Question

The type (pollution tolerance level) and number of indicator species can tell you a lot about a stream. Which of the

following describes an unhealthy stream?
A. Intermediate species outnumber intolerant and tolerant species.
B. There are no species of any type of organism.
C. Intolerant species are absent and the number of tolerant organisms exceeds that of the intermediate species,
D. Tolerant species are absent and the number of intolerant organisms exceeds that of the intermediate species.

Answer 1

An unhealthy stream is indicated by the absence of intolerant species and a higher number of tolerant species, pointing to significant pollution or environmental stressors.

Step-by-step explanation:

An unhealthy stream can be characterized by the types and numbers of species it supports, particularly indicator species with known pollution tolerance levels. A stream where intolerant species is absent and the number of tolerant organisms exceeds that of intermediate species signals poor water quality, since intolerant species are unable to survive in polluted conditions, whereas tolerant species can. Thus, an unhealthy stream can be described as one in which intolerant species are absent and tolerant species are predominant. This condition suggests that the stream has a high level of pollution or other environmental stressors that prevent the survival of more sensitive species.