1. Producers: These are organisms that make their own food through photosynthesis, using sunlight, water, and carbon dioxide. They form the base of the food chain. Examples include plants, algae, and some bacteria.

2. Consumers: These are organisms that obtain their energy by consuming other organisms. They can be herbivores (eat plants), carnivores (eat other animals), or omnivores (eat both plants and animals). Examples include animals, fungi, and some bacteria.

3. Decomposers: These are organisms that break down dead organisms and waste products, returning nutrients to the ecosystem. They play a crucial role in recycling matter. Examples include bacteria and fungi.