Terms to Remember:

1. Living Planet 4. Antarctic Circle

2. Equator 5. Zonal Time

3. Arctic Circle 6. International Date Line

1. Living Planet – The Earth has been described as the ‘Unique planet’ or the ‘Living planet’ due to its life-supporting features such as its appropriate location from the Sun, the presence of life-supporting gases and the water cycle.

2. The Equator – It is the longest line of the latitude known as the Great Circle.

3. Arctic Circle – The 66 1/2 degree North latitude is known as the Arctic Circle.

4. Antarctic Circle – The 66 1/2 degree South latitude is known as the Antarctic Circle.

5. Zonal Time – In countries where the longitudinal extent is large often there is a difference of three to four hours. In such places, the land surface is divided into times zones, each zone differing (in time) from the other.

6. International Date Line – International Date Line is a line passing through 180° meridian diametrically opposite to the Greenwich Mean Time (GMT). It was adopted to overcome the problems faced by circumnavigators in keeping the track of correct date and day of the week when traveling. It is known as the International Date Line because the date and day are changed whenever people cross these lines by ships or airplanes.