How is energy defined in biological terms?

In biological terms, energy is defined as the capacity to do work. This definition encompasses the various forms of energy that organisms utilize to perform vital functions such as movement, growth, reproduction, and maintaining homeostasis. In living systems, energy can be transformed and transferred between different forms, allowing for metabolic processes that sustain life.

The concept of energy as the capacity to do work is fundamental to understanding biological processes such as cellular respiration and photosynthesis. During cellular respiration, for example, organisms break down glucose molecules to release energy, which is then used to synthesize ATP, the energy currency of cells. This ATP can then be utilized to power various biological activities throughout the organism.

In contrast to this, the other options do not universally capture the broader definition of energy in biological contexts. The ability to capture sunlight pertains specifically to photosynthesis in plants, conservation relates more to physical systems and the laws of thermodynamics rather than a biological definition, and the output of cellular respiration describes a specific process related to energy production, rather than a definition of energy itself.