abiogenesis
Tags
bio/astro
bio/eco
cegep/3
Word count
224 words
Reading time
2 minutes
Origin of life from inorganic compounds
early Earth
- CO2, H2, N2, water vapor
- Reducing atmosphere (no oxygen)
- Electrically charged
- Hot
abiotic synthesis
Spontaneous formation of small organic molecules from inorganic molecules
2 hypotheses:
- Prebiotic soup hypothesis
- Organic molecules formed in the atmosphere
- Supported by Urey-Miller experiment that forms sugar, nucleotides and amino acids
- Iron-sulfur world hypothesis
- Organic molecules formed at hydrothermal vents on the ocean floor
protocell
Origin of first cells
- Spontaneous assembly of macromolecules from small organic molecules
- Packaged into vesicles surrounded by phospholipid bilayer
- Maintains homeostasis
- Information: may have RNA
- Metabolism: RNA because more catalytic than DNA, e.g. ribozymes
- Reproduction: binary fission
early organisms
- Anaerobic prokaryotic heterotroph feeding on prebiotic soup
- Prokaryotic autotroph using photosynthesis and producing O2
- Aerobic prokaryotic heterotroph capable of cellular respiration
- Eukaryotic heterotroph (endosymbiosis with mitochondria)
- Eukaryotic autotroph (endosymbiosis with chloroplast)
oxygen revolution
Allows evolution of aerobes
formation of ozone layer
- UV forms O3 from O2 in the upper atmosphere
- O3 absorbs UV
- Decreases mutagenesis
- Enables living in surface waters and on land
LUCA
Last common ancestor of all life on Earth
Very similar to modern bacteria
Ajitani Hifumi