Explain gravitational pull of aphelion vs. Perihelion for Earth (technically it's an Earth Science question)

Acommon kind of mechanical weathering is called

9. the history of life on earth is recorded in

Fossils of ancestors of the modern horses show a small 4-toed almost dog-like browsing animal named eohippus over time the horses got larger lost toes and changed to a grazing diet what is the best explanation of why this change occurred