Final answer:
The energy necessary for life functions in animals comes from cellular respiration, where ATP is produced. Similar to humans using energy in exercise, plants use energy in photosynthesis, and single-celled organisms use energy to move cilia or flagella.
Step-by-step explanation:
The energy animals need for their life functions is released when their cells carry out cellular respiration. During this process, adenosine triphosphate (ATP) is produced, which serves as the primary energy carrier in all living organisms. Cells obtain energy through the breakdown of food, which is then converted to ATP. This energy is crucial not only for physical activities but also for fundamental processes such as synthesis of new molecules, transport of materials, and waste elimination.
In different organisms, various cellular functions require energy that is parallel to human energy-requiring functions. For example, plants harness energy through photosynthesis, creating glucose that serves as an energy source for them and ultimately for the animals that consume them. Another example is the movement of single-celled organisms using cilia or flagella, which is also an energy-dependent process similar to muscle contractions during exercise in humans.