envs lecture 4 Flashcards
adaptation
features that enhance survival/reproduction in its environment
how have these features evolved
via natural selection
darwin’s dangerous idea
idea that adaptive traits evolved via natural selection
what was the explanation for adaptive design prior to Darwin
supernatural omnipotent designer
what did darwin’s idea challenge
this supernatural designer
why was darwin’s idea dangerous
b/c it challenged the idea of a supernatural creator
what were the intricacies of adaptation attributed to prior to Darwin
goal oriented intelligent design
is adaptive evolution via natural selection goal oriented
no; it just happens
how does adaptive evolution via natural selection happen
via differential survival and reproduction of individuals that have traits that allow individuals to survive & reproduce, passing on genes to next gen
could darwin point to specific cases where evolutionary change in populations was observed
no; but today we can
today where can we cite examples of adaptive evolution
in morphology, physiology, behavior, etc.
examples of adaptive evolution
plants that live in arid environments have adaptations to reduce water loss
describe adaptations in these plants in arid environments
lack leaves, thick stems (photosynthesis); hairs that reflect light and reduce temp.
another example of adaptation
rapid adaptation of soapberry bugs ito introduced host plants
how do soapberry bugs eat
pierce seed pod to feed on the seeds
describes the plants in Texas and Florida
smaller in Florida, larger in Texas
how have soapberry bugs evolved in these states
longer beaks in Texas, shorter in Florida
another example of adaptive evolution
resistance of arthropod pests insecticides
example of adaptive evolution in nature
cryptic coloration
what is cryptic coloration
butterfly that mimics color of bark, green katydid that mimics color of leaf, etc. to help insect avoid predation
another example of adaptive evolution in nature
beach mice are lighter, allows them to match sand and hide from predators; inland form has more melanin
why do these mice have diff color patterns
single base pair change in coding region of mc1r gene
what is variation in mc1r gene lead to
effects on coloration of many organism’s plumage and pelage
describe selection and adaptation in the world of avian parasites
adaptation to their host’s background coloration (evolving coloration to help blend in w/ plumage of hosts)
what kinda parasites are avian chewing lice
permanent parasites
what are permanent parasites
live their entire life cycle on the host
what is chief mechanism that most hosts use to rid themselves of parasites
visual preening
what is visual preening
see parasites, then use their bill to remove them from plumage
what kinda lice do dark birds have (color wise)
dark lice
what kinda coloration do lice have
cryptic coloration
what are feather feeding lice adapted to
to color of their host’s plumage (adapt to host’s background color)
how do hosts defend themselves against parasites
by preening w/ bills
what does cryptic coloration allow
allows lice to hide from preening
what does host preening select for
cryptically colored lice
what did pigeons that could preen normally have more of
more cryptic than conspicuous lice at the end of experiment
are all traits adaptations
no
what are some traits if not adaptive
epiphenomena, vesitigal
epiphenomena
secondary products or incidental features
examples of epiphenomena
redness of blood in mammals (like in glass catfish, selection can act to make blood less colorful)
examples of vestigial traits
not used; like remnants of eyes in cave fish
what kind of trait is an incidental feature
redness of blood
is redness of blood nonadaptive
yeah
example of a nonadaptive trait being co-opted and serving an adaptive function
during aggressive displays chough shows red bulging eyes by increasing blood flow to eyes [uses nonadaptive property of red hemoglobin for adaptive function]
who introduced term exaptation
Stephen Jay Gould and Elizabeth Vrba
what term did exaptation replace
preadaptation
why did exaptation replace preadaptation
b/c preadaptation implies evolution has a direction
what is an exaptation
trait that evolved for one purpose but co-opted for another
another explanation for exaptation
feature that now enhances fitness but was not built by nat selection for its current role
does an exaptation always start from an adaptation
no; but often does
give example of exaptation starting from an adaptation
red eyes in chough (co-opted for a new use)
example of exaptation in puffin
wings; puffin uses its wing for flight and swimming, use in swimming is exaptation
what is puffin using wing to swim example of
exaptation
what was the old function of wings
to fly
what happened to the old function
removed; no more flight
what is the adaptive force driving its evolution
ability/need to swim
another avian exaptation
origin of feathers
what reason did feathers evolve
not rlly for flight; for display
one of most famous fossils in evo bio
archaeopteryx
what was archaeopteryx an example of
intermediate fossil/form
when was archaeopteryx form
2 yrs after 1859 (origin of species)
describe evolution of feathers
evolved for display, later co-opted for flight
what is flight
exaptation
what other purposes did feathers serve
probably a lot; thermoregulatory, etc.
what did archaeopteryx have
trousers
what did ‘trousers’ support
supported origin of feathers for function other than flight; like display
exaptation of feathers
feathers evolved for one purpose (maybe display or physiological), ultimately led to flight
what did early literature assume feathers evolved for
flight
why is the idea that feathers evolved for flight not true
feathers found in theropod dinosaurs had nothing to do w/ flight
other candidates for purpose of feather
insulation, camo, courtship, water-proofing
when did first feather emerge
after a tubular feather formed in a skin follicle, and proto feather led to adaptive advantage
how do we know feathers didn’t evolve for flight
found in early theropod dinosaurs
did feathers evolve from scales? or from where
no; evolved from skin
what does ontogeny do
ontogeny recapitulates phylogeny
did feathers evolve as adaptations for flight?
no; evolved for insulation, display, etc. then were adapted/modified for flight
what is needed for natural selection in a population
variation in phenotype, inheritance of phenotype, fitness differences among phenotyeps
rephrase inheritance of phenotype
basically phenotype has a genotype
reword fitness differences
there is a phenotype/fitness correlation
what happens within a generation if a population has these effects
some individuals will get more resources
what happens between a generation if
some individuals have more offspring
how does natural selection operate
only by differential reproductive success among genes and heritable individual phenotypes
adaptedness
ability to survive and reproduce in a given environment
what is cumulative product of nat selection
adaptedness
what is adaptation
the process thru which adaptedness is acquired (genetic)
what else is adaptation (noun)
characteristic that enhances survival and reproduction of organisms that bear it
what is fitness
relative measure of reproductive success of individuals
is it easy to measure fitness
no; hard to follow an organism over its life, may look at it over a few years, or annually, etc.
differential fitness
genotype A has a fitness of 3, B has a fitness of 4 (higher fitness); genotype B grows more rapidly due to higher fitness –> more individuals in population have genotype B
who overtakes who
B more quickly overtakes A (more fit)
what do these graphs show
evolution; change in frequency/proportion of genotypes over time
who described sexual selection
darwin
what is sexual selection
differential mating success and thus reproductive success
what does differential mating/reproductive success result from
either competition for mates or mate choice (female choice for traits in males)
is fitness just as simple as nat selection and fitness in sexually reproducing organisms
no; more complicated
what does sexual selection involve
differential mating success on account of 2 things: competition for mates, and mate choice
does natural selection always cause evolution
no
what else can cause evolution
genetic drift
what is genetic drift
random fluctuations in genotypic frequencies within a population (can cause change in gene frequencies in population over time AKA evolution)
neutral alleles
do not alter fitness and frequency of these allele changes via genetic drift
are neutral alleles affected by nat selection?
not strongly; can undergo frequency changes only via genetic drift
neutral/synonymous change
mutation in 3rd position; doesn’t change AA
non-synonymous change
mutation in 2nd position –> changes AA
is a non-synonymous change neutral allele
no
natural selection
differences in fitness among phenotypically and genotypically different individuals within a population
genic selection
natural selection acting at level of gene
example of genic selection
selfish genetic elements; transposable elements
what can selection act on
genes, cell types, individual organisms, populations, species
what will natural selection cause an allele to increase in frequency
if it leaves more copies of itself in subsequent generations
does natural selection work on individuals, populations, species
selection acts on individuals, changes things in species
what are selfish genes
transposable elements
transposons
self-replicating DNA sequences
another word for transposons
jumping genes
who discovered transposons
barbara mcclintock
what do transposons do
transpose form copy site to other places in genome
are transposons highly conserved
yeah; even tho initially considered junk DNA
what causes majority of mutations
transposons
what did Wynne-Edwards come up with
group selection
can natural selection act on group selection
not rlly
what is group seelction
differential survival and reproduction of groups that differ in genetic composition
what was group selection used to explain
explain the purpose of territories; argued that territoriality, which guaranteed that the population did not overexploit its resources
what is altruism
individuals might do things for the good of the group
who said altruism evolving for the good of the group is faulty reasoning
george williams
what did george williams do
criticized group selection
how does selection acts
directly and indirectly
how does selection act directly
as a result of an individuals own reproductive success
what is this indirect component of selection
kin selection
how does selection act indirectly
when the individual helps relatives, who also carry a proportion of their alleles (carry individual’s same genes)
why is it called indirect selection
isn’t directly acting on individuals; indirectly benefiting individuals by helping
describe kin selection
helping relatives who carry proportion of alleles of helper
what did Wynne-Edwards say about altruistic behavior
altruistic behavior will evolve b/c group selection favors it (i.e. b/c more ‘selfish’ populations go extinct)
what does Williams say
within-population selection favors the ‘selfish’ allele and increases it more rapidly than whole-population selection can act, so the ‘selfish’ allele will become fixed
does group selection makes sense
not really
what did Williams say
b/c individual selection operates more rapidly than group selection, the selfish genotype increases rapidly within populations and may spread by gene flow into populations and altruists and replaces them
what happens to selfish genotype
genotype becomes fixed, even if it increases chances of extinction
why does the selfish genotype become fixed
b/c its just easily transmitted and advantageous
what illustrates problem w/ Williams argument
Lemming Myth
Lemming Myth
when populations of lemmings in the high arctic become hella high that they throw themselves into the sea for the good of the group
but what can happen w/ lemmings
all it takes is one cheater that doesn’t do this; if altruism and cheating traits are heritable, then cheaters will prevail
what did JBS Haldane say
would sacrifice himself to save 2 brothers or 8 cousins; b/c he is reproducing more than himself
what did JBS Haldane come up w/
inclusive fitness
what is relative number of an individual’s alleles that are passed onto future generations
both directly and indirectly
directly
as a result of an individual’s own reproductive success
indirectly
when individual helps relatives who also carry proportion of alleles
can selection act on species and clades
yeah
does species selection have inheritance
no
example of species selection
if larger bodied species lineages tend to speciate more rapidly or avg. rate of extinction is lower over time, a clade will become more speciose and each species will have larger body size
microevolution
result of natural selection on individuals
macroevolution
aspects of history of life which determine diversification and resilience to extinction of clades
what have some paleontologists suggested
overwhelming determinants of patterns in nature are macroevolutionary rather than microevolutionary changes
what can adaptation lead to
complexity
Paley’s divine watchmaker analogy
as complexity increases, probability of an event being the outcome of chance diminishes to the point where a conscious designer is invoked
who is Paley’s analogy used by
those who invoke extrinsic or divine intervention to explain complex patterns in nature
why does this misapplication arise
- random nature of mutation necessitates that end phenotype be created from scratch
what is another reason this misapplication arises
intermediate stages have no intrinsic value, only the finish product is functional (like human eye)
why is the 2nd one an incorrect assumption
b/c evolution proceeds by cumulative change, not just random shuffling; each stage is functional
sometimes it doesn’t have to lead to complexity, what can it lead to
simplicity
if traits are so complex, how can they just end up happening
adaptation
convergent evolution
eyes of octopus and vertebrate; many similarities but hella differences
evidence for evolutoin
convergence and suboptimal designs
what does natural selection work on
available variation (panda’s thumb)
what did stephen jay gould argue
argued that textbooks illustrated adaptations w/ optimal ‘designs’ but suboptimal designs are just as illustrative of nat selection
what did gould say about suboptimal designs
just as illustrative of natural selection
examples of panda’s thumb
not a thumb, but modified extension of radial sesamoid wrist bone that evolved to be as big as a thumb
what is ‘thumb’ used by pandas for
to strip leaves off of bamboo before eating
how did this false thumb evolve
convergently
who has false thumb
lesser panda and giant panda
are lesser and giant panda closely related
no, so false thumb evolved independently in both groups –> convergent evolution
what is convergence evidence of
nat selection acting on variation in nature
can evolution simplify or does it always complicate
can simplify
does evolution always proceed in direction of complexity
not always; can simplify traits
does evolution proceed in a direction?
no, just happens
example of evolution simplifying
army ant has eyes reduced to single ommatidia; burrowing blind snake can detect light but not form an image
where do reduced visual systems come from
vestigial, natural selection
what if reduced visual systems are vestigial
mutation reducing them doesn’t hurt fitness
what if reduced visual systems are from nat selection
mutation reducing them increases fitness; means resources can allocated elsewhere –> lower chance of infection or damage
historical constraints on selection
since evolution doesn’t design organisms from scratch, each step is contingent on preceding steps
what are other constraints
ontogenic constraints
what are ontogenic constraints
shape and developmental constraints
what is another constraint
phylogenetic constraint
what is phylogenetic constraint
availability of variation
pleiotropy
a gene can have more than one effect
what is phylogenetic constraint
species retain features due to ancestry
what do all mammals ahve
seven neck vertebrae
why do they have seven neck vertebrae
result of phylogenetic constraint
birds w/ longer necks have more what
more vertebrae
is birds having longer necks and more vertebrae adaptive
yes
what can natural selection lead to
evolution of diversity
what was bill size of G. fortis when small seeds were there
small
what happened to bill size after drought where small seeds became less abundant
bill size increased
what happened where another bird invaded and ate large seeds
bill size decreased again
