Effects of Rotation on the Earth?

It creates the 24 hours of the SI day, which is actually defined as 86,400 seconds, not in terms of hours. In UTC, leap seconds come in, so a UTC day can be between 86,399 or 86,401 seconds. The benefit of the SI day is that it has the action of distributing heat across the globe, instead of just concentrating it on just one side, with nothing on the other side (or through a very slow rotation, basically the same thing).

It spins up the liquid outer core, which is what creates our magnetosphere, which is what keeps us from instant death by protecting us from gamma- and cosmic-rays.

Along with the Moon, our rotation assists the movement of ocean tides, which are critical to ocean survival (at least, as it has evolved).

They create our Coriolis forces, which is what drives large scale circulation in both atmosphere and ocean. This distributes thermal energy around the globe, and also, with ocean currents, moves nutrients around, and creates different habitable zones.

Earth's rotation does NOT create gravity. Gravity is the force of "pull" between two objects, as given by the equation F = (Gm1m2)r^2 Where F = force of pull, G = Universal Gravitational Constant, m1 and m2 are the masses of the two objects, and r (sometimes d) is the distance between the centers of the two objects. In fact, the spin has somewhat of a different effect of trying to throw us away. If you've ever tied a tennis ball to a string, then spun it over your head, you'll feel the ball trying to "get away." In my experience, if you spin it hard enough, it will finally separate itself from your string, and fly off across the yard and hit your wife's favorite bay window. Thankfully, it was just a rebound.

Rotation is very important to those of us on Earth who enjoy living. Revolution is important, too.

Well, on the physical shape of the earth, the rotation causes a bulging at the equator.

The rotation effects global wind patterns (due to coriolis effect) such as the trade winds.

As one answer alluded to, the rotation also causes the time-average temperature around the world to be basically independent of longitude, which increases the size of any potential zone of habitability by quite a lot.

The rotation has an effect on the apparent strength of gravity, but it is quite small (reduction of less than ~5%), thus rotation is not necessary to stop us being crushed in anyway. Though, it's significant enough that NASA built a launch site on the equator in the middle of a marsh, because it was actually cheaper than spending the extra on rocket fuel O_O

The rotation of the earth and orbit of the moon around earth relative to one another produces the bulk of tidal effects on earth.

Daily temperature change and most of the daily changes about climate

The radius of the earth is larger on the equator because of rotating, so gravity is smaller.

Gravitational force is even smaller on equator because of centrifugal force.

Rotation of the earth crust wrt the the core results in magnetic field.

One effect is life can survive better than say mercury who is locked into position towards the sun (one side always faces the sun) and as such has one side cold as hell and the other is ever boiling. If earth had this issue life would be incredibly different or maybe impossible

It also has a significant impact on the prevailing winds. Its changes the direction of the winds as they blow from high pressure latitudes to the lows.

Force of gravity