The term ecosystem was first proposed by A.G.Tansley in1935.
He defined it as “the system resulting from the integration of all the living and non- living factors of environment”.
Ecosystem is most preferred, where ‘eco’ implies the environment, and ‘system’ implies an interacting, inter-dependent complex.
Thus any unit that includes all the organisms i.e. the communities in a given area, interact with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity and material cycle within the system, known as an ecological system or ecosystem.
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving, physical components of the environment with which the organisms interact, such as air, soil, water and sunlight.
The structure and function are the major aspects of an ecosystem.
STRUCTURE OF AN ECOSYSTEM
the composition of biological community including species, numbers,biomass, life history and distribution in space, etc.
the quantity and distribution of non living materials like nutrients, water etc.
the conditions of existence such as temperature, light etc.
The structure of an ecosystem is characterized by the organization of abiotic and biotic components.
a bios = abiotic without life without life abiotic components. Inorganic substances Organic substances Climatic factors
Two major types of food chains: 1. Grazing food chain
It starts with green plants (primary producers) and culminates in carnivores.
Phytoplanktons water fleas small fish Carnivorous fish (Pond ecosystem)
2. Detritus food chain:
It starts with dead organic matter which the detritivores and decomposers consume.
Thus grazing food chain derives its energy basically from plant energy while in the detritus food chain it is obtained primarily from plant biomass, secondarily from microbial biomass and tertiarily from carnivores.
Food Web Thus food web is a network of food chains where different types of organisms are connected at different trophic levels, so that there are a number of options of eating and being eaten at each trophic levels.