midterm 4.2

populations traits moves in a particular direciton

average organism has the highest firness extreme varisants are selected against

most common variant has the lowest fitness leas to evolution of a population with 2 or more variants (can result in speciation)

all traits come from alleles, if circumstances change quickly there might not be an allele that that help(adaptations are random)

organisms do not predict the future as there are often tradeoffs associated with a adaptation

organisims dont choose when to evolve or change

a group of organisms that in nature can interbreed and produce fertile offspring(a group hwose memebrs have the greatest resemblance)

ritual displays prepare partners to mate (birds peacocks)

if mating occurs at different times then two species in the same area may be separated in time even though they could poetentially mate (skunks)

the genitals of two different species do not physcially fit together, plants; plants

the two species are separated in space they do not contact one another and therefore do not mate

inerspecies hybrid produces is unable to mate with other byhrids or with either parent species (donkey and horse to make mule)

zygot cannot ocmplete development because it does not have all of the genes

interspecies hybrid is simply less successful and does not survive to mate in the wild

actual egg and sperm cells are unable to fuse with egg/sperm from another species

evolution of 1 or more species from an ancestral form

1. isolation:populations of original species must be iolated into gene pools
2. divergence: evolutionary change occurs to on e or both of the isolated populations
3. reproductive isolation: Evolutionary change produces reproductive isolation between these populations, preventing mating if the popuylations are unisolated

occurs when a population is separated and isolated either by distance of a barrier

the founder effect is a small population of individuals is relocated to a far away area; islands usually have few competitive species so new species will grow and adapt to the new habitat

occurs when populations live near one another but become reproductively isolated for some alternate reason (ex. african cichlids only breed to people of the same color) is more common

results from a chromosome copying mistake in plants (self fertilization in plants allow for them to create instant new species)

divergence is the timeperiod between separation of the gene pools but before the volution of reproductive isolation (sub species are created such as different dog breeds)

- this does not always lead to reproductive isolation because not all interbreeding leads to genetic incompatabilties

gradualism-diveregence occurs over millions of years
punctualism- divergence occurs over thousands of years and quickly