Gardeners sometimes plant clover between productive growing seasons. Why would this practice be beneficial?
A. Several types of nitrogen-fixing bacteria form a symbiotic relationship with the roots of clover. This would increase the amount of nitrogen in the soil available for subsequent seasons of other plants' growth.
B. Clover is consumed by a number of animals. This would encourage the animals to feed/graze on the areas, leaving behind nitrogen-rich manure that would act as a natural fertilizer for subsequent seasons of other plants' growth.
C. Clover is a unique plant that is capable of atmospheric nitrogen-fixation (pulling nitrogen directly out of the air and turning it into ammonia or amino acids). This directly provides nitrogen compounds for the soil for subsequent seasons of other plants' growth.
D. The beneficial effect is more for water retention and elimination of soil erosion in between growing seasons. It has nothing to do with nitrogen compounds in the soil.
Treponema pallidum
A. is the organism that causes syphilis.
B. is a spirochete.
C. can be more easily viewed with dark-field illumination.
D. has become less virulent over time.
E. All of the above are correct.
How can the biomass of fungi in soil be greater considering that bacteria are more numerous?
A. Fungi are always multicellular organisms, while bacteria are unicellular. As such, biomass of fungi would always be larger than that of bacteria, since they possess more cells in each individual organism.
B. This is a matter of size. Fungi, whether unicellular or multicellular, are eukaryotic. As such, they will generally be larger than bacteria (which are prokaryotic). This means that, even with a lower overall number, they will have more total biomass.
C. It depends on where they grow. Fungi generally grow in the most moist areas near the top of soil. This gives them an advantage over bacteria. They may not be as numerous, but this advantage in location and nutrients is what makes them larger than the bacteria (and therefore having more biomass). If the bacteria evolved to take over the top portion of the soil, THEY would have the larger biomass than the fungi.
D. Fungi are capable of incorporating the dead materials around them into themselves as nutrient sources (while bacteria are not). This capacity allows them to greatly increase their biomass per each organism, well beyond what a simple bacterial cell could hold. This capability is what allows them to achieve higher biomass than bacteria.
Explain how nutrient-rich runoff can cause waters to become hypoxic
A. Algae and cyanobacteria flourish on the nutrients in the run-off. Heterotrophic microbes then flourish on the organic molecules produced by these organisms, using oxygen in the process. This consumption of oxygen leads to a hypoxic state in the area. Larger animals cannot survive in the hypoxic area.
B. Algae and cyanobacteria flourish on the nutrients in the run-off, using oxygen in the process. This consumption of oxygen leads to a hypoxic state in the area. Larger animals cannot survive in the hypoxic area.
C. The nutrients in the run-off often include chemicals that spontaneously oxidize in the presence of oxygen. As such, they tend to deplete the amount of oxygen present in an area simply by being present themselves. This consumption of oxygen leads to a hypoxic state in the area. Larger animals cannot survive in the hypoxic area.
D. It doesn't. This claim is a scare tactic used by environmental extremists to prevent farmers and individuals from fertilizing their crops and lawns. There is no induction of a hypoxic state in bodies of water where run-off occurs.
No eukaryotic organisms have been shown to fix nitrogen without the aid of prokaryotes.
Indicate whether this statement is TRUE or FALSE.
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