test 2: speciation Flashcards
gene pool
alleles in a population
large gene pool
good variability, can survive
small gene pool
less variability, less likely to survive
harvey-weinberg equilibrium assumptions (artificial baseline)
- large pop size
- no migration
- no mutations
- random mating
- no natural selection
why do we have an artificial baseline for harvey-weinberg?
represents stability of gene pool, any change usually results in evolution
harvey-weinberg equilibrium equation
p^2+2pq+q^2 = 1 p+q = 1
individual scale = natural selection
pop scale = evolution
types of polymorphism
genetic and balanced
genetic polymorphism
different genetic alleles, wide variation
balanced polymorphism
stable frequencies of two or more forms, heterozygote advantage (ex: sickle cell anemia)
natural selection
- adaptions as a result of selective pressure
- relative contribution to next generation’s gene pool
- acts on physical traits, metabolism, physiology, behavior
3 modes of natural selection
directional (change fur colour), disruptive (multiple fur colours), stabilizing (one very specific shade of certain colour)
directional
selection happens for extreme, during environmental change
- competition from other species (ex: peppered moth)
graph: peak shifts
disruptive
intermediates are selected against
ex: peppered moth in region with varied pollution
graph - peak splits into two
stablilizing
selection against extremes, prefers intermediates
happens in stable environments
ex: human birth weight a specific range
graph - peak is compressed
mating
intrasexual, intersexual,
intrasexual
one sex competes for the other
- direct comp (fighting)
- males patrolling large group of females
- harem system
intersexual
females choose showy male
- traits related to good genes
- can also be resource related
- show sexual dimorphism (male “choose me”, females more bland)
circumventing the competition
cheaters: sneaker squids
successful enough to not die out, but not enough to drive away dominant males
morphological species concept
concept is inaccurate and not reliable
(group of organisms that have same morphology = anatomy) easy to make mistakes
biological species concept
group of actual or potential interbreeding natural populations, fertile offspring & reproductive isolation
- natural pop with some gene flow
- concept has problems, but better than morphological species concept
allopatric speciation
populations are separated geographically, over time you get genetic drift/new mutations and selection for particular environment
sympatric speciation
populations in same area
- habitat difference
- host specificity (mutations in hosts can cause a new species)
- chromosomal speciation (chromosome changes result in new species)
pre-zygotic barriers
habitat isolation, temporal, mechanical, gametic, behavioural
post-zygotic barriers
reduced hybrid viability, reduced hybrid fertility, F@ generation feeble/sterile
habitat isolation
never meet
temporal isolation
different reproductive times
behavioural isolation
doing the right dances, having the right morphs
mechanical isolation
pieces need to fit together
gametic isolation
egg and sperm, enzymes need to cooperate
reduce hybdrid vitality
offspring won’t survive to mating season
reduced hybrid fertility
offspring is sterile, cannot reproduce
hybrid breakdown
survives one generation, but not 2nd
gradualism
species change over time, one form evolves slowly into a new form
punctuated equilibrium
long periods of no change; short periods of evolution with major environmental change; once sub species buds off it changes little
phylogenies
compare relationships to determine evolutionary history of species or group (who is closer, when did the brand off occur…)
systematics
classification and evolutionary relationship use taxonomy
hierarchy of classification (large to small)
domain kingdom phylum class order family genus species
scientific names are binomial
first part - genus
second part - species
who set up phylogenetic trees?
linnaeus
- each level called a taxon
- done both for sake of knowledge and problem solving
analogy
convergent evolution (phylogenetic trees always divergent)
homology vs analogy
homology - true shared ancestry, divergent
analogy - similarity, convergent
depends on feature being examined (ex: pentdactyl limb vs development of flight)
