evolution and natural selection Flashcards
4 aspects of biological evolution
- heritable (descent w/ modification)
- genetic change (common ancestry)
- over generations (time)
- at population-level
natural selection
1 mechanism that drives biological evolution
phenotypic plasticity
phenotypic ability to acclimate to environments (NOT evolution)
- ex: over time adjust to high elevation
3 types of selection
directional, stabilizing, disruptive
directional selection
favors 1 extreme range of variation
- either favors left or right
stabilizing selection
favors moderate/middle range trait
disruptive selection
favors both extremes
- right and left but NOT center
homologous traits
similar appearance due to common ancestry; shared genotype
- not caused by environmental pressure
analogous traits
similar appearance due to independent evolution but similar environmental pressures; shared phenotype
- brought about by convergent evolution
convergent evolution
process that brings about analogous traits
- species develop similar appearances due to similar environmental pressures NOT common ancestry
mechanisms for evolution (4)
- natural selection
- genetic drift
- sexual selection
- horizontal gene transfer
genetic drift
change in allele frequency due to chance
- common in small populations
- ↓ diversity
2 types of genetic drift
founder and bottleneck effects
founder effect
small portion of population leaves and starts a new population
- ↓ genetic variation = ↓ genetic diversity
bottleneck effect
extreme reduction in population size due to bottleneck event (environmental disasters)
- ↓ genetic variation = ↓ genetic diversity
genetic drift always causes…
↓ genetic variation = ↓ genetic diversity
extirpation
localized extinction
- at least 1 population goes extinct
sexual selection
1 sex chooses partner based on specific traits
2 types of sexual selection
intErsexual, intrAsexual
intErsexual selection
members of 1 sex choose a mate by preference
- usually females selecting males
- “female mate choice”
intrAsexual selection
members of same sex compete w/ others for sexual access to members of other sex
- (usually competition b/w males)
why do females usually choose (intErsexual selection)?
they have a larger investment (pregnancy) and have to choose most successful male (males don’t even always know whose their offspring)
sexual dimorphism
difference in appearance b/w females and males in secondary sex characteristics (related to sex; ex: puberty changes)
sexual dimorphism is a result of ____
intrAsexual selection
example of sexual dimorphism
males are larger than females
sexual dichromatism
difference in coloration or plumage b/w males and females
sexual dichromatism is a result of ___
intErsexual selection
example of sexual dichromatism
male peacock feathers/colors
horizontal gene transfer
non-sexual movement/transfer of genes b/w genomes
- 2 organisms “swap” genetic material through cell walls
- material replaces/introduces new genes
horizontal gene transfer can occur between…
members of related AND unrelated species
rotifers
example of horizontal gene transfer; take up genetic info (DNA) from bacteria in new location before un-hibernating
microevolution
genetic changes w/in a population; mechanisms for evolution
macroevolution
evolution leading to speciation
- population becomes new species
- lots of micro- leads to macro-
3 drivers/types of speciation
allopatric, parametric, sympatric
allopatric speciation
speciation due to vicariance (geo isolation)
vicariance
geographic separation (isolation) driven by continental drift (Pangea separating)
parapatric speciation
(similar to allopatric) but has a narrow overlap of land
- inter-mating occurs but ↓ fitness
- drives isolation
which drivers of speciation are the slowest/fastest?
(slowest): sympatric > parapatric > allopatric (fastest)
sympatric speciation
speciation occurs w/in larger population; occupy the new range
- random mutations = new behaviors = behavioral isolation –> 2 diff species
- no geographic isolation = most hybridization
which driver of speciation leads to the most hybridization?
sympatric speciation
species concepts
ways species are defined
morphological species concept
morphometrics- measuring and comparing appearances
which species concept was the most dominant historically?
morphological
pros of morphological species concept
fossils records and asexual species
cons/downfalls of morphological species concept
natural variation, sub-species, subjective (human observed), convergent evolution
biological species concept
“lumpers”; if 2 individuals from 2 populations can mate and have viable offspring (can reproduce) = same species
which species concept is most used today?
phylogenetic species concept
cons of biological species concept
doesn’t consider asexual selection (no mate for reproduction), what if two populations are so isolate they will never meet?
phylogenetic species concept
“splitters”; uses DNA and genetic code to determine species
- species should be “diagnosably similar” w/ __ % DNA in common
which species concept is generally used for sub-species?
biological species concept
cons of phylogenetic species concept
vague, how much % similar DNA = enough to be same species?
- taxonomic inflation?
taxonomic inflation
inflating too many species; over speciation- can be good for awareness (less there are, more important it feels to save them)
adaptive radiation
lineage rapidly diversifies w/ new lineages w/ new adaptations
- short period of time = ↑ diversity = ↑ # of species in 1 population
3 instances/causes of adaptive radiation
- mass extinctions (new/empty niches)
- invasion of under-used/un-used land and resources
- development of key innovations to a species (ex: bird wings)
