How do arteries differ in structure from capillaries and veins?
a)arteries have more elastin in tissue than veins and capillaries.
b) arteries appear flatter in a cross section than veins and capillaries.
c) arteries have valves which are absent in veins and capillaries.
d) arteries have walls that are thinner than veins and capillaries.

The kidney filters potentially toxic substances in the blood, and thus “clears” the blood of those substances. this clearance function is dependent upon and proportional to the diffusion gradient of the substance across filtering capillaries, i.e. if the concentration of the substance is doubled, twice as much will be cleared from each ml of blood that is filtered. suppose that the body produces a constant amount of a substance x per unit of time. the kidneys eliminate substance x at a rate directly proportional to the concentration of the substance and the volume of blood cleared each minute (c): elimination = c × [x], where [x] is the steady-state concentration of substance x. imagine an individual with an initial concentration of x equal to [x]0 who develops kidney disease. her baseline clearance c0 drops to one half of the original (½c0). what is the new steady state concentration of x? (for simplicity, assume that substance x is 100% filtered by the kidney).

Describe how a non-resistant staphylococcus aureus bacterium can produce a bacterium that is resistant to methicillin

In the ocean why are the greatest amount of primary producers found in the epipelagic zone and how does that affect biodiversity