What are the advantages of unicellular to multicellular cells?

Answer 1

I'm assuming you mean unicellular organisms, because there is no such thing as a multicellular cell (one cell is one cell, no more, no less :P)

Anyway, to answer the question I think you were trying to pose here, a unicellular organism can multiply at rates that seem almost unimaginable in comparison to how fast multicellular organisms reproduce.

This ability offers several evolutionary advantages:

Because of the extremely rapid rate of replication, unicellular organisms can evolve and adapt to their surroundings much faster. For example, if someone were taking antibiotics, and stopped taking them because the infection they were using them for seemed to be gone, there would most likely still be at least a few of the infectious microbes left in their body, and they could quickly become immune to the antibiotics by starting to multiply again.

Multicellular organisms do not have this advantage, and evolve much slower, though it is also often much harder to kill them. Most cannot multiply fast enough to generate a gene that would make them immune to a poison when their population is dwindling (and if the animal multiplies sexually, it would have yet another disadvantage, as it only takes one unicellular organism to repopulate an ecosystem, since they can do it on their own).