3. 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.
4. ECOSYSTEM AND ITS
COMPONENTS
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 :-
Natural ecosystems:- like forests, deserts,
grass lands, mountains,ponds, lakes, rivers,
oceans etc.
Artificial ecosystems :- like gardens,
parks, crop fields, aquarium, zoo etc.
5. COMPONENTS OF AN
ECOSYSTEM
AN ECOSYSTEM CONSISTS OF TWO MAIN
COMPONENTS. THEY ARE BIOTIC AND ABIOTIC
COMPONENTS.
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.
6. 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.
ABIOTIC COMPONENTS :- ARE THE NON LIVING
COMPONENTS LIKE AIR, WATER, SOIL,
MINERALS, SUNLIGHT , TEMPERATURE, WIND
ETC.
7. 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)
eaten by eaten by eaten by
Grass Insects Frog Snake
(producer) (primary consumer) (secondary consumer)
(tertiary consumer)
eaten by eaten by eaten by
eaten by
Grass Moth Frog Snake Hawk
(producer) (primary consumer) (secondary consumer) (tertiary
consumer) (quarternary consumer)
8.
9.
10. 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.
11.
12. 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.
13.
14. 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.
15.
16. BIOLOGICAL
MAGNIFICATION
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.
17.
18. HUMAN ACTIVITIES AFFECT
THE ENVIRONMENT
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.
UV radiation
O2 O + O
O2 + O O3
19.
20. 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.
21.
22.
23.
24. 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
