Flagellates are microbes that have a rod-shaped flagellum that helps with their locomotion. Certain flagellates reside inside termites. These flagellates provide enzymes for the termites to digest cellulose, which helps them survive. In turn, the termites provide nourishment to these flagellates. Termites need cellulose for their survival, and flagellates obtain nutrition only from termites. Which statement can be true about the association between these microbes and termites?
A.
The flagellates share a facultative mutualistic association with the termites.
B.
The flagellates and termites share an obligate mutualistic association.
C.
The flagellates share an obligate parasitic association with the termites.
D.
The flagellates and termites share a commensal association.
E.
The flagellates and termites share a facultative parasitic association.

B.

The flagellates and termites share an obligate mutualistic association

Explanation:

Organisms of same or different species tend to interact with one another in an ecosystem. The close interaction between two organisms is referred to as SYMBIOSIS. A type of symbiotic relationship is MUTUALISM, which is when both organisms benefits from the relationship.

However, mutualistic relationship can be of different types depending on how dependent the involved organisms are on each other. The example in this question illustrates OBLIGATE MUTUALISM, which is when the organisms involved in the mutualistic relationship depend on one another for survival. This is the case of the termites and the flaggelates where the termite depends on the flaggelate for enzymes that helps them digest cellulose while the flaggelates depend on termite for nourishment/food.

The termite will not survive if it doesn't get enzymes to digest its cellulose while the flaggelates will also not survive if they do not get nourished. Hence, the two organisms share an OBLIGATE MUTUALISTIC RELATIONSHIP.

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.