Early Earth and Prokaryote Flashcards
when was the Earth formed?
~4.5 bya
when was the earliest life form found?
~3.5 bya
what is the earliest life from known as?
LUCA - last universal common ancestor
what were the earliest fossils found? where?
prokaryotes found in sedimentary rocks called stromatolites
why did the layers in the rocks of stromatolites form?
the prokaryotes had slime layers/capsule and sediment would have stuck to them
when did the first photosynthetic prokaryotes originate? who were they?
~2.5 bya
cyanobacteria
what did photosynthetic prokaryotes do?
their waste product O2 created an aerobic environment
how long were prokaryotes the sole inhabitants of Earth for?
~2 billion years
what two groups can prokaryotes be split into?
Archaea and Bacteria
when did eukaryotes first arise? how?
~1.7 billion years ago
endosymbiosis - the coming together of prokaryotes
for nearly 90% of its existence, life on Earth has been confined to what environments?
H2O
what were the first land organisms?
plants in a mutualistic relationship with fungi living on the roots
what do most biologists agree that life evolved from?
evolved from inorganic materials that becomes ordered into the the molecules of life
what were these inorganic molecules able to do?
replicate and perform metabolism
early condition of the earth
lightning, volcanic activity, meteorite bombardment, acidic oceans, and high radiation were all more intense in the primordial universe
what do some scientist postulated that the primitive earth favored?
favored reactions that formed organic compounds from inorganic sources
why cant inorganic sources form organic compounds present day?
the atmosphere is rich in O2 and O2 affinity for electrons attacks chemical bonds
making organic compounds requires what? what provided this?
much energy probably provided by lightning and UV radiation because they early Earth lacked ozone (O3)
who created laboratory conditions comparable of those to primordial Earth?
Miller in conjunction with Urey
what did the primordial lab atmosphere consist of?
CH4, NH3, H2O, H2
what mimicked lighting in the lab?
sparks that were discharged in the synthetic atmosphere
what happened to the solution in the flask?
went from clear to murky brown as a variety of organic compounds, amino acids, and monomers had formed
“primordial soup”
what happened to the monomers in the flask? without the help of what?
come together to form polymers without the aid of enzymes, unlike monomers today
how did polymerization occur in early earth?
in vitro when monomers are dropped onto hot clay, sand, or hot rock
this process evaporates water and concentrates monomers that then form proteinoids
what are proteinoids?
polypeptides, primary level, made by abiotic means
why might’ve clay been important in polymerization?
monomers could bind to charged sits on clay particles
clay could’ve functioned as a lattice that brought monomers close together and then metal ions could function as catalysts joined them into polymers
what is an alternative to clay?
Fe pyrite - fool’s gold
that could’ve provided charged surface and electrons from this iron/sulfur compound to support bonding between monomers
what could have living cells have been preceded by?
protobionts - “early life”
droplets of macromolecules that maintain an internal environment separate from their surroundings
what properties of life do protobionts show?
metabolism and respond to a stimulus
what do protobionts produced in labs have
surrounded by a shell that is semipermeable and some form a phospholipid bilayer
what was the first genetic material?
RNA
what happened as protobionts droplet grew?
they split and split again and their molecules would become diluted if they could not replicate before division
if a metal atom is added as a catalyst, what happens to the RNA nucleotides made?
it goes from 5-10 to sequences up to 40 nucleotides long copied with less than 1% error in base-pair rules
what are the first proteins believed to be made from?
RNA alone
what would’ve the first proteins made been?
enzymes that aided in replication of RNA
since laboratory simulations cannot prove that life evolved this way, what is another idea?
life on Earth can from space
panspermia - idea that meteorites hitting early Earth brought organic compounds with them like monomers and cells
what is the debate for where life began?
most favor shallow water or moist sediments as the most likely sites for life’s origins
now some feel that life evolved in hydrothermal vents and early life lived off of sulfur compounds (H2S) and it would’ve protected the first life forms from the inhospitable surface of Earth
what effect does the change from 5 kingdom classification to 3 domain systems have?
it assigns more significance to the ancient evolutionary split between bacteria and archaea by using the super kingdom/domain
older word for bacteria
monera
where are prokaryote on earth?
almost everywhere on earth
how many prokaryotes are in a handful of soil?
more than the total number of people that have lived
what is the largest bacteria the size of?
a period
how much of prokaryotes are dangerous?
only a minority of prokaryotes cause diseases and a majority are essential to all life of Earth
how are prokaryotes essential?
some decompose dead organisms, returning essential nutrients to the soils which plants then use
how many prokaryote species are there?
an estimated ~4 million species on earth
what does archaea mean?
ancient
