Species and Speciation Flashcards
define speciation
origin of new species is at key point where microevol intersects macroevol
What causes the formation of new species
repro isolation
define species
repro compatible and cannot interbreed wit other pops
what allows repro compatability
gene flow
what causes repro incompatability
dec gene flow btwn pops so pops can diverge in allele freq by drift or NS or both and become repro isolated
define repro isolation
bio factors/barriers that keep 2 species from producing viable and fertile offspring
what is the bio species concept
groups of actually or potentially interbreeding pops which are repro isolated from other such groups and produces viable, fertile offspring…absence of gene flow between pops
mechanisms of isolation
temporal/habitual, ethological/behavioral/sexual selection, mechanical, incompatability, hybrid inviability, hybrid sterility, hybrid breakdown
which mechs of isolation are prezygotic
temporal/habitual, ethological/behavioral/sexual selection, mechanical, incompatibility
which mechs of isolation are post-zygotic
hybrid inviability, hybrid sterility, hybrid breakdown
which mechs of isolation are pre mating
temporal/habitual, ethological/behavioral/sexual selection
which mechs are post mating(mating is attempted)
mechanical, incompatibility, hybrid inviability, hybrid sterility, hybrid breakdown
habitat isolation
live in/on diff habitats
flies on apple vs flies on peach
potential mates, but do not meet
temporal isolation
mate in diff seasons/time of day
potential mates but do not meet
behavioral isolation
diff courtships shows…mates not chosen by females
mechanical isolation
mating attempted, but physically can’t do it. 2 snails having diff chirality..genital openings don’t match up
gametic isolation
incompatible egg and sperm molecularly
lock and key for species-species interaction
define prezygotic barriers
impede mating, or hinder fert, or prevent attempted mating
define postzygotic barriers
after a zygote is formed and fert is successful
reduced hybrid viability
fert occurs but hybrid offspring is weak, sickly, can’t rlly survive well
reduced hybrid fertility
vigorous but sterile
mules–> able to survivie fine but can’t mate with other mules
hybrid breakdown
F1 hybrid are fine, but a backcross w/ organisms of 1 or other parental species causes recess alleles to be homozygous so less fit and sterile in F2
only affects F2 and later
limitations of bio species concept
doesnt apply to fossils or asexual organisms
morphological species concept
body shape and structural features w/o taking into account repro isolation
used for fossils alot
subjective
ecological species concept
ecological niches, ex. polar bears and grizzlies
phylogenetic species concept
defines species as smallest group of indiv that share a common ancestor forming 1 branch of the tree of life
based on dna seq
define sympatric speciation
subset of a pop forms a new species w/o geographic separation… still living in same region
define allopatric speciation
more common
pop forms a new species while geographically isolated from its parent pop
what are the 2 types of allopatric speciation
vicariance and dispersal patterns
vicariance
barrier is being formed while speciation occurring
population preexists and occupied both areas before but smth like a road or river intervenes and separates the two areas
dispersal
2 diff islands, 1 large pop on one island, some migrate to other island and distance acts as barrier if no more migration
how is speciation maintained in sympatric pops
habitat diff
polyploidy
sexual selection
habitat diff
apple maggot flies on domestic apples and on smaller native fruits…flies emerge and return to fruit they were born in
autopolyploidy
both chromosomes from same species
if all indiv in original pop are diploid, if cell div error occurs now tetraploid
tetraploid produces diploid gametes and if gametes mate then form a new species that is 4n
tetraploid isolated from diploid
allopolyploidy
chromosome sets are derived from diff species
fertile w/ each other but sterile to other species
exhibit characteristics of both parents…a blend
new species has diploid chromosome number equal to the sum of diploid chromosome number from each parent
diploid 2n=6 + diploid 2n = 4 –> offspring 2n = 10 that is viable and fertile
sexual selection
fish with red and blue backs
define hybrid zones
regions where diff species w/ incomplete repro barriers mate and produce hybrids
yellow and fire bellied toads
enables us to study the process of speciation and mech of repro isolation
repro barriers are incomplete
when hybrids don’t become repro isolated from parent species….what are the 3 possible outcomes
- reinforcement
- fusion
- stability
reinforcement
NS favors indiv of 1 species to mate w/ indiv of same species….eventually limit hybrid zone
keeps 2 distinct species
fusion
speciation starts but stops
collapse of repro barrier
stability
formation of stable hybrid zone occurring cont
key points on speciation
bio species concept emaphsizes repro isolation
speciation can take place w/ (allopatric) or w/o (sympatric) geographic separation
hybrid zones reveal factors that cause repro isolation and insight in speciation process
speciation can occur rapidly or slowly
speciation can occur through mutation (polyploidy), drift (geo iso), and/or selection
speciation can result from changes in few or many genes
all organisms are related to each other via tree of life
trueeeee
what does tempo of speciation depend on
lineage and env
