High velocity of wind, air currents,flowing water, landslides, human activities.

Wild life refers to the undomesticated animals living in their natural habitats (forests, grasslands and deserts) an area without human habitation.

Electronic wastes are generated from the spoiled, outdated, non - repairable electrical and electronic devices such as computers, calculator, toys etc.

The sun gets its energy through nuclear fusion. In this reaction hydrogen atoms fused to form helium atom. As a result huge energy is radiated on the surface of the sun. This reaction is repeated again and again resulting in the energy output continuously.
\(4 \mathrm{H}^{1} \rightarrow{ }_{2} \mathrm{He}^{4}+2+{ }_{1} e^{0}+\text { energy }\)

i) Non-renewable energy.
ii) Formation of these fuels is a very slow process and takes very long period of time for renewal.

The various devices used for harvesting sun's energy are called solar energy devices.
Solar cells:
(i) Solar cells (Photovoltaic devices) is made up of silicon that converts sunlight directly into electricity.
(ii) Solar cell produces electricity without polluting the environment.
(iii) Since it uses no fuel other than sunlight, no harmful gases, no burning and no wastes are produced. These can be installed in remote and inaccessible areas (forests and hilly regions) where setting up of power plant is expensive
Uses of Solar cells:
(i) It can be used for street lighting, traffic signals, water pumping, battery charging system etc.
(ii) It is used in artificial satellites and space probes.
(iii) It provides radio and TV transmission to remote areas
(iv) It is used in calculators, electronic toys and watches.

The 4R approach such as Reduce, Reuse Recovery and Recycle may be followed for effective waste management.
Reduce:
Avoid the use of material which increases the solid waste.
Reuse:
Repeating use of items such as bottles, old clothes, books and anything else that is used again for a similar purpose to that originally intended.
Recovery:
We can be able to use our waste to recover energy or produce biofuel.
Recycle:
Using recycled material of glass, paper, meta etc..

(i) It burns without smoke and therefore causes less pollution.
(ii) An excellent way to get rid of organic wastes like bio-waste and sewage material.
(iii) Left over slurry is good manure rich in nitrogen and phosphorus.
(iv) It is safe and convenient to use.
(v) It can reduce the amount of green house gases emitted.

(i) Overcome the rapid depletion of ground water levels.
(ii) To meet the increase demand of water.
(iii) Reduce flood and soil erosion.
(iv) Used for drinking purpose.

a) Forests are an important component of our environment.
b) Forest is dominated by
i) microorganisms
ii) flowering plants
iii) shrubs
iv) climbers
v) dense trees
vi) provide a vast habitat for wild animals.
a) Forests also contribute to the economic development of our country.
b) Forests are vital for human life.
c) It is a source for a wide range of renewable natural resource.
d) They provide wood, food, fodder, fibre and medicine.
e) Forest are major factor of environment concern like.
i) carbon sink
ii) regular climatic conditions
iii) increase rainfall
iv) reduce global warming
v) prevent natural hazards like food and landslides
vi) protect wildlife
vii) act as catchments for water conservation.
f) They also play a vital role in maintaining the ecological balance.