What has occurred when large numbers of species die out over a short period of time

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

Which is a function of vascular tissue? a. to perform photosynthesis b. to transport water and nutrients c. to absorb minerals and sugar d. to interact with soil fungi

How do disease caused by bacteria and disease caused by viruses react to antibiotics