question_answer

(i) State two major causes of air pollution.

(ii) Mention the reason for making the buses of Delhi to run on CNG by the end of the year 2002.

(iii) Draw a labelled diagram of electrostatic precipitator that is used to remove fine particles from a flowing gas using the force of an induced charge.

Or

(i) An ecological succession is known to be a sequential, gradual and a predictable change in the species composition over a period of time. Define the following terms related to succession.

(a) Pioneer species

(b) Sere

(c) Ecological succession

(d) Climax community

(ii) What is parasitism?

Answer:

(i) Causes of Air Pollution

The major causes of air pollution are as follows

Excessive use of fossil fuels by automobiles.

Use of leaded petrol and diesel.

Paniculate and gaseous air pollutants released by various industries.

Garbage decomposition also releases air pollutants.

(ii) All buses were made to run on CNG by the end of 2002 because CNG is better than diesel or petrol, in the following ways

I. It bums more efficiently than petrol or diesel in the automobiles and very little of it is left unburnt.

II. It is known to be cheaper than petrol or diesel and cannot be siphoned off by thieves and adulterated like petrol or diesel.

III. It is a clean fuel and prevents air pollution.

(iii) The diagram given below is showing the working of electrostatic precipitator

Or

(i) (a) Pioneer species The species invading a bare area are called pioneer species. Like phytoplanktons are the pioneer species during primary succession in water.

(b) Sere The entire sequence of developmental stages of biotic succession from pioneer to a climax community is known as sere. The individual transitional communities are termed as serai stages.

(c) Ecological succession The gradual and fairly predictable change in the species composition of a given area is called ecological succession. During succession, some species colonise an area and their population become numerous, while some decline and even disappear.

(d) Climax community The composition and structure of community constantly changes in response to the changing environmental conditions. These changes finally lead to a community that is near equilibrium with the environment and is called as climax community.

(ii) Parasitism It is a relationship between two living organisms of different species in which one organism, called parasite, obtains its food directly from another living organism called host, e.g. Cuscuta on plants, Ascaris in human gut. In this process the parasite is benefitted and the host gets harmed.