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
