The heart has four valves that control the flow of blood. two of the valves (the av valves) normally prevent blood from flowing upwards. the other two valves (semilunar valves) normally prevent blood from flowing downwards. the av valves and semilunar valves have different shapes. which principle of anatomy and physiology does this example represent?

For the strategies below, decide whether they are best described as demand-side solutions or supply-side solutions to meeting human needs for fresh water. remember that a demand-side solution reduces demand for fresh water, whereas a supply-side solution increases the supply of fresh water. (a) damming a river to create a reservoir (b) desalinating seawater (c) a nation invading a neighboring country to access their rivers (d) raising water prices for consumers and businesses (e) providing tax breaks for companies that use less water (f) replacing inefficient irrigation with more-efficient drip irrigation to grow crops (g) requiring low-flow showerheads in all new homes