Before revision: Microbes upA microscopic mite Lorryia formosa The first form of life to develop on the Earth were microbes , and they remained the only form of life until about a billion years ago when multi-cellular organisms began to appear.
After revision: Microbes upA microscopic mite Lorryia formosa The first form of life to develop on the Earth were unicellular , and they remained the only form of life until about a billion years ago when multi-cellular organisms began to appear.