Evolution Cont'd Flashcards
is natural selection the main process behind most evolution?
yes
disruptive
type of natural selection
both extreme morphs are selected for and the average morph is selected against
ex. cameroon seed cracker birds (large/small beaks successful, medium beaks unsuccessful)
stabilizing
type of natural selection
both extreme morphs are selected against and the average morph is selected for
ex. human birth weight (7 lbs.)
directional
type of natural selection
one extreme morph is selected for
ex. TB amino acid 153 point-mutation
speciation
the splitting event of one species into 2 or more species
2 types
3 definitions
2 types of speciation
allopatric
sympatric
allopatric speciation
geographic barrier
ex. stream/Darwin’s finches
sympatric speciation
speciation that occurs in the same area
ex. birds of paradise in Papua New Guinea
3 definitions of speciation
biological species constant (we use this definition)
phylogenetic species
morphospecies
biological species constant
reproductive isolation
in nature, speciation occurs and populations no longer interbreed and produce viable, fertile offspring
phylogenetic species
smallest phylogenetic grouping of phylogeny
ex. variation in horseshoe crab species
morphospecies
based on morphology (organisms that look alike are same species)
hybrid
offspring from two different species
barriers that prevent hybridization
maintains speciation
2 types
2 types of barriers that prevent hybridization
pre-zygote
post-zygote
pre-zygote barriers
prevent formation of zygote
isolation events: habitat, temporal, behavioral, mechanical, gametic recognition
habitat
1 species is aquatic, 1 is terrestrial
ex. garder snake
pre-zygote
temporal
1 mates in late winter, 1 mates in late summer
ex. spotted skunk
pre-zygote
behavioral
bouncing tempo is species specific
ex. courtship dance of fruit-fly
pre-zygote
mechanical
genitalia doesn’t fit, 1 is clockwise, 1 is counterclockwise
ex. snail shell direction
pre-zygote
gametic recognition
egg proteins only recognize same species
ex. sea urchin
pre-zygote
post-zygote barriers
zygote forms but hybrid is unlikely to survive
isolation events: reduced viability, reduced fertility, hybrid breakdown
reduced viability
offspring don’t survive to reproductive age
ex. salamander
post-zygote
reduced fertility
offspring survive to adulthood, but can’t reproduce
ex. mules
post-zygote
hybrid breakdown
subsequent generations of hybrids are no longer viable
ex. rice
post-zygote
species
group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding