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scsc 301 exam 2 tamu smith Questions With Complete Solution1
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scsc 301 exam 2 tamu smith Questions With CompleteSolutions
an organism that can use CO2or CO3- (i.e., inorganic C) as a C source, and obtain
energy from the sun (photo) - or from the oxidation of inorganic elements or
compounds such as iron, sulfur, hydrogen, ammonium, and nitrites (chemo)? -
ANSWER Autotroph such as plants, algae, cyanobacteria, etc.
an organism that can only get carbon and energy from organic compounds? -
ANSWER Heterotroph such as bacteria, fungi, protozoa, etc.
an organism that grows only in the presence of molecular oxygen? - ANSWER
aerobe such as nitrifying bacteria
an organism that only grows in the absence of molecular oxygen? - ANSWER
Anaerobe such as archaea, denitrifying bacteria, some N-fixing bacteria
an organism capable of both aerobic and anaerobic metabolism? - ANSWER
facultative anaerobe
What functions do microorganisms provide in soil? - ANSWER -soil organic matter
stabilization, organic matter mixing, and aggregate formation
-breakdown of toxic compounds
-inorganic transformations: nutrient cycling
-nitrogen fixation
-plant protection
plant roots - ANSWER release C into soil via exudates, aid in aggregate formation,
use O2 for respiration (produce CO2)
Earthworms - ANSWER eat detritus (waste), organic matter and microorganisms,
form burrows, "nature's tiller" create casts- aggregation
termites - ANSWER complex social colonies, mound builders, symbiotic gut
microbes degrade cellulose, fungi farmers
nematodes - ANSWER -microbial predator- controls populations and releases
plant-available N
-moist, well-aggregated soils
-moved by pushing or "swimming"
Tardigrades - ANSWER abundant in mosses and
lichens, pioneer species, eats algae, bacteria, plant cells and mesofauna, called
water bears, moss piglets
protozoa - ANSWER mobile, single-celled bacterial predators; amoeba, ciliate,
flagellates; moist, well-aerated surface soils
, Algae - ANSWER photosynthetic, autotrophs, primary producers; wet surface soils;
can form symbiotic relationship with fungi to form lichen
Fungi - ANSWER eukarytoes, heterotrophic, diverse morphology, moist
environments; can be single-celled yeasts, filamentous molds or mushrooms with
macroscopic fruiting bodies
Bacteria - ANSWER prokaryotes, most abundant and diverse in soils; important for
many soil functions(bioremedation, decomposition, nutrient cycling)
Actinomycetes - ANSWER filamentous bacteria (branching morphology), aerobic
hetertrophs, non-acidic, moist, high C environments; produces antibiotics
compounds, some fix N especially in forests (frankia sp.)
Rhizobia - ANSWER -N-fixing bacteria
-Forms root nodules in leguminous plants
-important in grasslands and agricultural systems
mycorrhizal fungi - ANSWER symbiotic with plants, gets C from plant roots,
provides water and nutrients especially Phosphorous to plants
-provide protection to plants
Saprotrophic fungi - ANSWER gets C from ecosystem, degrades organic matter,
important for lignin degradation and SOM decomposition
Rhizoshpere - ANSWER layer of soil closely surrounding the plant's roots
Prime conditions for high microbial activity - ANSWER -Carbon availability
-quality C:N
-oxygen availability (greatest zone of activity is top 5 cm of soil bc good balance of O
and H20
-Good temperature is 20C-40C
-High calcium and neutral pH soils
-bacterial diversity increases with soil pH (acidic to alkaline soils)
Soil microbiome includes - ANSWER prokaryotes (bacteria), eukaryotes, and
archaea
Stable Organic Matter (humus) slow pool - ANSWER -Stable C, protected from
more degradation! Could be from mineral sorption, isolation in micro-aggregates, an
unfavorable environment. Overall, conditions that limit microbial access to and
degradation of C
-POM, biomolecules, degradation, complex molecules like lignin and phenols
-Biochar (VERY stable, charcoal)
-Colloidal characteristics: High surface area, High Cation exchange capacity (holds
onto cations or nutrients), High water holding capacity, negative charges, dark color
Labile organic matter (Fast pool) - ANSWER -living biomass
-free (detritus, POM, biomolecules, degradation products)
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