A disadvantage of being multi-cellular is how long it takes to reproduce. For single-celled organisms, it's sometimes as simple a splitting in two, but multi cellular organisms, like humans, have to wait 9 months until they see their child.
Another disadvantage is it take more energy to do things. Some bacteria have flagella that they move like a tail that drives them forward. Multi-cellular organisms have to intake calories that are burned when we move and we have to keep intaking them to perform tasks.
