Maria wanted to learn more about the birds that visit her backyard. She installed several bird feeders and offered a variety of bird seed mixes in order to attract a mix of species. For a month, she observed the bird feeders three times a day for an hour each day and counted the types of birds that she saw. Then, she made a pie chart to represent her findings. What is the most likely reason that she chose a pie chart? To show the total number of birds that she observed. To show the number of times that each bird visited the feeders. To show which bird species were most common. To show how the bird species changed over time.

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).