scsc 301 exam 2 tamu smith Questions With Complete
Solutions
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
/.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
