(a) With suitable examples, elaborate human ecological adaptations. Explain its impacts on ecology and environment in various…

(a) Human ecological adaptations and their impacts

Human ecological adaptation is how groups adjust, physically, culturally and technologically, to the limits of their environment. The adjustment in turn changes that environment.

Examples: the Inuit of the Arctic live by seal and whale hunting, with insulated clothing and snow houses; the Bedouin and Tuareg follow desert nomadism between wells and oases; the Masai graze cattle in African savanna; Amazonian tribes practise shifting cultivation and forest gathering; Andean highlanders have large lungs and haemoglobin for altitude, plant terraced potatoes and herd llamas; Himalayan Bhotia and Gujjar groups move livestock seasonally (transhumance); Ifugao farmers of the Philippines built rice terraces.

Impacts on ecology and environment: shifting cultivation with short fallow causes forest loss and soil erosion; overgrazing and fuelwood demand in the Sahel and Rajasthan cause desertification; canal irrigation in arid lands causes salinity; terracing and transhumance, when balanced, conserve soil and let pastures recover; traditional hunting-gathering has little impact. Modern technology has freed people from many limits, but it has raised the pressure on forests, water and soil, so adaptation now needs sustainable use of resources.

(b) Stream basins and drainage divides in watershed delineation

A watershed is the land area that drains to a common outlet. Its extent is fixed by two features.

A stream basin is the area drained by a stream and its tributaries; it holds the streams, whose order (Strahler) and pattern show how water moves. A drainage divide is the ridge line that separates one basin from the next, as the Western Ghats crest separates west-flowing from east-flowing rivers.

To delineate a watershed, one traces the divide on a contour map or digital elevation model around the outlet, lines it up with the streams, and checks it against satellite images. India's land-use survey codes watersheds in hierarchy: region, basin, catchment, sub-catchment, watershed, sub-watershed and micro-watershed. Delineated units are the base for soil and water conservation, flood control, irrigation planning and land use. Divides matter because a change inside the unit, such as a dam or deforestation, is felt downstream within the same basin.

(c) Lightning: causes and threats

Lightning is an electrical discharge from a cumulonimbus cloud.

Causes: strong updraughts carry water droplets and ice crystals in the cloud. Collisions of graupel with ice crystals separate charge, leaving positive charge in the upper part and negative charge in the lower part, with a small positive pocket at the base. When the potential difference exceeds what the air can bear, a leader stroke from the cloud meets a streamer from the ground, and a return stroke carries the current. Hot, humid pre-monsoon air and strong convection make storms more frequent.

Threats: India records nearly 2,800 deaths a year from lightning (NCRB), mainly rural farmers, in Bihar, Uttar Pradesh, Madhya Pradesh, Odisha and Jharkhand. It also kills livestock, damages buildings, power and telecom lines, starts forest and crop fires, and endangers aircraft. Early warning (IMD, the Damini app), lightning arrestors, safe shelters and public awareness reduce losses.