What form of energy is stored when an animal takes in more energy than it uses over time?

The correct response is fat. When an animal consumes more energy than it expends, the surplus energy is stored in the form of fat. This process involves converting excess calories from food into triglycerides, which are then stored in adipose (fat) tissues. Fat serves as a significant energy reserve for the body, allowing animals to tap into these stored calories during periods of low food availability or increased energy demands.

While glucose and sugars are critical forms of energy, they are typically utilized for immediate energy needs rather than being stored for long-term use. Proteins are primarily used for growth, repair, and cellular functions, rather than being a primary energy storage form. Thus, fat is the predominant energy storage molecule for animals, making it the correct choice here.