An ecosystem is a community made up of living organisms and nonliving components such as air, water, and mineral soil. Ecosystems can be studied in two different ways. They can be thought of as interdependent collections of plants and animals, or as structured systems and communities governed by general rules. The living (biotic) and non-living (abiotic) components interact through nutrient cycles and energy flows. Ecosystems include interactions among organisms, and between organisms and their environment. Ecosystems can be of any size but each ecosystem has a specific, limited space. Some scientists view the entire planet as one ecosystem.
Energy, water, nitrogen and soil minerals are essential abiotic components of an ecosystem. The energy used by ecosystems comes primarily from the sun, via photosynthesis. Photosynthesis uses energy from the sun and also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecosystems. They influence the amount of plant and microbial biomass that lives in the system. As organic matter dies, carbon is released back into the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.
Ecosystems are controlled by both external and internal factors. External factors such as climate, the parent materialthat forms the soil, topography and time each affect ecosystems. However, these external factors are not themselves influenced by the ecosystem. Ecosystems are dynamic: they are subject to periodic disturbances and are often in the process of recovering from past disturbances and seeking balance. Internal factors are different: They not only control ecosystem processes but are also controlled by them. Another way of saying this is that internal factors are subject to feedback loops.
Humans operate within ecosystems and can influence both internal and external factors. Global warming is an alleged example of a cumulative effect of human activities. Ecosystems provide benefits, called “ecosystem services“, which people depend on for their livelihood. Ecosystem management is more efficient than trying to manage individual species.