LS 1 midterm 1 study guide questions
Define ecological adaptive radiation.
• Evolution of ecological and phenotypic diversity within a rapidly multiplying lineage (the lineage is responding to opportunities presented to it) • Includes both [speciation] + [phenotypic adaptation to divergent environments]
What are Laggerstatten and how do they help us understand the history of life on earth?
-Laggerstatten = 'mother lodes' of fossil information -most famous one: Burgess Shale (Cambrian Explosion) -505 MYA [Cambrian period]; found ~65,00 specimens from ~93 species; soft tissues were even preserved -it gives us a really good idea about the flora and fauna of the Precambrian -it helps us understand the history of life on earth because it gives a snapshot of the entire community with great detail
How did a phylogeny help Neil Shubin test an evolutionary hypothesis about the transition from fish to tetrapods? What fossil did he discover? Why is it significant?
-by being able to place Tiktaalik on a phylogeny (and thus locate its place on the tree of life) it showed the connection between fish and tetrapods -he discovered Tiktaalik (375 MY old; the ancient relative of tetrapods) -it is the connection between aquatic fish and terrestrial tetrapods
What is the evidence for the earliest life
-oldest evidence of life dates back to 3.7 BYA (this is controversial) -found from carbon contained in zircon rocks that suggests life (carbon from photosynthesis is lighter than carbon in air) -oldest stromatolite (bacteria) fossils date back to 3.5 BYA
You can think of parsimony as an algorithm that generally tries to explain the evolution of a trait in the simplest way possible whereas likelihood tries to explain trait evolution by considering ALL of the ways that trait might have evolved. Given this description, can you explain why a parsimony reconstruction might lead to 100% certainty that a trait like parental care is one state while likelihood, for that same node, might show that two states are almost equally likely?
-parsimony doesn't take into consideration time; parsimony doesn't look "forward" on the tree and it is sensitive to sampling -likelihood method takes into consideration time (the length of the branches) and close relationships; considers the possibilities that there was switching of traits within the branch; can correct of incomplete sampling; can run analysis multiple times to quantify uncertainty
Think of some examples of homologous and homoplasious traits in animals or plants you know. How do you know whether a trait is a homology or homoplasy in two species?
Flippers - Dolphins vs. Similar-looking reptiles (ichthyosaurs) -flippers are a homoplasy -flippers of dolphins were derived from a terrestrial mammal ancestor & since the other species was a reptile, the common ancestor between these two species did not have flippers -Wings - Bee vs. Dragonfly -wings are a homology -wings were found in the common insect ancestor of both bees and dragonflies -Wings - Pterodactyl vs. Bat -wings are a homoplasy -bats are mammals & pterodactyl are reptiles; their common ancestor did not have wings
How do we infer ancestral traits from a phylogeny of living species? As you move from the most tipward nodes of the tree back to the root node, does your ability to confidently infer an ancestral trait change?
In biodiversity/macroevolution, we make inferences about ancestral states that are dependent on the ability of biologists to use extant species and the fossil record to make inferences of the state of the characters in the ancestor [ex: feathers & forelimbs]. If we have a phylogeny, we can map traits that we know on to it and make predictions about ancestral traits. -using parsimony: based on the distribution of the states on the tips, we infer if nodes further back in the tree displayed a certain characteristic; the more common a trait is distributed across the tree, the more likely the common ancestor will have it -yes, as you move further back towards the root node, one's ability to confidently infer an ancestral trait decreases
Are living taxa ever the ancestors of other living taxa in a tree?
NO never
Did dinosaurs keep the mammal radiation in check? What is the evidence for your answer?
No -from the extensive time-calibrated phylogeny (presented in lecture) we see why mammals radiated before dinosaurs went extinct -the colors originate BEFORE dinosaurs went extinct -therefore, the molecular phylogeny shows that there is diversification in mammals that began before dinosaurs went extinct because there was already a radiation that began
When did fossils first appear for the three domains of life?
bacteria: 3.45BYA -archaea: 3.5 BYA -eukarya: 1.8 BYA
What does the study of diversity patterns across the three eras reveal about the nature of biodiversity through time?
biodiversity over time is uneven and not proportionate -we see that many of the most diverse existing plant and animal lineages evolved relatively recently
How can fossils tell us about behavior?
can capture behaviors: -ichthyosaur: giving birth -fish: eating another fish -dinosaurs: parental care
What are exaptations?
exaptation: natural selection co-opts a trait for a new function -ex: evolution of feathers -ground-up hypothesis - flapping of wings to try and catch dragonflies -trunk-down hypothesis - glide off of trees to escape predators
Why are fossils so important to inferring the character states of deep (old) nodes in a phylogeny?
fossils allow us to see what the state of a character is close to an internal node -with living taxa, we don't know the state of the taxa of the ancestor, but fossils help solve this uncertainty -fossils tell us about: morphology, behavior (birth, eating, parental care), and development -ex: wovles/canids - if we just looked at the tip species, we would think that the common ancestor was much bigger than we would expect when taking into consideration the fossil record
When were the 'big five' mass extinctions?
• End of Ordovician; 450-440 mya; glaciers & low sea levels • End of Devonian; 375-365 mya; global cooling • End of Permian; 225 mya; volcanoes & temperature drop • End of Triassic; 205 mya; sea level increase & shallow inland seas form • End of Cretaceous (K-T); 65 mya; meteorite
Why is homoplasy a headache and why is it biologically interesting?
homoplasy = character state similarity not due to common descent (there's not a shared evolutionary history, between species with similar traits) -convergent evolution: independent evolution of similar trait -evolutionary reversals: reversion back to an ancestral character state -homoplasy can be a headache because it can be misleading in the reconstruction of phylogenies; when using parsimony to construct a tree on the computer, it will try to put groups together if they have the same trait even if the trait is homoplasious and the groups are not related. -homoplasy can also be biologically interesting because it shows the influence of the environment on diversity; groups evolved similar traits under similar selective pressure (roles in their ecosystem/environment)
What are the problems with the fossil record?
many organisms do not fossilize -(from demo section 2) Conditions for Creating Fossils: 1. organisms must be buried in an oxygen poor environment to reduce decomposition 2. organic matter will be replaced with minerals 3. surrounding sediment must harden to form rock -of the organisms that do fossilize, many of them are not found
Do these traits predict survival during periods of mass extinction?
no
You discover a clade of garter snakes in the Sierra Nevada Mountains. These species are allopatric and live in geographically isolated meadows where they feed upon worms and insect larvae. Would you consider them to be an adaptive radiation? Why or why not?
no
What are the four criteria of adaptive radiations? What kinds of data do you need to evaluate each of these? Explain how the Galapagos finches demonstrate these criteria.
o common ancestry (phylogenies) o trait-environment correlation (phylogenies + trait data) o trait utility (functional morphological or biomechanical studies) o rapid diversification (phylogenies & comparative methods) • • data to evaluate: o species richness data o morphospace • explanation of why Galapagos finches demonstrate AR o recent common ancestry: they are monophyletic o trait-environment correlation: looking at differences in bill length, depth, width, and curvature relates to their particular environment o trait utility: use biomechanical studies to show that certain beaks enhance ecological performance o rapid diversification: rapidly diversified and filled niches on the island
• Good macroevolutionary hypotheses:
o concern patterns across (rather than within) species o generate historical questions about processes that have played out over a long time o develop fundamental questions about conspicuous patterns of biodiversity. (look @ Lect. 1, slide 48). o A good hypothesis makes testable predictions.
What was the ancestral function of feathers? Do we know? What are the best hypotheses? What is the evidence for them?
possible ancestral function of feathers: protection, thermoregulation, display, mating behaviors -we don't know for sure, but these are some of the most widely accepted hypotheses (note that flight has been ruled out as the reason that feathers evolved)
What is wing-assisted running and how does it help us to understand how flight in birds has evolved from flightless ancestors?
scientist Ken Dial from University of Montana ran a study on wing-assisted running in flyless birds (partridges) -he observed that even birds that do not fly can use their forelimbs along with their wings to navigate steep inclines; the partridges could traverse a 105o incline! -thus, it has helped us understand the possible use and advantages of wings in ancient, flightless theropods; over time, those that were able to harness their feathers for flight had great advantages and were dominant/successful in accordance to natural selection
Compare the fauna of the Burgess Shale and the Edicaran. Which is older? What kinds of animals are preserved in these deposits? Which is more closely related to living animal groups?
the fauna of the Ediacaran are older -*only a fraction of Ediacaran fauna share traits with existing lineages -almost all of them become extinct within 40 million years -**most existing lineages are found in the fossil record during the Cambrian period -includes our own lineage, the chordates -Burgess Shale fossils (soft tissue preserved)
How do phylogenies help us understand the evolution of feathers?
we can organize and visualize the ancestors and relatives of modern extant birds that also displayed feathers -from a phylogeny (ex given in class), we infer that feathers did NOT appear separately in each lineage; it is a synapomorphy (an ancestral trait found in all species of a clade) -we also hypothesize that flight evolved after feathers; therefore, the function of feathers were not originally for flight [recall: ground-up hypothesis & trunk-down hypothesis] * if archaeopteryx was the "first feathered bird" why is it in its own lineage on the phylogenetic tree? Instead of serving as a stem group on the lineage of living birds? - it is a stem lineage (look at more recent lecture with stem groups & crown groups). Compare it to the phylogeny of theropods; archaeopteryx is a separate lineage than living birds.
Explain the difference between the 'gambler's ruin' and 'red queen' hypotheses to explain background extinction. What predictions do these hypotheses make about how long clades will persist or how birth and death rates will change through time?
• "Gambler's Ruin" [not supported] o fluctuating diversity around constant birth and death rates lead to 'gambler's ruin' o that is, you will hit a point (of bad luck) when the clad will just go extinct as birth and death rates are constant o this model estimates the speciation and extinction rate over entire history & ask if clade survives as long as predicted • "Red Queen" [supported] o as clades age, their ability to originate new species declines due to shifting environmental factors o that is, the environment often shifts faster than species can adapt to it; thus, for speciation rates, things go south.. birth rates go down and death rates go up o this model looks at the speciation and extinction rates over both the rise and decline phase & asks if the birth rate is higher or lower during the decline phase
) The tuatara: ultimate evolutionary survivor or the little lineage that couldn't (diversify)?
• -it could be either; know both arguments • -survived for a long time, but low species diversity • -tuataras split from the lineage that gave rise to lizards and snakes ~230-250 MYA, thus they have survived for much longer than the average 10 MY that a species is expected to survive • -on the other hand, they also have not diversified - there's only one species of tuataras - in the 250 MY that they have been around
Explain how phylogenies can be used to test questions about when clades appear or become diverse.
• A phylogeny is a visual representation of the evolutionary history of populations, genes, or species; it is similar to a family tree in that it traces descendants (aka species) throughout generations (evolutions) over time. • Phylogenies consist of nodes and branches off of nodes. o Nodes represent a common ancestor of a clade, and clades represent all descendants of a node. • Thus phylogenies show when species split and become a diverse group, and it also tells us the relative ages of different clades in a tree.
What is required for a lineage to diversity?
• Adaptive differentiation depends on 2 things: o Resources (empty niches; opportunity in the environment) o Traits (allowing organisms to exploit opportunities)
Why is the theory of ecological adaptive radiation important to explaining a fundamental pattern about biodiversity across the tree of life?
• Adaptive radiation leads to → species richness • It's one way to see the uneven diversity in the tree of life
) What are some evolutionary advantages to large size?
• Avoid being eater, better at eating others • Better at finding mates • Better at your 'job' • Live longer • Bigger bodies → bigger brains • Thermal inertia • Better at weathering bad times
Compare the diversity of lampreys and cichlids in terms of species richness and morphological disparity.
• Cichlids: o there are over 1600 species of cichlids; therefore high species richness o in Lake Malawi, over 100 species have evolved over 10,000 years through adaptive radiation o this has led to tremendous morphological diversity in terms of where they live (trophic diversification) and how/what they eat (diverse diets) o different species have different body shapes, jaw shapes, and fins to best suit each species in their living environment and eating behaviors • Lampreys: o there are only about 40 species; therefore, low species richness o there is much less morphological diversity as well o all have similar body shapes and suckers
What is the difference between a cladogram, phylogram, and a chronogram or time-tree?
• Cladograms: show the relative ages of nested splits only • Phylograms: show the proportional genetic distances between species by their branch lengths • Chronograms: are trees in which branch lengths are scaled to explicit times
) What is Cope's rule? Does every lineage follow this rule?
• Cope's Rule = lineages tend to evolve towards larger body sizes • Ex: the graph of dinosaur sizes shows that over time they increase in size after they originate • Not all lineages follow this rule
What is a crown group and what is a stem group? Draw a phylogeny of placental and marsupial mammals and indicate a) crown age and stem ages for each lineage and the common ancestor of those lineages b) placement of Dimetrodon (what term would you use to describe this taxon relative to modern mammals c) placement of whales (what term would you use to describe this taxon relative to modern mammals?)
• Crown age = age of common ancestor to all living species • Crown group = monophyletic group defined by crown age (can include recently extinct taxa) • Stem age = age of split from closest sister group • Stem group = All groups that arose between stem age and crown age o [total group/clade] - [crown group] (**does NOT include crown group!)
Does the mammal fossil evidence favor or disfavor the gambler's ruin hypothesis?
• Disfavors it o Overall: the red dot shows that on average, the empirical rate of all the mammal clades is less than the expected rate of survival o This does NOT support the Gambler's Ruin hypothesis
What is ecological opportunity?
• Ecological opportunity = potential to diversify along an ecological axis
Give an example of a key innovation hypothesis?
• ex: insect wings, mammalian hair, amniotic egg of amniotes (reptiles and mammals)
What are evolutionary trends? How can ecology drive them?
• Evolutionary trends = the tendency of traits to evolve in a specific direction within a lineage over time o There could be random fluctuations within the trend, but the over direction must be in one way • Ecology can drive trends ('evolutionary escalation'): o Growth and reproduction are limited by access to resources, competitors, and dangerous prey o Selection will favor traits that improve performance in these arenas (weapons, armor, locomotion, crypsis, growth rates)
Why does the rate of dinosaur speciation contradict the racial senescence and insect/mammal competition hypotheses for dinosaur extinction?
• Examining at a graph of diversification rates in dinosaurs, one can see that the speciation rate and extinction rate are quite similar over the time period of dinosaur existence. • Thus, the mean diversification rate stays consistent over time. o In other words, the difference between the speciation rate and the extinction rate for dinosaurs does not change over time. • From this, we can conclude that the species did not just skyrocket in its extinction rate as its speciation rate fell; instead dinosaurs just disappeared without a change in its speciation or extinction rates.
Does the mammal fossil evidence favor or disfavor the red queen hypothesis?
• Favors it o Overall: the average origination rates graph shows that there's a drop in origination rate from the rise phase to the decline phase o This holds true for nearly all mammal clades; the origination rates are higher in the rise phase than in the decline phase o This supports the Red Queen hypothesis because it shows that there are changes in the environment that happen faster than the clade can adapt to
Know when flowering plants and insects originated.
• Flowering plants: o 200-245 MYA: split from gymnosperms o but ~135 MYA: crown age • Insects: o ~400 MYA: emerged o but most current lineages appear much later
Why do we think that percomorphs evolved new ecological roles in the Paleocene?
• From the morphospace graph, we see that the percomorphs expanded to fill a wide range of niches after the mass extinction • During the recovery period, these fish radiated to fill the newly open niche
How could key innovation, time, and adaptive radiation produced uneven patterns of biodiversity?
• It provides opportunities for isolation and morphological differentiation which leads to the creation of new species
What are some evolutionary advantages to small size?
• Less time to grow up • Fewer resources • Better able to adapt to sudden changes • High fecundity
How did we use a phylogeny and richness data to test the idea that angiosperm-feeding beetles had diversified more quickly?
• Looking at a phylogeny we could tell that there were switches over in beetle species that went from an ancestor that didn't feed on angiosperms to ones that did feed on angiosperms. • Looking at richness data we could see that the amount of beetles that feed on angiosperms is much greater than those that feed on non-angiosperms. • Thus, the phylogenetic tree shows the switching over to eating angiosperms leads to greater species richness - evidence that supports the hypothesis.
What is maxillary KT and how does it relate to the ecology of wrasses?
• Maxillary KT = the maxillary transmission coefficient • MaxKT is the ratio of the rotation of the maxilla to the jaw; a ratio of how much motion you get out of the maxilla for the amount of rotation that you put into the jaw. • this describes the movement of the wrasses' mouths, which they use in feeding behaviors • the higher the KT, the faster/more the jaw moves
What are 'dead clades walking'?
• One type of recovery pattern after a mass extinction • Dead Clades Walking = surviving clades sometimes become marginalized; after the extinction event, survival rate is still lower than earlier intervals! • Examples from class on graphs
Do any traits of species or clades predict survival across mass extinctions?
• Only geographic range (widespread vs. local) • widespread CLADES (not species) tend to survive mass extinctions better than restricted clades
When did the biggest mass extinction occur?
• Permian! In which 96% of multicellular life was wiped out
How is good classification related to phylogeny?
• Phylogeny based on homologous characters and molecular data to see related species • Compare it with Linnaean classifications (bad) only based on looks
What are some reasons for the high diversity of beetles?
• Rate of Speciation: high speciation from greater genetic variation on microevolutionary scale and by high reproduction rates • Key Innovative Characteristics: sometimes traits evolve on the tree of life that confer great ecological advantages in which the species has evolved o in this case, the elytra trait is a 'key evolutionary innovation' which might help explain beetles' evolutionary success • Older Species: the older a species is, the more time it has to evolve; thus, if beetles have been around longer than a species that it is being compared to, beetles have had more time to evolve • Rate of Extinction: a lower extinction rate means that the species will survive and endure life on earth for a longer time than a species with a higher extinction rate
How long is the recovery phase following a mass extinction compared to the mass extinction phase itself?
• Recovery = diversification after mass extinction • Recovery periods are generally longer than the mass extinction
What is the significance of long fuses leading to crown radiations when considering potential causes of radiations?
• Since stem ages and crown ages can differ substantially, the causes of crown diversification can be different than those which lead to the origin of the group • If you're looking at possible causes of diversity patterns, need to make sure considering the correct timeframe that correlates to the environment those key traits may have evolved in
What traits are associated with extinction risk during periods of background extinction?
• Species richness (high vs. low) • Reproductive mode (sexual vs. asexual) • Local abundance (high vs. low) • Geographic range (widespread vs. local) *also applies to mass extinction, but in terms of clades* • Body size (large vs. small) • Trophic strategy (predator, herbivore)
What is the difference between species richness and morphological diversity? Are they the same?
• Species richness = simply the number of species of a group • Morphological diversity = the physical characteristics/traits of species within a group • No they're not the same
Why do multiple evolutionary transitions (as seen in transitions to angiosperm feeding in the beetle example) provide power in testing macroevolutionary hypotheses?
• Such phylogenetic comparisons are useful and important to diversity studies because they provide multiple instances of recordable transitions in evolutionary history that allow scientists to piece together information about macroevolution.
How can the timing of the origin and subsequent radiation of a lineage be different?
• The origin of a lineage could come way before a subsequent radiation of that lineage o Think of the canid example from class; the lineage originated ~55 MYA but the modern radiation of candids happened ~10MYA
What are the 'rise' and 'decline' phases of a fossil clade? How do you recognize them from the fossil record?
• The rise phase of a fossil clade is the period in which the clade increases in the number of genra until the maximum point • The decline phase of a fossil clade is the period from the maximum point of genra until its extinction • From fossil record graph locate the maximum point and split the two phases at that point
What are the main differences between the adaptive radiation examples we discussed in class and the paleontological radiations listed in table 14.1?
• The scale of radiation between the two are different o The paleontological radiations: • are on a global scale and play out over many millions of years • used for higher taxonomic groups (mammals, birds, animals) which is more difficult to assess o While the other AR example: • applied to a shallow phylogeny • more specific lineages of organisms
What is the sister group to living whales? What is the evidence for this relationship?
• The sister group to living whales is the hippopotamus (artiodactyls). • Paleontologists have found many fossils of different species of whales with legs. Scientists have also compared DNA from cetaceans and other mammals and concluded that cetaceans are most closely related to hippos in genetic material. This is known as the whippo theory.
Explain why a slow-down over time in the rate of speciation and/or character evolution is a prediction of clades that are undergoing ecological adaptive radiation.
• The speciation rate will be very high at first as the species is adaptively radiating, but once they have filled to niches of ecological opportunity, speciation rates will decrease
What kinds of data are used in macroevolution? Be able to explain the kinds of questions that these data can help answer.
• There are several kinds of data used in macroevolution: o Counts of species richness + phylogenies; o Character distributions; o Fossil morphologies; o Fossil occurrences; o Spatial distribution of species richness; o Statistical models and simulations - models allow us to use data from today to work backwards & look at a specie's ancestors; simulations allow us to use data from an ancestor and work forwards to see if a certain pattern/evolution is found in modern species -examples of macroevolutionary questions: why are there so many species of beetle? What caused dinosaurs to go extinct? How and when did whales evolve? Are wings the reason why there are so many kinds of birds? Are there evolutionary 'arms races' between predator and prey species? ?-where did they come from? What are their closest relatives? When did they appear? What environmental factors affect speciation?
What is the evidence for asteroid-caused extinction of the dinosaurs?
• There is evidence for asteroid-cause extinction of dinosaurs found in rock sediment in which an iridium ash layer is sandwiched between rocks that date back to the time of dinosaur extinction. Yucatan area.
Why are time-calibrated phylogenies important to testing hypotheses about changes in the rate of evolution?
• They allow us to test for changes in speciation rate • If we only had molecular phylogeny and some trait data, we wouldn't be able to rigorously examine all 4 criteria of AR
What is meant by 'wanton' extinction?
• Wanton extinction: clades surviving mass extinctions are lucky, not necessarily better adapted than extinct clades • traits which promote survival during mass extinctions are NOT linked to traits which evolve during background periods
How are fossils used to time-calibrate the branches on a phylogenetic tree?
• analyze molecular data and see how many differences there are; translate it to phylogeny to use the difference/million year to time-calibrate tree • (look at notes from mentor OH) • Radioactive dating of fossils can give scientists estimates of the date that a species lived on earth. Translating that over to a phylogenetic tree allows scientists to establish time-calibrated branches.
What are background extinctions and what are mass extinctions?
• background extinction = rate of species loss in between times of mass extinction o 99% of all species now extinct o things associated with background risk: local abundance, reproductive mode, body size, trophic strategy, geographic range, species richness • mass extinction = periods of extraordinarily high species loss o >50% of animals driven extinct in each
Explain birth, death, and net diversification rates.
• birth or speciation rate (b) = the rate of new species formation • death or extinction rate (d) = the rate of species loss • net diversification = b-d = the difference in the birth/speciation rate and the death/extinction rate
How can asteroids or volcanic activity cause a mass extinction?
• both of these are major catastrophic events that would have impacted a very large portion of earth and thus led to the extinction of dinosaurs
When did dinosaurs exist and why did they go extinct?
• dinosaurs dominated terrestrial environments from ~235 million years to 65 million years ago (that's over 100 million years!) [Mesozoic Era: Triassic, Jurassic, Cretaceous] • they went extinct about 65 million years ago due to a meteorite that slammed into earth
How would you describe the distribution of biodiversity across the Tree of Life? What branch of biology studies factors which produce these patterns?
• diversity is unevenly distributed across the tree of life; some species evolve quicker with more diversity, while others evolve very slowly • evolutionary biology
What are homoplasies?
• homoplasy = a character state similarity that is NOT due to a shared descent o it is produced by: convergent evolution (independent evolution of similar trait) or evolutionary reversal (reversion back to an ancestral character state).
Why is ecological adaptive radiation easiest to detect in clades that have radiated recently?
• if a short time has passed since the crown of the radiation, then we are more confident that the environment that we see them in is the environment that they diversified their trait in
What are key innovation hypotheses? What do they attempt to explain?
• key innovations may trigger adaptive radiations o ex: insect wings, mammalian hair, amniotic egg of amniotes (reptiles and mammals) • however, they often only evolve a single time so testing it is hard! • It attempts to predict that rates will shift at a point on the phylogeny
What are the differences between microevolution and macroevolution?
• macroevolution looks at patterns across groups at or above the level of species. Macroevolution can seldom be tested in a lab. • Microevolution, on the other hand, looks at patterns across groups lower than species (ie: populations and individuals). Microevolution occurs so rapidly that scientists can watch traits change from generation to generation and link the shifts with altered gene expression or mutations that lead to protein-coding differences
Why are macroevolutionary hypotheses challenging to test? What makes a good macroevolutionary hypothesis?
• macroevolutionary hypotheses are challenging to test because looks at patterns across groups at or above the level of species, and many species that are examined to test a macroevolutionary hypothesis are no longer alive. • In other words, macroevolution can very rarely be tested in a laboratory.
Describe the relationship between morphological and mechanical evolution in the four-bar system.
• morphological (lever variance) and mechanical (KT variance) diversification is related • the four-bar has a morphological trait (made up of the 4 links) and an emergent mechanical/functional property (the maxillary KT). • the morphology and mechanical properties are weakly related but NOT IDENTICAL o macroevolution studies the patterns across the two traits. For instance, there could be a morphological difference (that is, a difference in the shape of the four-bar) between two species, but the species could have the same maxKT.
Describe how morphological or molecular characters allow us to infer evolutionary relationships.
• morphology of a species can tell the: presence, size, shape, or other attribute of body parts, which allow scientists to construct phylogenies with extinct species • molecular data of species uses DNA sequences to construct phylogenetic trees
What is a morphospace and how does the bill morphospace shown in lecture provide evidence that honeycreepers have diversified adaptively?
• morphospace = a plot that gives us an idea of the disparity (form, shape, or function) of a species • the graph shows that HH, a young clade, displays as much morphological breadth as all passerines combined o they're especially diverse for their age o more diverse than their sister mainland clade
) You discover a clade of beetles where species differ primarily in the size and shape of horns, which males use to compete for mates. Is this an ecological adaptive radiation? Why or why not?
• no; it is not ecological ? (it's more behavioral - the trait isn't used to exploit an environmental opportunity)
) Know your way around a phylogeny! What are nodes, clades, sister taxa, monophyletic groups, paraphyletic groups?
• nodes: represent common ancestors of clades • clades: represent all descendants of a node • sister taxa: are clades that are each others closest relatives • monophyletic groups: groups/clade that shares a single common ancestor o common ancestor + all descendants • paraphyletic groups: descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups o common ancestor + some descendants • polyphyletic groups: no common ancestor + all OR some descendants
What are some testable predictions of a key innovation hypothesis?
• one prediction is that rates will shift at a point on the phylogeny
How does sampling intensity of fossil formations affect the calculation speciation rates?
• some fossils are incomplete; there could be a lot of one species' fossils found; fossils from a time period could never be found at all • it makes calculating speciation rates hard • Because the dating of fossils is not precise, error is accounted for in the calculation of speciation rates by calculating the mean diversification
What are synapomorphies?
• synapomorphy = a derived form of a trait that is shared by a group of related species (ie: one that evolved in the immediate common ancestor of the group and was inherited by all its descendants) o a shared, derived character
How many beetles are there? How does the richness of beetles compare to species richness in vertebrates?
• there are more than 375,000 (and perhaps more than 1,000,000) • there are 60,000 species of vertebrates and there are nearly 400,000 species of beetles; thus, the species richness of beetles is much greater than all vertebrate species combined • this further supports the idea that diversity is unevenly distributed across the tree of life • order of species richness: beetles > (all vertebrates combined) > fishes > birds > mammal
Why does the anole example in class support the hypothesis of ecological adaptive radiation as the cause of anole diversity?
• they are a diverse species • inhabit many niches • looking at the plot of morphological evolution, the trend is decreasing o therefore, the average rate of morphological evolution was higher at the beginning and then slows down
Is the FSGD a key innovation for teleosts? Why or why not?
• yes (fish specific genome duplication) o there was a complete duplication of genomic sequence in the common ancestor of teleosts • scientists believe that genomic duplication is a key innovation because this extra genomic duplication helped stir the species diversity of teleosts • from the graph, we can see that the rate of speciation has changed from teleosts; it has increased