There are two main ways in which molecules are transported into and out of cells - active transport and passive transport. which of the following statements is true of passive transport?

a.) energy, in the form of atp, is essential for passive transport.
b.) endocytosis and exocytosis are two forms of passive transport.
c.) molecules move up a concentration gradient during passive transport.
d.) carrier proteins are sometimes used during passive transport.

science-ocean floors and habitats study guide by volleyballqueen3817 a major advance in ocean-floor mapping. list four sections of the ocean floor. algae that use sunlight to produce their own food through photosynthesis. all of the feeding relationships that exist in a habitat. drying out, predators, find food.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".