Question

pond ecosystem
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when a pond freezes, the ice begins to seal the surface of the pond from the surrounding environment. as the ice thickens, the pond no longer undergoes the normal exchange of gases between air and water. aquatic plants, including microscopic algae and phytoplankton, continue to use the sunlight that passes through the ice for photosynthesis but at a slower rate. elodea, a common water weed, produces only half the oxygen in winter that it does during summer.
the ice on the pond also protects the pond life from the extremes of the cold weather. the temperature of the water under the ice hovers just above freezing. some eggs, like those of wood frogs, have a protective gel that prevents them from freezing, and the eggs wait safely under the protective ice layer for spring.
scientific studies have shown that for every 10°c drop in water
based on the information in the passage, which statement best provides evidence to support the claim that energy is being conserved in the pond ecosystem during winter?
a) the plant elodea produces about half the oxygen than it does in summer.
b) plants in the pond continue to use the sunlight that passes through the ice for photosynthesis.
c) the water temperature at the bottom of the pond is warmer than the water temperature at the surface.
d) the normal exchange of gases between air and water does not occur when ice covers the surface of the pond.

Explanation:

Energy conservation in an ecosystem involves the transfer and transformation of energy (like solar energy to chemical energy via photosynthesis) to sustain life. Option B describes plants using sunlight through ice for photosynthesis, which is the process that captures and converts solar energy into usable chemical energy for the ecosystem, showing energy is being retained and used rather than lost from the system. The other options do not relate to energy conservation: A is about reduced oxygen output, C is about temperature stratification, D is about gas exchange disruption.

Answer:

b. Plants in the pond continue to use the sunlight that passes through the ice for photosynthesis.