Why Does Life Exist on Earth?

There are several conditions that exist on Earth that make it the "just right" planet. Life is very picky and can only exist in a certain temperature range. Some planets like Venus are too hot and others such as Mars are too cold. However, the Earth's climate is perfectly suitable to sustain all of the biodiversity and life that you witness everyday. The most essential ingredient for life is the presence of liquid water. As we surely know, water spans somewhere between 70 to 75 percent of the entire surface area of the Earth. The reason that temperature is so important is because water is solid at temperatures below 0 Celsius and a gas at temperatures exceeding 100 Celsius.
The distance of the Earth's orbit around the sun is what creates the perfect temperature balance. Any closer and the Earth would be too hot and any farther away would cause it too be much too cold. Also, since the Earth spins, it creates a good distribution of heat across the entire surface area. If the Earth did not spin, one side would be too hot while the other would be too cold for life to even hope to exist. The Earth is also the perfect size to allow life to flourish. It has enough gravitational force to keep the core in liquid state and to keep the light gas molecules in the atmosphere from flying off into space.
Earth is also a very versatile planet. Over the 3.7 billion years that life has been around, the average temperature globally has only increased 10-20 degrees on average though the sun is outputting at 35% more energy now than before. It is also fortunate for life on this planet that there is a good concentration of oxygen in the atmosphere (around 21%). Any less oxygen and life on earth would literally suffocate and any more would cause any spark to ignite atmospheric oxygen into a giant flaming fireball visible from space. Also, thanks to some organisms that developed billions of years ago, we have the ozone layer to shield us from harmful incoming UV radiation.