tree of lifffffe

earth timeline

earth is about 4.6 billion years old, life first appears at about 3.6 billion years old

early earth atmosphere

nitrogen gas, carbon dioxide, hydrogen sulfide, hydrogen cyanide, water vapor, ammonia, and methane (very little oxygen)

hostile conditions of earth

poison atmosphere, lightning, volcanic eruptions, metorite bombardment, UV radiation

primordial soup hypothesis

Miller and Urey test whether organic molecules are produced from inorganic molecules dissolved in water with added lightning

protobionts

membranes that enclosed proteins and carried out growth and division and had a semipermeable membrane, formed in the lab using simple lipids that form capsules

RNA world hypotheis

RNA existed before DNA and proteins would be earliest genetic material, in early conditions it is thought that RNA could have formed and replicated itself

early cells

bacteria-like organisms ate organic molecules in primordial soup, eventually turning into autotrophs who make their own food from toxic chemicals, then photosynthetic prokaryotes

how did photosynthetic prokaryotes help things

produced oxygen, changing the atmosphere to have more oxygen, also producing an ozone layer to protect from UV radiation

endosymbiont theory

prokaryotic cell engulfs another cell and forms a symbiotic relationship

causes of mass extinction

rapid climate change, asteroid impact, afterwards massive adaptive radiation produces new groups that take advantage of new ecological opportunities

permian extinction

250 million years ago, 90% of all marine animals went extinct, pangea emerged

cretaceous extinction

65 million years ago, 50% of all marine species went extinct, low angle comet, cooling of the earth

ecological stress caused by humans has increased extinction rate

global climate change, habitat destruction, direct hunting