Eco-Systems (and some natural systems/functions) 4th Grade

An ecosystem is a community of living organisms (plants, animals and microbes) in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system. These biotic and abiotic component are regarded as linked together through nutrient cycles and energy flows. As ecosystems are defined by the network of interactions among organisms, and between organisms and their environment, they can be of any size but usually encompass specific, limited spaces (although some scientists say that the entire planet is an ecosystem).

Coral Reefs are a highly productive
marine Eco-system

Source: http://en.wikipedia.org/wiki/Ecosystem

Source: Link is Shortened for Convenience

Photosynthesis

The Water Cycle