Write short notes on the following:

(i) Altitudinal biomes.

(ii) Oligotrophic lakes.

(iii) Boundaries of Eco-system.

Ans. A series of biomes can be noted along the slopes of high mountain ranges like the Himalayas, Andes and Rockies. These mountain ranges have the gradual change in the biome-type according to the altitude rather than the latitude. Temperature and precipitation rates are most important determinants of these biomes. In the tropical mountains the sequence of communities and conditions from the base of the mountain to the suow-line are tropical forest, deciduous forest, coniferous forest and Tundra.

(ii) Oligotrophic lakes.

Ans. The deep lakes with steep and rocky sides and poor in circulating nutrients such as phosphates are called oligotrophic lakes. The physical factors of the lakes contain saline or brackish water (Sambar lake of Rajasthan).

(iii) Boundaries of Eco-system.

Ans. An ecosystem is an area in which the living and non-living components can be demarcated by a boundary, for convenience in study. It is important to recognise that ecosystem are not strictly isolated. Their boundaries are indistinct and overlapping. Some movement always occurs from one eco-system to another in terms of energy and materials. This movement may be from an adjacent or distant eco-system. A pond may be separated from a grassland but some birds may break the barrier and feed on the fishes of the pond. The top soil from the Himalayas is washed down in massive amount by rivers. Siberian crane can migrate from Siberia to Bharatpur in India.