Theme 5C Flashcards
1
Q
Age of Earth
A
- 4.5 Billion years old
- Unicellular Prokaryotes by 3.5 billion
- Multicellular life by 2.1 billion years ago
- Complex multicellular animals 650 million years ago
2
Q
Early Earth Atmosphere
A
- Little oxygen - reduced atmosphere
- Oxidation prevented by removal of oxygen & other oxidizing gases or vapours
- Input of E would transform these into organic compounds in ‘primordial soup’
3
Q
Urey Miller Experiment
A
- Simulated early Earth conditions & tested chemical origin of life
- 2% of carbon was in amino acids, 13 of 22 used in living cells
- Still debate about Earth’s original atmosphere & reducing molecules present
4
Q
Ocean Environment
A
- Reducing like atmosphere
- Some pockets still present in deep oceans, sulfur bacteria/thermophiles habitats
- Vent communities possbile model for early evo of life
5
Q
Chemolithotrophy
A
- Allows prokaryotes to maximize ATP production by using dif “food” source - i.e. dif electron donors
- Electron transport chain
6
Q
Archean - Proterozoic
4 billion -
A
- Archaean where first evidence of life formed
- Prokaryotes, Eukaryotes, Multicellularity
- Great oxygenation event
7
Q
Ediacaran Fauna
A
- First animal fossils
- Evolution wild west - new traits all the time
8
Q
First Prokaryotes
A
- Oldest known specimens from 3.2-3.4 billion years old, from northern Canada, South Africa & Australia
- Many found in stromatolites, where cyanobacteria form a biofilm that traps layers of sediment
- Stromatolites appear in fossils dating to 2.7 billion years ago, decline in abundance by 500 million years ago
9
Q
Cyanobacteria (3 bya)
A
- Obtain E through photosynthesis
- Producing gaseous O as a byproduct of photosynthesis –> converted early reducing atmosphere into an oxidizing one
- Dramatically changing composition of life forms on Earth by stimulating biodiversity & leading to the near-extinction of oxygen-intolerant organisms
10
Q
Great Oxygenation Event
A
- Free oxygen accumulates in atmosphere ~2.5 bya, with huge increase 850 million years ago
- Evidence - Many new rock types formed (hydrated & oxidized), banded iron formations
11
Q
Why long gap b4 O2 atmosphere?
A
- Long period of anoxygenic photosynthesis
- Free O2 reacted with ocean chemistry
- Banded iron formations - O2 reacting with iron & sulpher from these rocks
- Since Cabrian O2 has been b/w 15-30% of atmosphere, high of 35% in Carboniferous
Anox - photosynthesis with no oxygen biproduct
12
Q
First Eukaryotes
A
- Larger than prokaryotes; nucleated; membrane bound organelle
- Mitochondria & plastids were free-living bacteria engulfed by another cell as an endosymbiont
13
Q
Endosymbiosis
A
- Origin of key eukaryotic organelles result of symbiosis b/w separate single-celled organisms
- Archae + bacteria = eukaryote?
14
Q
Evidence for endosymbiosis
A
- Organelles bound by membranes
- Organelles have own DNA separate from DNA in nucleus
- Mitochondrial DNA sequences similar to bacteria/chloroplast DNA sequences similar to those of some cyanobacteria
- Reproduction: Mitochondria replicate by pinching
15
Q
Major episodes in history of life
Paleozoic
A
- Cambrian explosion; invasion of land; appearance of gymnosperms; major groups of tetrapods
- Edicaran fauna - lots of weird forms of animals now extinct, 640 mya
16
Q
Major episodes in history of life
Cambrian Explosion
A
- Rapid appearance of many groups of organism ~530 mya
- Preceded by appearance of small shell parts
- Unusually high # of sites with soft body preservation
- Includes evidence of arthropods, echinoderms, & large # of extinct forms
- Features of many modern groups appear: Heads, mouths , eyes, legs
17
Q
Why was Cabrian Explosion of Life?
A
- Genetic diversity present
- Increasing O2 lvls from eukaryotic algae
- Evo of grazing, reduction of algal mats - opening of new niches
- Shift in ocean chem favouring production of calcium carbonate
18
Q
Extinction
A
- Normal background rate of extinction varies but usually less than or equal to rate of speciation over time
19
Q
A
