Final answer:
The heat created by living organisms is eventually lost from the ecosystem due to the second law of thermodynamics, which states that every energy transfer increases the entropy of the universe. Living systems lose some amount of usable energy through chemical reactions and produce waste and by-products that aren't useful energy sources, increasing the entropy of the system's surroundings.
Step-by-step explanation:
All physical systems can be thought of in this way: Living things are highly ordered, requiring constant energy input to be maintained in a state of low entropy. As living systems take in energy-storing molecules and transform them through chemical reactions, they lose some amount of usable energy in the process, because no reaction is completely efficient.
They also produce waste and by-products that aren't useful energy sources. This process increases the entropy of the system's surroundings. Since all energy transfers result in the loss of some usable energy, the second law of thermodynamics states that every energy transfer or transformation increases the entropy of the universe.
Even though living things are highly ordered and maintain a state of low entropy, the entropy of the universe in total is constantly increasing due to the loss of usable energy with each energy transfer that occurs. Essentially, living things are in a continuous uphill battle against this constant increase in universal entropy.