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