Individual organisms vary in their sensitivity to the drug used and some with greater fitness may be capable of surviving drug treatment.

Because the individual organisms vary, some are bound to be better able to survive in particular circumstances than others.

While all organisms vary from individual to individual, plants exhibit an additional type of variation.

Contaminating organisms vary greatly, and include skin flora, gut flora, or environmental organisms.

Conspecific organisms can vary in color, size, diet, behavior, and morphology due to differences in environmental pressures.

Because gardeners may have different goals, organisms considered "garden pests" vary from gardener to gardener.

Not being a true phylogenetic group, soft-bodied organism vary enormously in anatomy.

Darwin needed no knowledge of molecular genetics to see that organisms varied and that some left more descendants.

Flexible organisms can vary their models and pay more attention to the versions that prove better guides to action.

But the sense that "random" means to convey is crucial: nothing about genetics predisposes organisms to vary in adaptive directions.