ANSC 2251 Lecture Notes - Parahippus, Miohippus, Merychippus
Document Summary
Evolution = gradual process/change to a usually more complex form. Genetic drift = change in allele frequency due to chance. Mutation = permanent change in dna sequence of gene. Natural selection = nonrandom tendency of alleles to change frequency in population. Earliest ancestors of horse ~ 50 million years ago (after the dinosaurs were extinct, before humans) Eohippus / hyracotherium (55 mil years ago) Cuboid bone in contact w/ enlarged middle toe. High crowned teeth w/ cement steppe. Merychippine radiation = gave way to at least 19 new grazing horse species. 3 hoofed toes, only central one touched ground. 1st single hoof (side toes present but weak) Some made it to land bridge in asia (2. 5 mil years ago) Migrated from na to throughout world via bering strait (ice age) Classic horse body, rigid spine, long neck/muzzle. 1 toe, side ligaments to prevent twisting. Found in asia, africa, europe, north america. Returned to continent at the age of exploration.
