JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ENVIRONMENTAL STUDIES Previous Question Paper (March - 2021 - R15/R13)

A biogeochemical cycle is the natural pathway by which essential elements and nutrients move through the biotic (living) and abiotic (non-living) components of an ecosystem. These cycles ensure the continuous circulation and recycling of matter, such as water, carbon, nitrogen, and oxygen, which are vital for sustaining life.

The water cycle (hydrologic cycle) describes the continuous movement of water on, above, and below the surface of the Earth. Its mechanism involves several key processes:

1. Evaporation and Transpiration: Solar energy heats water bodies, causing evaporation. Simultaneously, plants release water vapor into the atmosphere through transpiration.
2. Condensation: As water vapor rises, it cools and condenses to form clouds.
3. Precipitation: Water returns to the Earth's surface as rain, snow, or hail when clouds become saturated.
4. Collection and Runoff: Water flows into rivers, lakes, and oceans or infiltrates the soil to replenish groundwater, eventually returning to the atmosphere to repeat the cycle.

The oxygen cycle is the biogeochemical process that maintains the level of oxygen in the atmosphere and biosphere. Its mechanism is driven by the balance between production and consumption:

1. Production: The primary source of atmospheric oxygen is photosynthesis, where green plants, algae, and cyanobacteria use sunlight to convert carbon dioxide and water into glucose and oxygen.
2. Consumption: Oxygen is utilized by aerobic organisms for cellular respiration to produce energy, releasing carbon dioxide as a byproduct.
3. Atmospheric Exchange: Oxygen is also consumed during combustion (burning of organic matter) and the weathering of rocks (oxidation).
4. Ozone Formation: A portion of atmospheric oxygen is converted into ozone (O3) in the upper atmosphere, which protects the Earth from harmful ultraviolet radiation.

Both cycles are interdependent; for instance, the water cycle facilitates the transport of nutrients necessary for photosynthetic organisms, which in turn regulate the oxygen cycle.

Floods and droughts are extreme hydrological events that significantly impact ecosystems, human infrastructure, and economies.

Floods

Floods occur when water overflows onto land that is usually dry. Causes: Intense or prolonged rainfall, rapid snowmelt, failure of dams or levees, deforestation which reduces soil infiltration, and urbanization which increases impermeable surfaces. Impacts: Loss of life, destruction of infrastructure and crops, displacement of populations, and the spread of waterborne diseases. Preventive Measures: Constructing levees, dams, and floodwalls; restoring wetlands to act as natural sponges; implementing effective urban drainage systems; and enforcing strict land-use planning in floodplains.

Droughts

Droughts are prolonged periods of abnormally low rainfall leading to a shortage of water. Causes: Climate variability (such as El Niño), global warming, excessive groundwater extraction, deforestation, and poor agricultural practices that deplete soil moisture. Impacts: Crop failure and food insecurity, water scarcity for domestic and industrial use, loss of biodiversity, increased risk of wildfires, and economic instability. Preventive Measures: Implementing rainwater harvesting and watershed management; promoting drought-resistant crop varieties; efficient irrigation techniques like drip irrigation; reforestation; and sustainable groundwater management.