NCERT Exemplar Class 10 Science Solutions

Chapter 16-Sustainable Management of Natural Resources-Short Answers

Short Answer Type Questions
Q.25. Prepare a list of five items that you use daily in the school. Identify from the list such items that can be recycled.
Answer. List of items used daily in school: Paper, pen, plastic box, scale, eraser, rexin bag, blade, compass and dividers (metallic), steel lunch box, steel spoon, etc.
Recyclable items: Paper, plastic box, eraser, blade, compass, steel lunch box and steel spoon.
Q.26. List two advantages associated with water harvesting at the community level.
Answer.
(i) Water keeps on percolating the ground, resulting in recharging of wells.
(ii) Ground water keeps the layers of soil above it moist preventing soil erosion.
(iii) The stored water provides moisture to the vegetation in and around the area.
Q.27. In a village in Karnataka, people started cultivating crops all around a lake which was always filled with water. They added fertilizers to their field in order to enhance the yield. Soon they discovered that the water body was completely covered with green floating plants and fishes started dying in large numbers.
Analyze the situation and give reasons for excessive growth of plants and death of fish in the lake.
Answer.
Use of fertilizers increased the level of organic nutrients which in turn support the growth of small, green, aquatic plants and the surface of water was completely covered with plants. The process is called as eutrophication. Consumption of oxygen by these plants led to death of fishes and other aquatic animals. Since water surface is covered with these planktons, underwater plants deprived of light and died.
Q.28. What measures would you take to conserve electricity in your house?
Answer.
(i) Switch off fans and lights when not in use.
(ii) Practices using renewable resources like solar radiation and energy and cost efficient CFLs.
Q.29. Although coal and petroleum are produced by degradation of bio-mass, yet we need to conserve them. Why?
Answer. Coal and petroleum are produced by a long process of degradation which cannot keep pace with exponentially increasing demand of growing population. If not used in sustainable way, these resources will exhaust soon.
Q.30. Suggest a few measures for controlling carbon dioxide levels in the atmosphere.
Answer.
(i) Use of eco-friendly fuel CNG, practices to reduce consumption of fuel in vehicles such as car pool, public transport etc.
(ii) Use of filtering devices to removes carbon dioxide from smoke of thermal power stations and other industries.
(iii) Check deforestation and practice afforestation.

Q.31. I. Locate and name the water reservoirs in figures (a) and (b).


II. Which has an advantage over the other and why?
Answer.
I. (a) pond (b) underground water body
II. Underground water bodies are at advantage because:
(i) water does not evaporate by Sunlight, does not support the growth of pathogens (mosquitoes), does not get contaminated by human and animal waste.
(ii) It serves as source of moisture for crops over a wide area.