Science [5 marks Questions]

	Food Chain	Food Web
1.	Units: It consists of a single unit of food relations.	It is a complex formed by several units of food relations.
2.	Sequence: It is a straight sequence of organisms.	It is a network of many linkages among the connected food chains.
3.	Populations: It has a maximum of 4-6 populations of different species.	A food web consists of numerous populations of different species.
4.	Food: Only one type of organism is used as food by a patricular type of organism.	An organism can use two to several types of organisms as food.
5.	Disturbance: A disturbance in food chain is difficult to overcome.	A disturbance is overcome after some time.
6.	Endangered Species: It does not help in restoring population of endangered species. Rather it may decline further.	A food web helps in increasing population of endangered species.

Although agriculture is important but there are some harmful effects of agricultural practices on the environment which are as follows:
Excessive cutting down of trees for agricultural purposes causes deforesting and during rain fall it may also result in soil erosion.
Excess drainage of groundwater for irrigation purposes lowers the water table. This results in acute water shortage at many places.
Synthetic fertilizers and pesticides used in the field during rain fall washed away to rivers and other bodies which cause water pollution.
The chemical pesticides, being non-biodegradable accumulates in organisms in increasing amounts at each trophic level commonly known as bio magnification.

A pond or a lake forms a natural and complete ecosystem. All the food chain presents in these ecosystems are complete. These ecosystems have plenty of producers, consumers and decomposers.
On the other hand an aquarium is an incomplete artificial ecosystem. An aquarium does not have enough population of decomposers to decompose waste material produced by aquatic animals. Due to this reason aquarium needs to be cleaned frequently.

Following are some methods which should be used for waste management in fertilizer industries:
Use of catalytic converters in chimneys: Chimneys of a factory may produce many harmful gases and SPMs (suspended particulate matters). A catalytic converter helps in minimizing the harmful gases in the exhaust fume.
Electrostatic precipitators in chimneys: Electrostatic precipitator helps in minimizing SPMs in exhaust. Thus, it helps in minimizing air pollution.
Effluent treatment: All steps should be taken to prevent direct discharge of effluents into the nearest waterbody. An effluent treatment plant should be installed in the factory. It should have proper facilities for physical, chemical and biological treatment of effluent. Sedimentation, flocculation, filtration and chlorination are the various steps of effluent treatment. This will help in checking the pollution of waterbodies. It will also help in utilsing the treated water as source for irrigation. This water can also be used as drinking water after further treatment.