Deck 9: An Ecologists Guide to Microbiology

Question 1

Describe why decomposers are so important in ecosystems.

Answer 1

Decomposers, primarily bacteria and fungi, are organisms that absorb organic material in the environment and covert this material into inorganic substances, which are then released into the environment. They are essential in ecosystems, because these inorganic substances are required by producers.

Question 2

Which of the following statements is true?

A) The biomass of producers in an environment will be greater than the mass of primary consumers.
B) The biomass of secondary consumers will be greater than that of primary consumers.
C) The biomass of tertiary consumers will be greater than that of quaternary consumers.
D) Both "a" and "c" are true.
E) Both "b" and "c" are true.

Answer 2

D

Question 3

What exactly is a biofilm? Where are biofilms found?

Answer 3

A biofilm is a microbial community is which the cells are encased in a layer of polysaccharide, secreted by the cells. The cells within a biofilm may or may not be of the same species. The biofilm is generally organized in such a way that water can circulate through the biofilm. Biofilms can be found on any hard surface such as rocks in a stream, pipes, or dental enamel.

Question 4

In aquatic environments, the ________ zone represents the part of the environment where sunlight reaches the bottom.

A) photic zone
B) littoral zone
C) profundal zone
D) benthic zone
E) pelagic zone

Question 5

Why does the addition of extra nutrients into a lake often result in a die-off of fish and other animals?

Question 6

Which of the following processes directly require the activity of microorganisms?

A) release of organic carbon into the environment from animal and plant remains
B) absorption of sulfate from the environment by green plants
C) release of organic nitrogen into the environment by dead plants and animals
D) conversion of organic phosphorus in animal and plant remains into inorganic phosphorus
E) All of the above require microbial activity.

Question 7

Most of the bacteria that live in lakes can be classified as:

A) oligotrophs.
B) eutrophs.
C) Gram-positive.
D) Gram-negative.
E) thermophiles.

Question 8

Which of the following statements about competition is true?

A) Compared to plants or animals, competition between microorganisms is a rare event.
B) The principle of competitive exclusion suggests that two organisms in competition will eventually reach a stable equilibrium, where both organisms can coexist and survive.
C) A commensial relationship is an example of competition.
D) If you take an environmental sample, and find numerous microbial species within that sample, it suggests that none of these species are in competition with each other.
E) Compared to animals and plants, the resolution of competition between microorganisms is rapid.

Question 9

Consider two organisms, X and Y, which are involved in a type of ecological interaction. Which of the following statements is false?

A) If X and Y are mutualists, both organisms have a positive effect on the growth of the other.
B) If X is a commensal organism on Y, X has a positive effect on Y, but Y has no effect on X.
C) If Y is a commensal organism on X, X has a positive effect on Y, but Y has no effect on X.
D) If X and Y are competitors, both organisms have negative effects on each other's growth.
E) If X is a predator and Y is prey, X has a negative effect on Y, but Y has a positive effect on X.

Question 10

Which process in the nitrogen cycle, carried out by certain microorganisms, converts atmospheric nitrogen into ammonia, which can then be utilized by plants?

A) nitrogen fixation
B) ammonification
C) nitrification
D) denitrification

Question 11

Mycorrhizal associations would most likely be found in:

A) benthic marine environments.
B) a freshwater lake.
C) a stream or river.
D) the soil environment.
E) microbial biofilms.

Question 12

Which of the following represents a producer in a food web?

A) a fungus that is parasitic on plants
B) a herbivore
C) a carnivore
D) bacteria that break down organic material and return inorganic nutrients to the environment
E) photosynthetic cyanobacteria

Question 13

Which of the following statements comparing freshwater and marine environments is true?

A) The marine environment is generally far more stable than the freshwater environment.
B) A seasonal thermocline may develop in a marine environment, but not a freshwater environment.
C) Benthic zones occur in marine environments, but not in freshwater environments.
D) In a marine environment, the pelagic zone usually has the highest species diversity, while in freshwater environments, diversity in the pelagic zone is usually low.
E) In marine environments, phosphorus is usually the principal factor limiting microbial growth. In freshwater environments, iron is usually the most principal limiting factor.