Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell? Answer A: Specific genes are activated.

Answer B: A second messenger molecule is produced.

Answer C: A ligand binds to a receptor.

Answer D: Specific proteins are synthesized.

Migration is a. the movement of organisms from a native location to a foreign location b. the movement of organisms from a foreign location to a native location the movement of organisms from their water supply to their food supply d. the seasonal movement of organisms between locations c. select the best answer from above

Isotopes of the same element have differ in their

Veins have a much lower blood pressure than arteries. which of these prevents backflow of blood in veins? a. pressure applied by the heart b. one–way valves in veins c. thin muscular walls of veins