LEC 8/27 Speciation Flashcards
Natural selection works on variation already present in a population?
True, you need variation for adaption.
what is a species?
pop or group of pop, members potentially interbreed & produce FERTILE offspring, appearance is not important
DEF Speciation
process by which new species come into being
DEF new species
they originate as modified descendants of other species
what are the 3 steps in speciation
Genetic isolation, pop diverge genetically, reproduction isolation
DEF: genetic isolation
gene flow between two pop is interrupted (pop becomes genetically isolated from each other
DEF: Pop diverge genetically
genetic diff gradually accumulate between the 2 pop
DEF: Reproductive isolation
some of these genetic diff (traits) will be reproductive barriers (traits that prevent 2 individuals from interbreeding with each other
list the 3 Pre-zygotic barriers
Temporal isolation, habitat isolation, behavioral isolation.
DEF: temporal isolation
mating or flowering occurs at difft seasons or times of day
DEF: Habitat isolation
pop live in difft habitats and do not meet
DEF: Behavioral isolation
little or no sexual attraction between males and females
DEF: Mechanical isolation
structural diff in genitalia or flowers prevent copulation or pollen transfer
DEF: Gametic isolation
female and male gametes fail to unite in fertilization
what are the two post-zygotic barriers?
Hybrid inviability and hybrid sterility
DEF: Hybrid inviability
hybrid zygotes fail to develop or fail to reach sexual maturity
DEF: hybrid sterility
hybrids fail to produce functional gametes
DEF: Allopatric speciation
gene flow is reduced due to a geographical barrier “other country” squirell example
DEF: sympatric speciation
switch in the use of a resource by some individuals reduces gene flow “same country” ex with ants and apples
descent w/ modification over 3.8 billion yrs all organism are genetically related? TorF
True
how do scientists reconstruct these speciations events?
systematists, evidence and results
DEF: systematists
are the detectives of life’s history
DEF: Evidence
observable characters need to be derived (unique) and shared
DEF: result
produce a tree-like diagram called phylogeny or cladogram
is evolution a climb up ladder of progress where organism are always getting better?
No it is not. ex humans did not evolve from chimpanzees, share a recent common ancestor that was not chimp or human
DEF: Stasis
some species don’t change much for a long time. ex coelacanth (1930) the same for 80 million yrs
DEF: extinction
is the disappearance of an entire species from the face of the earth
Fact
99% of species that existed are extinct today
DEF: Mass extinctions
events that have wiped out anywhere from 50% to 95% species
DEF: adaptive radiation
event in which a group of species rapidly diversifies
DEF: convergent evolution
unrelated species develop similarities due to adaptation to similar environments
DEF: analogous characters
similar looking structures due to adaptation to similar environments not due to common ancestry
DEF: homologous characters
characters in different organisms that are similar because they were inherited from a common ancestor that also had that character
