Without gravity, there would be no life on Earth at all. Anything that rests on the planet would float off into space; this includes everything from human beings to all the water on Earth.
It is interesting to imagine how, without gravity, humans would be able to easily hop and flip from place to place the way astronauts on the moon or in space stations do. However, humans would have little time to enjoy weightlessness, as catastrophe would follow any sudden loss of gravity.
Everything on Earth would begin to float, but another vital piece of Earth's survival would also float away: the moon. The moon orbits Earth because it is pulled in by the planet's gravity, creating a relationship that influences Earth's tides, seasons and weather. Of course, the loss of these relationships would not be too important if Earth had no gravity because all the water, plants, people and animals would not survive in the atmosphere.
Another vital piece of Earth's delicate ecosystem that's often forgotten when imagining a loss of gravity is the atmosphere. The atmosphere is essentially a protective coating, shielding Earth from space debris and allowing water and air to remain close to the planet to encourage life. Without gravity, the atmospheric security blanket would be stripped from Earth.