Ecology and Environment Questions and Answers

Answer: C

Species restricted to a particular area are called endemic species.

An endemic species is found naturally only in one region and nowhere else, for example sal and wild mango, which the NCERT Class VIII textbook names as endemic flora of the Pachmarhi Biosphere Reserve, or the Nilgiri tahr of the Western Ghats.

The other terms mean different things. Endangered species are those at risk of extinction, wherever they live. Extinct species no longer exist anywhere. Migratory species move between regions, often seasonally, which is the opposite of being restricted to one area.

Answer: D

The gases responsible for acid rain are (d) and (e), sulphur dioxide and nitric oxide.

Sulphur dioxide from burning coal and oil, and nitrogen oxides such as nitric oxide from vehicle engines and power stations, react with water and oxygen in the atmosphere to form sulphuric and nitric acids, which fall as acid rain.

Nitrogen and oxygen are the main gases of clean air and do not cause acid rain themselves, and ozone is an oxidant and greenhouse gas but not a source of the acids.

Answer: B

On the key's reading, the features that help polar bears adapt to extreme cold are white fur, long curved sharp claws and fat under the skin.

The white coat hides the bear against snow and ice, a layer of fat under the skin keeps heat in, and long, curved, sharp claws give a grip for walking and hunting on ice. A Class 7 NCERT-based exemplar question names these features together for the polar bear, and this is the option that lists all three.

The other options bring in 'flat feet', which is not the usual wording for the bear's adaptation (large, wide paws spread its weight on ice), and 'layers of fur' or 'strong smell', which also appear in descriptions of the animal. The key could not be confirmed from the NCERT textbook text itself, so the answer rests on the exemplar item and elimination.

Answer: B

Ozone depletion is caused by chlorofluorocarbons.

CFCs, once used in refrigerators, air conditioners and aerosol sprays, are stable enough to reach the stratosphere. There ultraviolet light breaks them down and releases chlorine atoms, and each chlorine atom can destroy thousands of ozone molecules in a chain reaction. This is why the Montreal Protocol phased them out.

Carbon dioxide and methane are greenhouse gases linked to global warming, not ozone depletion, and carbon monoxide is a poisonous gas from incomplete combustion. Acid rain is caused by sulphur and nitrogen oxides and damages buildings, soil and lakes, not the ozone layer.

Answer: C

The species is endemic.

An endemic species is found naturally in only one particular region and nowhere else in the world, however common it may be there. The stem's 'found only in Y part of India in the whole world' is the definition of endemism.

'Abundant' refers to numbers, not range. Exotic species are introduced from elsewhere, and endangered species are at risk of extinction, which does not fit a plant that grows in huge numbers.

Answer: A

The effect not caused by excessive fertilizers and pesticides is soil erosion.

Soil erosion, the removal of topsoil by wind and water, is caused mainly by deforestation, overgrazing, poor tillage and the loss of plant cover, not by chemicals added to the soil.

The others are linked to agrochemicals: fertilizer run-off rich in nitrogen and phosphorus causes eutrophication of water bodies; persistent pesticides such as DDT build up along food chains through biomagnification; and ammonium-based fertilizers increase the microbial nitrification that contributes to nitrate leaching and soil acidification.

Answer: C

Statements (a), (b) and (d) are true.

Rainwater harvesting collects rainwater from roofs and land and stores it or directs it into the ground. It recharges and so conserves groundwater (a), reduces surface run-off and hence local flooding (b), and the stored water can be used for purposes such as irrigating crops (d).

It does not create drainage problems; by reducing run-off it eases the load on drains, so (c) is false and every option including it is wrong.

Answer: D

The pyramid of energy is always upright.

Each trophic level passes on only about 10% of the energy it receives to the next, the rest being lost as heat in respiration. Energy flow at each higher level must therefore be smaller than at the level below, in any ecosystem.

Pyramids of number or biomass can be inverted: a forest has few large trees supporting many insects, so its pyramid of numbers is spindle shaped or inverted. But energy cannot increase up the chain, so the energy pyramid is never inverted, spindle shaped or dumb-bell shaped.

Answer: D

The statement that is not correct is Average temperature in Tundra is above 30 °C.

The tundra is the coldest biome on land. Its mean annual temperature is below freezing, winters fall far below 0 °C, and even the warmest month averages only about 10 °C, which is too cold for trees. An average above 30 °C would describe a hot desert, not the tundra.

The other statements are the standard textbook account. Many northern mammals, such as bears, ground squirrels and bats, hibernate through winter. Tundra vegetation is low and herbaceous: mosses, lichens, sedges, grasses and dwarf shrubs. Broadleaf deciduous trees dominate the temperate forests of the Northern Hemisphere, which is the sense in which the paper states it.