unit 1: evolution Flashcards
living species show
common ancestry
do individuals evolve?
no, populations evolve
geographic distribution of living organisms
biogeography
change in the frequency of alleles in a population
evolution
loss of all variants except one
fixation
traits whose similarities are explained through common ancestry
homology
tendency for genetic variants that enhance fitness to go to fixation
natural selection
existence of multiple variants within a population
polymorphism
fossil taxa that have some of the derived traits of a living group
transitional fossil
hierarchical nesting of biological taxa
classification
type of reproduction that yields a tree for
asexual reproduction
homogenizes populations
sex
glues local populations together
gene flow
lineages isolated for long enough
lose ability to interbreed (speciation)
all the descendants of an ancestral lineage
clade
represents lineage splitting
node
remove tips or clades from tree without changing the topology
pruning
list of all clades in a tree
topology
biological classifications
taxonomy
if there are multiple hypotheses, the most likely is the most simple
parsimony
same trait develops separately in 1 or more lineages
convergent evolution
trait lost and never reevolves
reversal
recency of common ancestor
relatedness
are all living species equally evolved?
yes
unethical attempts to increaser the frequency of desirable traits
eugenics
no change in underlying heritable traits
phenotype plasticity
particular variant of a gene
allele
place in genome where alleles are encoded
locus
majority of traits are
continuous
more than one allele at given locus
polymorphic
no new alleles, mating is random, all alleles equally fit, population is infinitely large
harvey weinburg assumptions
2pq
equation for frequency of heterozygote
gains and losses are
equally likely
changed caused by the environment leads to
plasticity
allele that enhances fitness
beneficial mutation
allele that decreases fitness
deleterious mutation
selection that arises when one allele consistently raises fitness, beneficial allele will be fixed eventually
directional selection
most traits are
genetically complex
in haploids, allele frequency equals
genotype frequency
x+y/2 =
frequency of A1
z+y/2 =
frequency of A2
occurs when genotypes differ in fitness
directional selection
average number of offspring produced by one genotype relative to another
relative fitness
violates assumption that populations are infinitely large, allele frequency always changing
genetic drift
population lineage shrinks to small size for a period, decreasing variation
genetic bottleneck
genetic drift only overpowers directional selection if
small allele frequency and small population
frequency of deleterious alleles that have accumulated in a population
genetic load
compare homozygote to other homozygote (compare offspring or reproductive ability)
relative fitness
explains adaptive change
directional selection
when no genetic variation
evolution stops
the rate of mutations is independent of
need
when differing fitness, causes fixation of favored, variation replaced by mutation
directional selection
probability that an allele is fixed under drift is
equal to its frequency
genetic drift means
small populations have less genetic variation and are vulnerable to pathogens
result in genetic disorders
deleterious alleles
influenced by mutation rate and strength of selection
frequency of a disease
tend to have higher prevalence because mutant alleles can hide in carriers
recessive disease alleles
expected frequency of dominant lethal alleles is equal to
mutation rate
can result in different frequencies of disorders
genetic drift
heterozygotes have highest fitness, conserves both alleles in a population
overdominant selection
both alleles preserved
polymorphism
extent to which variation in a continuous trait has a genetic basis
heritability
is all variation heritable
no, there is a mix of genetic and environmental variation
mean of reproducing individuals minus mean of whole population
strength of selection (s)
mean of offspring generation minus mean of parent population
response to selection (r)
heritability
h^2
breeders EQ
r = h^2 x s
individual who is heterozygous for disease
carrier
selection in which heterozygote has lowest fitness
underdominant selection
alleles shared between closely related species
trans-species polymorphisms
selection that favors trait values at the extremes
disruptive selection
shape of distribution when disruptive selection and assortative mating
bimodal
selection that disfavors extremes, favors average individual
stabilizing selection
complex traits
multiple coordinated components
dramatic traits in an organism that decrease and organisms variability but evolve because they are favored by sexual selection
exaggerated secondary sexual selection
secondary sexual characteristics become exaggerated due to feedback between male traits and female preferences
runaway sexual selection
movement to breed for desirable traits, unethical
eugenics
does heritability tells us about differences between groups
no
occurs when fitness is highest near the middle of the distribution (common when on stable adaptive peak)
stabilizing selection
reduces trait variation
stabilizing selection
increases trait variation
disruptive selection
traits that reduce individual ability to survive, caused by
sexual selection
fitness gain from mating outweighs fitness cost for survival
sexual selection
speciation driven by geographic isolation
allopatric speciation
phenomenon in which individual organisms tend to mate with other organisms with traits like theirs
assortative mating
species defined by ability of members to reproduce and interbreed
biological species concept
gradual changes in traits as a function of geo separation
clinal variation
genetic variation among geo separated populations where each population contains genetically similar individuals
discrete variation
2 organisms no longer able to reproduce
intrinsic reproductive isolation
view that species are defined by clades
phylogenetic species concept
splitting of ancestral species into distinct species
speciation
speciation without geographic isolation, RARE, driven by assortative mating
sympatric speciation
females choose desirable males and have desirable sons, increasing fitness
female choosiness, leads to sexual dimorphism
species are populations, applies only to sexual taxa
biological species concept
species are taxa, products of evolution
phylogenetic species concept
subspecific groups need to be genetically distinct
subspecies on tree
focuses on the evolution of reproductive incompatibility
speciation biology
if a mutation decreases reproductive ability
the allele is selected against
trait that is beneficial in a species for one function but originated to fulfill a different function
expatation
evidence that all cellular life shares common ancestry
proteins, L amino acids, genetic molecules, genetic system, metabolic system
reduction of CO2 to organic molecules using light energy, no O2 released
anoxygenic photosynthesis
theory that mitochondria and nucleus both evolved within the same eukaryotic lineage
autogenous hypothesis for eukaryotes
clade of bacteria characterized by ability to perform oxygenic photosynthesis
cyanobacteria
phenomenon in which prokaryotic cell comes to live and divide within a host cell
endosymbiosis
theory that mitochondria are derived from endosymbiotic bacteria taken up by host cells whose genome is found in the eukaryotic nucleus
endosymbiotic hypothesis for eukaryotes
cells with outer membrane and internal membrane bound organelles
eukaryotes
theory for development of eukaryote internal compartments that suggests outer plasma membrane or prokaryote ancestor was pushed outward
inside out theory
most recent common ancestor of all life
LUCA
theory for the development of eukaryotes that starts with production of vesicles within cytoplasm by internalization
outside in theory
reduction of CO2 to organic molecules using light energy in which water is the electron donor, 02 gas released
oxygenic photosynthesis
cells with an outer membrane containing no internal membrane structures
prokaryotes
rapid expansions of clades to give rise to many diverse species adapted to different ecological niches
adaptive radiations
a clade of tetrapods characterized by an egg that can persist on dry land, complex lungs, protective skin
amniotes
a clade characterized by exoskeletons
arthropods
specialized filter feeding structures found in whales
baleen
trait of having a single plane of symmetry
bilateral symmetry
first period of the paleozoic era, rapid radiation of bilaterians
cambrian period
cycle of measures and countermeasures between interacting lineages
evolutionary arms race
trait that allows a lineage to occupy a new niche
key innovation
clade of eukaryotes characterized by flagellum
opisthokont clade
traits in a lineage that existed prior to a transition that give that lineage some advantage in a new ecological niche
pre adaptations
rapid expansions of clades to give rise to many species
radiations
idea that populations must keep adapting via directional selection because other species with which they interact are also constantly evolving
red queen principle
clade of vertabrates characterized by four limbs and lungs
tetrapods
theories to explain how life developed
self replicating RNA, protocell, surface associated chemical ecosystem
was there life before LUCA
yes
how do prokaryotic archaea differ from bacteria
membrane chemistry, genetic systems (similar to euks)
only cells that can do oxygenic photosynthesis
cyanobacteria
more cells in humans are
bacteria
ozone layer built up, high oxygen levels, chemical env of earth changes
results of cyanobacteria
mitochondria derived from
alpha proteobacteria
chloroplasts (plastids) derived from
cyanobacteria
two competing theories for mitochondria
endosymbiotic (own genome) and autogenous
merger of bacterial and archaeal lineages
eukaryotes
oxygenic photosynthesis, invasion of land, agriculture and tech
evolutionary events that changed the planet
adapted to tree climbing, mainly eat fruit
arthropoids
are modern chimpanzees the ancestors of humans
no, they share a common ancestor
apes remained in forested adaptive zones, resulting in
stabilizing selection
homonins (human ancestors) transition to more open grassy environments, resulting in
directional selection
hypotheses for the evolution of bipedal movement
looking for predators or prey, carrying stuff and throwing, more efficient
gradual shift to meat eating then hunting using rocks
scavenger hypothesis
resulted in sweat glands, lighter frame, longer legs, less hair
hunting in daytime african savanna
selected for overarm throwing (result of clasping hands, binocular vision, shoulder flexibility)
hunting
required technological and social coordination, led to tools, larger brain, true language
hunting
face muscles, white eyes, laughing, crying, democracy
physical and behavioral traits of humans
technology and teamwork led to
homonin migration
recent spread of humans explains why
genetically homogeneous and why genetic diversity decreases with distance from africa
is the homonin clade tree like
no, very complex evolution
Fst
measure of genetic differentiation between populations
why does reproductive isolation not typically evolve within a single population?
Because individuals that cannot mate with other members of their population generally have lower fitness
What is the most important role of geographical isolation in allopatric speciation?
The splitting of the ancestral population into geographically isolated regions prevents them from exchanging genes
What provides the best evidence of universal common ancestry?
Traits that are not obviously essential or optimal yet they are still shared by all cellular life
how long ago did life originate on Earth?
4 Ga
what were important effects of oxygenic photosynthesis?
The accumulation of ozone which shielded the earth from ultraviolet light and helped make land more easily colonized, The “rusting” of the oceans as dissolved Fe(II) was oxidized into reddish Fe(III), A change to the atmosphere that allowed for the evolution of large aerobically respiring species such as eukaryotes
What character is was NOT likely to be present in LUCA, the last universal common ancestor?
Aerobic respiration
What is the difference between oxygenic photosynthesis (OP) and anoxygenic photosynthesis (AP)?
In OP oxygen in H2O is the electron donor; in AP H2S is the electron donor
responsible for cycling of elements such as C, N, S, and Fe
bacteria
Where does the nucleus come from under the outside in model
Internalization of the plasma membrane
Where does the nucleus come from under the inside-out model?
The original cell, which became surrounded by the cytoplasm
What about the recently discovered Asgard archaea, the closest relatives of eukaryotes so-far discovered, supports the inside-out theory
The cell have extracellular protrusions that interact with ectosymbiotic prokaryotes
What trait(s) differentiates humans from other great apes
bipedality, knee locking, twisted upper arm
About when did anatomically modern humans migrate out of Africa
100 Ka
sexually dimorphic means likely
polygamy
Which is the best explanation for why exaggerated secondary sexual characteristics are more common in males than females
Because males often differ greatly in mating success, selection more strongly favors traits that improve mating success (even if they lower survival)
What does an internode on a phylogenetic tree represent
A set of local populations linked together by enough gene flow that they tend to remain genetically similar
What does a node on a phylogenetic tree represent?
When the descendant lineages first became genetically isolated, splitting of ancestral population lineages, and last common ancestor of the clade
all the descendants of a particular ancestral lineage
clade
The rate at which a particular kind of mutation occurs is independent of the fitness of the resulting allele
true
Is a change in the environment necessary for evolution by directional natural selection
no
explains why organisms tend to be well adapted, can only act on loci that have at least two alleles segregating, requires genotypes differ in fitness, non random
directional selection
What needs to apply for a trait in two species to be homologous
two traits are homologous if they derived from the same evolutionary origin
what type of disease allele occurs at the highest frequency (under directional selection)
large gene, recessive, mildly deleterious
Why does local inbreeding increase the incidence of genetic disorders
It lowers the population size, increasing the rate of genetic drift AND it leads to more homozygous individuals who will express recessive genetic disorders
eugenics fails to consider
environment
genetic drift can cause fixation of deleterious alleles, population might lose so much variation all are susceptible to same disease, beneficial alleles may be lost despite being favored
problems with small populations
