Intro to Bio 1.3 Early Evolution on Planet Earth

1) Protocells(Origin of Life) ~4 BYA
2) Bacteria ~3.8 BYA
3) Archea ~3.7 BYA
4) Photosynthetic Bacteria ~3.5 BYA
5) First Eukrayotes ~2.7 BYA
6) Oxygen Revolution ~2.2 BYA

- Hadean Eon led to possibility of protocells ~4 BYA
- Prokaryotic (most ikely bacterial domain) ~ 3.8 BYA
- Conditions were anaerobic on Earth

- thought to arise slightly after Bacteria ~3.7 BYA

- Beginning of anaerobic bacterial photosynthesis ~3.2 BYA
- Aquifex is an example of a living fossil. It has a cyclic photosynthesis and is an extremophile growing at 95C

- Stromatolite fossil
- North Pole, Australia, 3.5-3.0 BYA
- Constructed by Cyanobacteria
- AKA "blue-green algae"

- Beginning of more complex life ~2.7 BYA
- Eukaryotes can be considered a single branch of the Asgard archaea

1) Bacteria
2) Archaea
3) Eukarya

-Explains the origin of eukaryote cells including the organelles starting as a symbiotic relationship between cells of varying types that ultimately resulted in engulfing one of th eorganisms into the other.

-No oxygen early because there was no source. Oxygen is highly reactive.
- Development of oxygenic or non-cyclic photosynthesis led to slow increase of oxygen present in the atmosphere
- Detect oxygen by presence of iron an dsulfer oxidized compounds (seen in fossil deposits)

- O2 levels in the atmosphere slowly increased
- Originally only .000001% (1ppm)
- When O2 reached ~15% of atmosphere, reacted with iron to form iron oxides
- Layers of iron oxide 1000s of m thick deposited on bottom of oceans 2 BYA
- Aerobic respiration became dominant form of metabolism amongst Bacteria
- Anaerobes retreated to marginal enviornments

- Chromosome: Circular DNA
- Ribosome synthesize its own proteins
- Grows divides, an dduplicates its own DNA
- Eukaryotic cell withought chloroplasts cannot make chloroplasts
- Synthesizes ATP using light energy (photosynthesis)

1) Snowball Earth 800-600 MYA
2) Ediacaran 600-540 MYA
3) Cambrian explosion 540 MYA
4) Colonization of Land 360 MYA
5) Permian Extinction 250 MYA
6) Cretaceous Extinction 65 MYA