1. Conditions for Life http://www.youtube.com/watch?v=9ZyrmxvIcIE&feature=related Are we ALONE Who’s out there? Click!

2. The Sun The Sun is the closest star to Earth. The strong gravitational pull of the Sun holds Earth and the other planets in our solar system in orbit. The Sun's light and heat influence all of the objects in our solar system and allows life to exist on Earth.

3. ENERGY the SUN provides The oceans store this energy and help keep the temperature of Earth at a level that allows a wide variety of life to exist. Plants use the Sun's energy to make food. Plants provide food for other organisms.

4. The Earth's Atmosphere. atmosphere.The Earth is surrounded by a blanket of air called the atmosphere. atmosphereThe atmosphere is made up of various gases that act as a protective shield for the Earth and allow life to exist. Without it, we would be burned by the intense heat of the Sun during the day or frozen by the very low temperatures at night. atmosphere The atmosphere is held around the Earth by the force of gravity.

5. The blue glow surrounding the Earth is its atmosphere. The atmosphere not only produces important weather features, such as clouds and rain, but also has considerable influence on the overall climate of the Earth.

6. Climate The temperature on Earth does not go from one extreme to the other. There are areas of extreme cold and heat, but overall, the Earth’s climate is stable. This is due to Earth’s distance from the Sun as it orbits around it and its axial tilt during rotation.

7. Water Water on the Earth unique is that it can exist on the planet in all three states: liquid in oceans, lakes, rain solid in glaciers and frozen bodies of water; gaseous Our Thirsty World - YouTube Click to watch

8. All planets receive light from the Sun. Among other factors, the amount and length of time each planet is exposed to periods of light and darkness can have an effect on the possibility of plant life surviving on it.

9. Summary: what is necessary for life to exist on Earth: The proximity of the Sun The availability of liquid water and the presence of water vapor A nonpoisonous atmosphere