An ecosystem is a community of living things interacting with each other and their physical environment. It can be as small as a pond or as large as a rainforest. The boundaries are defined by the observer. What matters is the flow of energy and matter between organisms and their surroundings.

Every ecosystem has producers, consumers, and decomposers. Plants and algae capture sunlight. Herbivores eat them. Carnivores eat herbivores. Fungi and bacteria break down dead matter and return nutrients to the soil. Energy flows in one direction, from sun to producer to consumer. Nutrients cycle endlessly.

Ecosystems provide services that humans depend on. Forests clean air and regulate rainfall. Wetlands filter water and buffer floods. Pollinators support food crops. Coral reefs protect coastlines. These services are often invisible until they are lost. A degraded ecosystem costs more to replace than to protect.

Key components

• Producers
• Consumers
• Decomposers
• Abiotic factors: soil, water, climate
• Energy flow and nutrient cycles