Symbiosis is a relationship in which there is a close and permanent association between organisms.
The bat benefits from the cactus by eating the nectar. As the bat eats, it unknowingly transfer pollen to the next cactus.
Mutualism is when both species benefit from each other.
Commenalism is when one species benefits and the other is
neither harmed nor benefited.
The cactus wren is benefiting because the cactus is providing protection for the bird and its young by building a nest on it. The cactus is not being affected by the bird building a nest on it.
The fly benefits by drinking the camels blood because it gains nutrients from the blood, but the fly harms the camel and the camel receives a fever, weakness, and sometimes death.
Parasitism is an interaction; it is harmful for one and benefits the other.