1. What is an ECOSYSTEM?

Consider sitting in the middle of a natural area. The “natural” means that it is not created, maintained, or managed by humans. It is simply what nature provides/has provided without human inputs. It may be an area of forest, grassland, desert, tundra, or something in between. (Google: kinds of natural ecosystems images) It may be terrestrial or aquatic.) It is not just the trees and/or other plants. It is also all the different animals, birds, insects, spiders, mushrooms, molds, bacteria, and other things that live there as well.

Ponder that this collage of living things is far from static; every individual plant, animal, fungus, or microbe is at its own stage of growing, reproducing, and dying while offspring are taking its place. Over a period of years, every individual plant, animal, fungus, and microbe is a different individual from the one before, but the collage as a whole remains much the same. Furthermore, this has gone on for thousands, even millions, of years. 

There is something remarkable here. How can a particular grouping of organisms sustain itself without significant change over many generations (thousands of years)? Delving into answering this question is the study of ECOLOGY. We look at our forest, grassland, desert, or other natural area with its associated plants, animals, fungi, and microbes as a complex system. We call it an ECOSYSTEM. 

Defining an ecosystem more succinctly: 

An ECOSYSTEM is an assemblage of plants, animals, fungi, and microbes interacting with each other and their environment in such a way as to perpetuate the assemblage indefinitely. 

There is a multitude of different kinds of ecosystems, determined largely by the specific climatic regimes (temperature and rainfall/soil moisture) regimes they face. There are aquatic ecosystems as well. How specific plants and animals, hence ecosystems, are adapted to the climatic conditions they face is a related study that may be pursued to any degree. (See: adaptations of desert plants; adaptations of desert animals; main types of ecosystems)