Difficulty: Medium
Correct Answer: Amphibians such as frogs and salamanders
Explanation:
Introduction / Context:
Environmental scientists often use certain organisms as bioindicators to detect changes in ecosystems. These organisms respond quickly to pollution, habitat alteration, or climate shifts. This question asks which major vertebrate or invertebrate group is widely recognised as particularly sensitive to environmental change, especially in freshwater and moist terrestrial environments. Understanding this helps you appreciate why declines in specific animal groups often serve as early warning signs of ecological problems.
Given Data / Assumptions:
Concept / Approach:
Amphibians, which include frogs, toads, salamanders, and newts, have life cycles and body features that make them especially sensitive to environmental changes. Most amphibians have permeable skin that readily absorbs water and dissolved substances, including pollutants. Many species spend part of their life cycle in water (as eggs and larvae) and part on land (as adults), exposing them to contaminants in both environments. They rely on moist conditions and are affected by small changes in temperature, precipitation, and water chemistry. For these reasons, amphibian populations often decline earlier and more sharply than those of reptiles, mammals, or many insects when habitats are disturbed or polluted. Reptiles and mammals generally have more protective skin or fur and can be more tolerant of moderate environmental changes. Insects can be sensitive to specific changes but also include many highly adaptable species. Therefore, amphibians are widely considered the most sensitive indicators of environmental change among the listed groups.
Step-by-Step Solution:
Verification / Alternative check:
Conservation biology studies have documented global declines in amphibian populations, often described as the amphibian crisis. These declines are linked to habitat destruction, pesticide use, disease (such as chytrid fungus infection), climate change, and ultraviolet radiation. Researchers frequently refer to amphibians as ecological canaries in the coal mine because they provide early warnings of environmental deterioration. Environmental agencies and scientists use amphibian surveys to assess the health of wetlands, streams, and forests. This widespread practice confirms that amphibians are recognised as particularly sensitive indicators of environmental change.
Why Other Options Are Wrong:
Reptiles such as lizards and snakes are wrong as the most sensitive group because their dry, scaly skin and different life histories often make them less immediately affected by certain pollutants and moisture changes compared with amphibians.
Mammals such as deer and rodents are incorrect because, although they are impacted by long term habitat changes, they are generally more mobile, more internally regulated, and less sensitive to subtle water quality changes than amphibians.
Insects such as beetles and butterflies are also wrong in this general question because insects as a group are extremely diverse, and while some species are good indicators, many can tolerate or adapt to a wide range of environmental conditions.
Common Pitfalls:
Students may mistakenly choose mammals or insects because they are familiar or abundant. Another pitfall is not considering the biological reasons for sensitivity, such as permeable skin and dual life stages. To avoid such errors, remember that amphibians are particularly sensitive to environmental change due to their permeable skin, dependence on water, and complex life cycle, which is why they are widely used as ecological indicators.
Final Answer:
Thus, the group most sensitive to environmental change among the options is amphibians such as frogs and salamanders.
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