Biology Today — January 2018

(Jacob Rumans) #1

  1. What are the causes of global warming? Also explain why
    is it a warning to mankind.
    OR
    Compare narrowly utilitarian and broadly utilitarian approaches
    to conserve biodiversity with the help of suitable examples.

  2. Study the population growth curves shown below.
    A


B

(a) Identify curves A and B.
(b) Mention the conditions responsible for the curves A
and B respectively.
(c) Give the necessary equation for the curve B.


  1. Differentiate between xerarch and hydrarch succession.

  2. Construct a pyramid of energy when 10,000 joules of energy
    is available at the producer level. Label all its trophic levels.

  3. (a) Name the two types of nutrient cycle existing in nature.
    Where are their reservoirs present? State the functions
    of reservoirs.
    (b) Explain the two ways by which carbon is returned to
    the atmosphere.

  4. (a) Name the two metals used in a catalytic converter that
    help in keeping the environment clean.
    (b) Lichens are regarded as pollution indicators. Explain.

  5. (a) Differentiate between grazing and detritus food chain.
    (b) Herbivores are considered similar to predators in the
    ecological context. Explain.

  6. Define the following:
    (a) Allen's rule (b) Photochemical smog
    (c) Diapause (d) Hotspots
    SECTION - D

  7. Rekha was waiting at a bus stop. Many passengers along
    with their kids were on the way to school. A bus passing
    by, ejected dark black smoke from the exhaust pipe. Rekha
    immediately stopped the bus and called the conductor
    and driver to show what they were contributing to the
    environment. Passengers waiting at the bus stop supported
    Rekha. She explained the driver about use of CNG and
    catalytic converters which help in reduction of vehicular
    emission.
    (a) Why one should use CNG instead of petrol or diesel?
    (b) How do catalytic converters reduce vehicular gas emission?
    (c) We often see some cars with Bharat stage IV stickers.
    What does it imply?
    (d) What values are shown by Rekha through her action?


SECTION - E


  1. (a) How does the algal bloom choke the water body in an
    industrial area?
    (b) What preventive measures should be taken to stop algal
    bloom?
    (c) Why Eicchornia crassipes is also known as "Terror of
    Bengal"?
    OR
    With the help of a simplified model, explain how carbon
    cycle is a biogeochemical event occurring in nature.

  2. What are the different ways by which organisms manage
    with abiotic stresses in nature?
    OR
    (a) Explain why is the ozone layer required in the stratosphere.
    How does it get depleted?
    (b) How ozone depletion is a threat to mankind?

  3. Enumerate the advantages of a healthy ecosystem.
    OR
    How does a hydrarch succession progresses from hydric to
    mesic condition to form a stable climax community?


SOLUTIONS


  1. Standing crop is the amount of living matter present in a
    unit area of an ecosystem or biome. Standing state is the
    amount of biogenetic or inorganic matter present in the
    abiotic environment at any given time.

  2. Incineration and landfilling

  3. X - Fish, Y - Birds, Z - Amphibians

  4. (i) Organisms (ii) Populations
    (iii) Communities (iv) Biomes

  5. Lotus plants in the pond = 40
    Plant died in a week = 10
    Death rate of lotus population ==


Plants died
Totalnumberofplants

10
40
= 0.25 individuals per lotus plant per year


  1. Mutualism is found between fig and wasp as both are
    beneficial for each other with none of the two capable of
    living separately. The fig species can be pollinated only by its
    partner wasp species and not other species. The female wasp
    uses the fruit not only as an oviposition (egg-laying) site but
    uses the developing seeds within the fruit for nourishing
    its larvae. The wasp pollinates the fig inflorescence while
    searching for suitable egg-laying sites. In return for the
    favour of pollination, the fig offers the wasp some of its
    developing seeds as food for the developing wasp larvae.

  2. The four measures that can control vehicular air pollution in
    cities are as follows :
    (i) Use of CNG as fuel in the vehicles because it burns
    more efficiently and is also cheaper
    (ii) Use of unleaded petrol
    (iii) Use of catalytic converter in the vehicles as it reduces
    emission of poisonous gases

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