Final answer:
Amphibians are called Environmental indicators because their sensitive nature to environmental changes allows them to signal ecosystem health issues before they affect other species.
Step-by-step explanation:
Amphibians are sensitive to environmental changes due to their permeable skin that easily absorbs substances, indicating when an environment is suffering from pollution and other damages. Thus, these organisms are often referred to as Environmental indicators because of their ability to signal changes in environmental conditions before other species are affected. This encompasses understanding threats like pollution, disease, and climate change, as well as recognizing the role frogs play in bridging aquatic and terrestrial habitats as part of the food web.