NOTES (X)
CHAPTER-16 (OUR
ENVIRONMENT)
BIOMAGNIFICATION
The increase in the concentration
of harmful chemical substances like pesticides in the body of living organisms
at each trophic level of a food chain is known as biomagnification. Pesticides
are non biodegradable chemicals and hence get accumulated at each level. Humans
occupy the top level in any food chain. So maximum amount of harmful chemical
pesticides get accumulated in our bodies.
ENERGY TRANSFER IN A FOOD CHAIN
About 1% of the sun’s energy falling on the leaves is used by the plants
in the process of photosynthesis and stored as chemical energy of food.
The plants utilize
this energy stored in them for respiration and growth. Some of this energy
however is not utilized and is released as heat into the environment.
# The flow of energy in ecosystem is said
to be unidirectional because the energy lost as heat from the living organisms
of a food chain cannot be reused by the plants in photosynthesis.
The 10% Law
According to this
law, only 10% of the energy entering a particular trophic level of organisms is
available for transfer to the next trophic level . this means that the energy
available at each successive trophic level is 10% of the previous level.
CHAPTER 17-
MANAGEMENT OF NATURAL RESOURCES
Sustainable development
The development which meets the
basic human needs of the current generation and also ensures to preserve the
resources for the future generations.
Biodiversity hotspots
An area with a large number of
plants and animals(flora and fauna) is known as biodiversity hotspot.
Inspite of good monsoons we are not able not able to meet the demand
for water of all people. Highlight some of the reasons to explain it.
·
Due to rapid explosion of population, it has
become impossible to meet the needs of all people through the available water
resources.
·
Due to insufficient vegetation cover on the
ground, only a little rain water is allowed to seep into the ground and be
stored as groundwater.
·
Increasing urbanization has brought about a
change in the lifestyle of people that require more water.
·
Discharge of untreated sewage and industrial
wastes into the water bodies reduces the availability of water that is fit for
human consumption.
·
A lot of water is used for irrigating High
yielding Varieties of crops.
WATER POLLUTION
The river water gets contaminated majorly by two factors:
1)
Presence of Coliform Bacteria
2)
Measurement of pH.
Coliform Bacteria are a group of
rod shaped bacteria found in the human intestines. Its presence in water
indicates contamination by pathogens. The coliform is itself harmless but its
presence in the river indicates that other harmful intestinal bacteria may also
be present.
If the pH of river water is below
7, it is considered acidic and hence polluted.
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