Class 7 Science · 20 questions · 20 with answers
The microorganisms present in the soil require moisture (water) and nutrients for growth and survival. Choose from the options below the habitat (place) where the soil has plenty of water and nutrients.
(b) Forest
Availability of water and minerals in the soil for maximum absorption by roots is in the –
(c) A-horizon
Soil conservation measures are mainly aimed at protecting which of the following?
(b) Top soil
Read the following statements with reference to soil. (i) Weathering is a very fast process of soil formation. (ii) Percolation of water is faster in sandy soils. (iii) Loamy soil contains only sand and clay. (iv) Top soil contains the maximum amount of humus. Choose the correct statements from the above.
(a) (ii) and (iv)
Soil has particles of different sizes. Arrange the words given below in increasing order of their particle size. Rock, Clay, Sand, Gravel, Silt
Rock > Gravel > Sand > Silt > Clay
The components of loamy soil are ______, ______ and ______.
sand, silt, clay
Read the following statements and give the appropriate terms for each of them.
(a) The process of breakdown of rocks by the action of wind, water, sunlight.
(b) Removal of top soil during heavy rains or strong winds.
(c) Accumulation of wastes in the soil generated by human activity which alter the features of soil.
(d) The process of movement of water into deeper layers of soil.
Unscramble the following jumbled words related to soil.
(a)
(b)
(c)
(d) (e) (f)
Which of the following situations – ‘A’ or ‘B’ – is advantageous for absorption of water and minerals? Why? Situation ‘A’ : Growth and branching of roots in the C-horizon. Situation ‘B’ : Growth and branching of roots in A and B- horizons.
Situation ‘B’ is advantageous to plants because A- and B- horizons are rich in water, minerals and humus.
How can a farmer convert acidic soil to neutral soil? SOIL 49
He can add a small quantity of quick lime or slaked lime solution to the soil. This will make the acidic soil neutral.
Is it a good practice to remove grass and small plants that are growing in an open, unused field? Give reason to support your answer.
No, it is not a good practice. Plants cover the soil surface and their roots bind the soil particles and hold them in place. During strong winds and rains they prevent soil erosion and thereby protect the top soil.
A man digging a pit found that he could dig with ease initially but digging became difficult as he went deeper. He could not dig beyond a depth of 5 feet. Provide a suitable scientific explanation.
The soil surface has loose top soil which is easier to dig. At deeper layers, partially weathered rocks or bedrocks are present, which are hard making digging difficult. ANSWERS 117
Locate the following zones given as boxed items in Figure 9.1 which shows a diagram of soil profile. Top soil, Subsoil, C-horizon, Bedrock Fig. 9.1
This question refers to a figure in the original PDF.
Topsoil Subsoil C-horizon Bedrock
Rajasthan is a desert state in India. Once while travelling to Rajasthan by train, Boojho observed several streams and rivulets of rain water during the journey but to his surprise he did not see streams of water in the desert region even during rains. Help Boojho find a suitable explanation for this.
Deserts are vast stretches of sand where the falling rain water immediately percolates downwards in the spaces between sand particles. Due to this he did not see streams of water in the desert region.
Match the animals in Column I with their natural place of dwelling (habitat) in Column II.
(a) (vi); (b) (iv); (c) (i); (d) (ii); (e) (iii); (f) (v) LONG ANSWER QUESTIONS
Continuously water-logged soils are disadvantageous for plant growth. Why?
Roots, although underground, possess living cells that require oxygen for respiration and production of energy. They absorb oxygen that is present in the spaces between soil particles. But in water-logged soils, water occupies the spaces between soil particles and pushes the oxygen out into the atmosphere. Thus, roots are deprived of oxygen and this affects root and plant growth.
Why is soil erosion relatively less in dense forests as compared to barren, open fields?
In dense forests, the tree cover (canopy) prevents rain water from directly falling on the ground/soil. Also roots of the vegetation bind the soil particles and hold them together. As a result soil erosion is minimised. But in barren, open fields the soil is exposed to the falling rain. The soil particles become loose due to the impact of raindrops and the flow of water carries them away. The flowing water further erodes the soil surface aggravating erosion.
Gardeners gently dig up the soil around the roots of garden herbs (plants) frequently. Give reasons.
(a) For enabling easy root growth; (b) For easier percolation of water; (c) For aerating the soil/enabling air to get into deeper layers of soil; (d) For removing the weeds.
In towns and cities, generally, the bore wells have to be dug very deep to get water as compared to bore wells dug in villages. Give suitable reasons.
(a) This is so because of excessive use of water which depletes the ground water. (b) Towns and cities have asphalted roads and vast areas of soil are concreted. As a result, rain water cannot percolate to recharge ground water and the ground water level further decrease. Villages have larger areas of open soil surface and fewer asphalted roads and concrete surfaces. Thus, larger soil surface area is available for rain water to percolate into the soil easily and recharge the ground water. As a result, even shallow borewells yield water.
Several terms related to soil are hidden in the squares given as Figure 9.2. Spot them and make a list.Two examples are given for you. SOIL 51 Fig. 9.2
This question refers to a figure in the original PDF.
Humus, Sand, Water, Clay, Gravel, Weathering, Horizon, Percolation, Mineral, Plant, Erosion, Profile. ANSWERS 119