Final answer:
Energy flows directionally through ecosystems from producers to consumers and is eventually lost as heat. It is not recycled, necessitating a constant inflow of energy, primarily from the sun, to maintain life processes.
Step-by-step explanation:
An important feature of the flow of energy through the living world is that energy flows directionally through an ecosystem and is not recycled, in contrast to matter which cycles within ecosystems. In ecosystems, energy usually enters as sunlight or chemical energy and is converted by autotrophs (like plants) through photosynthesis into chemical energy stored in organic compounds. Then, energy flows from producers to consumers, through herbivores and carnivores.
This is illustrated in food-web diagrams which show the energy transfer from one organism to another and eventually, a lot of this energy is lost as heat to the environment. To satisfy the continuous energy demand, organisms, particularly autotrophs, need a constant inflow of energy to maintain their metabolic functions. The first law of thermodynamics tells us that while energy can change form, such as from light to chemical energy, it is never created or destroyed but constantly transformed.