When two or more species live intimately together with their fates linked, occurs.

The scenario you described refers to "symbiosis." Symbiosis is a biological term that describes the interaction between two or more different species living closely together, where their lives are so intertwined that the survival of one may directly affect the others.

There are several types of symbiotic relationships, including:

1. Mutualism: Both species benefit from the relationship. For example, bees and flowering plants; bees obtain nectar while helping plants with pollination.

2. Commensalism: One species benefits while the other is unaffected. An example is barnacles attaching to a whale; barnacles gain mobility and access to food while the whale is neither harmed nor helped.

3. Parasitism: One species benefits at the expense of the other. Parasites like ticks or tapeworms thrive on hosts, deriving nutrients while harming them.

These interactions can significantly influence the ecology of communities, the evolution of the species involved, and the overall functioning of ecosystems. Symbiotic relationships illustrate the complex interdependencies present in nature.