Origins of Early Life Flashcards
How old is the earth?
4.6by
How did the earth form?
by the gradual accumulation of 9dust and larger objects
When are the earliest fossil evidence for life dated?
3500MYA
By what point was earth cool enough for life to exist?
3800MYA
What is the Panspermia theory?
suggests that life on earth didn’t originate on earth, but arrived on a meteorite from another planet.
What are the problems with the panspermia theory?
No other planet has been found with conditions suitable for life, and the bombardment of meteorites created conditions that would have killed any early life forms
What is the evidence that eukaryotes evolved from prokaryotes?
prokaryotes apper earlier in the fossil record
Prokaryotes simpler in virtually every aspect
Have fundamental similarities
What are the similarities between Prokaryotes and Eukaryotes?
method of transmitting information is in the triplet code
Aino acids are laevorotary, nucleic acid sugars are dextrorotary
What is LUCA?
Latest Universal Common Ancestor, suggests all recent populations and everything on earth have one common descent.
What are the similarities between all lineages of extant organisms?
DNA, RNA, Pseudogenes, amino acids
What are pseudogenes?
genes that have lost their function, no longer code for a protein
What is the Miller-urey experiment?
Conditions of early earth simulated in the lab to see what chemicals it would yield and if these would be able to support early life?
What chemicals were created in the miller Urey experiment?
Amino acids, Purines/Pyrimidines, Sugars, Porphyrins, Tar like substances
What were the possible energy sources on earth?
Sun
Radioactivity
Lightning
Volcanoes
What are the four main steps in the creation of the earliest cells?
1 - abiotic synthesis of small organic molecules
2 - joining of small molecules into macromolecules
3 - Packing of molecules into probionts
4 - Origin of self replicating molecules
What are probionts?
An aggregation of organic molecules, surrounded by a membrane, that abiotically coalesces into resemblances of living matter
What did self replicating material make possible?
Inheritance
What was the first genetic material?
RNA
What was discovered that scientists base the origin of early life on?
Self splicing RNA, capable of catalysing their own excision from parent molecules
What is the primordial soup theory?
life began in an ocean as a result of a combination of chemicals from the atmosphere and some form of energy to make amino acids etc.
What are chemoheterotrophs?
Carbon source and energy both come from organic compounds
What are chemoautotrophs?
Carbon source from Co2, energy from inorganic chemicals
What are photoheterotrophs?
Carbon source from organic material, energy from light
What are photoautotrophs?
Carbon source from CO2, energy from light
What are Obligate Aerobes?
requires oxygen
What are Obligate anaerobes?
only anaerobic respiration
What are facultative anaerobes?
both aerobic and anaerobic respiration
What are the three types of evidence for presence of prokaryotic life?
Fossil Stromatolites, Fossil microorganisms, Carbonaceous matter
What are stromatolites?
layered rocks that form when certain prokaryotes bind thin films of sediment together, form in hyper saline conditions
Where is evidence of fossilised microorganisms found?
silicified in cherts, and acritarchs
How can carbonaceous matter be chemically tested for evidence of early life?
Rubisso has preferential carbon isotope uptake -C12 is better, so signals seen in isotopic ratios in carbonaceous remains
What do cyanobacteria produce as a byproduct of metabolism?
Oxygen
How is most atmospheric 02 produced?
Photosynthesis step of splitting water
What happened when photosynthesis first evolved?
free oxygen dissolved into surrounding water, very reactive
What are the early oxygen sinks?
Volcanic gases, dissolved iron in the ocean, microorganisms carrying out respiration aerobically
What are BIFs?
banded iron formations, formed when oxygen dissolved into the ocean and reacted with iron to precipitate out as an oxide. , O2 could only gas out once all iron was reacted and sea is saturated with oxygen
