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The history of biological evolution is marked by a number of metasystem transitions,
including: the origin of life itself, the development of the modern cell from the aggregation of
pre-cellular organelles (the transition from prokaryotes to eukaryotes); the coordination of single cell organisms into
multi-cellular organisms; and the origin of sexual reproduction.
A detailed treatment of these different developments can be found in:
Maynard Smith J. & Szathmàry E. (1995): 
Major Transitions in Evolution, (W.H. Freeman, Oxford).
From the book cover:
(...). This is the first book on all these major transitions. In discussing such a
wide range of topics in one volume, the authors are able to highlight the
similarities between different transitions- for example, between the union
of replicating molecules to form chromosomes and of cells to form
multicellular organisms. The authors also show how an understanding of one
transition sheds light on others.
A common theme in the book is that entities that could replicate
independently before the transition can replicate afterwards only as as
part of a larger whole. Why, then, does selection between entities at the
lower level not disrupt selection at a higher level? In answering this
question, the authors offer an explanation for the evolution of cooperation
at all levels of complexity.
