ecological diversity
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114 Terms
What are the three major types of microbial diversity?
Phylogenetic diversity (evolutionary relationships), Metabolic diversity (biochemical transformations), and Functional diversity (form and function of organisms).
What is phylogenetic diversity?
The evolutionary relationships among organisms.
What is metabolic diversity?
The variety of biochemical pathways organisms use to obtain energy and nutrients.
What is functional diversity?
The diversity of functions organisms perform and how they interact with their environment.
What are the three components of functional diversity?
Physiological diversity, Ecological diversity, and Morphological diversity.
What is physiological diversity?
Differences in metabolism, function, and biochemistry.
What is ecological diversity?
Differences in how organisms interact with their environments.
What is morphological diversity?
Differences in cell shape and physical structure.
Why doesn't functional diversity always match phylogeny?
Because of gene loss, convergent evolution, and horizontal gene transfer.
What is gene loss?
The loss of genes or functions that ancestors possessed.
What is convergent evolution?
Independent evolution of similar functions in unrelated organisms.
What is horizontal gene transfer?
The transfer of genes between unrelated organisms.
What is phototrophy?
The use of light energy to produce chemical energy.
What is photosynthesis?
The conversion of light energy into chemical energy.
What is a phototroph?
An organism that uses light as its energy source.
What is a photoautotroph?
An organism that uses light for energy and CO₂ as its carbon source.
What are the two major requirements of phototrophy?
Convert light into ATP and generate reducing power (NADPH) to reduce CO₂.
What pigment is primarily responsible for photosynthesis?
Chlorophyll.
What is bacteriochlorophyll?
A photosynthetic pigment found in photosynthetic bacteria.
What is the role of a light-harvesting complex?
Captures light and transfers energy to the reaction center.
What happens in the reaction center?
Excited electrons are transferred through an electron transport chain.
What is photophosphorylation?
The production of ATP using light-driven electron transport.
What is the proton motive force (PMF)?
A proton gradient used to drive ATP synthesis.
What is oxygenic photosynthesis?
Photosynthesis that uses water as an electron donor and produces oxygen.
What organisms perform oxygenic photosynthesis?
Cyanobacteria, algae, and plants.
What is the electron donor in oxygenic photosynthesis?
Water (H₂O).
What is produced when water is oxidized?
Oxygen (O₂), electrons, and protons.
What are the two photosystems in oxygenic photosynthesis?
Photosystem II (P680) and Photosystem I (P700).
What does Photosystem II primarily produce?
ATP through photophosphorylation.
What does Photosystem I primarily produce?
NADPH (reducing power).
What is anoxygenic photosynthesis?
Photosynthesis that does not produce oxygen.
Why doesn't anoxygenic photosynthesis produce oxygen?
It does not use water as the electron donor.
What electron donors do anoxygenic phototrophs commonly use?
H₂S, elemental sulfur (S⁰), or organic compounds.
Where are anoxygenic phototrophs commonly found?
Lighted environments lacking oxygen.
Why are anoxygenic phototrophs important evolutionarily?
They were likely the first phototrophs on Earth.
What is the Calvin cycle?
The primary pathway used to fix CO₂ into organic carbon.
What enzyme fixes CO₂ during the Calvin cycle?
Rubisco.
What are carboxysomes?
Protein structures that concentrate CO₂ around Rubisco in many bacteria.
What are cyanobacteria?
Oxygenic photosynthetic bacteria.
What pigments do cyanobacteria contain?
Chlorophyll a and phycobilins.
Do all cyanobacteria perform oxygenic photosynthesis?
Yes.
Can all cyanobacteria fix nitrogen?
No, only some species.
What specialized cell performs nitrogen fixation in filamentous cyanobacteria?
Heterocysts.
Why are heterocysts important?
They protect nitrogenase from oxygen.
Approximately how much of Earth's photosynthesis is performed by cyanobacteria?
About 35% overall and about 80% in marine environments.
What is chemolithotrophy?
The use of inorganic compounds as electron donors.
What are chemolithoautotrophs?
Organisms that oxidize inorganic compounds and fix CO₂.
What determines how much energy is produced during respiration?
The difference in reduction potential (ΔE₀') between electron donor and acceptor.
What does a larger ΔE₀' produce?
More energy and ATP.
Name four common inorganic electron donors.
H₂, H₂S, NH₃, and Fe²⁺.
Why does iron oxidation produce relatively little energy?
The difference in reduction potential between Fe²⁺ and O₂ is small.
What organism is a classic iron-oxidizing bacterium?
Acidithiobacillus ferrooxidans.
At what pH do iron oxidizers usually thrive?
Acidic conditions (around pH 2-3).
What is respiration?
The transfer of electrons from donors to acceptors through an electron transport chain.
What proteins are commonly found in electron transport chains?
Cytochromes, quinones, and iron-sulfur proteins.
What generates ATP during respiration?
The proton motive force.
What is fermentation?
An anaerobic process in which organic molecules serve as both electron donors and acceptors.
Does fermentation require an external electron acceptor?
No.
How is ATP produced during fermentation?
Substrate-level phosphorylation.
What regenerates NAD⁺ during fermentation?
The reduction of fermentation products.
What is syntrophy?
A cooperative interaction where two organisms together degrade a compound that neither can degrade alone.
Why is syntrophy beneficial?
One organism removes products that would otherwise inhibit the other's metabolism.
What is the sulfur cycle?
The cycling of sulfur between reduced and oxidized forms by microorganisms.
What reduced sulfur compounds commonly serve as electron donors?
H₂S, S⁰, and S₂O₃²⁻.
What happens to pH during sulfur oxidation?
It decreases because H⁺ is produced.
What is a sulfur-oxidizing bacterium?
A bacterium that gains energy by oxidizing reduced sulfur compounds.
What is Beggiatoa?
A filamentous sulfur-oxidizing bacterium found at oxic-anoxic boundaries.
What is sulfate reduction?
The anaerobic reduction of sulfate (SO₄²⁻) to H₂S.
Name a sulfate-reducing bacterium.
Desulfovibrio.
What is the nitrogen cycle?
The movement of nitrogen among atmospheric, inorganic, and organic forms.
What is nitrogen fixation?
The conversion of atmospheric N₂ into ammonia (NH₃).
What enzyme performs nitrogen fixation?
Nitrogenase.
Why is nitrogenase unusual?
It is extremely sensitive to oxygen.
What are diazotrophs?
Organisms capable of fixing atmospheric nitrogen.
Name three free-living nitrogen-fixing bacteria.
Azotobacter, Azospirillum, and Beijerinckia.
What is nitrification?
The oxidation of NH₃ to NO₂⁻ and then NO₃⁻.
Is nitrification energy-rich or energy-poor?
Energy-poor.
Why do nitrifying bacteria grow slowly?
Because nitrification yields little energy.
Are most nitrifiers aerobic or anaerobic?
Aerobic.
What environments favor nitrification?
Environments rich in ammonia, such as sewage treatment plants.
What is anammox?
Anaerobic ammonium oxidation.
What is the overall result of anammox?
Conversion of NH₄⁺ and NO₂⁻ into N₂ gas.
What special organelle do anammox bacteria possess?
An anammoxosome.
Why is anammox important?
It removes nitrogen from wastewater.
What is denitrification?
The anaerobic reduction of nitrate to gaseous nitrogen compounds.