61. what is the ph scale? 62. what range of numbers on the ph scale indicate an acid? 63. what range of numbers on the ph scale indicate a base? 64. what is eutrophication? how does it occur? 65. what would happen to fish in a pond if the dissolved oxygen levels decreased?

How are rocks that cooled within magma chambers found on earth’s surface today? they are pushed up by magma under earth’s surface. they are revealed by erosion of earth’s surface over time. they are pushed to earth’s surface because of their larger size. they are revealed at earth’s surface due to their low density.

The health, management and conservation of biodiversity, is a challenge facing ecosystems worldwide. the major factors that affect the health and function of the great barrier reef are climate change and pollution. which question investigates the effects of a biotic factor on the reef ecosystem?

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).