Various levels in the food chain are called Trophic levels.

The ozone layer shields the earth’s surface from the harmful effects of the UV radiation.

The electron dot structure of ethane molecule, C₂H₆ is as follows:

Earth’s atmosphere is a mixture of different gases, it consists of 21% oxygen, 78% nitrogen, 0.93% argon and 0.03% CO₂ along with other gases making up the remaining percentage. The composition varies at different places and times thus the Earth’s atmosphere is a heterogeneous mixture. 

Characteristics of a good fuel are:

i. It should possess low ignition temperature.

ii. It should not leave residue after burning, i.e., it should burn completely.

iii. It should burn without producing too many pollutants.

iv. It should be easily available and accessible

v. Good fuel must be economical.

vi. It should be easy to store and transport.