midterm 1 vocab Flashcards
what are the steps to the scientific method?
observation, hypothesis, measurements, results, conclusion (accept)
goal of stats
make strongest conclusion possible with limited information
2 main uses of stats
estimation (descriptive) and hypothesis testing (inferential)
population
total “universe” of all possible observations
sample
set of characteristics that make up subset of the population
variables
characteristics of individuals (age, color, etc.)
data
measurements of variables made on a sample (yellow/purple, male/female, etc.)
types of variables
numerical/quantitative or categorical/qualitative
types of numerical observations
continuous (range) or discrete (only select data values, counting)
types of qualitative data
nominal (no order) or ordinal (ordered)
what determines the type of stats test used?
type of variables and number of treatments
4 reasons why the sample can differ from the population
imprecision error (tools/tech), biological variability, mistakes (user error), non-representative data (bias)
bias
systemic differences between sample estimations and true population characteristics
random
every individual has an equal and independent chance of being selected for sample
purpose of random sampling
reduce bias and spread experimental error over all observations/treatments
types of bias
order, seasonal (only observing during a certain time of year), observer (Menke is a better evology info observer)
descriptive stats
describing a population based on sample data
what does descriptive stats measure?
central tendency (mean, median, mode) and spread (SD, variance, range)
what makes a good hypothesis?
identification of dependent and independent variables and is testable (can be run through tests) and falsifiable (can be proven wrong)
independent variable
predictor or explanatory, causes a response
dependent variable
response, the effect one is interested in
what does hypothesis testing do?
compare means while considering spread and sample size
calculates the probability of observing the results assuming the null hypothesis is true
what does the p-value represent?
probability
when can we reject the null hypothesis?
when the p value is less than 5%
t-tests are for testing __ categories
2
ANOVA tests are for testing __ categories
3 or more
what are mechanisms for evolution (changes in allele frequency)?
natural selection, sexual selection, mutations, genetic drift, bottlenecks, and founder effects
what are founder effects?
when a small colony of the original population becomes its own separate population, leading to a reduced amount of genetic variation bc the group is small (violates “large” HW)
not adaptation!
what are bottlenecks?
a population’s size is reduced for one or more generations, leading to reduced genetic variation (violates “leaving” HW)
not adaptation!
what is genetic drift?
the random occurrence of shifts in allele frequency over time
not adaptation!
what is gene flow?
movement of individuals to/from a population (violates “leaving/coming” HW)
what is natural selection
mechanism of evolution that promotes adaptation for biological fitness (violates “advantageous genotypes” HW)
what are mutations?
where genetic variation comes from! random changes in genetic material
what is a species?
individuals who can interbreed
population
individuals in the same location that can interact and interbreed
what is the result of evolution?
genotype and environment -> development of phenotype
what is an allele?
multiple forms of a given gene that result in the production of different forms of a protein specified by that gene
A POPULATION IN HW EQ. IS NOT _____!!
EVOLVING
why do we use HW if it never really occurs?
it can serve as a null hypothesis in evolution studies and is an approximate mathematical model
natural selection acts on ___
populations!
changes in individuals over time as a population
effects of evolution are seen in ___
populations and species
evolution does not necessarily lead to ___
adaptation
evolution isn’t purposeful
microevolution
changes in allele frequency within a population
macroevolution
large evolutionary changes beyond the formation of a new species (origin of mammals)
when does natural selection occur?
when there is variability that is heritable and that influences fitness
scientific theory
body of statements that is strongly supported by all evidence we know of and explains some aspect of nature
ecology
the study of interactions between organisms and their physical and living environment
proximate factors
direct cause of a biological process/phenomenon
ultimate factors
deeper cause of a phenomenon that explains when it occurs
organismal level
level in hierarchy of biology pertaining to the individual
population ecology
study of the interactions between a group of individuals of a given species and their environment
ecological community
a group of coexisting species
ecosystem
all the biotic and abiotic components of a community
biosphere/ecosphere
all ecosystems on Earth
biotic
biological factors
predation or competition
abiotic
physical factors
temperature or pH
environmental science
the study of humans’ impact on the environment
adaptation
a trait or characteristic that increases a individual’s fitness in a specific environment
evolutionary fitness
an individual’s ability to survive and reproduce as determined by its characteristics
selection pressure
biotic and abiotic environmental factors that determine fitness
homeostasis
regulatory mechanisms that help an organism stay within a given set of biological parameters/limits
who can have fitness?
individuals
predictions
a result or observation that we can expect if the hypothesis is true
falsifiable
trait of a good hypothesis that allows for data/observation to prove it is incorrect
adaptations are ___ created
evolutionarily
what did Darwin establish?
natural selection as a mechanism for evolution via adaptation to promote evolutionary fitness
natural selection occurs to…
populations
NOT INDIVIDUALS!
p = ___ allele
dominant
q = ___ allele
recessive
evolution
changes in allele frequency
HW equilibrium (math)
p^2 + 2pq + q^2 = 1.0
when is HW equilibrium applicable?
when no mutations or gene flow occur, the population is infinitely large and randomly mating, and there are no advantageous genotypes
genetic drift
random change in allele frequency
gene flow
net movement of alleles because of individuals’ movement in/out
s
selection coefficient, proportion of a specific genotype not represented in the next generation
directional stability
favoring one side of the phenotypic bell curve
one extreme trait
stabilizing selection
intermediate trait is favored in phenotypic bell curve
disruptive selection
favoring extreme traits over intermediate ones
evolutionary trade-offs
when a given characteristic has fitness advantages, but also costs
think of colors and reflectance of guppies
why is genetic drift not darwinian?
occurs by chance, not because of natural selection
chronic genetic drift can lead to …
allele loss and/or fixedness
gene flow can do what to natural selection?
promote or slow the process
incoming/outgoing individuals alter allele frequencies
phenotypic plasticity
ability of organisms to present different phenotypes in different environments
heritability
cause of phenotypic variation because of genetic differences between individuals
rate of evolution is determined by …
changes in character over time
strong selective pressures can lead to ___ and eventually ___
more distinct local changes in species and an ecotype
ecotype
genetically distinct population that has adapted to a local environment
limits of natural selection
physical and chemical limitations (like size)
evolutionary landscape
3D model of fitness and particular genotypes that identify best genotypes for evolutionary fitness by tallest peaks
example of organisms with sex roles reversed
jacanas or seahorse
male incubates egg (more energetically invested), females compete and are more aggressive
sexual selection occurs when:
there’s a heritable variation of a trait that influences mating success or fertilization success
which sex often experiences stronger sexual selection?
the competing sex
logic: non-competing sex can get with whoever they want, but competing one is limited. there’s more selective pressure on the limited one to pass on genes
elaborate traits usually occur in the ___ sex
competing
sexual selection can occur:
before or during/after sex
intrasexually or intersexually
example of intrasexual selection before mating
mooses
male-male or female-female competition for access
example of intersexual selection before sex
peacocks
display by competing sex for mating choice by non-competing sex
example of intrasexual selection d/a sex
frogs
compete to have their sperm fertilize egg
example of intersexual selection d/a sex
“cryptic mate choice”
female chicken can choose which sperm fertilizes their egg after sex
intrasexual selection
individuals within a sex compete DIRECTLY for access to mates and their gametes
examples of evolution of traits for intrasexual selection
weaponry, fast sperm, sexual size dimorphism
sexual size dimorphism
competing sex is larger
intersexual selection
indirect competition for access to mates and their gametes
what traits can help intersexually selecting organisms win access to mates?
mating displays and signals, courtship behavior, or genitalia
sexual selection is the result of:
direct or indirect competition for mates
benefits of sexual reproduction must ___ ___ ___
overcome non-trivial costs
pros of only passing on 1/2 of genetic material must be better than the cons of potentially risking survival
think: color of guppies finding balance between mating visibility and predation avoidance
sexual selection often results in traits that ___ natural selection
oppose
where does natural variation come from?
mutations!
process of including mutation in population
created, generates alleles, natural selection hopefully favors it, adaptive trait selected
selection ___ ___ ___
edits existing variation
genes are:
composed of DNA and specify how to build proteins
what are mutations caused by?
DNA copying errors, chemicals, or ionizing radiation
what is important about ionizing radiation?
can’t reach gametes
frequencies of mutation can change due to:
meiosis/recombination, natural selection, genetic drift, or gene flow
mechanisms that DECREASE variation
stabilizing selection, inbreeding, and genetic drift
“silent” or “synonymous” mutations
don’t change the amino acid
“nonsynonymous” mutations
change amino acids and potentially the function of the following protein, can then be acted upon by NS
what are the structural mutations that can occur?
deletion, duplication, inversion, fission, or fusion
mutation rates are very low! so…
mutations likely won’t change allele frequencies in one generation
recombination during meiosis can …
exchange maternal and paternal chromosomes to produce new combinations more rapidly
what is the molecular clock?
Kimura’s theory that most mutations are neutral
we accumulate mutations constantly and we can use that to date how long ago different populations diverged
a lot of DNA isn’t used much (has since been disproven) and mutations of thrid codon don’t always have an impact
phenotypic plasticity
a change in an individual’s PHENOTYPE in response to their environment
natural selection example:
soapberry bugs
introduction of new host plants with different fruit sized, bugs shifted hosts
NS resulted in beak adaptation to reach seed
what are the types of selection?
directional, disruptive, and stabilizing
example of directional stabilization
darwin’s finches in the drought
favored large beaks to open harder seeds
example of stabilizing selection
gall-making flies
larvae produce galls on goldenrod plants, but large and small galls were targeted by predation, so intermediate size was favored
example of disruptive selection
african seedcrackers (birds)
small beaks can eat soft seeds, large can eat hard, medium aren’t optimal for their
what does stablizing selection do?
maintain mean and reduce variance
what does disruptive selection do?
maintain mean and increase trait variance
what does directional selection do?
change the mean and potentially reduce trait variation
sexual selection
selection due to within-population competition for access to mates and their gametes
sexual selection is responsible for:
more diverse and extravagant traits in nature, rapid evolution, and increased speciation
anthropomorphism
attributing human traits or intentions to non-human entities
innate tendency that we should avoid with this content
sexual selection occurs as a result of ___
variation in mating success
not everyone gets to mate or the same amount of mates
what causes variation in mating success?
competition
gametes are the ___
main difference between males and females
egg
large and sessile gametes
sperm
small and mobile gamete
sexual possiblities
none (no gametes), two separate sexes (lions), hermaphroditism, sequential hermaphroditism
hermaphroditism
male and female gametes are produced in the same individuals
common in plants
sequential hermaphroditism
individual start life as one sex and later transition into the other
sex roles
dependent on differences in parental investment between sexes
higher parental investment ->
limiting sex, has mating preferences
lower parental investment ->
limited sex, has mating competition
anisogamy
differences in gamete size
our ancestral state is ___
isogamy
isogamy
single mating type, everyone can mate with everyone else
all gametes are same size
universal compatibility
gamete trade-offs
large but slow/non-moving gametes with lots of resources vs. small but faster gamete with little resources
anisogamy is ___ distributed
disruptively
Bateman’s principle
in most species, females invest more in reproduction than males, making them the limiting sex
male lifetime fitness is limited by …
how many mates they can obtain
female lifetime fitness is limited by…
how much resources they have available to allocate reproduction
result of Bateman’s principle?
females can be the more choosy sex and males have to compete for them
roles can be reversed
can phenotypic plasticity evolve?
yes, it can be an adaptation
ability to get fit more efficiently is heritable, but looking fit is not a heritable trait
reactive norm
range of phenotypic expressions of genotype across range of environments
example of phenotypic plasticity
male horned beetles
use horns and body size to fight for females
morphology determined by amount of food in larval period
why spend resources on large body is you have small horns and you’ll lose anyways?
common garden experiment
individuals with different phenotypes are grown under same conditions
genetically controlled in GCE if…
individuals maintain their wild traits
phenotypic plasticity in CGE if…
individuals shift to similar traits
what is the purpose of the common garden experiment
distinguishing genetic variation from phenotypic variation
what are mechanisms that maintain genetic variation?
meiosis/recombination, natural selection, gene flow, disruptive selection, negative frequency-dependent selection
mechanisms that decrease genetic variation
stabilizing selection, inbreeding, genetic drift, positive frequency-dependent selection
frequency dependent selection
fitness of individual is dependent on its relative frequency amongst the population
positive frequency-dependent selection
majority phenotype wins
reduces genetic variation in population
think mullerian mimicry butterflies
mullerian mimicry
two poisonous species mimic each other
whatever looks like this won’t get eaten
negative frequency-dependent selection
minority phenotype wins, promotes genotypic and phenotypic variation in population
example of negative frequency-dependent selection
purple/yellow morph flowers
naive pollinators will switch between them as they search for different reward (nectar/pollen)
sampling effects
changes in allele frequency over time that are random with respect to their function or selection
founder effect
loss of genetic diversity bc of migration event in which smaller group “founds” their own population
example of founder effect
less genetic diversity as humans spread out from Africa
bottleneck effects
loss of genetic variation from dramatic reduction in population size and then recovery from it, new population descends from small number
example of bottleneck effect
northern elephant seals
hunting reduced population to 20-40 individuals, today have extremely low genetic variation
genetic drift
changes in allele frequencies in population due to chance events
random sampling effects can lead to…
differences in numbers, sex ratio, or survival of offspring
genetic drift leads to…
evolution at random
example of genetic drift
beetles being crushed by shoe image
4 conclusions about genetic drift
its is unbiased, affects smaller populations ore, decreases genetic diversity over time, and generates divergence among populations
imagine plots of multi-colored lines
endangered species example
florida panther
caused by: poaching, vehicle collisions, habitat loss, and fragmentation
extinction vortex
cycle of factors worsening extinction status
in extinction, drift can increase…
inbreeding load
can increase the frequency of deleterious alleles
example of morphological sign of inbreeding
kinked tails in florida panthers
88% had them in florida, only 9% in other cougar species
what does increase in genetic variation allow for?
better survival of the species
can better withstand disease or deleterious alleles
what mechanisms of evolution did cheetahs experience?
genetic drift, bottleneck, and inbreeding
biological species concept
species are groups of interbreeding natural populations that are reproductively isolated from other such groups
what is the biological species concept largely based on?
reproductive isolation
limitations of biological species concept
1) problematic for species that can’t feasibly be tested for reproductive isolation (spatial/temporal differences)
2) issues with getting species to mate in artificial conditions
3) hybridization is more common than we think
steps to speciation
1) genetic isolation
2) divergence of traits accumulate
3) reproductive isolation
vicariance
physical barrier causing dispersal
geological events
river formation, mountain ranges rising, continental drift
example of vicariance by climate change
pleistocene period
cycle of glacial and interglacial periods that can lead to refugia and separate populations
refugium
places that isolated populations of once widespread species survive major environmental changes
species that experienced speciation by climate change vicariance
toucanets
found glacial period refugia in separating forest canopies, but as they disconnected the species behaviorally wouldn’t fly to other areas and they speciated
continental drift
movement of landmasses on earth’s surface
consequences of continental drift on ecological systems
creates and breaks down barriers for dispersal
weather impacted as positioning of continents and major oceans influences weather patterns
examples of vicariance by continental drift
pangaea (one large) -> gondwana and laurasia (two regions) -> n/s america, afria, asia, antarctica (5 regions)
population impacted by continental drift for speciation
ratites - type of flightless bird
hypothesized they lived together in gondwana but as it fragmented, they were split apart and then speciated
genetic isolation can occur by…
physical barriers (vicariance), dispersal, or genetic barriers
dispersal example
islands or “sky islands”
what are sky islands?
mountain tops for alpine species with extreme arid climate in valleys between
species don’t behaviorally move from mountain top to mountain top because of these climate differences
examples of genetic barriers for dispersal
polyploidy, major chromosomal changes, other genetic changes
genetic barrier to dispersal meaning
egg and sperm can’t fertilize each other
polyploidy problem
incompatible amounts of chromosomes
example of genetic isolation by genetic barrier
tree frogs
Hylaversicolor = tetraploidy
H. chrysosceli = diploid
versicolor likely originated from chrysoscella genome duplication
morphologically identical but different mating calls
diverge
accumulation of differences from each other (when populations have separated)
what can cause mutations to become fixed/lost in different populations?
selection and/or genetic drift
many species ___ reach full reproductive isolation
DON’T
hybridization can happen more often than we may think
what are the classifications of isolating barriers?
premating, postmating prezygotic, postzygotic
what are premating barriers
prevention of transfer of gametes
what are postmating prezygotic barriers?
mating occurs, but zygote doesn’t form
examples of prezygotic barriers
ecological (temporal, habitat, etc. prevent mates from meeting)
sexual isolation or pollinator isolation (can meet, but don’t ex: different mating calls or female not attracted to male)
what is temporal isolation?
periods of reproduction or emergence aren’t compatible
think cicadas in 13/17 yr cycles
what is habitat isolation?
species occupy different habitats in same geographic region
think ladybugs feeding and mating on different species of plants
what are postzygotic barriers?
mating occurs, and zygote forms but hybrids have lowered fitness
examples of postzygotic barriers
heliconius butterflies- hybrids have lower fitness because they don’t have appearance that camouflages them as poisonous species like parental species do (example of positive frequency-dependent selection, parent surviving bc of majority pheotype)
what are the two models of speciation?
allopatric and sympatric
what is allopatric speciation
speciation in non-overlapping regions
more common
1) physical barrier
2) no gene flow
3) genetic differentiation
what is sympatric speciation?
speciation in overlapping regions
1) temporal/seasonal/ecological barrier
2) individuals can still come in contact and there can be significant gene flow
3) significant genetic differentiation
reminder about speciation
species ranges are subject to change, can be sympatric at one time and then allopatric at another
examples of sympatric speciation
1) soapberry bugs
- adaptation of different beak lengths because of introduction to nonnative plant (smaller fruit)
2) palms of Lord Howe island
- early flowering couldn’t transfer pollen to later flowering ones
convergent evolution
organisms evolving to have similar traits because adapting to similar environments
not necessarily recent common ancestor
example of convergent evolution
sugar glider (oceania) and flying squirrel (north/central america)
what is phylogeny?
evolutionary history of a group
what does a phylogeny tree do?
summarize evolutionary history
can depict timing and pattern of branching events
most closely related species should have the most traits in common
choose parsimonious tree
this will minimize the amount of evolutionary change, keep it simple!
keep in mind, phylogenies are ___
hypotheses
based on data we have
homo sapiens are the ___ ___ of an otherwise extinct group of species
lone survivor
how long ago did human and chimp lineages diverge?
about 6-7 million years ago
what preceded H. sapiens?
several other species of hominin
what does hominin mean?
any species more closely related to human than chimpanzee
how are H. sapiens and chimps different?
1) fully upright posture
2) relatively hairless
3) smaller incisors
4) fully opposable thumbs
5) larger brain size for language
6) recognition of complex cause and effect
7) development of complex culture
anatomical differences between chimps and humans
1) flat face
2) long legs, short arms
3) very different pelvis shape
4) anterior foramen magnum (head is more central on spine, not sitting in forward posture)
5) s-shaped spine
6) curved feet
what is not so special about humans?
technology/tool use
innovation
communication
cultural inheritance (evolution of a culture over time)
what are all anatomical differences adaptation for?
bipedalism
what is a trade off for our bipedalism traits?
terrible childbirth
a lot of complications and death
additional differences between humans and chimps
a) extremely fine motor control (hands, lips, tongue, oral cavity)
b) opposable thumbs and shorter fingers
c) descended larynx (trade off: choking)
cost of humans having larger brains
higher metabolic rate relative to fat-free body mass than chimps, gorillas, and orangutans
what’s an important consideration when forming a phylogenetic tree other than appearance?
geography
benefits of humans having larger brains
social brain hypothesis
social brain hypothesis
living in large social groups could have resulted in natural selection that favored larger brains
bigger groups are more successful because of cooperation and accumulated and transmitted knowledge
we need big brains for language to maintain those large groups’ organization
what does radiation mean?
the rapid evolution of multiple species from a single ancestor
why do we not have a great understanding of human evolution?
we have a lot of incomplete skeletons because hominin bodies are terrible at fossilization, which is what we base a lot of ancestry info on
there’s also a lot of closely related lineages, leading to a lot of uncertainty
what are some limitations of fossil records?
we don’t know when hominins lost body hair or started wearing clothing
lice
are highly specialized blood sucking parasites that live on a single host species
a lot of ape relatives have one species, humans have three
co-speciation hypothesis
two sets of two species diverge at the same time
in terms of humans and chimps, their lice diverged at the same time as them (6-7 mya)
where is it hypothesized that humans picked up pubic lice?
early gorillas
sleeping in nests that were recently used by them or preying on them (lice are known to jump from prey to predator)
we can use phylogenies to…
test hypotheses about speciation
such as when hominins lost body hair or started wearing clothing
key events in human evolution
1) shrewlike ancestors climbed scrubs and trees 80 mya
2) arboreal ancestors provided humans with binocular visions and skillful hands
3) as african climate dried, ancestors descended from trees 5-10 mya
all lineages of hominins originate in africa except…
neanderthals, denisovans, and H. floresiensis
what lineages migrated out of africa?
h. erectus, h. heidelbergensis, and h. sapiens (in that order)
other lineages that originated outside of africa
h. floresiensis, h. neanderthalensis, and denisovans
where did h. floresiensis originate?
indonesia
where did h. neanderthalensis originate?
europe
where did denisovans originate?
siberia
other hominins spread out of africa at least ___, before humans did so
twice
led to new populations establishing and speciation events due to isolation and divergence
all but h. sapiens went extinct
basic info of homo erectus
first lineage to leave africa
long lineage, existed for about 1.5 my
extinction likely due to climate change
never coexisted with h. sapiens
range of h. erectus
all over africa, parts of europe, south and east asia, indonesia
migration led to new populations establishing
speciation event in indonesia originated h. floresiensis
h. floresiensis basic info
skull the size of modern day toddler’s
in indonesia
why were h. floresiensis skulls so small?
likely bc of island dwarfism
island dwarfism
typically large organisms evolve to have smaller bodies when on smaller geographic areas, like islands
island gigantism
opposite of island dwarfism
typically small animals evolve to have larger bodies when on smaller geographic areas, like islands
h. heidelbergensis basic info
second lineage to leave africa
migration led to new populations establishing
speciation events due to isolationg and divergence: neanderthalensis in europe, denisovans in asia, h. sapiens in africa
homo sapien basic info
originated in africa from heidelbergensis population that didn’t migrate
continued to evolve in africa until 60 kya, 2000 individuals migrated out of africa
all humans outside of africa descended from those 2000 individuals - founder’s effect
much higher genetic diversity within native african populations what between populations on different continents
what is the leaky replacement hypothesis
genes of other species of humans are still around today in non-african populations due to hybridization
not a complete replacement by h. sapiens, some genetic mixing involved
“leaky” = genes still around due to hybridization
out of africa hypothesis
h. sapiens spread out from africa and replaced existing species of hominins, such as neanderthals or denisovans with no interbreeding
multiregional continuity hypothesis
modern humans didn’t originate from a single population in african but as multiple interconnected populations around the world
also evolved from h. erectus
disproven bc ethiopian fossils are the oldest ones we’ve ever found
why were h. sapiens likely the lone survivor?
neanderthals and denisovans were better adapted to colder climates
during interglacial periods, h. sapiens were able to expand upward and compete with other hominids for their niche
h. sapiens had potential advantages: bigger brains, larger populations, pelvis adaptations for running, and division of labor in group living
evidence of founders effect in humans
more deleterious mutations as we move away from africa
less genetic variation and less room to evade them
