Horses adapt to their environments by developing helpful physical characteristics, such as long, broad teeth for chewing flat leaves, long ears sensitive to detecting subtle sounds, and sturdy hooves and fast legs which help horses run from danger. Modern horses come in seven distinct species and classify into many different breeds. Some physical features vary among breeds, such as weight, height and color patterns, but all horses bear the common characteristics of four legs, a barrel-shaped body, long neck, tail and fur-covered coat.
These core features help horses survive in different types of environments. Generally, wild horses survive in temperate or colder climates, and in areas with wide open spaces and plenty of grass. Ancient horses lived in forested areas, differing from modern horses in size and hoof structure. The hooves of ancient horses branched into three or four distinct toes, much like modern deer. Over time, horses developed the single-toed hoof structure found on surviving species. These hooves give horses power and stability for moving across large tracts of land. Ultimately, this trait enhances horses' chances of survival in the wild, as they naturally flee from predators and danger. Hard hooves also help horses travel across rocky and uneven terrain, valuable for escaping predators and to keep moving. Longer legs also give modern horses more power and speed, helping them flee. Horses have long teeth, helping them chew tough vegetation without suffering tooth loss. Large eyes give horses exceptional vision, while large nostrils and ears help detect danger.