BIOLOGY Volume 1 - A Guide to General Biology - 2004

10. ORGANISMS AND THE ENVIRONMENT

10.2. Ecosystems

10.2.1. Definitions and Basic Concepts

An ecosystem consists of a biotic component and an abiotic component. The organisms that make up the biotic component are collectively referred to as a community.

KEY FEATURES OF Ecosystems

1. Living (biotic) and non-living (abiotic) components are closely interrelated. These components influence one another and are equally vital to the ecosystem.

2. Ecosystems can be studied at various Levels of Organization. For example, the same principles can be applied to:

Class="center">a puddle → a pond → a lake → a sea → an ocean → the planet.

You can also study ecosystems over different time scales. A period of a few hours or days is best suited for a puddle, whereas ecological processes in a lake may only become fully apparent over many years.

3. The preservation and flourishing of an ecosystem require all of its organisms and all Components of the physical environment. The tendency of a system to maintain stability—a balance among all its parts—is known as Homeostasis (self-regulation). This balance is continually disrupted by external impacts. Minor disturbances are typically compensated for by negative feedback mechanisms, which restore the initial state. Major interventions cannot be offset through self-regulation, causing the system to transition into a new state that gradually achieves equilibrium and develops its own regulatory mechanisms. In effect, one system is replaced by another, sometimes entirely different from the original. Such changes do not necessarily imply degradation. For instance, during ecological succession on bare ground, wind-borne seeds may first give rise to scrub vegetation, which is later succeeded by a forest (sec. 10.6.1). However, there are numerous Examples where anthropogenic intervention has led to unexpected and even catastrophic side effects, such as massive pest outbreaks in simplified agroecosystems. Furthermore, changes are not always immediately apparent. For instance, The Link Between fuel combustion products and the acidic degradation of lakes and forests has only recently been traced (sec. 10.8.1).