Cơ sở vật chất di truyền ở cấp độ phân tử là

The negative impacts of nonnative species generally outweigh the positive impacts

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).

Some species of wasps are social. the queen starts a colony from scratch each spring. she builds a small nest, and lays and raises a group of female workers. the workers enlarge the nest while the queen continues to lay eggs. unfertilized eggs become males that mate with newly hatched females. all of the wasps except the newly fertilized females die by the summer. which best describes this behavior? a)it is beneficial only to the males that do not fertilize eggs. b)it is beneficial only to the female workers that are not fertilized. c)it is beneficial to each one of the individual colony members. d)it is beneficial to the whole species, but not to all of the individual members.