Mechanisms (Evolution) Flashcards
traits
can be preferentially selected for or against which can cause rise of a new species
disruptive selection
two extreme traits are preferentially selected for
moderate traits slowly become less common and then disappear
stabilizing selection
extreme traits are preferentially selected against
moderate traits become more common and extreme traits become less common and slowly disappear
directional selection
when a trait moves slowly over time towards one extreme
4 ways of evolving
divergent, convergent, parallel, coevolution
divergent evolution
when two or more related species become more and more dissimilar
ex. red fox and kit fox
red fox and kit fox
example of divergent evolution
evolved differently because of their environments
red fox- farmland and forests
kit fox- deserts
convergent evolution
unrelated species become more and more similar
adapting to the same environment
American cactus and African euphorbia
example of convergent evolution
adaptations help to store water and protect themselves from predators
parallel evolution
2 species with similar characteristics evolve similar traits in a similar timeframe
might be due to being exposed to similar/identical selective pressures
aren’t necessarily interacting with each other
coevolution
joint evolution of 2 or more species in close interaction
evolution of predators and their prey
example of coevolution
bats and the flowers they pollenate
example of coevolution
bats adapt to be better at retrieving pollen
flowers adapt to be lighter in colour so the bats can see them better
species
the event by which a new species arises
Ernst W. Mayr’s definition of a species
- can breed or reproduce with one another
- produces offspring of both sexes that are capable of reproducing offspring of both sexes
- do not ordinarily breed with organisms from another group
requirements for a mating
have to be in physical contact
mechanism for speciation
geography
natural selection leads to speciation
requirements for the rise of a new species
- must arise independently from an existing species
2. cannot breed with cousins in the same species
reproductive barriers
- pre-zygotic
- post-zygotic
ensure that inbreeding doesn’t happen- essential in the rise of a new species
pre-zygotic barriers
all the things that can prevent mating
examples of pre-zygotic barriers
geographical isolation
ecological isolation
ethological isolation
geographical isolation
cannot mate because they are not in the same geographical area
ecological isolation
can be in the same geographical are but different niches
ethological isolation
behaviour based
not sexually attracted
post-zygotic barriers
only in hybrid species
ex. mules- cannot successfully have offspring
4 types of speciation
- allopatric
- peripatric
- parapatric
- sympatric
allopatric speciation
when a geographical location is physically divided
selective pressures in different geographical locations cause sub-populations to evolve differently
earthquake, moving glaciers, drifting continents
peripatric speciation
no geographical division
a new colony is established
new colony cannot go back (for some reason) and therefore don’t mate with initial population
parapatric speciation
new colony in continuous or adjacent to the population it divided from
ex. mountain goats that moved farther up the mountaine
sympatric speciation
ethological pre-zygotic barriers
based on mating rituals
no geographical barriers
ex. bowerbird that builds nests to attract females
new species within the existing population
