1. Metabolic Processes: This is the most fundamental way living things use energy. This includes all the chemical reactions that occur within the body to sustain life. These reactions involve building complex molecules (anabolism), breaking down molecules for energy (catabolism), and various other processes like transporting substances across cell membranes. Examples include:

* Photosynthesis: Plants use sunlight energy to convert carbon dioxide and water into glucose (sugar) for energy.

* Cellular Respiration: Organisms break down glucose to release chemical energy (ATP) for cellular activities.

* Protein Synthesis: Cells use energy to create proteins for various functions.

* Muscle Contraction: Animals use energy to move their muscles for locomotion.

2. Maintaining Homeostasis: Living things need energy to maintain a stable internal environment, despite changes in the external environment. This includes processes like:

* Temperature Regulation: Animals use energy to maintain a stable body temperature, whether it's through sweating, shivering, or other mechanisms.

* Osmotic Regulation: Organisms use energy to maintain the right balance of water and solutes in their cells and tissues.

* Waste Removal: Energy is required for filtering waste products from the body and eliminating them.

These are just two examples of the many ways living things use energy. Ultimately, energy is essential for all the activities that allow organisms to survive, grow, and reproduce.