原题
Thermodynamics and Ecosystems
When students first encounter the laws of thermodynamics, educators often rely on simplified analogies—billiard balls, falling stones—to convey foundational principles. Yet these laws extend far beyond mechanical systems, offering a powerful framework for interpreting complex phenomena such as energy flow in ecosystems. The first law, which asserts that energy cannot be created or destroyed but only transformed, is clearly exemplified in nature: sunlight becomes chemical energy via photosynthesis, which fuels plants, then herbivores and, ultimately, carnivores. This cascading energy transfer underscores the conservation principle while revealing the intricate interdependence among trophic (food chain) levels, with each organism depending on the energy efficiency of those occupying the level below.
In contrast, the second law—which states that entropy, or disorder, tends to increase—illuminates why ecosystems evolve toward less efficient energy use. While simple organisms at the base of the food chain convert energy with relative efficiency, larger animals lose much of their energy intake. This disparity is not merely a biological curiosity; it reflects a fundamental thermodynamic constraint. As ecosystems mature, energy becomes increasingly fragmented and less available for productive work. Exceptions exist—some top predators exhibit surprising metabolic efficiency—but the general trend remains: Complexity breeds energy loss.
According to the passage, what principle explains the trend toward less efficient energy use in ecosystems?
ASmaller systems tend to combine into larger ones.
BAs entropy increases, less energy is available for work.
CEnergy is never lost but takes on many different forms.
DTop predators are vulnerable to changes in an ecosystem.
正确答案：B
解题思路
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