Final answer:
The primary process by which animals derive energy from food is cellular respiration, which involves the oxidation of carbohydrates and lipids using oxygen to release energy, carbon dioxide, and water.
Step-by-step explanation:
The main process by which animals obtain energy from food is cellular respiration. This biological process allows organisms, including humans and animals, to convert food, particularly carbohydrates and lipids, into usable energy. During cellular respiration, oxygen is used to oxidize carbohydrates, resulting in the production of carbon dioxide (CO2) and water (H2O). This process releases energy that is essential for organisms to perform life functions.
However, it is worth noting that other processes are also relevant to how energy is acquired in a broader sense. For instance, photosynthesis is the method by which plants, algae, and some bacteria produce their food using sunlight, carbon dioxide, and water, later utilized in cellular respiration. Chemosynthesis is another process found in some organisms where chemical energy is used to produce carbohydrates.