Five true-or-false statements on productivity, water use, ground-level ozone, food webs and savannahs

(i)False Primary productivity depends on the plants of an area and on environmental factors such as water and nutrients, so it differs widely between ecosystems. A desert, with very little rain and sparse plant cover, produces far less plant matter than a forest, so desert productivity is low, not high.

(ii)True Agriculture uses much more water in India than industry: about 90 per cent of water use is for agriculture against about 7 per cent for industry.

(iii)True Ozone high in the stratosphere protects life, but at ground level it is a pollutant and a health hazard, causing breathing problems such as asthma and bronchitis and harming crops and materials. It forms in traffic-heavy cities on sunny days.

(iv)True The interconnection of many food chains in an ecosystem, through animals that eat more than one kind of food, is called a food web.

(v)False Savannahs are tropical grasslands with scattered trees, a habitat the held text names alongside semi-arid regions. Mangrove forests are quite different: they grow along the coast, especially in river deltas, in salty, tidal water, as in the Sundarbans of West Bengal.