Early Life on Earth & Prokaryotes: Bacteria & Archaea

Eons

1. Hadean

2. Archaean

3. Proterozoic

4. Phanerozoic

Hadean Eon

4.6-4 bya. Before life arose

Archaeon Eon

4.0-2.5 bya. featured the evolution of early life, including bacteria, archaea, and the first cyanobacteria capable of oxygenic photosynthesis. 1st fossil evidence of early life

Proterozoic Eon

2.5 bya - 542 mya. oxygenic accumulation. First unicellular and multicellular eukaryotes. microbial and multicellular life flourished

Phanerozoic Eon

542 mya to present. Begins with Cambrian explosion. Proliferation of animal, fungal, and plant life

oxygen revolution

Early Proterozoic

1. Cyanobacteria split water making oxygen as byproduct

2. Free oxygen reacted with soluble iron in the oceans, causing iron oxide (rust) to precipitate out of the oceans

3. Evidence is banded iron formations in sedimentary rocks

Cambrian explosion

Early Phanerozoic

1. Accumulation of oxygen facilitated evolution of larger bodies, organs, and tissues with higher metabolic rates

2. Resulted in mass extinction of anaerobic organisms

Bacteria and Archaea

1. prokaryotic

2. produce asexually by binary fission

3. lack a nuclei and organelles

4. single circular chromosome

5. unicellular

6. horizontal gene transfer

Eukaryote

1. unicellular and multicellular

2. has nuclei and membrane-bound organelles

3. multiple, linear chromosomes wrapped around histones

4. mitosis and meiosis

5. vertical gene transfer

6. plant cell wall-cellulose,

fungi cell wall- chitin

cell membranes

1. Bacteria and eukaryotes have similar membranes with phospholipids with fatty acid chains

2. Archaea has unique plasma membrane with phospholipids with branched isoprene chains

Ribosomes and RNA polymerase

1. Bacteria has distinct

2. Archaea and Eukarya have similar

Evidence for domains

1. Microfossils

2. Biosignatures

3. Fossilized stromalites (layered sedimentary structures formed by microbes)

phototroph

use light to make ATP

chemotroph

gain energy from chemical compounds

autotroph

makes own organic molecules by reducing inorganic compounds like carbon dioxide

heterotroph

require carbon already in form of organic molecules

photoautotroph

energy source: light

carbon source: CO2

chemoautotroph

energy source: inorganic chemicals

carbon source: CO2

photoheterotroph

energy source: light

carbon source: organic compounds, cannot fix carbon dioxide into organic carbon

chemoheterotroph

energy source: organic compounds

carbon source: organic compounds

Importance of Prokaryotes

1. Protect us from pathogens, help digest food, make vitamins/nutrients, regulate moods, influence activity levels

2. biogeochemical cycling of nitrogen, carbon, phosphorus, and other nutrients

3. microbial bioremediation to remove pollutants