91: Identify the correct order of the processes of soil-erosion from the following:
(a) Splash erosion, Sheet erosion, Rill erosion, Gully erosion
(b) Sheet erosion, Splash erosion, Gully erosion, Rill erosion
(c) Rill erosion, Gully erosion, Sheet erosion, Splash erosion
(d) Gully erosion, Rill erosion, Sheet erosion, Splash erosion
Explanation:
The correct order of soil erosion process is Splash-Sheet-Rill-Gully and Ravine erosion.
92: Assertion (A) :
Mangroves are very specialised forest ecosystems of tropical and subtropical regions bordering certain sea coasts.
Reason (R) :
They stabilise the shoreline and act as bulwark against encroachments by sea.
In the context of the above two statements, which one of the following is correct ?
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
93: Salinization occurs when the irrigation water accumulated in the soil evapo- rates, leaving behind salts and minerals. What are the effects of salinization on the irrigated land?
(a) It greatly increases the crop production.
(b) It makes some soils impermeable.
(c) It raises the water table.
(d) It fills the air spaces in the soil with water.
Explanation:
Salinization is a process that results from:
- High levels of salt in the soils
- Landscape features allow salts to become mobile (Movement of water table).
- Climatic trends favour accumulation.
- Human activities such as land clearing, aguaculture activities, irrigation, and the salting of icy roads
The consequences of salinity are
- salt makes some soils impermeable that have detrimental effects on plant growth and yield
- damage to infrastructure (roads, bricks, corrosion of pipes and cables)
- reduction of water quality for users, sedimentation problems
- soil erosion ultimately, when crops are too strongly affected by the amounts of salts.
Salinity is an important land degradation problem. Soil salinity can be reduced by leaching solube salts out of soil with excess irrigation water. Soil salinity control involves water table cantrol and flushing in combination with tile drainage or another form of subsurface drainage.
94: The "Red Data Books" published by the International Union for Conservation of Nature and Natural Resources (IUCN) contain lists of
1. Endemic plant and animal species present in the biodiversity hotspots.
2. Threatened plant and animal species.
3. Protected sites for conservation of nature and natural resources in various countries.
Select the correct answer using the codes given below :
(a) 1 and 3
(b) 2 only
(c) 2 and 3
(d) 3 only
Explanation:
The IUCN Red List of Threatened Species or The Red Data Book is the state document established for documenting rare and endangered species of animals, plants and fungi as well as some local sub-species that exist within the territory of the state or country. This book provides central information for studies and monitoring programmes on rare and endangered species and their habits.
95: Assertion (A): To orbit around the Sun, the planet Mars takes lesser time than the time taken by the Earth.
Reason (R) : The diameter of the Planet Mars is less than that of the Earth.
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Explanation:
To orbit the Sun, the planet Mars (Red planet) takes more time (687 days) than time taken by Earth (365 1/4 days). The diameter of the planet Mars (6,787 km) is less than that of the Earth (12,756 km)