Suppose that, among related host species that carry related symbionts, the relationship is mutualistic in some pairs and parasitic in others. how would you determine (a) which relationship is mutualistic and which is parasitic (0.5 pt), (b) what the direction of evolutionary change has been (1 pt), and (c) whether the change from one to the other kind of interaction has been a result of evolutionary change in the symbiont, in the host, or both (1 pt)? (hint: for (b) and (c), think phylogenies! )

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).

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic

You want to cultivate some exotic plants at your farm. however, the climate is chillier than the temperature range favorable to the crop. which is the best method to use for the cultivation of this exotic crop? a. use a crop rotation method b. use a lot of fertilizer c. prepare the seed bed properly d. use a greenhouse e. use irrigation