4. Differentiate between biodegradable
and non biodegradable substances?
⚫Substancesthat are broken down bybiological processes are
said to be biodegradable.These materials are broken down by
specific enzymes produced bybacteria or other saprophytes.
⚫Substancesthat are not broken down bybiological processes
are said to be non-biodegradable.Thesesubstances maybe
inert and simplypersist in the environment for along time
or mayharm the various members of the eco-system.
5. Why are some substances biodegradable
and some non-biodegradable ?
⚫The microorganisms like bacteria and other decomposer organisms
(called saprophytes) break down biodegradable substances with the
help of enzymes.
⚫Enzymesare specific in their action, specific enzymesare needed for
the break-down of aparticular substance.Theybreakdown the
materials or products made from natural materials like paper but
many human-made materials like plastics will not be broken down by
the action of bacteria or other saprophytes.
⚫So, it is due to the property of decomposer organismsof being
specific in their action that some waste materials are biodegradable,
6. Give any two ways in which biodegradable
substances would affect the environment.
(i)Flies breed at huge heaps of biodegradable wastes,
carrying the germs and spread diseases such astyphoid,
diarrhea ,tuberculosis, cholera etc.
(ii)Decomposition of biodegradable substances produces
foul smell which spreads in the environment and makes the
life of people miserable.
7. Give any two ways in which non-biodegradable
substances would effect the environment.
(i)Some of the non-biodegradable wastes on apiece of land
convert the same into barren land and enter the food chain
and affect human beings and other biotic components of the
(ii)Theymaycause bio-magnification in the food chain.
Human beingsare harmed the most becausehumans are at
the top of the food chain.
8. How can you help in reducing the problem
of waste disposal ?
⚫ Reduce – using less resources and avoiding wastage of resources. e.g.,
not wasting food.
⚫ Recycle – the materials like paper,plastic, glass,metals etc. used as
raw materials can again be used for making new things instead of
synthesizingor extracting newpaper,plastic, glassor metals. . Inorder
to recycle, we first need to segregate our wastesso that the material
that can be recycled is not dumped along with other wastes.
⚫ Reuse- using thingsagain and again.Instead of throwing awayused
envelopes,reverse it and use it again.The plastic bottles in which we
buy various food-items like jam or pickle can be used for storing things
in the kitchen.
⚫ Repurpose –when aproduct can no more be used for the original
purpose ,use it for some other purpose.
⚫ Refuse –to sayNo to things people offer you that you don’t need.
Refuse to buy products that can harm you and the environment ,say No
to single -use plastic bags.
9. What are the problems caused by the non-
biodegradable wastes that we generate ?
The problems caused bythe non-biodegradable wastes are :
⚫The non-biodegradable wastes cannot be decomposed by
microorganismslikebacteria. Sothe volumeofthese wastes
will not decrease,creating the problem of their disposal.
⚫Ifdumped on land , the land becomes unfit for other
⚫Pesticides and other toxins pollute underground water ,
surface water and soil.The chemicals enter food chain
therebyharming animals and humans, and the soil may
become acidic or alkaline.
10. If all the waste we generate is biodegradable, will
this have no impact on the environment ?
⚫Ifall the waste we generate is biodegradable, it will still have
an impact on the environment.
⚫Biodegradable wastes pollute the environment only when the
amount is large ,which cannot be degraded into harmless
substances in nature at the right time .
⚫ Ifit is disposed offproperly,the problem of air,water and
soil pollution can be lessened to an extent.There would be
less health problems and humans would be disease-free.
But if it is not disposed offproperly,it will affect the
12. What is ozone and how does it affect any
ecosystem? ? How is ozone formed in the
higher levels of atmosphere?
⚫ Ozone (O3) is amolecule formed bythree atoms of oxygen.
⚫ While O2, is essential for all aerobic forms of life Ozone (O3), is a
deadlypoison.At the higher of the atmosphere, it shieldsthe
surface of the earth from ultraviolet (UV) radiation from the Sun.
⚫ Ozone at the higher levels of the atmosphere is aproduct of UV
radiation acting on oxygen (O2) molecule.The higher energy UV
radiationssplit apart some moleculer oxygen (O2) into free
oxygen (O) atoms.These atoms then combine with the molecular
oxygen to form ozone.
⚫ O2 uv
13. Why is damage to the ozone layer a cause for
concern? What steps are being taken to limit this
⚫ The decline of Ozone layer thickness inAntartica wasfirst observed in
1985 and was termed as OZONE HOLE.
⚫ The amount of ozone in the atmosphere began to drop sharply in the
1980s.This decrease has been linked to synthetic chemicals like
chlorofluorocarbons (CFCs) which are used asrefrigerants and in fire
⚫ The ozone shields the surface of the earth from ultraviolet (UV)
radiation from the sun.These radiations are highlydamaging astheycan
cause cancer, damage to eyes and immune system. Due to these reasons,
damage to the ozone layer is amajor cause for concern.
Steps which are taken to limit this damage :
⚫ In 1987, the United Nations Environment Programme (UNEP)
succeeded in forging an agreement to freeze CFC production at 1986