ECOSYSTEM

CLASS - XII

Developed By:Dr.U.P.PaniPGT (Biology)JNV Durg (CG)

The term ecosystem was first coined by A.G.Tansely.

Ecosystem consists of two Words :

ECOSYSTEM

Ecosystem

EcoEnvironment

SystemInteraction

According to E.P.Odum, an American ecologist, the ecosystem is the basic functional unit of organism and their environment interacting with each other and with their own components.

e.g. Grassland, Forest, Aquarium, Pond, Lake, River and Ocean.

Ecosystem - Definition

Grassland Ecosystem

Forest Ecosystem Ocean Ecosystem

Types of Ecosystem

EcosystemTerrestrialEg.Forest, Grassland and Desert

AquaticEg. Pond,

Lake, Wetland, River and Estuary

Structure of Ecosystem

EcosystemAbiotic

non-livingEg. soil, water, light, inorganic nutrients and weather

Bioticliving

Eg. producers and consumers

From nutrition point of view, the biotic components of ecosystem can be grouped into three categories:

Biotic Components

Biotic components of Ecosystem

Producers

Consumers

Decomposers

The vertical distribution of different species occupying different levels is called stratification.

Eg. Trees occupy top vertical strata or layer of a forest, shrubs the second, herbs and grasses occupy the bottom layers.

STRATIFICATION

The components of the ecosystem are seen to function as a unit when we consider the following aspects:

ProductivityDecompositionEnergy flowNutrient cycling

Function of Ecosystem

Productivity - The rate of biomass production is called productivity.Units: g–2 yr –1 or (kcal m–2) yr–1

Gross primary productivity - The rate of production of organic matter during photosynthesis is called gross primary productivity.Gross PP (GPP) = total energy fixedNet PP (NPP) = GPP – respiration

Secondary productivity – The rate of formation of new organic matter by consumers is called secondary productivity .

PRODUCTIVITY

Components of Productivity

The breakdown of complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition.

DECOMPOSITION

Steps in decomposition

Fragmentation

Leaching

Catabolism

Humification

Mineralization

Decomposition cycle in a Terrestrial Ecosystem

The flow of energy is one way direction from producer to consumers, and ends in decomposition process.

However, a part of the energy is lost as heat and agrees with the phenomenon of second law of Thermodynamics.

ENERGY FLOW

GRAZING FOOD CHAIN

Goat (Primary Consumer)

Grass (Producer)

Detritus is non-living particulate organic material includes the bodies or fragments of dead organisms as well as fecal material.

Decomposers are heterotrophic organisms also called saprotrophs. Eg. Fungi and Bacteria.

Detritus Food Chain

A food web depicts various feeding connections in an ecological community.

Natural interconnected food chains make a food web.

FOOD WEB

TROPHIC LEVELThe trophic level is the position of an organism it occupies in the community or a food chain.

Energy flow in different Trophic Levels

An ecological pyramid is a graphical representation of trophic levels in a given ecosystem.

ECOLOGICAL PYRAMIDS

Ecological

Pyramids

Pyramid of

Number

Pyramid of

Biomass

Pyramid of

Energy

The pyramid of biomass in sea is also generally inverted because the biomass of fishes far exceeds that of phytoplankton.

PYRAMID OF NUMBERS

The pyramid of biomass in sea is also generally inverted because the biomass of fishes far exceeds that of phytoplankton.

PYRAMID OF BIOMASS

Pyramid of energy is always upright. It can never be inverted.

PYRAMID OF ENERGY