Energy Flow in Ecosystems is Unidirectional

Steps:

• Energy enters ecosystems from the sun via producers like plants through photosynthesis.
• It transfers to consumers and decomposers, with some lost as heat at each level.
• Unlike nutrients, energy cannot be recycled because it's dissipated into the environment.
• Thus, flow is non-cyclic, requiring constant input from the sun.

Why A is correct:

• According to the second law of thermodynamics, energy transformations increase entropy, dissipating usable energy as heat that cannot return to its original source.

Why the others are wrong:

• B: Energy does change form within organisms, such as from light to chemical energy.
• C: Energy is not passed in its original form; it converts between types like chemical and kinetic.
• D: Energy transfers to organisms of any size, not just larger ones, across trophic levels.

Final answer: A