History of Life Flashcards
Timeline for history of life
Timeline has changed a lot BUT only push back never push forward
How long has all of this been going on
The change from sheep hoof mammals to blue whales took place over 50 million years
Before then = history of animal life on earth
- Have huge amount of time before braod scale change in mamales
END – ALL of multicellular animal life - small in history of earth
- Animals are small in history of earth
All animal life Vs. All life
All animal life = result of 600 MU of evolution BUT the history of life is 6X longer –> Evolution of biochemical pathways is longer than history of animal life as whole
How old is earth
4.85 BYO (based on radiometric dating)
How did earth form
Earth formed out of the Sun’s primordial dust/debris disk
Debris in orbit around sun (early starts as dust then collapse on own gravity and form planets)
Hadeon Eon
Start of earth – for the first few hundred million years conditions were extremley unstable
Earth started very hot and was constaly bombarded by objects in the solar system
- Earth was getting hit by lots of stuff (smashing = unstable)
- Early collison with ither small thing created the moon (part of
Creation of moon
Part of earth was knocked off to space around earth and made moon
Life during Hadean
Earth was unstable + hot = not hospitable
Everything = very volatile = not much chance for life to get started
Archean eon
Overall: Earth started to cool = get solid crust + formed continents and oceans
- Still more voltile (volcanism is active)
- Earth starts to look somewhat more recognizable
- Still a lot of bombardment from space (metiores)
When do we start to get life
Archean – start to get life
- Get life early –> within 100 MY
Stability started 4 Billion YO and by 3.7 BY get signs of biologic activity
How did we get oceans
During Archean – have commet bombardment = where you get most water –> filled oceans
First signs of biolgic actiivuty
Get signs in archean 3.7 BYO – shift in carbon isotopes = suggests biochemical processes drive isotope
NOT direct evidence but compelling indirect evidence
Fossile evidence of life
May date back further – doesn’t get to 3.7 BY but gets close
In fossils = see geologic formatting –> Interpret as microbial communities that date 3.5 BYO
- Not individual microfossils BUT overall patterns are similar to microbial communities we see today (Similar stromatotes)
- Have stromatolites in same area of the wrold
- Found arcgean rock that suggests the presence of micrbial communities 3.5BYO
Stomatolies
Early evidence for life 3.5BYO
Lay fine layers of silicae + is laminated in a stratified fashion
- Similar structure from 3.5BYO
Shows that orgin of life in complex microbial communities
Microfossils
Some oldest unambigous microfossils date to 3.5BYO
Give direct evidence of indiviual organisms going back nearly 3.5 Billon years
Evidence of life in Archean
IS SCANT – have isotopes + Starting in microbial communities + microfossils
- More recent evidence of microbes are more readily avalble
Evidence is scarce because rocks from a long tine ago are rare on the surface BUT in places where we do have them we see signs of living world
Proteozoic evidence of life
Get more evidence of microbial communities (evidence is more readily avalible)
- Found strong evidenve of thruving microbial communities for 2 BY
Vs.
Archean – solid traces of life are rare from the archean BUT know life starts
Proterozoic eon
Start to get solid traces of life (2.5 BYO)
The transition to the proteozoic marks a shift in the fossil record to forms that can unabigously tied to modern forms
- Have transition from scant to see life 2-2.5 BYO – life we can connect to life today
Example evidence in Proterozoic
Proteocoin old = very similar to modern red algea (modern microbes that we have today)
What happened during Proteozoic
The chemistry of the atompshere and the ocean became more like they are today + have organisms similar to organisms that we have today
Change = due to action of life – driven by living world itself
Example - Great oxygentaion event
Great Oxygenation event
Started in the Proteoic
Early microfossils were similar to photosynthetic microorganisms today –> the photosythetic start to proloferate = have change on earth
Photosynthesis = Energy + Water –> Glucose + O2
- Photosynthetic take CO2 out and spit out O2 = profound effect on overall earth systems as a whole
- See increase in O2 in ocean first
Length of Great oxygenation event
LONG - 2.4 - 1.8 BY = took 600 MIllion years – same amount of time as ALL animal life
Evidence of Oxygenation
Seen in ocean first – evidence = banded iron formations
- See fossil evidence of photosynthestic microbes in Proteozoic
O2 in coean increase = binds with Iron in ocean = bind all Iron out = iron sinks to sedimemnt and O2 builds again
Rocks = have layers of Iron oxide then other sediemnts building as make O2
- 600 Million years to get all Iron out of ocean – Since no Iron in ocean = O2 proliferates to atmosphere = get O2 in atmosphere
Action of living world + Atmosphere
Action of living world influenced atmosphere that plays into living world
Oxugenation + determanistic
Example of thinkning about determinalistic
If Decrease in O2 and increase in CO2 = prime for Photosynthesis to evolove
Here photosynthesis is lilley = oxygenation of earth might have been inevitible based on evolution of photosynthesis
Dawn of Eukaryotes
The end of banded iron Formation = 1.8 BYO
At the same time as Eukaryotes show up + complex fossils 100X larger than bacteria show up
- Increase in Oxygen = start to get evidence of Eukaryotic fossils (still microfossils but more complex shape and stucture)
Evolution of Eukaryotes
Eukaryotes Trace their origins to endosymbiotic relationships among earlier prokaryotes
- Have Endosymbiotic with Eukaryotes and microbes
Allowed for aerobic metabolism
Progentors of Eukaryotes are more closley related to Archea than Prokaryotes
Eukaryotes
Structuraly complex cells with distict orgenelles
Importance of Prokaryotes
Prokaryotes are important with evolution of mitochondrial –> Spurring diversification of Eukaryotes
Evolution of Mitochondria
Likley only occured once
Have Eukaryotic protists that lack mitochondria –> have evidence of horizontal gene transfer = they evoloved from ancestors with mitochondria
Fossil dates for Eukaryotic
Fossil dates for Eukarya match well with molecular evolution estimates of mitochondria acquisition
Evolution of Multicelularity
Multicelularity first shows up in algea 1.6 BYO
Doesn’t occur in animal like forms for another billion years
- NOT in our ancestors for a while
Recap
Hadean –> Unstable hot earth + bombarded
Archea – life evolved but less evidence because no rocks from archean
Proterozoic –> microbial + interaction of living world and atmopshere paved way for mitochondria evolution
Phanerozoic
Means visibile life – see big things –> Dawn of multicell animals
Orginally this eon coincded with dawn of metazoan diversity (multicellular animals) BUT orginals stretch back into proteozoic
- Not just multi animals show up on own 541 MYO –> roots of multi cell streatch to protozoic
Strange beginings
Earliest fossil evidence of animal life forms include sponges 600 MYO
- See same deposits that have fossils that are similar to internal sticture of sponge (not whole sponge just have small peices)
Motile animals date back to 585 MYO BUT mostly trace fossils of tunnels and tracks
- Have evidence of things movingar around
Evidence of things moving around
Trace fossils – not body of organisms but have fossils that detects the activity of organisms (trails + burrowing in the sea floor)
See animals doing things but don’t know what they are but know things are around ocean floor 585 MYO
Ediacaran fauna
Starting 575 MYO – have first ecological assemblages of the large organisms –> Ediacaran Fauana
- Evidence of Muti cell animals
NOW = see animal life in complex ecological communities
- Seen in Australia + South Africa BUT now have evidence from 25 Sites across world –> ALL have similar groups of organims
Example Ediacaran Fauna
Some organsims = 1 mete long OR some are a few cm
SHOWS it is NOT just small things
- Almost all of the sudden have big things + big shift in composition of biodiversity (Microbes –> Multi cell)
False start?
Most fossils found are very weird – weird because we can’t connect them to types of animal diverity we have today
Weird we have today fiots into our own classification BUT These weird organisms have such different body plans that they might not be in animal phyla or in a classification that doesn’t exist today
Question in Edacaran
Major Questions surrounding this time - what if any realtionships do these organims have to modern aniamls
- Basic body plans are very different from current phyla
- Was this a false start? –> they don’t seem like they are related to us
Vendobionata
Proposal that many Ediacaran forms are so fundementally different that they comprise an extict kingdom outside of Animalia altogether
- Maybe these things are not animals at all – differemnt multi cell heretotrophs that are
not animals
Have branch of phylogeny for Vendobionata branch – before common ancestor of animals today
- Found different groups of animals – if they kept evoloving things would be different than they are today
Answer: ALL are equally related – Need to look at internal nodes
- They all share the same common ancestor with humans at the same time = none are more closely related to humans
Roting nodes on Phylogeney
Gives Identical phylogeny
Pushback on Most closley related
People say that the Fish and Seaslon have more nodes between them and humans BUT this is just set up this way (just a function of the species we chose to include in the cladogram)
IF we change organisms = we get a different answer
- Arbitrary number doesn’t tell you anything about being more related to humans
How do you form a clade in phylogeny
Form a clade by sharing a common ancestor
Ediacaran Fauana (overall)
First large multi cellular organisms
- In end of Protorozoic
Metazoan ancestors during Edicaran Fauana
Even if Edicaran Fauana arn’t related to us some of our metazoan ancestors must have been around
- Know ancestors during time were around but they are not seen in fossils
Protorozic –> Phanarazoic
Do see living things in high abundance
Why don’t we see our ancestors in Edicaran fauan
Perhaps the issue is in Tophanomic bias
- Maybe in different places or maybe taphanomic bias
***Maybe our ancestors don’t fossilize well
Tophanomic bias
Processes related to the fate of organisms remains
- bias in porcess that leads to fossilization
- Fossil record is not compelete –> cam’t actuallyf ind organaism – bias in what are fossils or not
Example Tophanimic Bias
Permian = Fossils are weird compared to modern in that the trophic structure is different (Have more autotrophs that heterotrophs = higher prey than predator BUT in the fossils in the permian it is flipped - have tons or predator and few prey)
- Food web might gave been the same as ours it is just that there is bias that we get fossils of predators and not herbivores)
Result: Unusual patterns wherte fossils are biased
Glimer in fossils in Protorozoic
Some glimer of hope of organisms related to modern phyla in fossils but not what we recognize as adults –> The fossils seem similar to embryos + microfossils of embryos
- Shows embryogenesis similar to modern phyla
- Perhaps ancestors were thing
- Some connections to bilaterans maybe fossilized embryos from Doushantuo formation
Cambrian explosion (overall)
Start of the Phanarazoic
Represents period were modern animal phyla appear
Multi cell show up very abruptly
See diverse large animals but almost all modern phyla are present in fossils
- By middle of the cambrian all of our major phyla are present
- Rapid doversification of animal morphology = Cambrain Explosion
Connections to modern phyla
Connections to modern phyla are tenous in the Ediacaram BUT by the middle of the Cambrian all of our major phyla are present
First Evidence for Cambrian Explosion
Burgess shale – first thoroughly studied aseemblage of early animal life
- See laminated sedimentary rock –> have small fossils + animal fossils – earliest multi cell animal fossils
- See fine detail + in high abundance
- Struck by tremendous diveristy
- Many very bizzare animals BUT we see the foundations of modern phyla
Example of a Lagerstatte
Lagerstatte
A particularly rich fossil deposit including organisms that don’t typically fossilize well
- Have lots of organisms including things that have lots of taphonomic bias (like fossils of warms)
Good because of the type of sediment with degree of well preserved organisms
What is found in the Burgess shale
See foundations of modern phyla –> Clearly arthropods – can draw direct connection to animals alive today
See:
1. Clear Arthrodpod relatives
2. Joint Appendages
3. Exoskeltons segments
4. Segmentaled body plans
(All things Artrhopods have today)
What is the basis for Phylum level diveristy
Phylum level diveristy is based on diversity of basic body plans (Bauplane)
- Blueprint for how make organisms = what decides what phyla
- All fundemental animal diversity = based on organisms having different body structures driven by development
ALL body plans = in place in the cambrien
All basic body plans in Cambrien
If all phyla are present in the cambrien = all basic animal body plans are present
- All of the diversity in fundamental body stricture that we see today dates back to the cambiren
Question about phyla/body plans?
Why do animals have the set of Bodyplans that they do?
Is there something optimal about them that natural selection was going to inevitable reach OR is this due to historal accicent
- Why do we have the set of phyla that we do (essntially fixed) –> was anything inevitable or are phyla today result of happenstance
Evolutionary Developmental Biology
The study of how developmental processes (ultimately controlled by gene expression) evolve - resulting in new morphological features
- How organisms develop + how developmental processes evolve + hows does variation arise
- Use underlying genes of developmental paths
Is there something optimal about NS choosing phyla or is it historical happenstance?
To Answer = could look at evolutional Devlopmental Biology
Answer: Understanding coming out of Evo Devo = there is a shared tool kit of almost all animals that allow different body plans to develope
- Diversity in body plans = based on set of key homogous genes (orthopgies) that control process
Developing Fly Vs. Developing mice
Fly has set of HOX genes + have set pf Mice HOX genes –> Pattern across fly = similar to pattern in mammals
- Have different morphologies from the same tool kit
- Genes occur along the chromsome in the same order
What triggered the cambiren explosion + development of phylogeny?
Evolution of base level tool kit
Constraints for ways for genes to be expressed for body plan development = constrains in limited number of phylogeny
- Limited way to produce functional body plans
Example Body plans from Camberin
Chordates – Body plan that certainly dates back to Cambrien explosion
- Clear they are early ancestors
Fossil = dorsal groove + similar bilateral plan – similar to modern lancelet
Second Cambrien Logerstatte
Chengjang – more recently discovered but older than Buregess
Haikoichtyhas – oldest known vertabrete
- See gill nodes + eyes on head + fins more developed
Why did the cambiren explosion happen in the cambiren
Why did it take so long for animals to get bigger –> partly took kit – get organisms to develope in multi cell ways that have funcational body plans takes long
AND – leading hypothesis = Simply could not have happened until oxygen reached critacal threshold
- Waited for atmosphere to get even more modern
- Oxugen increased in cambrien = can reach critical threshold to allow developemy of larger organisms (support comlex fast moving animals)
Pace of evolution in Phanarazoic
Compared to the Archean and proterozoic - the pace of evolution seems much faster during the phanerozoic (at least from a human persepctive)
- From our perspective things pick up rapidly
Did organisms outcompete Ediacaran Fauna
During Cambrien = earth had lots of climate change (warm –> Cold swings)
- Ediacaran = might exist during a breif warm period and our ancestors might benefit from being able to survive ocelations of warm –> cold
Animal life at the end of the cambrian
Aquatic life continues to flourish
Oridivician period
Oceans = still dominated by invertabretes (arthrpods + Molluscs)
- Oceans = filled with animal life
- Some animals get larger (7 feet long)
Vertabrets are still confied to jawless fish
- Have vertabretes BUT are little jawless fishlike creatures (Still have today)
- Jawless = helpless
When did we get vertabretes
Vertabretes have been around since the Cambrien BUT oceans were dominated by Invertabreted into the Oridivician period
- Still have these jawless vertabretes today but they are not the dominant form of vertabretes
Example - Hagfish
Silurian Period
Fish begin to diversify – most species are heavily armnored but still jawless
- Start seeing diversifcation of vertabretes
AND - Jaws evolve from gill patches in another armoered taxons
Where did jaws evolove
Jaws evoloved from gill patches in Placoderns (Armored taxon)
Done in the end of Sullarian
Animals in the Sulurian
Most fish = jawless BUT do better because they evoloved armor (Ostracoderms) – survive more by being armored BUT are still Jawless (limited in what they can do)
End of Sullarian
Critical to reshaping biodiversity –> process that was critical is the evolution of jaws
Gills arch moves to shovel things to mouth = evoloves to power of jaws –> change selection of ecological oppertunities for relatives
Change in fossil record leading to new period of Deveonian
Devonian period
Age of fishes – Jawed armored fishes + plancoderms = take over = means our ancestors are doing well
- Transition is NOT accompanied by a mass exitiction event (have major reordering of biodiverity without event)
Placoderms
Likley to ancestor to all modern Gnathostomes (Jawed vertabretes)
Effect of Jaws
Allowed vertebrates to quickly dominant the seas
Diveristy = owed to the evolution of powered Jaws
Evolution of innovation = allowed ancestors to outcompelte Jawless + invertabretes
- Take over seas + diversify early
- See pattern of one organsim outcompeting others as soon as jaws show up
Continuing Rapid diversification (After got Jaws)
Rapid diversification of form continued with bony fish splitting into two major lineages early in the devonian
- Split is important because we are lobe fish
Bony Fish –> Actinoptergian (finned fish) + Sarcoptergians (lobe fish)
- We are lobe fish
Split in Jawed fish
Split bony vs. Cartaligounous fish
THEN have another split in lineages
Cartligenous fish split –> Sharks + Rays + Spiny shark)
***Fish Split early in the devonian where we can trace ancestors of sharks and rays vs. diveristy of bony fish
Why care about fish
Humans are in the same clade as lobe fish
- Clade includes other vertabretes with bones (IN the clase that had split from bony fish)
- All individuals with bines in limbs = dates to early devonian
Sets stage for vertabretes moving towards land
Shift from Aquatic lobe fish to terrestrial
The shift form aquatic love finned fish to terestial tetrapod might seem like a huge leap BUT the fossils clearly show the transition from lobed fin skeletons to tetrapod limbs and the development of Pecteral and pelvic Girdles
- Series of Transitional fossils that are complete to say when first tetrapods evoloved
- Once found the right geologic time and setting (freshwater) –> see these organsims of Jawed tertopods = lead to ancestors on land
Lobe fish vs. Ray fins
Lobe fish = Have joints appendages at the based on limbs that allow for difference used of appendegaes
Differnces in Lobe fish = allows them to go to land
Transition in tetrapods
First have body structure of tetrapods then support limbs = smooth transition to land
- Well documented
When did the first tetrapod exist
Transitional fossils form such a smooth series of limb form that it is hard to say when the first tetrpod exists
What did tetropods evolove as
Tetrapods evolved as Ambush predators in shallow freshwater environments
- Began taking advantages of terrestrial resources (take advantage of arthrpods)
Arthropods on land
Arthropods had been on land since the Silurian
First on land
Vertabretes were NOT the first on land – arthrpods were the first on land
- Tetropods = not too far after Arthropods
Aquatic maybe went to land to takes advantage of Arthrpods
How much of tetropod body plan was driven by NS? How much was inevitable?
Early transitional forms from lobe fish and tetropods = divrse in the number of digits
- Have the same Humuras + Radius + Urna
THEN the earliest joint = existent but number of digits is very variable
BUT now = ancestral stat in existing = 5 –> basic body plan for all vertebrates alive today
Is there anything optimal about 5 digits?
5 fingers = could show constraint on body parts –> more developmental stability through time - do we have a limitations on ways we can evolove?
When had no wrist bones = lots of digits BUT tetrpods that want to use = have 5 or evolove from ancestor with 5
- Don’t see starting from 5 and increasing
- Otehr groups of tetrpods have basic body plans of 5 digits (earliest dinasour had 5) – don’t get woth more
Even though it is sueful to have extra digits it hasn’t happened
Is it useful to have more digits?
Example - panda has an extra thumb –> used to grasp bamboo = it is useful
BUT if you look at skeloton it is not a digit un developmental way – bone is just the wrist elongated
What about Polydactalism
Hands with extra digits –> happens within indiviauls BUT not broad because way it happens in development
- Humans can have fingers in development (it is a mistake in development) – split development pattern and grow futher in hand
It is a developmental mistake NOT a new finger
Interpretaion on 5 digites
Interpretation by is it optimal or are we constrained
Answer: Maybe in the devonian we could have changed BUT we didn’t – now we are past the point of no return = can’t go back and revise development from begining
What happened in devonian
Have rapid diversification of Jawed vertabretes including tertrapods –> had an ecological take over
The tetrapods are in habiatats to use limbs and do so well = have chnage in devonian
End of Devonian
Vertabretes move onto land in the end of the devonian and begin divergive into major tetrpod groups during the Carbonigerous period
Emergence of our teropod ancestors
Our tetrpod ancestors emerged during rapid vertebrate diversification of the devonian
Plants on land
Plants beat us out of the aquatic envirnment (Moved to land first)
Carboniferous period
Vertabretes begin diverging into major tetropod groups
- Have ancestors to modern amphibians + Amniotes
- Terestrial life included gigantic arthropods
THEN have split between Diapsid Amniotes (reptiles and brids) and Synapsid Amniotes (Pelycosaurs and us)
Warm with Abundence of Swamp like habitats
Where do carbon deposits come from
Carboniferous period –> Had big plants that now turn into coal
Animals in Carboniferous
Have explosion of biomass on land with Arthrpods dominating
Split in Carboniferous
Ancestors diverged early on land – Split between Amphibians and Amniotes
THEN Aminiotes start to diversify
As SOON as you have amniotes –> have split into diaspid reptiles + Synapspid reptiles
- We evoloved from Synapsid Reptiles
Ancestors = mostly small lizard like amphibians that are more mammal like that led to us
Evolution of Amphians to reptiles
Developed reptiles from Aquatic by having eggs that can deal without water
Habitats in Carboniferous
Have swap and wetland habitats occupied by organisms + big arthrpods (ancetsors were also big)
Ancestors = mostly small lizard like amphibians that are more mammal like that led to us
End of Carboniderous
Get period with climate change
- Shift in climate + break in pangea (change ocean current = change weather)
Get collapse of swamp ecosystem
In direer habiats the Synapsid reptiles (mammal side) thrive and diverisfy –> Our Ancestor get footing because synapsid reptiles do well) until volcanic acitivity bin siberia ruined things
Effect of climate change in Carboniferous
Leads to more diverse habiatats and eventually large + diverse + thriving terestial ecosystems
Dominant in Permian
The synapsides were the dominant terestrial vertabretes during the permian
Reign of Therapsids
Crashes in the eprmian
Go from mammal like reptiles –> Dinasours –> Mamals like us
Mammaliaformes
Earliest Mamaliaforms in Triassic within the Therapsid clade survived the Permian Extiction
Order or events from Mammaal like reptiels across dinasours to mamals like us
Have permian (Have dinasours)
THEN Biodiveristy rebounds
Earliest mamamles in middle of triassice (things wee call mammals show up in Triassic)
- Might technically be outside of clade of mammals we have today – different group of mammals but have traits we use to destiguish mammals
THEN the clade constaining all existing mammals started diverging (Split Monotremees/Marsupials and Therians)
- Recent common ancestor of all mammal today (last common ancestor of us and Acindia)
- Split in Modern mammals dates to Dinasours
THEN Have split between Marsupials and Placentals
- Diversity of mammals occuring in background of dinasours
- Split between two major clades of exicting live bearing mammals happens in Mid-jurassic
THEN the have divergbnce in Marcupials or Placental/Eutherins through the Cretacous
- Through Cretacoues = Mammals hang on in dinasour dominated ecosystems (mostly small but some ecological expansion and evolution of size)
- Have existing predatoring mamamls that we would diverge in shape
Important = Ancestors eveoloving are NOT as succesful as dinasours
Mammals + Dinasours
Mammals + Dinasours on earth for same amount of time
