You could argue that in early succession areas species may have not been adapted or evolved. In Darwin's theory, life began in a shallow, warm pond. If that is the case, species would then venture deeper when their area they are in is suitable and having success
I think it might be the first one: hiv infections. (hope this helps!)
Any characteristic, whether a physical trait, a behaviour, a physiological adaptation etc can make an organism more or less likely to survive in a particular environment.
A dark colour could help a rabbit survive if it lives in a dark forest, because predators can't see it so well, but it would be less likely to survive in the arctic, where the environment is all white and it would show up.
In terms of the characteristics, think about: does it help the organism get food? Does it help protect the organism from predators? If it does, that organism is more likely to survive, and pass the characteristic on to it's offspring. If a bacterium has a characteristic of not being killed by antibiotics, this will help it to survive and breed.
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Pumps, also called transporters, are transmembrane proteins that actively move ions and/or solutes against a concentration or electrochemical gradient across biological membranes. One moves with the concentration gradient (high to low) which powers the movement of the other against the gradient (low to high).
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