26-07-2014, 11:13 AM
OUR ENVIRONMENT
OUR ENVIRONMENT.pptx (Size: 972.65 KB / Downloads: 12)
Effect of adding waste to the environment :-
Human activities produce a lot of waste materials which
are thrown away into the environment. These wastes cause
pollution of air, water and soil.
The waste materials produced are of two main types. They
are biodegradable wastes and non biodegradable wastes.
i) Biodegradable wastes :- are wastes which are
decomposed into harmless substances by microorganisms.
Eg :- vegetables, fruits, pulses, cereals, cotton, jute, wool,
wood, leather, paper, animal dung, animal bones etc.
ii) Non biodegradable wastes :- are wastes which are not
decomposed by microorganisms.
Eg :- polythene bags, plastics, synthetic fibres, glass,
metals, synthetic rubber, insecticides, pesticides etc.
. Ecosystem and its components :-
) Ecosystem :-
An ecosystem consists of all the living organisms in an
area along with the non living components and their interaction.
There are different types of ecosystems. They are :-
i) Natural ecosystems :- like forests, deserts, grass lands, mountains,
ponds, lakes, rivers, oceans etc.
ii) Artificial ecosystems :- like gardens, parks, crop fields, aquarium, zoo etc.
b) Components of an ecosystem :-
An ecosystem consists of two main components. They are biotic and abiotic
components.
i) Biotic components :- are the living components like plants, animals and
microorganisms. They consist of producers, consumers and decomposers.
Producers :- are green plants which produce food by photosynthesis.
Consumers :- are herbivores which get their food directly from plants,
carnivores which get their food indirectly from plants and omnivores which
get their food directly or indirectly from plants.
Decomposers :- are microorganisms which decompose dead plants and
animals. They decompose complex organic substances into simple inorganic
substances in the soil which are again used by plants.
ii) Abiotic components :- are the non living components like air, water, soil,
minerals, sunlight , temperature, wind etc.
Trophic levels :-
Each step in a food chain where transfer of food energy takes place is called trophic level.
The first trophic level consists of producers.
The second trophic level consists of primary consumers.
The third trophic level consists of secondary consumers.
The fourth trophic level consists of tertiary consumers.
Since the transfer of food energy decreases at every trophic level, the number of trophic levels are limited and do not exceed four or five.
Biological magnification (Biomagnification
Harmful chemicals like insecticides and pesticides which are used to protect crops from insects and pests are absorbed by plants and enter the food chain. Since these chemicals are non biodegradable, they get accumulated at every trophic level and their concentration increases. Since human beings occupy the highest trophic level, the concentration of these harmful chemicals is maximum in our bodies.
The increase in concentration of harmful chemicals in the bodies of organisms at higher trophic levels is called biological magnification.