Ecology and Environment Questions and Answers

Answer: B

The correct matching is a-v, b-iv, c-i, d-ii, e-iii.

Biodegradable materials made from plants and animals decompose at very different rates. Kitchen waste such as a banana peel breaks down in a week or two, paper in a few weeks (about 10-30 days), a cotton shirt in a few months (2-5 months) and a silk scarf, made of animal protein fibre, is usually given as about 4 years. A plastic bottle is not biodegradable in any useful sense and lasts for many years.

The answer can be fixed from the two clearest pairs alone: plastic lasts several years (a-v) and cotton cloth decays in a few months (c-i). Only option 2 has both; options 1 and 3 give plastic only 4 years, and option 4 gives cotton 1-2 weeks.

Answer: A

The correct matching is (a) - (iii), (b) - (i), (c) - (iv), (d) - (ii).

• Large circular leaves, like those of the water lily, spread on the surface and help in providing buoyancy.
• A waxy coating keeps water off the leaves and protects them against decay.
• Stems with large air-filled tunnels and holes help the plant stay afloat.
• Narrow ribbon-like leaves bend with the flow and offer little resistance to water currents.

Only option 1 pairs the waxy coating with protection against decay and ribbon-like leaves with water currents.

Answer: A

The true statement is that soil with low water holding capacity has good aeration and high percolation rate.

Sandy soil has large particles with big spaces between them. Water drains through quickly, so it holds little water and has a high percolation rate, and the large air spaces give good aeration.

Clayey soil is the opposite, with fine particles, high water holding capacity, poor aeration and slow percolation; the other options mix the two.

This is why sandy soils need frequent watering, while clayey soils can become waterlogged.

Answer: A

Both (A) and (R) are true and (R) is the correct reasoning for (A).

Trees and their roots hold the soil, slow down rainwater and, with the humus they add, help water soak into the ground. When forests are cut, infiltration falls: more rainwater runs off the surface at once into streams and rivers, which can overflow and cause floods. Soil eroded from bare land also silts up river beds, adding to flooding.

So deforestation can lead to floods, and reduced infiltration is the reason it does. Options B, C and D deny that the two are true or linked.

Answer: D

The practice not likely to increase soil fertility is maintaining minimum distance between the crops while sowing.

Sowing seeds too close together does not add anything to the soil. It causes overcrowding, so plants compete for the same nutrients, water and sunlight, and the soil is drained faster rather than enriched.

The other practices all help restore fertility. Organic manure adds humus and nutrients and improves soil texture. Leaving a field fallow between crops lets the soil recover its nutrients. Crop rotation, especially with legumes, replenishes nitrogen.

Answer: A

The Red Data Book records endangered species.

The Red Data Book, maintained by the International Union for Conservation of Nature (IUCN), keeps a record of species of plants and animals that are threatened with extinction, classified as critically endangered, endangered, vulnerable and so on. Countries such as India keep their own Red Data Books.

Its purpose is to record species at risk, not extinct ones, and it covers both plants and animals rather than flora or fauna alone.

Answer: D

The correct sequence is (iv), (iii), (i), (ii).

• Canopy: the roof formed by the branches of tall trees in a forest.
• Decomposers: microorganisms such as bacteria and fungi that break down dead matter.
• Humus: the dark organic matter formed from dead plant and animal tissues.
• Porcupine: a wild animal of the forest.

The other sequences give humus the microorganisms or the canopy dead tissues, so only D matches each term.

Answer: D

The one different from the rest is conservation.

Deforestation (clearing forests), desertification (fertile land turning into desert) and soil erosion (removal of the top soil by wind and water) are all forms of damage to land and the environment, and each can lead to the others: cutting forests exposes soil to erosion and can eventually turn land into desert.

Conservation is the protection and careful use of forests, wildlife, soil and other resources, a remedy for these problems rather than one of them.

Answer: C

A is true but R is false.

Sewage carries disease-causing microbes and harmful substances; untreated, it contaminates water and spreads diseases such as cholera and typhoid. Treating it is essential to prevent disease and death, so A is true.

R is false because sewage is a liquid waste: water from homes, industries and hospitals carrying dissolved and suspended impurities. It is not a solid waste, so the options calling R true are wrong.

Answer: A

The step not done is removing inorganic impurities such as nitrates and phosphates by chlorination.

Chlorination disinfects water: chlorine kills disease-causing microbes in the clarified water. It does not remove dissolved salts such as nitrates and phosphates, so the statement is wrong.

The other three are genuine steps. Waste water passes through a grit and sand removal tank, where its speed is reduced so that sand, grit and pebbles settle. In the clarifier, the sludge that settles is scraped out and a skimmer removes floating grease and oil.