Ch. 19-23 Flashcards
evo-devo means
evolution of development
gradualism vs punctuated equilibrium
gradualism suggests long term, slow changes
punctuated equilibrium suggests short periods of rapid and large change
evo-devo falls into which of the main two evolutionary frameworks?
punctuated equilibrium
the conceptual reconcile between development and evolutionary genetics is:
role of gene regulation
the birth of evo-devo came from discovery of:
HOX genes
essentially, HOX genes are important for:
gene regulation
5% of a wing problem
problem: assuming evolution occurs as gradualism, how could a wing ever develop if 5% of a wing wouldn’t benefit/improve flight
solution: co-opting/exaption of traits, 5% of a wing might increase thermoregulation and then later be used for flight
co-option or exaptation
a trait is initially developed for one purpose, then later used for another function
6 key insights from evo-devo
- all animals share a conserved toolkit
- small change in developmental gene expression can create huge changes in phenotype
- developmental constraints limit the types of adaptations that are possible (biased development)
- evolution happens/can happen in leaps
- evolution often co-opts pre-existing forms/functions to create new phenotypes
- adaptive alleles can come from both de novo mutations and standing variation
adaptations from new mutation
a new selective pressure arises, causing alleles that encode a new adaptive phenotype to appear
adaptation from standing genetic variation
a new selective pressure arises, causing a previously existing allele (present at a low frequency, either previously neutral or even slightly deleterious) to rise in frequency
2 types of adaptation that allow populations to evolve in response to changing selective pressures:
adaptation from standing genetic variation
adaptation from new mutation
a key difference between marine and freshwater sticklebacks:
marine forms have bony armor plats down their body
freshwater forms do not have bony armor plates
the loss of bony armor plates in sticklebacks was shown to be from ___ adaptations
standing variation
pleiotropic
a gene that affects more than 1 trait AND/OR
a mutation that affects more than one trait
AND/OR
same gene can function repeatedly at different times and places during development
developmental bio & evolution are related:
dev. bio is the study of the process by which a zygote forms a reproductive adult
evo. bio is the study of changes in populations across generations
evolutionary changes are rooted in corresponding changes in development
evo bio asks: why the changes occured?
dev bio asks: how did the changes occur?
heterochrony
alterations in the relative timing of developmental events
alterations in ____ genes can cause enormous changes in development
regulatory
HOX genes are ____ across distantly related animals
conserved
when homeotic genes/HOX genes are mutated:
appendages develop incorrectly: appear in the wrong places, do not develop at all…
HOX genes are :
developmental regulatory genes
HOX genes ___ with DNA
directly interact
HOX genes are ___ factors
transcription
HOX genes are HOMOLOGOUS/ANALOGOUS genes/traits?
homologous
meaning they are found in all animals because of shared ancestry, they were conserved
homologous traits are shared because:
they were present in, and inherited from, a common ancestor
homoplasy is when traits are similar due to:
independent evolution, not common descent
2 types of homoplasy
parallel evolution (similarity results from same underlying developmental mechanism) & convergence (similarity results from different dev. mechanism)
developmental bias/constraint
likelihood/directionality in phenotypic variation due to developmental factors
mechanisms of evolutionary leaps:
cross-species hybridization
horizontal gene transfer
mobile genetic elements
cross-species hybridization
two different species produce offspring together, and sometimes no mis-expression/defects, just unique features
horizontal gene transfer
foreign DNA integrates into a new genome, common in microbes or parasites
some parasitic pathogens have enzymes that degrade cell walls and allow them into cells
foreign genes are either integrated into host genome or not = leaps!
3 examples we discussed of single genes that can have major life-history + pop.-level effects:
butterfly wing color - Optix gene
sticklbacks - Ectodysplasin gene, armor
honeybees - female bees can asexually produce other female eggs, requeen competitive hives (social paratism)
social behavior
interactions among individuals, normally within the same species
benefits to being social
increased vigilance
cooperative hunting
enhanced defense capability
dilution effect
costs of being social
more conspicuous to predators, increased parasitism/disease, increased competition, uncertainty in paternity
4 kinds of social behavior
donor/recipient
++ cooperation
+- selfishness
-+ altruism
– spite
how does communal nesting in ani birds show cooperation?
female birds can work together to raise the young, nestlings fledged per female increases in larger groups of mothers
benefits to selfishness
decreased competition, enhance your own survival by stealing from others
why might spite evolve?
as a form of interference competition
like when 2 strains of a bacteria make mutually lethal compounds
direct fitness
the fitness an indvl achieves by their own reproduction, without help
indirect fitness
fitness an indvdl achieves through reproduction of relatives that was made possible by their own actions
inclusive fitness
direct + indirect fitness
kin selection
selection arising from the indirect benefits of helping relatives
ie that increases inclusive / indirect fitness
Hamilton’s Rule
altruistic behavior will continue as long as
rB > C
meaning the costs are less than the benefits * relatedness
relatedness is measured: parent - offspring have 0.5 r
sibling-sibling have 0.5 r
grandchild has 0.25 r
kin recognition
the costs involved in mistaking another individual’s offspring for ones own are high, so recognizing your kin is important (done through visual, chemical cues… )
reciprocal altruism
an individual acts in a way that temporarily reduces their fitness while increasing the fitness of another individual, with the expectation that the other indvdl will return the favor at a later time
2 requirements for evolution of reciprocity:
a mechanism for detecting ‘cheaters’
large number of opportunities to exchange aid
eusociality
non-reproductive indivdls help rear offspring cooperatively
why would eusociality evolve?
monogamy hypothesis
when an indvdl can be certain that future siblings will be full siblings (parents are monogamous), a new sibling would increase their inclusive fitness as much as an offspring (0.5 for both)
microevolution
evolution occurring within populations
macroevolution
evolution at or above species level
relates to origination, diversification, extinction
leads to temporal and spatial patterns of biodiversity
originations occur when:
fossil record indicates a lineage split into distinct clades
extinctions occur when:
last member of a clade dies
when origination > extinction, you get
adaptive radiation
adaptive radiation occurs when:
a single/small group of ancestral species rapidly diversify into a larger number of descendant species that occupy a wide variety of ecological niches
3 things that can trigger adaptive radiation:
new ecological opportunities
key innovations
co-evolutionary relationships
cambrian radiation opportunity
increased O2 availability, increased dev. capacity to diversify, new lifestyles available
beetle diversity is linked to:
coevolution with plants
coevolution drives species diversity because:
prey (like plants) evolve innovations to escape predation
predators (like beetles) evolve to overcome defenses
coevolution
reciprocal evolutionary change between interacting species, driven by NS
Mullerian mimicry
poisonous species tend to resemble each other
Batesian mimicry
a harmless species mimics a harmful species
what does the biotic hypothesis say that explains global patterns of vertebrate species diversity?
biotic hypothesis says:
ecological interactions like competition, predation, mutualism, parasitism are stronger in the tropics
these interactions promote species coexistence and specialization, leading to greater speciation
what does the low extinction rate hypothesis say about patterns of biodiversity?
having a low extinction rate is more influential than having high speciation/immigration
low extinction could be from topographic complexity, climatic buffering favor persistence of species
biogeography
the study of where organisms’s live and how they came to be there
2 major forces of biogeography
dispersal & vicariance
dispersal (force of biogeographic patterns)
movement of populations from one region to another with limited return exchange
vicariance (force of biogeographic patterns)
formation of geographic barriers to dispersal that divide once continuous populations
types of fossils/fossilization processes
amber - insects
freezing - can be large organisms
permineralization - petrification
natural molds/casts - plants, small animals
trace fossils - footprints
ediacaran biota
first unequivocal evidence for macroscopic life in fossil record, mostly sponges, jellyfish
burgess shale fauna (fossil record, 505mya)
dominated by large, bilaterally symmetrical animals, segmentation, heads, appendages
what caused the cambrian explosion?
leading hyp: mass extinction of ediacaran fauna, increase in atmospheric oxygen, developmental innovations that allowed radiation to occupy lots of new eco. opps.
fish-tetrapod transition animal
titaalik
birds are related to WHAT ancient animal group?
dinosaurs
background extinction
the normal rate of extinction for a taxon or biota
mass extinction
a statistically significant increase above background extinction rate
examples of extinction we talked about:
Mauritius
dodo birds
carolina parakeet
causes of historical mass extinctions:
volcanic explosions
global climate change
glacial episodes
atmospheric/ocean chemistry changes
asteroid impact
tectonic plates moving - vicariance
now: humans
permineralization
form of fossilization when structures are buried in sediments and dissolved minerals replace or precipitate in and around it, preserving original shape
natural molds and casts
form of fossilization when unfilled spaces are left empty (molds) or when new material infiltrates the space and hardens into rock
these preserve shape but not internal details
trace fossils
type of fossil that records behavior, not form
the burgess shale fauna are from the ___ period
cambrian
K-T or K-Pg boundary
discovery of anomalous concentrations of iridium in sediments in a layer, clue that an asteroid hit Earth 65Mya bc iridium is not common on earth but is in meteorites
suggests that a meteorite hit at that time, causing mass extinctions/global changes in env./climate
morphological stasis
lack of morphological variation, present in ‘living fossils’
morphological stasis does not mean ____ stasis
genetic
stasis occurs under ___ selection
stabilizing
