SolveIt is under development
SolveItNCERT · CBSE · NEET

NCERT Exemplar · Class 10 Science Management of Natural Resources

37 questions · 37 still being checked

Short Answer Questions 25–31 (part 4 of 5)

  1. Exercise 25

    Prepare a list of five items that you use daily in the school. Identify from the list such items that can be recycled.

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    Paper, rexin bag, blade, pen, plastic box, scale, eraser, compass and dividers (metallic), steel lunch box, steel spoon. Paper, blade, plastic box, eraser, compass, steel lunch box and steel spoon can be recycled
    Five items used daily at school: 1. Paper notebooks 2. Plastic pencil box 3. Plastic/steel water bottle 4. Aluminium tiffin box 5. Plastic penAnswer: Notebooks (paper), the pencil box and bottle (plastic), and the tiffin box (aluminium) can be recycled; the pen (mixed plastic, metal and ink parts) cannot.

  2. Exercise 26

    List two advantages associated with water harvesting at the community level.

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    Hint- (a) The ground water level increases due to recharging of wells.
    (b)
    Ground water keeps the layers of soil above it moist and prevents loss of water by evaporation.
    (c)
    The water can be stored during rainy season and can be used when required
    Water-harvesting structures built and kept up by the community (check dams, percolation tanks, ponds): 1. Recharge the groundwater table, so wells and borewells stay functional through the dry season. 2. Cut surface run-off and soil erosion, and reduce dependence on distant or scarce sources without a big dam's submergence.Answer: Groundwater recharge, and reduced erosion/dependence on distant water sources.

  3. Exercise 27

    In a village in Karnataka, people started cultivating crops all around a lake which was always filled with water. They added fertilisers to their field in order to enhance the yield. Soon they discovered that the waterbody was completely covered with green floating plants and fishes started dying in large numbers. Analyse the situation and give reasons for excessive growth of plants and death of fish in the lake.

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    Since people used excessive fertilisers in the fields, they were carried down to the lake during rains. As many fertilisers contain phosphates and nitrates, the water body became enriched with these chemicals. These chemicals promote excessive growth of aquatic plants and the surface of water was completely covered with plants. (eutrophication) Depletion of light in the water body and insufficient availability of dissolved oxygen and nutrients resulted in the death of fish.
    Fertiliser draining off the field enriches the lake with nutrients. \[\mathrm{NO_3^-,\ PO_4^{3-}}\uparrow \;\Rightarrow\; \text{algal/floating-plant growth}\uparrow \] The green surface cover blocks sunlight and stops atmospheric \(\displaystyle \mathrm{O_2}\) from dissolving into the water below. \[\text{dead algae decomposed by bacteria} \;\Rightarrow\; \text{O}_2\text{ demand (BOD)}\uparrow \;\Rightarrow\; \text{dissolved }\mathrm{O_2}\downarrow \]Answer: Fertiliser runoff caused eutrophication; the algal bloom cut light/oxygen exchange, and its bacterial decay used up the dissolved oxygen, so the fish suffocated.

  4. Exercise 28

    What measures would you take to conserve electricity in your house?

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    Hint-
    (a)
    Put off the fans and lights when they are not required.
    (b)
    Maximum use of solar radiation.
    (c)
    Use of solar water heating system. during winters.
    (d)
    Use of fluorescent tubes or CFL
    1. Switch off lights, fans and appliances when not in use; use daylight and natural ventilation. 2. Replace incandescent bulbs and tube-lights with LED/CFL bulbs. 3. Choose BEE star-rated, energy-efficient appliances, and service them regularly. 4. Unplug chargers and idle electronics at the socket.Answer: Switch off unused devices, prefer LED/star-rated appliances, and use daylight/ventilation instead of artificial lighting and cooling wherever possible.

  5. Exercise 29

    Although coal and petroleum are produced by degradatioin of bio- mass, yet we need to conserve them. Why?

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    Both the energy sources coal and pertoleum take millions of years for their formation. As these resources are being utilised at a much faster rate than their formation, they will be exhausted in the near future, hence they need to be conserved.
    Coal and petroleum did form from buried biomass, but only by fossilisation under heat and pressure over geological time. \[\text{rate of natural formation} \;\ll\; \text{rate of human extraction/consumption} \] So on a human timescale the reserves cannot be replaced as fast as they are used up, and burning them also pollutes the air.Answer: Their natural formation is far slower than our rate of use, so the existing reserves are effectively fixed and must be conserved.

  6. Exercise 30

    Suggest a few measures for controlling carbon dioxide levels in the atmosphere.

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    Hint- (a) Reduce the consumption of petrol in the automobiles.
    (b)
    Use of CNG or clean fuel
    (c)
    Instead of burning litter prepare manure out of it.
    (d)
    Treatment of smoke to remove harmful gases before discharging into atmospheric
    (e)
    Plant more trees
    1. Burn less fossil fuel -- shift to solar, wind and hydro power. 2. Favour public transport/car-pooling and fuel-efficient engines over private vehicles. 3. Stop deforestation and plant more trees, so photosynthesis fixes more atmospheric \(\displaystyle \mathrm{CO_2}\): \[6\mathrm{CO_2} + 6\mathrm{H_2O} \xrightarrow{\text{sunlight, chlorophyll}} \mathrm{C_6H_{12}O_6} + 6\mathrm{O_2} \]Answer: Cut fossil-fuel burning (renewables, efficient transport) and enlarge the sink by afforestation, so more \(\displaystyle \mathrm{CO_2}\) is fixed than released.

  7. Exercise 31

    (a)
    Locate and name the water reservoirs in Figures16.1 (a) and (b).
    (b)
    Which has an advantage over the other and why?
    NCERT_Question_Class10_Science_Exemplar_Ch16_Q31
    NCERT_Question_Class10_Science_Exemplar_Ch16_Q31_2

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (A)
    The water reservoir is a pond in Figure $\displaystyle 16.1$ (a) and underground water body in the Figure $\displaystyle 16.1$ (b).
    (B)
    Figure $\displaystyle 16.1$ (b) has more advantage than Figure $\displaystyle 16.1$ (a), because the advantages of water stored in the ground are many. For example
    (a)
    It does not evaporate
    (b)
    It spreads out to recharge wells.
    (c)
    Provides moisture for vegetation over a wide area.
    (d)
    It is protected from contamination by animal and human wastes.
    (e)
    It prevents breeding of insects.
    (a)
    shows water lying in the open, at ground level, exposed to the air -- a surface reservoir (pond/lake/dam).
    (b)
    shows water held below a layer of soil and plant roots -- an underground (sub-surface) reservoir.
    Answer: (b), the underground reservoir, has the advantage: covered by soil it loses almost nothing to evaporation and needs no land submerged, unlike the open surface reservoir in (a).