Gravitational is only attracted and electromagnetic is both atrractive and repulsive since it depends what you are talking about
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.
