1. Autotrophy: This is the process of making food from inorganic materials, like sunlight and carbon dioxide. Plants are a classic example of autotrophs, using photosynthesis to create their own energy. Some bacteria also use this method.

2. Heterotrophy: This involves obtaining food from other organisms. All animals are heterotrophs, consuming plants or other animals for energy. Some fungi and bacteria are also heterotrophs, decomposing organic matter for their food source.