test 2: abiogenesis and natural selection Flashcards
the hadean (first geological eon)
- life originated under very different conditions
- atmosphere of early earth may have been a reducing atmosphere thick water vapor, nitrogen and its oxides, carbon dioxide, methane, ammonia, hydrogen and hydrogen sulfate (changes examined through ice/permafrost)
abiogenesis (chemosynthetic origin of life)
- conditions of early planet were very different from today
- gases like nitrogen, methan and hydrogen sulfide
- 1920s: oparin and haldane hypothesized that early oceans were a chemical soup
oparin and haldane
- independently hypothesized:
1. earth’s early atmosphere was a reducing (electron-adding) environment in which organic molecules could have formed
2. energy for this organic synthesis could have come from lightning and intense UV radiation
life arose from a “primordial soup”
miller and urey
- tested oparin and haldane’s theory
- using atmosphere thought to exist during early Earth
- under extreme heat situations, researchers have been able to create polymers without the help of enzymes
- WW2 and submarines allowed them to test in deep sea conditions
protobionts
- collections of abiotically produced molecules surrounded by a vesicle-like structure (rudimentary cell)
- replication may have originally have been through RNA; occasionally a copy error would occur and protein becomes more stable (better for selection)
- DNA more stable than RNA and less copy errors
synthesis of polymers
- lab simulations of early earth conditions produced organic polymers
- polymers made by dripping solutions of monomers onto hot sand, clay or rock
- nucleotides + hot sand/clay/rock = RNA
- everything started as RNA, became DNA because it was more stable
4 main stages to creating simple cells:
1 - abiotic synthesis of small organic molecules
2 - joining small molecules into macromolecules (ex: proteins)
3 - packaging protobionts with membranes capable of isolating an internal environment
4 - origin of self-replicating molecules; first RNA then DNA; eventually photoautotrophs became prominent (CO2 –> O2; leads to atmosphere)
self-replicating RNA came first
- first genetic material
- could catalyze protein formation
- molecules are flexible, single stranded and can assume a variety of shapes
ribozymes
RNA enzymes can make copies of RNA, provided they are supplied with monomers
evolution of eukaryotes
- endosymbiosis (mitochondria and chloroplasts were prokaryotes)
- entry gained as undigested prey or internal parasites
- anaerobic endosymbionts greatly favoured
evidence of endosymbiosis
- inner membrane have same transport mechanisms and enzymes as prokaryotes
- replicate by a splitting process
- have their own DNA and ribosomes, replicate independently of other DNA
early ideas of evolution
- philosophers had idea that evolution might exist
- book of genesis: judeo-christian culture took over
ie: creationists dogma, other cultures believed in some form of evolution
evidence began to accumulate (fought by church)
Carolus Linnaeus
- classify life’s diversity “greater glory of God”
- founder of taxonomy
- developed two part binomial format for naming species
Georges Cuvier
- studied fossils extensively
- idea of old fossils at bottom, newer ones on top
- idea of extinctions being a common occurrence throughout history
- opposed idea of evolution, advocated idea of catastrophism
catastrophism
Cuvier’s idea that boundaries between strata were due to local floods or droughts destroying present species
