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Practice succession-and-change with 20 free MCQ questions covering environment-and-ecology. Detailed explanations in English and Hindi, perfect for UPSC, SSC, and competitive exam preparation.
Attempt the quiz above first, then review every question with its correct answer and a short explanation below.
Q1.The removal of the fertile topsoil by wind and water due to human activities like deforestation and overgrazing is called:
Explanation: NCERT Class 12 Biology Chapter 16 states: 'The development of the fertile top-soil takes centuries. But, it can be removed very easily due to human activities like over-cultivation, unrestricted grazing, deforestation and poor irrigation practices, resulting in arid patches of land. This is called soil erosion.'
Q2.When large arid patches of degraded land meet and extend over time, creating new barren desert areas, the process is called:
Explanation: NCERT Chapter 16 states: 'When large barren patches extend and meet over time, a desert is created. Internationally, it has been recognised that desertification is a major problem now, particularly due to increased urbanisation.'
Q3.Heavy irrigation of agricultural fields without proper drainage systems leads to which of the following soil problems?
Explanation: NCERT Chapter 16 highlights: 'Irrigation without proper drainage of water leads to waterlogging in the soil. Besides affecting the crops, waterlogging draws salt to the surface of the soil.'
Q4.Why does waterlogging in agricultural soils draw dissolved mineral salts to the soil surface, forming a saline crust?
Explanation: In waterlogged soils, the high water table allows water to rise to the surface via capillary action through soil pores. As this water evaporates under the sun, the dissolved mineral salts are deposited on the surface, creating a saline crust (NCERT Chapter 16).
Q5.Which of the following is a major negative impact of soil salinization on crop growth?
Explanation: NCERT Class 12 Biology states that the accumulated salt on the soil surface starts damaging agriculture. High salt concentration in soil creates hypertonic conditions, causing osmotic stress which prevents roots from absorbing water, stunt growth, and can kill plants.
Q6.Soil salinization and waterlogging are major environmental issues that arose in India primarily as a green revolution side-effect of:
Explanation: NCERT documents: 'Waterlogging and soil salinity are some of the problems that have come in the wake of the Green Revolution.' Extensive canal irrigation networks in Punjab and Haryana brought water to dry fields, but the lack of drainage raised water tables, causing waterlogging and salinization.
Q7.The farming practice of ploughing along the natural elevation lines of a slope to reduce water runoff and soil erosion is called:
Explanation: Contour ploughing involves ploughing along the contour lines of a slope. This creates mini-dams that slow water runoff and prevent the formation of rills and gullies, conserving both soil and water (NCERT Class 10 Geography).
Q8.In steep mountainous areas, creating step-like flat areas (terraces) on slopes to grow crops and reduce the speed of water runoff is known as:
Explanation: Terrace farming (or terracing) is a classic soil conservation method in hilly terrains (like the Himalayas). Creating flat steps reduces the slope angle, cutting down the speed of surface water runoff, preventing landslides, and giving water time to soak into the soil.
Q9.Rows of trees planted along the edges of agricultural fields in dry, windy plains to break wind velocity and prevent wind erosion of topsoil are called:
Explanation: Shelterbelts (or windbreaks) consist of rows of trees or shrubs planted in a line perpendicular to the dominant wind direction. They lift wind currents away from the ground, significantly reducing wind speed and protecting dry loose topsoil from blowing away.
Q10.Covering the bare soil between crop rows with organic matter (like straw, dry leaves, or wood chips) to retain soil moisture and reduce erosion is known as:
Explanation: Mulching is the practice of applying organic (straw, grass) or inorganic (plastic sheet) cover to bare soil. It insulates the soil, blocks evaporation under sunlight, prevents weed growth, and protects the soil surface from the impact of raindrops.
Q11.Which of the following represents an biological conservation method to prevent soil erosion on steep road embankments or river banks?
Explanation: Cover crops (like clover, alfalfa) and fast-growing grasses develop extensive fibrous root networks that physically bind soil particles together, while their foliage protects the soil surface from rain impact, serving as a highly effective biological shield.
Q12.Which type of soil erosion is characterized by the uniform removal of a thin layer of topsoil over a wide area, often caused by sheet flooding?
Explanation: Sheet erosion is the gradual and uniform removal of a thin layer of topsoil from a large area of land due to surface runoff. It is often hard to detect initially because the change is subtle, but it leads to significant nutrient loss.
Q13.Heavy rains on sloped soils with poor vegetation cover often carve deep channels or ravines, making the land unfit for cultivation. This type of water erosion is called:
Explanation: Gully erosion occurs when runoff water accumulates and flows rapidly down a slope, carving out deep channels (gullies) and ravines (such as the Chambal Ravines in India). This degrades the land and makes farming impossible.
Q14.Which of the following states in India has suffered most from waterlogging and soil salinization due to the introduction of massive canal irrigation under the Green Revolution?
Explanation: Punjab and Haryana, which received extensive canal networks (like Indira Gandhi Canal linkages) during the Green Revolution, experienced rapid water table rises. Due to poor drainage, large areas of fertile land became waterlogged and saline.
Q15.What is the primary cause of soil erosion on steep hillsides in India?
Explanation: In hilly areas (like the Himalayas or Western Ghats), cutting down forests removes the tree roots that bind the soil and the canopy that intercepts rain. When heavy rains occur, the water runs off rapidly down the slopes, washing away the topsoil.
Q16.Which of the following describes the soil conservation practice of 'Strip Cropping'?
Explanation: Strip cropping involves growing alternate strips of close-growing plants (grasses/alfalfa) and row crops (wheat/corn) on a slope. The dense grass strips slow water runoff and trap soil particles washed down from the crop rows, reducing overall erosion.
Q17.When dry soil is exposed to strong winds in flat, semi-arid plains, the wind blows away the fine silt and clay particles, leaving behind coarse sand. This process is called:
Explanation: Wind deflation or ablation is the removal of loose, fine-grained particles (silt, clay, organic matter) from the soil surface by wind. This leaves behind coarser sand and gravel, reducing soil fertility and contributing to desertification.
Q18.Which of the following agricultural practices directly accelerates desertification in arid regions?
Explanation: In dry, fragile ecosystems, overgrazing removes vegetation cover, over-cultivation exhausts soil nutrients, and poor irrigation causes waterlogging and salinization. Together, these degrade the soil structure, leading to rapid desertification.
Q19.The Chambal Ravines in India are a classic, large-scale example of land degradation caused by which type of soil erosion?
Explanation: The Chambal river basin in central India has suffered severe gully erosion. Heavy rainfall on loose alluvial soil with little vegetation cover has carved deep ravines, creating barren 'badlands' that are unfit for agriculture.
Q20.Why does the presence of organic humus in the soil help prevent soil erosion?
Explanation: Organic humus acts as a biological glue. It binds small soil particles (sand, silt, clay) into larger, stable aggregates. This improves soil structure, creates pores for water to seep in (reducing surface runoff), and increases the soil's resistance to wind and water erosion.
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