Answer the
following questions
1. Explain the
Effect of adding waste to the environment
Ans ---Human
activities produce a lot of waste materials which are thrown away into
the environment. These wastes cause
pollution of air,
water and soil.
The waste
materials produced are of two main types. They
are biodegradable
wastes and non biodegradable wastes.
i) Biodegradable
wastes :- are wastes which are
decomposed into
harmless substances by microorganisms.
Eg :- vegetables,
fruits, pulses, cereals, cotton, jute, wool,
wood, leather,
paper, animal dung, animal bones etc.
ii) Non
biodegradable wastes :- are wastes which are not
decomposed by
microorganisms.
Eg :- polythene
bags, plastics, synthetic fibres, glass,
metals, synthetic
rubber, insecticides, pesticides etc.
2. Write a note on
the ecosystem and its component
Ecosystem and its
components :-
a) Ecosystem :- An
ecosystem consists of all the living organisms in an
area along with
the non living components and their interaction. There are different types of
ecosystems. They are :-
i) Natural
ecosystems :- like forests, deserts, grass lands, mountains, ponds, lakes,
rivers, oceans etc.
ii) Artificial
ecosystems :- like gardens, parks, crop fields, aquarium, zoo etc.
b) Components of
an ecosystem :-
An ecosystem
consists of two main components. They are biotic and abiotic components.
i) Biotic
components :- are the living components like plants, animals and
microorganisms. They consist of producers, consumers and decomposers.
Producers :- are
green plants which produce food by photosynthesis.
Consumers :- are
herbivores which get their food directly from plants, carnivores which get
their food indirectly from plants and omnivores which get their food directly
or indirectly from plants.
Decomposers :- are
microorganisms which decompose dead plants and animals. They decompose complex
organic substances into simple inorganic substances in the soil which are again
used by plants.
ii) Abiotic
components :- are the non living components like air, water, soil, minerals,
sunlight , temperature, wind
3. Explain food
chain and food web
3a) Food chain :-
A food chain is
the flow of food energy from one organism to the next and to the next and so
on. They usually start with a producer (plants) and end with a carnivore. In a
food chain an organism gets food from one group of organisms.
eaten by eaten by
Eg:- Grass
-----Deer ------------Lion
(producer)
(primary consumer) (secondary consumer)
Grass-------
Insects---------- Frog -------------------Snake
(producer)
(primary consumer) (secondary consumer) (tertiary consumer
Grass
----Moth----------------- Frog ---------------Snake ---------------Hawk
(producer)
(primary consumer) (secondary consumer) (tertiary consumer) (quarternary
consumer
b) Food web :-
Food web is a
group of several interconnected food chains. In a food web an organism gets
food from more than one group of organisms.
4. Explain trophic
level
Trophic levels :-
Each step in a
food chain where transfer of food energy takes place is called trophic level.
The first trophic
level consists of producers.
The second trophic
level consists of primary consumers.
The third trophic
level consists of secondary consumers.
The fourth trophic
level consists of tertiary consumers.
Since the transfer
of food energy decreases at every trophic level, the number of trophic levels
are limited and do not exceed four or five.
draw diagram from
text book
5. Explain
biomagnification
Biological
magnification (Biomagnification) :-
Harmful chemicals
like insecticides and pesticides which are used to protect crops from insects
and pests are absorbed by plants and enter the food chain. Since these
chemicals are non biodegradable, they get accumulated at every trophic level
and their concentration increases. Since human beings occupy the highest
trophic level, the concentration of these harmful chemicals is maximum in our
bodies.
The increase in
concentration of harmful chemicals in the bodies of organisms at higher trophic
levels is called biological magnification.
6. Explain energy
flow in an ecosystem
Energy flow in
trophic levels :-
Green plants
(producers) absorb about 1% of solar energy falling on the leaves and stores it
as food energy during photosynthesis.
During the
transfer of food energy from one trophic level to the next, 90% of the energy
is lost to the environment and only 10% is transferred to the next trophic
level. So there is a decrease in the amount of food energy transferred at every
trophic level by 10%. This is known as the 10% law.
7)Explain human
activities affect the environment
a) Depletion of
ozone layer in the atmosphere :-
Ozone molecule
contains three oxygen atoms (O3). At higher levels in the atmosphere the UV
radiation splits some oxygen molecules (O2) into free oxygen atoms which
combines with oxygen molecules (O2) to form ozone. It is highly poisonous.
UV radiation
O2
---------------O + O
O2 + O
-----------O3
The ozone layer
present in the higher layer of the atmosphere protects the earth from the
harmful UV radiation from the sun. UV radiation causes skin cancer in humans.
The ozone layer is
being damaged by the use of chemicals like chloro fluoro carbons (CFCs) used in
refrigerators and fire extinguishers. So the use of CFCs is now being reduced
to protect the ozone layer
b. Managing the
garbage we produce :-
The household
waste is called garbage. Some of the garbage is biodegradable and some are non
biodegradable. Garbage causes pollution of air, water and soil. So it should be
disposed properly.
Some of the
methods of garbage disposal are :-
i) Land fills
ii) Recycling
iii) Production of
biogas and manure
iv) Preparation of
compost
v) Incineration
vi) Sewage
treatment
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