What describes molecules moving down to a concentration gradient

A molecule diffuses down its concentration gradient by moving from one region of higher concentration to a region of lower concentration. No energy is needed because the molecules move down a concentration gradient.

humans are now responsible for causing changes in the environment that hurt animals and plant species. we take up more space on earth for our homes and cities. we pollute habitats. human activity often changes or destroys the habitats that plants and animals need to survive.

colors do exist. the color of the sky is actually violet; humans percieve the color of the sky as blue.