Why do we have a good evolutionary record of the horse

Adapting and reacting to the changing environment, the then living horses changed too. They became larger (Mesohippus was about the size of a goat) and grew longer legs: they could run faster. The teeth became harder in reaction to the harder plant material (leaves) they had to eat.

Person above is correct

Well, both latitude and intensity of light affect temperature because, the higher the light intensity, the higher the temperature and since latitude is the measure of how close you are to the equator, then the closer to the equator you are, the higher the temperature is.