RBSE SS Env Sci key terms

A self-regulating unit where living organisms interact with one another and with their physical surroundings, exchanging energy and matter. It includes producers, consumers, decomposers and the abiotic environment acting together.

A linear sequence showing how energy and nutrients pass from one organism to another through feeding, beginning with a producer and ending with top consumers or decomposers. Real ecosystems contain many interlinked chains.

A network of interconnected food chains in a community, showing that most organisms eat and are eaten by several species. It gives a more realistic picture of energy flow than a single chain.

The feeding position an organism occupies in a food chain, such as producer, primary consumer or secondary consumer. Energy transferred between successive levels is always partly lost, so higher levels hold less biomass.

Lindeman's principle that only about ten percent of the energy at one trophic level is passed on to the next, the rest being lost mainly as heat through respiration. It explains why food chains rarely exceed four or five links.

A graphical representation of numbers, biomass or energy at successive trophic levels, with producers at the base. It may be upright, inverted or spindle-shaped depending on which quantity is plotted.

The gradual, directional change in species composition of a community over time until a relatively stable climax stage is reached. It may begin on bare rock (primary) or on disturbed but soil-bearing land (secondary).

The first hardy organisms, often lichens and mosses, to colonise a bare or newly exposed surface. They trap moisture, weather rock and add organic matter, preparing conditions for later successional species.

The final, self-perpetuating community that develops at the end of succession in a given climate, remaining broadly stable until the environment changes. Its character is largely determined by regional temperature and rainfall.

A large terrestrial region with a characteristic climate and distinctive plant and animal communities, such as desert, grassland or tropical forest. Biomes are mapped mainly by temperature and precipitation patterns.

A region with exceptionally high species richness and endemism that has already lost a large share of its original habitat. Conservation funds are concentrated there because each unit of effort protects many unique species.

A plant or animal found naturally in one restricted area and nowhere else. Endemics are highly vulnerable to habitat loss because a single local disturbance can eliminate the entire global population.

Protecting species within their natural habitat, for example through national parks, sanctuaries and biosphere reserves. It preserves ecological processes and interactions that cannot easily be recreated in captivity.

Conserving species outside their natural habitat in zoos, botanical gardens, seed banks or gene banks. It is a safeguard for critically endangered species but does not preserve the ecosystem they came from.

The breaking up of continuous natural habitat into smaller, isolated patches by roads, farmland or settlements. Isolated patches support smaller populations, reduce gene flow and raise extinction risk.

The altered conditions, such as more light, wind and predation, found along the boundary between a habitat patch and surrounding land. Species needing deep interior habitat decline as edges increase.

The detachment and removal of topsoil by wind, water or human activity. It depletes fertility, silts reservoirs and, in severe cases, leads to desertification and loss of productive farmland.

A soil and water conservation practice in which embankments are built along contour lines on sloping land. They slow runoff, trap sediment and increase infiltration, reducing rill and sheet erosion.

Uniform removal of a thin layer of topsoil by unchannelled runoff across a slope. It is easily overlooked because no gullies form, yet it steadily reduces fertility and rooting depth.

Land degradation in arid and semi-arid areas caused by climatic variation and human pressure such as overgrazing, deforestation and poor irrigation. It reduces vegetation cover and productivity and can be irreversible.

Planned use and conservation of land, water and vegetation within a drainage basin to regulate runoff, recharge groundwater and reduce erosion. Community participation is central to successful watershed programmes.

Collecting and storing rain where it falls, on rooftops or in tanks and ponds, for later use or for recharge. In dry regions it supplements scarce surface and groundwater supplies.

The process by which water from rainfall, rivers or applied irrigation percolates down to refill aquifers. Recharge rates are slow, so extraction beyond them causes falling water tables.

Energy derived from sources that are naturally replenished on a human timescale, such as sunlight, wind, flowing water and biomass. It produces little or no greenhouse gas during operation.

Technology that converts sunlight directly into electricity using semiconductor cells. It suits decentralised rural electrification and is expanding rapidly in sun-rich states such as Rajasthan.

Energy obtained by burning or digesting plant and animal matter, including fuelwood, crop residues and cattle dung. It is renewable but causes indoor air pollution and deforestation if used unsustainably.

A pollutant released directly into the atmosphere in a harmful form, such as sulphur dioxide, carbon monoxide, particulate matter or hydrocarbons. It contrasts with secondary pollutants formed by reactions in air.

A pollutant produced when primary pollutants react chemically in the atmosphere, for example ozone formed from nitrogen oxides and hydrocarbons, or sulphuric acid mist. It may form far from the original sources.

A brownish haze of secondary pollutants, including ozone, aldehydes and peroxyacetyl nitrate, formed when sunlight acts on nitrogen oxides and hydrocarbons. It irritates eyes and lungs and damages crops.

The amount of dissolved oxygen consumed by microorganisms while decomposing organic matter in a water sample over a set period, usually five days. High values indicate organic pollution from sewage or agro-industrial waste.

Nutrient enrichment of a water body, usually by nitrates and phosphates, that triggers excessive algal growth. Decay of the algae depletes oxygen, harming fish and other aquatic life.

Any physical, chemical or biological change in water quality that harms living organisms or makes water unfit for use. Common sources include sewage, industrial effluent, fertiliser runoff and thermal discharges.

Unwanted or excessive sound that may damage hearing or cause annoyance, sleep disturbance and stress. It is measured in decibels on a logarithmic scale, and limits vary by zone such as residential or industrial.

The systematic handling of discarded material through generation control, segregation, collection, transport, treatment and disposal. The waste hierarchy prefers prevention and recycling over landfilling or open burning.

An engineered disposal site where waste is compacted and covered daily, with a liner and leachate collection to protect soil and groundwater. It differs from an open dump, which is uncontrolled and polluting.

The contaminated liquid that percolates through waste and dissolves organic and inorganic substances. If it escapes, it can pollute groundwater, so landfill design includes liners and collection systems.

Controlled aerobic decomposition of organic waste by microorganisms into a humus-like material used as fertiliser. It diverts kitchen and garden waste from landfills and returns nutrients to soil.

A formal process of predicting the likely environmental effects of a proposed project before approval, and of proposing mitigation measures. Public consultation and monitoring are normally part of the procedure.

The idea that where serious or irreversible environmental damage is possible, lack of full scientific certainty should not be used to postpone cost-effective measures to prevent it. It shifts the burden of proof towards the proponent.

The rule that whoever causes pollution should bear the cost of controlling it and of restoring the damage. It is applied through effluent charges, fines and remediation orders rather than being borne by the public.

Development that meets present needs without compromising the ability of future generations to meet theirs. It balances economic growth, social equity and environmental protection, and is central to international environmental agreements.

The maximum population or level of use that an area can support indefinitely without degrading its resources. Exceeding it leads to resource depletion, pollution and a fall in living standards.

The historical shift of a population from high birth and death rates to low birth and death rates as health care and living standards improve. It passes through a stage of rapid growth before stabilising.

An ancient hill system running diagonally across Rajasthan and neighbouring states, acting as a barrier against desert expansion and a source of minerals and water. Mining and encroachment have caused severe degradation.

A participatory arrangement in which local communities share responsibility for protecting and managing nearby forest land in return for rights to collect specified products. It links conservation with rural livelihoods.