Our Environment Test - 5

A volcanic eruption is both an international pollutant source and an international hazard. Active volcanoes can contribute to air pollution through the release of toxic gases.

Nitrous oxide occurs in small amounts in the atmosphere, but has been found to be a major scavenger of stratospheric ozone, with an impact comparable to that of the CFCs.  According to an estimation, 30% of the N₂O in the atmosphere is the result of human activity, chiefly agriculture. It also has a significant global warming potential as a greenhouse gas.

Soil is an abiotic (non-living) component of an ecosystem. It provides the substratum for plant growth as also water, nutrients and minerals. Soil contains a number of micro-organisms and it cannot provide a disease-resistant environment for plants.

An aquarium is not a terrestrial ecosystem. Forest, desert and grassland are terrestrial ecosystems. An ecosystem may be a terrestrial ecosystem or an aquatic ecosystem.

The following chain constitutes a food chain (organisms in order of who eats whom):-

Grass →Goat →Human

Plants are producers. The herbivores or the primary consumers come at the second trophic level. Small carnivores or the secondary consumers come at the third trophic level. Larger carnivores or the tertiary consumers form the fourth trophic level.

The flow of energy in an ecosystem is always unidirectional. It means that as the energy moves progressively through the various trophic levels, it is no longer available to the previous level. The energy that is captured by the autotrophs (producers) does not revert back to the solar input. The energy which passes to the herbivores (primary consumers) does not come back to the autotrophs (producers).

Pesticides and other chemicals that are used to protect our crops from diseases and pests, do not get degraded, enter the food chain, and get accumulated in human bodies. The human beings occupy the top level in any food chain. Therefore, the maximum concentration of the chemicals is in the human body. This phenomenon is known as biological magnification.

DDT is dichloro diphenyl trichloroethane. It is used as a pesticide.

Greenhouse gases (GHG) are gases in the atmosphere that absorb and emit radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. Green house gases trap solar radiations and increase the temperature of the Earth.