NCERT Solutions for Class 9 Biology Chapter 14 - Natural Resources
Chapter 14 - Natural Resources Exercise 193
(ii) Carbon dioxide is green house gas which maintains temperature on earth during night.
(iii) Oxygen is needed by organisms for survival.
Concept insight: Recall the difference in the composition of the atmosphere of Venus and Mars.
i. Excessive use and burning of fossil fuels like coal and petroleum.
iii. Smoke from industries and automobiles.
Concept insight: Students should recall the major causes of air pollution.
Chapter 14 - Natural Resources Exercise 194
(ii) All the substances are transported in the body in dissolved state in water.
(iii) All the metabolic activities require water.
(i) Dumping of sewage and wastes from factories into water bodies.
(iii) Dumping of hot water from the cooling towers also affect the aquatic life.
Chapter 14 - Natural Resources Exercise 196
- Sun- Sun rays heat the rocks during the day time which causes the rocks to expand. During night, the rocks cool and contract. Due to this contraction and expansion cracks develop in the rocks and they break down.
- Water- Water helps in the formation of soil both by freezing as well as fast flow. Water freezes in the rock crevices and widens the crack causing the rocks to break. Fast flowing water causes the rocks to break slowly and also carries it from one place to another.
- Wind- Under the effect of strong winds and storms, the stone pieces further break down and are also carried from one place to another.
- Living organisms- Lichens grow on rock surfaces and release certain substances that convert the rocks into powdery form and make thin soil layer. Other small plants like mosses grow on the surface of rocks that cause them to break further.
Concept insight: Recall the factors and process of soil formation.
The removal of the fertile top soil is called soil erosion.
Concept insight: Recall the definition of soil erosion.
i. By preventing over grazing.
ii. By planting more and more trees, as the roots of the trees hold the soil in place.
iii. By contour ploughing.
iv. By keeping the vegetation cover on the ground to reduce the effect of wind and water.
v. By reducing use of chemical fertilizers and using manure and practicing organic farming.
Concept insight: List the causes and methods to prevent soil erosion.
Chapter 14 - Natural Resources Exercise 201
The increase in the percentage of the gases which prevent the escape of heat from the earth, which cause the average temperatures to increase worldwide is called greenhouse effect.
Concept insight: Most popular Exam question from this topic.
Concept insight: Various forms of oxygen in atmosphere.
Chapter 14 - Natural Resources Exercise 201 (Ex.)
(ii) Water is necessary for all metabolic activities in the body.
(iii) It is required for transport of substances in the body.
(iv) It helps in maintaining body temperature.
The organisms that live in water are not totally independent of soil as a resource. The mineral nutrients are present in water in the dissolved form. But their recycling takes place with the help of decomposers that are present in soil. Water bodies like rivers get supply of minerals from the soil. Moreover, the minerals locked in rocks also can't reach aquatic organisms till rocks are converted into soil.
Concept insight: Importance of soil as a natural resource.
Chapter 14 - Natural Resources Exercise 202 (Ex.)
Concept insight: Effects of forest on the climate of a region.
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