Advanced Placement (AP) Biology Practice Exam

What does the first law of thermodynamics state?

1. Energy can be created or destroyed

2. Energy is constant and can change forms

3. Energy decreases over time in isolated systems

4. Energy only exists in chemical forms

The correct answer is: Energy is constant and can change forms

The first law of thermodynamics, also known as the law of energy conservation, states that energy cannot be created or destroyed, only transformed from one form to another. This means that within a closed system, the total amount of energy remains constant, but it can change from kinetic energy to potential energy, thermal energy, and so on. For example, when chemical energy stored in food is metabolized by living organisms, it is converted into various forms of energy, such as thermal energy to maintain body temperature, or kinetic energy for movement. This fundamental principle underpins many concepts in biology and physics, illustrating that while energy may take on different forms, the total energy within an isolated system remains unchanged. This understanding is crucial for analyzing biological processes, ecological interactions, and the workings of physical systems, providing a foundational framework for both biological and physical sciences.