prokaryotic cells have differing oxygen requirements · prokaryotic cells have differing oxygen...
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Prokaryotic cells have differing oxygen requirements.
OBLIGATE AEROBES
Use O2 for
respiration;
cannot grow
without it
FACULTATIVE ANAEROBES
Use O2 when
available;
ferment when
O2 isn’t
available
OBLIGATE ANAEROBES
Poisoned by O2; use
fermentation or live
by anaerobic
respiration. In
anaerobic respiration,
inorganic molecules
like SO4, NO3, and
Fe3+ are used instead
of oxygen.
A B C
BILL: For each sample, determine the oxygen requirements for the bacteria living within the bracketed area.
VITAL ROLES IN ECOSYSTEMS: Producers
VITAL ROLES IN ECOSYSTEMS: Decomposers
VITAL ROLES IN ECOSYSTEMS: Nitrogen Fixers in the Nitrogen Cycle
Nitrogen (N 2) in the atmosphere is converted into ammonia (NH3), making the nitrogen available to plants
and animals.
Go back…
The poisonous gas …Oxygen • The amount of free oxygen
in the atmosphere increased after the evolution of photosynthesis in prokaryotes
• O2 appeared from about 2 billion years ago and reached about 21% 1 billion years ago
• Obligate anaerobes either became extinct or found niches where oxygen is absent
Stromatolites, Shark Bay Australia
Oxygen atmosphere • Oxygen begins to accumulate 2.7 bya
• evidence in banded iron in rocks (rusting)
• makes aerobic respiration possible
Stromatolites Fossilized mats of prokaryotes resemble modern microbial colonies