An ecosystem is a community of living organisms and their physical environment interacting together. It consists of all the biotic (living) and abiotic (non-living) components that are linked together through nutrient cycles and energy flows. The biotic components include all the living things such as plants, animals, and microorganisms, while the abiotic components include the non-living physical conditions such as weather, earth, sun, soil, climate, and atmosphere.

The organisms in an ecosystem are usually well balanced with each other and with their environment. Each organism has its own niche or role to play in the ecosystem. Ecosystems can be natural or artificial, land-based or water-based, and can vary in size.

The fundamental source of energy in almost all ecosystems is radiant energy from the Sun. The energy of sunlight is used by the ecosystem’s autotrophic organisms, such as green plants, to convert carbon dioxide and water into simple, energy-rich carbohydrates through photosynthesis. The energy stored within the simple carbohydrates is then used by the organisms to produce more complex organic compounds, such as proteins, lipids, and starches, that maintain the organisms’ life processes.

Ecosystems are the foundations of the Biosphere and they determine the health of the entire Earth system. They provide essential ecosystem services such as air and water purification, nutrient cycling, and climate regulation. The resilience of an ecosystem is its capacity to absorb disturbance and reorganize while undergoing change so as to retain essentially the same function, structure, identity, and feedbacks.

In summary, an ecosystem is a complex system of living and non-living components that are linked together through nutrient cycles and energy flows. It is a community of organisms and their physical environment interacting together, and it determines the health of the entire Earth system.