Lecture 10 Flashcards
Atmosphere 3.5bya
Earth was very hot; atmosphere contained mostly CO2, Nitrogen, and water vapor
-Life only existed in the ocean
Deep Sea Vents
- Temperature up to 450ºC
- Highly Acidic (pH=2.8)
- 300 atm
- Could be where life originated on earth
- Primary producers (?)
Chemoautotrophs
- 3.5 bya
- Energy comes from chemicals, not light
- ATP is produced by cellular respiration serving as the electron donor
First Life Forms
- 3.5 bya
- Chemoautotrophs
- Photosynthetic Organisms (Did not produce oxygen)
Photoautotrophs
- 3.5 bya
- Energy Source= Light
- Carbon Source=CO2
- Electron Source= Hydrogen Sulfide
- Waste Product= Sulfur and water
- CO2 + 2H2S + Light –> CH2O + H2O + 2S
Cyanobacteria
- 2.5 bya
- Energy Source= light
- Carbon Source= CO2
- Electron Source= Water
- Waste Product= Oxygen and Water
- CO2 + 2 H2O + Light–> CH2O + H2O + O2
- Now O2 can become abundant
Photosynthesis and Oxygen Revolution
- Oxygen first accumulates in oceans and lakes–then begins to “gas out” into the atmosphere.
- Some organisms found new conditions impossible
- Some were able to adapt (cellular respiration using O2 as a final e- acceptor)
- Accumulation of O2 led to the formation of an ozone layer, making life on land possible
Endosymbiosis Theory
Organelles of modern eukaryotes derived from the stable incorporation of alpha-Proteobacteria (future mitochondria) into an archaeon host cell, and Cyanobacteria (future chloroplasts) into an early eukaryotic cell
Endosymbiosis Evidence
Both mitochondria and chloroplast have their own bacterial-like genomes that encode their own bacterial-like ribosomes. rRNA sequences show their relatedness to modern bacteria
Primary Endosymbiosis
-Acquisition of the mitochondria and the chloroplast
Multicellularity
- Evolution of the eukaryotic cell sparked the evolution of greater morphological diversity than was possible with simpler prokaryotic cells
- Single-Cell eukaryotes gave rise to multicellular forms
- 1st multicellular organisms were probably small algae
- life remain mostly unicellular, plus several lineages of multicellular algae, until about 565-575 mya
Cambrian Explosion
- 550 mya
- massive radiation
- 50m.y. after 1st animals appeared, almost every other major group of animal had appeared
What might explain the rapid diversification of animals during the cambrian explosion?
- Changes in ocean chemistry
- Oxygen concentrations were finally high enough to allow for high energy required fro motile multicellular life
- Gene duplication Event
end- Cretaceous Extinction
- 65 mya
- Asteroid impact and climate change
- 70% of large plant and animal species died, including dinosaurs
- some mammals survived
- adaptive radiation of mammals (60 mya)
end- Permian Extinctions
- 250 mya
- Widespread Volcanic Activity
- Increase in global temperature
- Ocean Currents changed, sea levels dropped
- seas may have become anoxic
- 90% of marine species died
- 70% of mammals died
