History of Life On Earth Flashcards
How long ago did the Earth form?
4.6 billion years ago
what did earths early atmosphere consist of and not consist of?
-lots of water vapor due to volcanic eruption
-methane, nitrogen, ammonia, and some CO2
-no oxygen
what 4 big stages were responsible for life forming on earth?
-abiotic synthesis
-synthesis of polymers
-packaging into protocells
-origin of self replicating molecules
what is abiotic synthesis?
-the accumulation of organic monomers: raw materials forming amino acids as well as sugars, lipids, nucleic acids
what is synthesis of polymers?
-abiotic synthesis of RNA can spontaneously occur from precursor molecules
-polymers can be formed through dripping amino acids and RNA onto hot rock
what are protocells?
-early cells: self replicating molecules with early enzymes & vesicles
what is the origin of self replication?
-RNA - carries out enzyme like activities
-can catalyze own reproduction with ribosomes, likely meaning world was RNA filled at first before DNA
what are the 3 main methods of documenting early life?
- sedimentary strata: used to determine age of fossils based on order in stratum
- index fossils: similar fossils found @ same strata in different locations
- radiometric dating: using 1/2 life of isotopes to determine age of fossils
when were the oldest fossils found and what kind of fossil were they?
-3.8 billion years ago: oldest fossils in the form of prokaryotic cells: anaerobic, heterotrophic (cannot produce own food)
when were the first cyanobacteria found and what did they do?
-3.5 billion years ago
-underwent photosynthesis, meaning O2 produced could react with iron to form iron oxide, rusting rocks
how did o2 become prevalent in the atmosphere?
-o2 dissolved in water, reacted with dissolved iron
-iron became iron oxide, accumulated in sediment
-eventually, o2 accumulated to the point where it became saturated and “gassed out” entering the atmosphere
when did oxygen accumulate in the atmosphere and when did the first eukaryotic cells show up?
2.7 bya - oxygen accumulates
2.1 bya - eukaryotes found
what is the endosymbiotic hypothesis?
-a theory that eukaryotic cells came into existence by including chloroplasts & mitochondria into their cytoplasm [AKA - saying that these are both bacterial organisms that are not “our own”
when did multicellular eukaryotes and organisms begin to show up?
1.2 bya - oldest fossils of multicellular eukaryotes
1.0 bya - 700 mya: complex multicellular organisms begin to show up
what was the cambrian explosion and when did it occur?
-cambrian explosion refers to an event that formed most of the major phyla: sponges, arthropods, molluscs, etc
-occurred 540-520 mya
