Macro evolution Flashcards
Change in perspective
Move to How does evolution pay out on grand time scales
- Not within popultion
- How do evolutionary porcesses scale up to long term change we see in fossil records
***Taking our understanding of mechansims of evolution to see if they explain patterns of larger change through time
Evolution as an on-going process
Evolution is an ongoing process –> see change in allele frequencey from one generation to next BUT now what happens when scale up 3 billion years
We are going to turn to how the mechansims of evolution have played out in the long run
- Is there meaningful distiction between micro and macro evolution
Micro vs. macro evolution
Micro –> evolution process within popultion
Macro –> patterns of change above species level
Micro –> macro – is this just allele frequencey change – can we look based on popultion genetics or do other factors come into play
Speciation + micro/macro evolution
Interface between micro and macro evolution (during speciation within species variation is converted to variation between species by our basic microevolutionary forces) – in this sense macroevolutionary change is just scaled up microevolutionary change BUT the vast time scale may add some important factors that are worth considering
- If Micro evolution is population genetic changes within populations and macroevolution involves patterns of change above the species level then speciation is the link between the two
Link = derived from mechanisms of evolution point of view – maybe can just extend mechanisms trhough time
Macroevolution
Large evolutionary change, usually in morphology, typically refers to the evolution of differences among populations that would warrant their placement in different higher-level taxa (beyond species)
Questions in unit
- Do we see trends NS favoring phenotypic change through time? Are certain directions of phenotypic change favored in the long run?
- Some level of predictability in process
- How might researchers see if reason is because SN is favoring rather than passive?
- What are the patterns of biological diversity through time? Consider both that diversity as a whole and the composition of that diversity by different major clades and their change through time.
- Increase or decrease diversity
- Process to drive turnover in biodiveristy
Determine trends of evolutionary change
Can extend gould’s wall of complexity –> complexity increases even if NS does not tend to favor complexity
- Just need limit on one end –> since have limit = distribution only goes one way –> means the average only goes one way because have limit
Before = discussed with complexity BUT we can apply to many phenotypes
Example - can apply to morphology or chemical reactions that are passive or NS favoring outcomes
Application of Goulds left wall
Example – body size
Apparent direction bias through time = Cope’s Rule –> body size increases through evolutionary time (larger organisms derived from smaller) = increase body size favored by NS
2 Hypothesis for increase in body size through time:
1. Conform to cope –> was small and have consistent favor in increase in body size
2, Gould –> have minimum threshold to how small –> pasisve chnage but in end increas ein trait value
Charts:
Left = NS favored
Right = Passive –> mimimum thrshold for how small can be that set wall to allow passove provess to increase trait value through time
Directions vs. Biased changes
Whether apparent directional patterns in evolution are the result of biases in directional selection or passive processes with constraint can be difficult to parse apart
- Try to parse out if apparent trend is driven by NS or passive process
Cope’s rule
Observation that body size appears to increase in lineages through time
2 hypothesis for change in body size predictions
These two hypotheses make specific predictions for how phenotypic change plays out:
- In driven trends both ends of the distribution change in the same direction through time (in passive trends the minimum remain unaltered) vs. passive where only one end of the distubution changes through time
First prediction about body size
In driven trends both ends of the distribution change in the same direction through time (in passive trends the minimum remain unaltered) vs. passive where only one end of the distribution changes through time
Left image = passive – can’t be smaller = through time trait value increases – Does so in passive manner
- Increase maximum
- Mean Trait value increase through time because max changes but the minimum stays the same
Right = Increase maximum and minimum through time –> shift on both sides = NS favoring dorection of change
- Entire distribution moves –> not only stretch ax – change both ends
Scaling Mechanisms of evolution
Some mechanisms (selection + migration) are deterministic –> can we predict across time y scaling up mechanisms or do other factors that some into play that make it more difficult
Are the dP equations enough to explain macroevolution
Body size example
Do we see NS favoring outcomes that let us infer inevitability about patterns of change
- Active vs. Increase in trait value based on passive trend
Cope = observed that large body organisms evoloved from smaller ancestors –> see tendency towards large body size
Cope could be true or could just be passive process
Inevitability of large from small
Larger organisms evolve form smaller because the largest organisms are necessarily larger than ancestors smaller than them
This observation is not sufficient to know this is a driven trend where NS favors large
Evidence for NS favoring Trait value
Change in bounds of distrubution = evidence NS favors Trait value
2nd hypothesis about passive vs. active
In Passive trends apparent driven pattern on the whole clade is built from even distributions of change within clades
- Entire phylogeny looks like decedents have larger trait value BUT how is it in the different components of the phylogeny
Looking at second hypothesis of Passive vs. Active
Image – Across phylogeny not one phylogeny does it match or is it equally likley to go both ways
Through time look at size of circle –> see large at end compared to when starts –> seems to confrom to Cope = favored by NS
BUT lookiing at subclaves across phylogeny = see increase TV BUT the increase is because of ONE change in one branch = only happened once
- Just had change once in phylogeny = Trait value chnage in the end BUT it is not favored in across lineage – just happend once
Curve showing second prediction of favored vs. passive
A and C = not chnaging and B changes –> change in one in common ancestor and then body size chnage in random way
A driven trend would have to be across subclaves
- B – larger in that subclave and A and C would also have to get larger in subclaves rather than just a chnage in one branch from smaller to larger
3rd prediction in Passive vs. Active
In driven trends individual ancestor descendents changes are biased in one directions
***Not the case in passive
Example – Diansours –> look at invidious change in body size across phylogeny and see if there is pattern change in particular direction
- Examine direction of trait evolution along indiviual lineages
See green is harger and red is snaller – see if randomly distrubuted in either driection
For driven – 8/12 lareger – trend to increase = biased in direction of evolution
For passive – trait change can be even number of increase of decrease but might have one big shift that chnages the mean across phylogeny
Null model
Passive trends are essentially the null model
Paleontologists are generally reluctant to assign patterns to driven trends without substantial corroborating evidence from multiple lines
- Are this way becasue know that paaasice can occur = high threshold to sat trait is due to favore by NS
- One prediction might not be enough = look for more lines of evidence to back hypothesis
Driven trends in fossil record
There are some definte driven trends observed in the fossil record
Example:
1. Body size being favored in horses (body size increases) – in horses have a trend in body size but other aspects of horse evolution that is driven such as specialization of digits (run on middle finger – 5 –> 3 –> 1)
- Seems to be across lineages –> driven NS favoring outcome in lineages
- Simplification of skulls in mammals
- Most mammalian reptiles Jaw joining is complex
- Through time complex reduces and some bones evolved in flexible jaw to become inner ear bones
- Process of simplification = driven change –> have many lineages favored by NS
- Solid Jaw + auditory bone for hearing = favored acriss ancestors
Seeing interactions in fossil record
Co-evolution – can’t see in fossil record to see specialized interactions (hard to see interactions)
BUT can see interactions we know today and can assume they went on in the pat
Example - long term co-evolutionary trend
Running mammals vs. Ungulates
Can understand how they interact today –> assume past interaction
Look at interactions – what dictates outciome of hunts = median term speed of predator and prey –> who wins in rates dictates outcome of interactoon
Can look at anatomy that correlates with speed and apply undersatdning to morohs in fossil and see how fast running speed over time
They went through fossils – looking at features coreelating to running speed
Reults: 3 clades of predator mammal that exists through time period
- #1 trait that correlatd with speed = metatarsal femur index
- Can see driven trend for speed in ungelates= ungelates min and max change through time – mives together –> ungelates = faster not just few are faster ALL are –> many are faster now
- Predators –> don’t show driven trend – speed is passiove - some are fatser but the minimum is not changing
Explaining co-evolutinoary. change
Overall: Outcome of capture deopends on footseed –> NS is string in prey but not in predator
3 options for why this might be the case:
1. Trophic structure and demographics
2. Stronger tradeoffs for predators
3. Selection on predators maybe weaker
Option #1 for co-evolutionary change
Overall: Trophic structure and demographics
Trophic structure – always have smaller amount of predator than prey
Looked at effective popultion size – predator smaller popultion size = weaker selection AND higher drift + get lower number of new mutations
- Prey = more indiviuals getting mutations = more mutations for faster in prey + NS is stringer in prey than the smaller predator (predator also has more dirft)
Option 2 for co-evolution outcome
Overall: Stronger tradeoffs for predators
Tradeoff is compenent of speed or can be limited on degree of how speciated fir speed
- Traits conbtrollubg limb developemnt
Tradeoff - example of Antagonistic pleitropy – gene for limb might increase soeed but might decrease other asoect of fitness
Option #3 for co-evolution
Overall: Selection on predators may be weaker
Prey killed –> predator can take advatantge of weaker in prey = this might be less consequence
Can look At functional repsinse curve
- If mean popultion fitness of prey increases = popultion density increase 00 as prey density invcreases = capture rate increases because more individuals to capture = predator might not need to adapt because more prey to begin with
Fuynctional response curve
Density of prey vs. Number of prey consumed
All explination for change in co-evolution
Pattern of evolution changes over time BUT all are explained by rooting in mechanisms of evolution in ecological context
- Same mechanisms occuring today
Constraint of NS or ecological interaction that shape strength of NS
Million years that change but by our mechanism of evolution –> Analyze large patterns and see from lense of mechanisms of evolution
Questions on Patterns of diversity through time
How has biodiversity changed over the history if life?
Are there patterns of diversity that indicative of macroevolutionary phenomama?
Potential trends of diverity
Has diversity been increasing
OR – did it saturate early (low then increase then plataue – stable through time)
Second question about diversity
Has taxonomic composition of diversity changed or did diversity stay constant?
Does the diversity stay constant or does change in composition if diversity come from moving alteration to diversity as a whole
OR were taxonomic changes associated with major changes in diversity?
What drives patterns of diversification
Patterns of diversification are driven by the balance between speciation rate (alpha) and the extiction rate of lineages
Pattern of diversification = result of two parameters acting against each other:
1. Speciation rate –> create new lineages
2. Extiction rate
Net result that drives pattern of biodiverity
Looking at patterns of biodiverity
People look at pattern of diveristy through time but looking fossilo reocord – specifcially lookung at marine organisms (mollusks) with hard shells because they fossilize a lot (good record)
Sedimentary rock form marine envirnment – have record of organisms that live there – see fossil record to see how diverity changes through time
Patterns of diversity over time
Family level diversity in marinbe invertabrete fauna through the phanerozoic era
Results: Doveristy has clearly chnaged through time + the diverity of that diverity has changed (rare groups become more abdundant and visa versa)
PLOT – shows diverity change through time
- Increase in diverity thorugh time then short decrease then increase through Parts of fossil
- Types of diverity change over time –> repaltive abundence shifts over time
- Have turnover in composition of diverity through time
Exitiction
We think about exitiction as this unnaturak thing that humans on biodiverity
Example – humans drive species to extivction through hunting
- We think about it from negeitive way that hurts the natural order
BUT doesn’t mean that how exoection operates in every case
Exiction = natural part of evolutionary processes –> understanding varaution in rate of extiction through time assumes that there is varaition in rate
- Use fossil record data to undersatnd varaition in backgroun exitction rates in ecosystems
Diverity is net result of
Diversity is net result of speciation and extinction
***Patterns of extinction are crucial to understanding macroevolutionary patterns
Background extiction
Normal rates of extinction are referred to as “Background extiction”
Species have
Geologic life spans
Calculating extiction rates
Extiction rates are calculated as the proportion of geologic lifespans that end over a given time interval
- For how long do we see a group of organisms before we don’t see them again
PLOT – Frequency plot of marine genus level excitations over 1 million year internals (look in given million years how many lineages go extict)
- Distribution that sounds high BUT doesn’t show distribution fully because has statistical anomalies on scale that have rates that are higher than expected of base background
Result: Mean genus lifespan = 4 million years
- Most of the time Shows extcition is high (a lot of lineages go extict)–> 25% of genera in fossil record go extict per million years
- AT the tail end = backgroun extiction is low – shows that there has been a lot of variation in exitction rates through time with some periods of higher rates
Exiction rate through time
Plot shows that there has been a lot of variation in exitction rates through time with some periods of higher rates
Plot of extcition rates through time
Shows spikes that appear at the junctions of many geologoc periods
- Plot = looks at genera –> very dramatic
- Shows 5 major mass exictions events that are statsitical anomlies
- Spikes = associated with shifts in composition of biodiverity –> see change in levels of diveristy and in what makes up the diversity
5 spikes were associated (not just identifiable shifts in fauana but ALSO have major restructuring of the biosphere)
***Have profound changes at the genus level
- 85% of gernera lost in one and 96% of genera lost in other – profound change in biodiveristy
What defines geologic periods
Defined by the different kinds of fossils
KPG exiction
Most famous – brought the cretaceous period (age of dinasours) to a close
- Brought in age of mammals
Ended 160 million years of dinasours being terestrial vertaberete dominance
- Profound change – all dinasours died –> makes room for mammals
***Was actually the smallest of the big 5 mass exitctions
What caused dinasour exitction (KPG)
Overall: Due to extraterestial impact – astroid put into motion quickly
Mechansism seen in the 1980s – Have Iridium deetcted in the rcok (thin black line) –> black iranium is abundent elswhere in solar system –> influx of iradium = result of extraterrestrial impact
- can see the depression crater of event
- Rock hit + fires + fell into ocean that causes Tsunamis + ash and dust + debris all over atmsophere that blocked the radiation = put nial in coffin for organisms living
Envirnmental change in KPG
Debate is if the astroid was smoking gun or other things ==> diversity decreased in some amount but now know impact set the stage for extiction
- Likely major envirnmental changes going on at the time BUT the effect on diverity was minor in comparasion
Size of rock in KPG
Big but not size of earth – size of binghamtont
Throws off ecosystems to through off biodiverity of the planet
Largest mass extiction
End of the permian - 252 Million YO
30 Million years before diansours existed
Earth had dramatic animal biodiverity –> dominant terrestrial = reptiles that are more closley related to us (our side - mammal like reptiles)
Permo-triassic
Wiped out 96% of the animal species on the planet
- Close to experiment of life ending
Eveolutionary recoveroty in the Triassic was very slow
The extiction appeared to happen relativley rapidly – in 200,000 years have creash
What caused permo-triassic
No evidence of an extraterestial impact – BUT in 200,000 years have evidence of envirnment changes building
- Atmosphere change + climate change + ecosystem change
Overall: Due to change in earyj –> change in volcanic activity
- Evidence –> siberian traps – have piles of ogneous rock - came from magma coooling on earth (huge amount of rock)
- Had massive volcanisms (like gaping wound on earth where rock bubbled for years) –> gasses change atmopshere = goty ocean anoxia + massive warming
Earth in Triassic
Earth was an ecological wasteland in the begiinning of the trassic (desolute)
- >90% of terestial vertabretes (biomass) 5-10 million years after exitction belongs to a single burrowing genus – underground = got through – all the diversity we had for a while
- 3 million years after mass exotction continue warming psuhed almost all animals out of the tropics
Atmospheric event in Permo-trisassic
Atmopsheric event continued through for 3 million years –> ocean temperatyres Averaged 40 celius (104 F)
Average across globe = life was pushed out of the tropics
Took long time to retrun to normal and stabilized to have diveristy
What changed the course of life in Mass exitctions
In all the ME historical events outside of the mechansims of evolution had a profound effect on the course of life (major change to bio diveristy)
Major shifts in taxonomic composition are usually assocated with extrinsic exitction evnets
Mechanisms of evolution + History
Mechanisms + history = can go hand in hand –> osoelation of warm to cold – can see changes due to mechanisms BUT large remodeling events we see are unable to explain just in our deltaP equations
Exception to being able to explain things in predictable ways
- Outside factors = important in picture of life on earth
- Need to think about macroevolution provess neeed to deal with external factors as well
Were people destined to take over
People think that mammals were detsined to take over the world BUT this is not the case that we would just outcompete over time
Image – Ecological competition of mamals vs. dinasours – can see what it would look like if outcompete iver time
- Can see that as mammals expand the diansours are driven to extiction
Reality = this is not what we see
Reality of mammals + dinasours
Diveristy to thin then get extiction before can take up space and take area
External event that allows other organisms to flourisg
Dinsours + mammals have been on earth for the same amount of time – nothing about mammals that would take over in world without astrpid –> wouldn’t outcomepete before astroid
Why did linease flurish after astroid
Astroid = major change in oceans
Before KPG = major plantin = radiolarians
After KPG = Dioatons took over as the main atotrophs
Radiolarian varaition decreased and Diatom increased over time
WHY – Diatoms in Crotesiuc = were in the poles AND diatoms odat and dormencey –> month have 6 months of light and then they go formnet until get more light –> good trait that is useful to get through the world wide darkness = have leg up to recievry
- Dormencey likley allowed them to better survive the climatic upheaval
Diatom evolution
Diatoms evoloved to do better in Mass extiction just happened ot have it happen to help
Act on traition varaition that exists (had it to begin with) – did not evolove it before to help for the ME
Patterns of new lineages outcompeting old in the absence of ME?
Have example where ecology cause one to beat another when came into contact
Look at indepentdent evolution and then what happens when converge with each other
Example - Great American Biotic intertage
Great American biotic intertage
For alsmost all Cenozoic SA animals had been evoloving in complete isolation –> Popultions by its own unique marsupials and placental lineages
- Before NA and SA were seoperated (SA was own weird species evoloving since dinasours)
THEN the Isthmus of panama formed and NA and SA animals came into contact
- As sea levels decreased = cause NA and SA to be connected = free to move back and forth (first things that can swim
Did one win in Great American biotic intertage
In one way = no win or lose vecayse diverity inreased in both continenets and are moving to habiatsts
- No win or loss as long as diverity increases in both places
BUT some win/lose
Example – NA things from SA orgin –> Few things are in NA and organisms that are the result of lineages of SA origin VS soun american mammasl of NA origin
Result: See Asymetry in which ecosoystem won – SA ecosystem = out competed by the NA lineasges that they were in cotact with (Have more SA mammals of NSA origin than NA mammals of SA origin)
Reason NA won
Face NS average not as isolated = mamamls in NA had been tested by competition with other organsims but SA organsims didn’t
Cause of becoming dominant through time due to NA + Asia diverging and coming back –> evolve –> then spill –> then outcompete
See competative exclusion –> Have evoloving ecological processes driving diverity
Two last Macroeveolutionary concepts
- Apparent evolutionary stasis – lack of change in some lineages in fossil record
- Uncanny similarities across lineages (between unrealted organisms)
Norm during earth’s history
Change has been the norm during earth’s history
- Earth is changing + organisms change
Change in the fossil record
We don’t often observe as much change as we expect in the fossil record + not as linear
- If morphospecies are lucky enough to survive for a long time in the fossil record they often show few signs of steady directional change
- If persists for a long time –> sometimes fossils don’t show patterns of driectional change – fossils seem to stay similar –> no directional to suggest drive by NS
Patterns for things not changing
Patterns for things not changing = seen in marine organisms –> would think they would adapt through time BUT this is not what we see often
Expected pattern of change
If evolution is a gradual process = we might expect to see pattern of change through time like image
IMAGE
X - Axis -= change in trait
Y - Axis = time/diverisfication
Have slanted lines –> gradual shift as linage diverge
- See Morphology changing gradually as lineages diverse
BUT this is not what we see
What do we see in the fossil record
IMAGE
1. Lineages stay the same through time and have no trends in one directions
2. Change in fossils is accompanied by speciation events
- Morphological change associated with new lineages occur very abruptly in geologic time and then remian constant within lineages for long stretches of time
Puntuated Equillibrium Proposal
In the 1970s Goulds and Elderge proposed a model that explains the pattern of morphological stasis followed by leaps of divergence – proposed Punctuated equilibrium
Puntuation Equillibium
Morphological stasis occurs because popultions are at an equilibrium where NS isn’t pushing them in a particular direction
- Model explains stasis in the fossil record
- Equilibrium driving lack of change and then being punctured by something that allows change
- Some equilibrium acts on lineage then that prevents them from evolving in either direction
Is punctuated equilibrium just envirnmental equilibrium
Envirnmental equilibrium = NOT actually puntuated equilibrium – just how it was interpreted
- People think that it is indicative of envirnmental Equilibrium – that the envirnment is not pushing one way or the other for a long time = Not pushed by NS –> and then have rapid envirnmental change
Equilibrium in Puntuated Equilibrium
Genomic Equilibrium based on mechanisms of evolution
Equilibrium = prevents NS allowed them to adapt
What is Genomic Equilibrium driven by
Driven by widespread epistasis – change in body requires complex epistasis = evolution is difficult
Epistasis = constraint on NS ability.to drive change
Why does morphological stasis occur?
Morphological stasis occurs because populations ate stuck on adaptive peaks surrounded by deep fitness valleys
- Lineage stays the same through time because stuck on peak of AT –> change requires pass valley
Stuck peaks in morphological stasis NOT like
It is not like you need to have a slight shift in fitness – more like population is on a peak and can’t shift in either direction because have massive fitness decrease due to polygenic constraint on traits
Book explination for process in PE
Just saying that the morphological change occurs during speciation events – oversimplifications
Type of speciation in PE
Peripatric speciation – have a satilote popultion elswhere = huge amount of drift
Have the kind of massive drift needed to knock off of peak
Process of Morphologocal change in PE
Peripatric speciation – from founding new popultion from 2 indiviuals = allows NS to get off peak to new one
***Hard to do without strng dirft
Example of PE
A large population of mice across a continent exists in evolutionary Equilibrium + there is some barrier that mice can’t cross
Mice = on an apdative peak –> not pushing off even if conditions change bevause of epistatic constraints
THEN some event and one mice gets across the barreier to new habitat = have a founder event
NOW have big change in alllele frequnecey + have drift –> leads to NS to change allele frequencey in way it couldn’t before
- Not just NS – first drift then NS acting on varaition
NOW say mice have bigger bodies –> eventually mice go back to habiatat and eventually only have big body left
What would PE look like in Fossil record
See something like image –> miss the change because it happens rapidly in a small popultion far away (in popultion that split)
Seems like population pop out of nowhere because its from peripatric speciation
PE vs. Wright
PE is like wrights theory –> NS can’t cause change in body structure on own = need to invoke other evolutionary forces
Shows how can happen in absence of environmental change
Why look at convergent evolution
See role of deterministic process – how predictable is evolution
What does Convergent evolution show
Evidence in favor of determinism – comes from striking examples of convergent evolution
- Striking similarity from unrelated individuals
- See the same solution to same problem in different lineages
NS as determinatistic
NS is determinanistic by itself –> can we scale that up to what happens to evolution
Example Convergent evolution
Placental vs. Marsupial predators
Similar in overall shape and body composition BUT they are of unrelated origin
- Get the same solution to be apex predators in 2 different envirnments in unmrelated lineages
Example convergent evolution on the broad scale
Flight – Asking would we get flight again?
Look at how many times flight has happened – Answer is 4 times
- Have 3 groups of organisms today and 1 extict
- Get very unrelated organisms find ways to fly BUT there are limits in the organisms that can fly
Result: Only 4 groups can fly – all others can’t fly
Would we get flight again? – Maybe because we got it 4 times BUT all the times are limited
- Possible it could occur independtely but many not inevitable if only happened 4 times
Question in looking at CE
Looking to see if certain traits are lilkley to evolove if start over again – are there certain traits that evolved multiple times
Evolution of marine predators
Solution to hydrodynamics -=-> get organisms with similar body designs from unrelated
Convergence over a range of timesclaes
Can occur over multiple timescales – show up across broad phylogeny across long periods of time
Looking at phylogeny across mamals
Across phylogeny of mammals = more convergene
First – 2 groups in mammals that evolove similarly independently –> then have marsupials limited range of patterns to being predators
THEN – Even further back to mamaml like reptiles = see similar patterns there –> have same body shape
Overall: Something about design to be predator showed up across 100s Million Years in many lineages
Marsupial Placental
Example of High CE in predators – have similarities between groups of organisms –> Arive at similar solutions
Ex. Skulls of Thyalcine + Gray wolf = very similar even though unrelated
Example of CE in mammals #2
Moles –> Same solution to be underground animals that leads to similar body pattern –> high convergent between groups of unrelated indiviuaks
CE in plants
Seen in plants –> thinks with suculent plants (have spikes + not regular leaves) BUT they are not cacti
They are an old world group of plants in Africa that are hard to tell from cacti
- Similar envirnment –> leads unrealted groups of plants that end woth the same design and development outcome to deal with harsh conditions
Convergent Evolution on Smaller Timescales
Convergence also occurs on smaller timescales
Example – Antillees islands –> All have the same ecological niche being filed with convergence in ecological niche
- Whole community convergent across groups
- Evoloved and radiated to fill same niche = get niche with parallele convergence
What does convergence tell us?
Does it tell us that NS is deterministic or is it determined due to constraints???
Is it a matter of repeated optimization or common constraints
Idea for same form appearing
Perhaps the same form appears over and over because of limits on the process generating variation
- Maybe have to do with the power of NS or limitation of NS (Common solution that is possible given constraints of living systems)
Don’t know which it is
Example Constaint
Centapeads – Very diverse BUT they inly ever have an odd Number of body segments even though they are very diverse
- Have the same construction (can’t have even number of body segments)
Final Answer to What does CE tell us
No final answer to what CE tells –> When we see it – how to reconcile with historical happenstance where see the same patterns – does it tell us anything about what biodiversity we expect if restarted earth
