Prepare a list of five items that you use daily in the school. Identify from the list such items that can be recycled.
Paper, rexin bag, blade, pen, plastic box, scale, eraser, compass and dividers (metallic), steel lunch box, steel spoon.
Paper, blade, plastic box, eraser, compass, steel lunch box and steel spoon can be recycled.
List two advantages associated with water harvesting at the community level.
The ground water level increases due to recharging of wells.
Ground water keeps the layers of soil above it moist and prevents loss of water by evaporation.
The water can be stored during rainy season and can be used when required.
In a village in Karnataka, people started cultivating crops all around a lake which was always filled with water. They added fertilisers to their field in order to enhance the yield. Soon they discovered that the waterbody was completely covered with green floating plants and fishes started dying in large numbers. Analyse the situation and give reasons for excessive growth of plants and death of fish in the lake.
Fertilisers containing phosphates and nitrates were washed into the lake, enriching the water with these chemicals. This promoted excessive growth of aquatic plants (eutrophication), covering the water surface.
Due to excessive plant growth, sunlight could not reach deeper layers of water. Dissolved oxygen levels decreased, causing death of fish.
What measures would you take to conserve electricity in your house?
Put off the fans and lights when they are not required.
Make maximum use of solar radiation.
Use solar water heating systems during winters.
Use fluorescent tubes or CFL.
Although coal and petroleum are produced by degradation of bio-mass, yet we need to conserve them. Why?
Both coal and petroleum take millions of years to form. Since they are being used at a much faster rate than their formation, they will soon be exhausted. Therefore, they need to be conserved.
Suggest a few measures for controlling carbon dioxide levels in the atmosphere.
Reduce consumption of petrol in automobiles.
Use CNG or clean fuel.
Prepare manure from waste instead of burning it.
Treat smoke to remove harmful gases before releasing it into the atmosphere.
Plant more trees.
(a) Locate and name the water reservoirs in Figures 16.1 (a) and (b).
(b) Which has an advantage over the other and why?
(a) The water reservoir in Figure 16.1(a) is a pond and in Figure 16.1(b) it is an underground water body.
(b) The underground water reservoir has more advantages because the water stored in the ground does not evaporate, spreads out to recharge wells, provides moisture for vegetation, is protected from contamination, and prevents insect breeding.