing on genes

1. reduced viability

2. reduced fertility

3. hybrid breakdown

divergent evolution

when one species evolves into two or more species with different characteristics; will see homologous structures in the species

convergent evolution

species that are not closely related evolve similar traits; will see analogous structures