Species & Speciation Chapter 22 Flashcards
species are ____ from other species
reproductively isolated
species are a ___ gene pool
closed
what does the biological species concept say?
species are groups of interbreeding organisms that are reproductively separated from one another
why does reproductive compatibility mean more than just making babies?
because it also has to do with making babies who can also have babies
____ still counts as reproductive isolation
geographical separation
which is the better concept to use and why?
morphospecies because it holds that members of the same species look alike-also extended to similar DNA sequences
___ discredit the morphospecies concept
polymorphisms
some species meet ___ criteria and not ___
biological species concept; morphospecies concept
what are cryptic species?
organisms that people thought were 1 species but in reality are 2
what are some problems with the BSC?
- doesn’t apply to asexual or extinct species
- ring species & hybridization complicate it
ring species
populations that are reproductively but not genetically isolated
how does ring species occur?
gene flow through intermediate populations
hybridization
interbreeding
why does hybridization complicate the BSC?
because these different forms should be considered one large species bc they are able to reproduce and produce fertile offspring but bc they maintain their distinct appearances, natural selection works against the hybrid offspring
what is the evolutionary species concept?
different species means having different nutritional needs
what is the phylogenetic species concept?
requires that all members of a species are descended from a single common ancestor. but it’s limited
why are the ESC and PSC used?
to broaden the BSC concept
what are pre-zygotic isolating factors?
prevent fertilization from taking place
what are post-zygotic isolating factors?
when fertilized egg develops into fertile organism
behavioral isolation is a type of
pre-zygotic factor
involves specific courtship rituals, songs, etc.
gametic isolation is a type of
pre-zygotic factor
2 different species can’t mate/cross because they’re incompatible
what is mechanical incompatibility?
pre-zygotic factor
repro parts don’t fit outside of species
temporal isolation is a type of
pre-zygotic factor
plants/animals don’t come in contact with one another b/c reproduce @ different points in the year
geographic/ecological isolation is a type of
pre-zygotic factor
2 species don’t mate b/c they’re not physically located near one another
post-zygotic isolating factors usually involve
genetic incompatibility
the more ___ a pair of species, the ____ the genetic incompatibility between their genomes
closely related; less extreme
speciation is a by-product of
genetic divergence of separated populations
genetic divergence
occurs over time & causes diff. populations to become reproductively isolated (results in speciation)
partial reproductive isolation
happens when members of different populations aren’t separate species yet but enough that when crossed, their kids have decreased viability/fertility
allopatric speciation
speciation that results from geographical separation of populations
speciation not only requires __ but ___
separation; time
subspecies
when pops haven’t yet achieved speciation, but have pop. specific traits
how do populations become allopatric?
dispersal & vicariance
dispersal
when orgs colonize distance place-away from main pop
vicariance
geographic barrier comes about w/n a single pop which separates it into 2 or more isolated pops
-easier to study
allopatric populations always
lead to speciation
dispersal is a kind of __
peripatric speciation b/c orgs from mainland pop. disperse on purpose or get separated from mainland pop. by accident making their own “island population”
why is change faster in peripatric speciation?
b/c island pops. are smaller & more susceptible to drift & b/c environment different so genetic divergence goes up & speciation occurs
adaptive radiation
rapid evolution which accelerates speciation & adaptation
how does adaptive radiation come about?
ecological opportunity & potential for allopatric speciation
what is co-speciation?
speciation that occurs in response to speciation in another species
separation can occur without
actual geographic barriers
how did malaria come to infect humans?
plasmodium population with chimps could’ve been subject to co-speciation
sympatric populations
those not geographically separated
- may undergo speciation
- natural selection can explain it
why do split populations get more & more different?
mutations that eventually become fixed
gene flow inhibits
genetic divergence
we don’t know how much of speciation is ___ or ___
sympatric; allopatric
instantaneous speciation
when speciation occurs quickly
- is sympatric
- caused by hybridization
plants can form new species through
polyploidy
what has been pivotal to the evolution of plants?
genome-doubling
speciation can occur without
natural selection
-can be entirely due to genetic drift
natural selection is involved in which kinds of speciation?
allopatric & sympatric
natural selection can enhance
reproductive isolation
