Life 'top-down' Flashcards
What is NASA’s working definition of life?
A self-sustaining, chemical system capable of undergoing Darwinian Evolution
When did Homo erectus emerge and name 4 of its adaptations
~2.0 Ma
- Larger brain
- Long distance running/walking
- Predator of mammoths
- Fire users
When did Homo habilis emerge and what was it capable of?
~2.5 Ma
- First tool maker
- No group activity but planning
When did the first biped emerge?
~ 3.7 Ma
When was the origin of the hominids?
~ 6 Ma
During which period were forests widespread?
~375 Ma - 40 Ma (grazers)
When does the first evidence for leaves and roots emerge? First vascular plants?
~ 420 Ma
~ 425 Ma
When is the fist evidence for land plants?
First spores from ~475 Ma, first plant fragments ~450 Ma
What were the ediacarans?
From 590 Ma till 540 Ma, often fern-like/frond-like. Now though to be ancestral to certain modern animals such as star fish
Required 5% of modern O2
When does fossil evidence for the eukaryotes emerge?
From around 2 Ga, however consensus opinion breaks up
Why is anoxygenic photosynthesis believed to have evolved first?
- oxygenic photosynthesis is the most complex of microbial metabolisms
- anoxygenic requires simpler machinery
Define a biomarker
compound found in geological materials that has a structure derived from a specific biological precursor
e.g hopanes (bacteria) and steranes (eukaryotes)
Arguments for and against carbon isotope factionation at 3.8 Ga?
- 13C less that 20% which is very low
- However, sample is very old and abiotic processes can produce this
Arguments for and against Apex chert being the oldest fossil at 3.5 Ga?
- fossil cyanobacteria, made of isotopically depleted carbon
- Branched abiotic graphite, depletion via abiotic processes
