Exam 11: Organisms and Ecology of the Soil

Which of the following organisms can commonly be seen with the unaided eye in organic matter-rich soils?

In nature, beneficial mycorrhizae form with the roots of _____.

Vesicles and arbuscules are structures typically formed ____.

The addition of large quantities of plant residues to the soil generally ____ the incidence and severity of soil-borne plant diseases.

Of all the groups of soil organisms, bacteria have the most diverse metabolic capabilities.

Mucigel is thought to improve the contact between plant roots and soil particles, thus enhancing the plant uptake of water and nutrients.

This (these) group(s) of microorganisms usually predominate(s) in sandy, acid soils.

An organism that subsists by eating predators would function as a(n) _____ in the soil ecosystem.

Organisms which use carbon dioxide or carbonates for their carbon source and either sunlight or inorganic chemicals for their energy source are called ____.

In most soils the overall population (numbers) of microorganisms changes with time, generally following changes in the _____.

Certain soil fungi and actinomycetes are known to produce specialized organic compounds that inhibit or kill other, competing microorganisms in the soil, but so far scientists have not been able to put any of these compounds to practical use.

Termites tend to enrich soils in the tropics much the same way as earthworms do in temperate region soils.

Which of the following groups is not considered to include important primary consumers in the soil ecosystem?

Mycorrhizae do not normally kill their host plants, but merely reduce the efficiency of the plant root system.

Which of the following groups of organisms are responsible for greatest amount of organic matter decomposition in soils?

Soil detritivores feed principally on ___.

Many members of which group of soil microorganisms are anaerobic heterotrophs?

Oxidation or reduction of inorganic soil constituents such as iron and sulfur is carried out by members of which group(s) of microorganisms.

Plant roots are an important source of carbon for many soil organisms which are beneficial to plants.

Algae are single-celled plants that function principally as primary producers in the soil ecosystem.