SYNOPSIS :
- The world of living thing is termed as “biosphere”.
- within the biosphere, there are a number of major eco-systems.
- The terrestrial eco-systems are being determined largely by the variations in climatic conditions between the poles and equator.
- The main climatic influences which determine these eco-systems are rainfall, temperature and the availability of light from the sun.
- Food chain shows-how energy passed from one organism to another.
- The arrows between each item in the food chain always point from the food to feeder.
- Pyramid of the numbers, pyramid of biomass and pyramid of energy are other ways to show food relationship and flow of energy among other living things.
- A pyramid is a structure whose shape is roughly that of a pyramid in a geometric sense.
- The concept of ecological pyramid was first introduced by a British ecologist CHARLES ELTON in 1927.
- Pyramid of numbers shows the population of organisms at each tropic level in a food chain.
- Biomass is organic material of biological origin.
- Pyramid of biomass represents the available food as a source of energy at each tropic level in the food chain.
- It is found that 10-20%of the biomass is transferred from one tropic level to the next in a food chain.
- Biomass can also be used as fuel
- Pyramid of energy represents the available energy at each tropic level in the food chain.
- The ratio between energy flows at different tropic levels along the food chain expressed as percentage is called “ECOLOGICAL EFFICIENCY “.
- SLOBODKIN (1959) suggested that transfer of energy from one tropic level to the next is of the order of 10%and this is called “GROSS ECOLOGICAL EFFICIENCY “.
- TEN percent law was initially observed by LINDEMAN (1942).
- STEELE proved that the gross ecological efficiency is about 20% to 30% in 1974.
- Toxic material used to prevent the pest, fungus and other disease away from the food crop and grains do harm the food crop and grains do harm the ecosystem in many ways.
- Bioaccumulation is the entering of the pollutants in the food chain.
- The tendency of pollutants to concentrate as they move from one tropic level to the next is known as “BIOMAGNIFICATION”.
- There are several alternatives of pesticides through which we can get more crops with less harm like rotation of crops, biological control,development of genetic resistant strains, etc….
BIO-MAGNIFICATION : “The tendency of pollutants to concentrate as they move from one tropic level to the next is known as bio -magnification.
1.pesticides get accumulated at each tropic level, as they are non -biodegradable substances.
2.since human beings occupy the top level in any food chain,so the maximum amount of toxic pesticides get accumulated into the bodies.
3.medical tests have proved that the most commonly used pesticides like D.D.T is accumulating in our bodies through food chains leading to health hazards.
