In this article we will discuss about:- 1. Definition of Ecosystem2. Structure and Dynamics of Ecosystem 3. Energy Flow.
Definition of Ecosystem
Ecological relationships develop on a physico-chemical platform. The physical or abiotic factors include basic inorganic elements and compounds in the form of water, carbon dioxide, oxygen, calcium, phosphates, wind, currents, solar radiations and the by-products of organism activity or death.
The biotic components are plants, animals and microbes. These components interact in energy-dependent fashion. An ecological system or Ecosystem is thus comprised of the abiotic physico- chemical environment and the biotic assemblage of plants, animals and microbes. Ecosystems are real but at the same time abstract being made up of conceptual schemes developed from a knowledge of real system.
Structure and Dynamics of Ecosystem:
In the final analysis all ecological relationships are energy oriented. Radiant energy in the form of sunlight is the prime source of energy for any ecosystem. This energy is used in the process of photosynthesis by which carbon dioxide is assimilated to give rise to energy rich and complex carbon compounds.
The chlorophyll-bearing plants are the only organisms that are capable of performing this vital function. These plants have been termed producers. The energy incorporated within the producer by the process of photosynthesis is utilized in the synthesis of other molecules that meet the nutritional requirements of the producer itself. So the producer may be referred to as autotroph, i.e., one who is capable of self-feeding.
Any organism whose nutritional requirements are met by feeding on other organism is called a heterotroph. A primary consumer then is a heterotroph that derives its nutrition directly from the plants. A secondary consumer is in the same token a heterotroph which derives its energy from the primary consumer. The autotroph and heterotroph relation may be present in an extended form.
Besides these there is another group of heterotrophs in an ecosystem. This group is represented by micro-organisms like bacteria and fungi and has been termed as decomposers. The decomposers do not take food in the in gesture manner as is the practice of the heterotrophs. The enzymes secreted by the decomposers act upon the dead plants and animals and some of the products of decomposition are then absorbed. The decomposers thus render an invaluable service to ecosystem.
The exo-enzymatic digestive activity of the decomposers releases the basic elements bound in protoplasm to the environment and makes the elements available to the plants for reuse. The producer-consumer arrangement in an ecosystem is called Trophic Structure (Trophic=Food).
Each food level is known as trophic level. The amount of living material present in different trophic levels or in a component population is called standing crop. The standing crop is expressed in terms of Biomass or number per unit area. Biomass is measured as living weight, dry weight, ash-free dry weight, carbon weight, calories, etc.
The abiotic materials that remain present at any given time is considered as standing quantity or Standing state. In studies of ecosystem it is important to distinguish between quantities of material and organisms present at any one time or the average over a period of time and also the change in the standing states and standing crops per unit of time.
It is now evident that there are two processes operating in an ecosystem. One is energy transfer from autotroph to heterotroph and the other one is movement of nutrient elements. The energy transfer is unidirectional and non-cyclic while movement of nutrition elements is cyclic.
Energy Flow in Ecosystems:
Living organisms utilize solar energy. In photosynthesis, this radiant energy is transformed into chemical energy and in cellular metabolism the chemical energy is again transformed into mechanical or heat energy.
Calculation on the basis of meteorological data has revealed that only about one fifty millionth of the tremendous solar energy reaches the outer atmosphere of the earth at a constant rate. This constant is called Solar flux.
The solar flux has been defined as the amount of radiant energy (of all wave-lengths) that cross a unit area or surface per unit of/time. The value has been estimated /to be 2 calories per square centimeter per minute (2 cal/cm2/min.).