Cause and Effect
The sun is the center of our solar system. Nine planets orbit around it in a circular pattern. Only Earth is known to support life. Earth is the third closest planet to the sun. The heat from the sun keeps Earth from freezing; it contributes to providing life with water, and it directly supplies energy to plants, as well as much more. Because of the sun, Earth has life.
The sun provides UV rays for plants to make into energy and food. This keeps the plants alive. Also those plants serve as food for humans and other herbivores. Organisms that eat plants also rely on the sun. Without the sun to give energy to plants so they can make food, there would be no plants. Furthermore, those organisms that only eat plants would have no food. With them dead, carnivores would have less food to eat, if any at all.
The sun also provides heat for Earth. This keeps it from freezing. It would be hard to live if everything was frozen over. If it were not for the sun, the entire world would look like the North and South poles made up of ice and snow. There is some life at the South Pole, but the poles receive some sunlight. If they received zero sunlight, they would be even colder, and no life would survive.
The sun also contributes to weather. It evaporates the oceans, and then the evaporated water turns into clouds. The clouds are taken around the world by the jet stream. Rain is produced from these clouds and provides plants and animals with water. Without water we would all die. Without the sun evaporating and helping turn salt water to fresh water, we would have a limited amount of drinking water.
So without the sun, all live on earth would die. Not just once, it would die at least three times. It would die once from starvation, once from freezing, and once from thirst. The sun is very important to life on earth. Not just for the reasons stated, there are many other ways the sun supports life. Without the sun no life would live on Earth.