origins of life Flashcards
earth formed how long ago
4.5 billion years
how did conditions on early earth contribute to rise of life?
lots of molecules around that are needed for life; NH3, CH4, H2, etc.
conditions in ‘reducing form’
miller + urey
mimic conditions on early earth; electricity (lightning) methane ammonia hydrogen, and show that when you boil these together, you get amino acids!!! shows how life formed
primordial soup
early ocean waters- all the right organic compounds for life present together in early earth. first cells , heterotrophs, came out of this.
clay layers + peptide bonds
Clay molecules- form exact same spacing as that between amino acids. Perhaps amino acids stuck to clay in perfect spacing and caused them to create peptide bonds. Clay layers as a catalytic effect to form macromolecules
RNA world hypothesis
Idea: first nucleic acids to form were RNA. More likely to get RNA precursors than DNA precursors
Maybe RNA molecules were first nucleic acids. DNA form evolved in order to provide more stability- DNA is more stable than RNA.
what coincides with the rise of life
free atmospheric oxygen
Saurischians and ornithischians
‘lizard hips’ vs ‘bird hips.’ ironically, birds evolved from the lizard hips ones
dates of the 2 major extinctions
65 mya- cretacean-tertiary ; dinos go extinct
250 mya; permian extinction; lost 95% of life including trilobites
trilobites
used to be the dominant animal in the ocean in permian times. like a horsehoe crab
which ancestor did the ammonites leave behind
chambered nautilus
evidence of meteor wiping dinos out
- Formed meteor theory when they found a high concentration of Iridium in the rock layer from 65 MYA. It’s usually a rare, trace element, but it’s found in meteorites
- Looked at the layers of rock around the planet from 65 MYA, everywhere. (Meteor hit, debris settled all over earth.)
- Looked for a crater of expected size (6 km across) – and there is one on the Yucatan, right size and age
when did primates arise
post-dinos
did branches of early humans ever overlap?
yes- homo sapiens overlap with neanderthals
what came first- upright walking or brain size
upright walking
