Scientists use indicator species as an early warning system for environmental problems. There are certain criteria that an indicator species must meet. They include ALL BUT ONE of those listed here. A) easily observable B) found at the base of any food chain C) not difficult to be sampled and/or counted D) sensitive to changes in environmental conditions

The criteria of the indicator species that does not meet is:

Found at the base of any food chain.

Option: B

Explanation:

As an early warning system for environmental problems, indicator species are chosen for their sensitivity to environmental conditions. If the selected indicator species decrease in numbers or any health factor, it symbolizes to see for detrimental effects such as soil impurity, pollution in water/air, habitat fragmentation or drastic variation in climates.

Apart from being sensitive to change, these species must also be representative of the other organisms in the ecosystem, easily observable and must be sampled, and they should react continuously to environmental changes. So from the above conditions, it is clear that species found in any base of food chain is not the criteria.