Short answers, pulled from the story.
British ecologist Arthur Tansley coined the word ecosystem in 1935 to describe the invisible web of connections between plants, animals, and soil. The term was actually suggested by Arthur Roy Clapham, who helped Tansley refine the definition to include physical factors forming the environment.
Photosynthesis is the engine that drives every ecosystem by converting sunlight into the substance of life. Plants capture energy from light to combine carbon dioxide and water to produce carbohydrates and oxygen, creating the foundation for all other life.
Decomposers break down dead organic matter to release nutrients for plant and microbial production and return carbon dioxide to the atmosphere. This process occurs through three distinct categories: leaching, fragmentation, and chemical alteration.
Nitrogen, phosphorus, and potassium are the primary nutrients required by all plants in large quantities and their availability often limits ecosystem production. Nitrogen fixation was the major source of nitrogen until modern times, while phosphorus enters ecosystems through weathering and diminishes as ecosystems age.
Resistance is the tendency of an ecosystem to remain close to its equilibrium state when a perturbation occurs. Ecological resilience is the capacity of a system to absorb disturbance and reorganize while undergoing change so as to retain essentially the same function, structure, and identity.
The Millennium Ecosystem Assessment concluded that human activity is having a significant and escalating impact on the biodiversity of the world's ecosystems. The report found that only four of the four major categories of ecosystem services have shown improvement over the last 50 years while 15 are in serious decline.