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Chapter 26
Early Earth and the Origin of Life
Major events in earth’s history:
Major events in earth’s history:
4.5 billion years ago
Earth is formed
Major events in earth’s history:
3.5 billion years ago
Earliest fossil prokaryotes
Major events in earth’s history:
2.7 billion years ago
Oxygen accumulates in atmosphere
Major events in earth’s history:
2.7 billion years ago
Oxygen accumulates in atmosphereCyanobacteria evolve oxidative photosynthesis
Major events in earth’s history:
2.1 billion years ago
First eukaryotic cells
Major events in earth’s history:
1.2 billion years ago
First multicellular algae
Major events in earth’s history:
600 million years ago
First animals
Major events in earth’s history:
540-520 million years ago
“Cambrian explosion”
Major events in earth’s history:
500 million years ago
Colonization of land
Major events in earth’s history:
The origin of life:
1.Abiotic (nonliving) synthesis of small organic molecules
2.Joining these monomers into polymers
3.Origin of self-replicating molecules
4.Packaging into “probionts” (droplets with membranes).
The origin of life:
1.Abiotic (nonliving) synthesis of small organic molecules
2.Joining these monomers into polymers
The Miller-Urey experiment.
The origin of life:
3. Origin of self-replicating molecules.
The origin of life:
4.Packaging into “probionts” (droplets with membranes).
Dumb
kings
play
chess
on
fine
green
sand
domain
kingdom
phylum
class
order
family
genus
species
eukaryote
animal
chordate
mammal
anthropoid
primate
homo
sapiens
Domains Kingdoms
Archaea
Bacteria
Eukarya
Monara
Monara
Protista
Plantae
Fungi
Animalia
Domains Kingdoms
Archaea
Bacteria
Eukarya
Monera
Monera
Protista
Plantae
Fungi
Animalia
Prokaryotes
Most have cell walls made of peptidoglycan
Many have polysaccharide capsule
Many have sticky fimbriae and pili
About half move with flagella
Some have specialized membranes
DNA in one big loop plus plasmids.
Prokaryotes
Photoautotrophs use sunlight
Chemoautotrophs use inorganic fuels
Heterotrophs consume carbon.
Oxygen
Aerobe uses oxygen
Anaerobe does not use oxygen
Obligate aerobes cannot grow without O2
Obligate anaerobes are poisoned by O2
Facultative anaerobes use O2 when it’s available but can also do fermentation.
Nitrogen
Prokaryotes are able to turn N2 into NH3 in a process called nitrogen fixation.
Archaeabacteria
Analysis of rRNA shows that some bacteria are more closely related to eukaryotes and belong in a domain of their own.
Extremophiles (thermophiles and halophiles)
Methanogens.
Symbiosis
Mutualism
Commensalism
Parasitism
.
