The purpose of this section is to review how some fundamental challenges in information transfer within a multicellular organism have been met, and how the mechanisms involved today evolved from simpler precursor states. First, we will look at the ways in which multicellular life has come about. We will look at various ways a modest number of basic "strategies" that are used have evolved, and how genes are used to achieve them. These strategies have been employed throughout the biosphere.
A major—if not the major—stage in the evolution of life as we know it was the evolution of the cell. Cells are more than gene-translating factories and are the essence of more complex organisms, constituting a fundamental organizing aspect of life. For an organism to function as a coherent whole, there must be an organized division of labor and communication among cells. We will look at how that occurs among nearby cells and then at the processes that allow longdistance communication among cells within an organism.
Finally, an organism develops generally from a rudimentary beginning, such as a single cell, through a highly orchestrated process of development, and we are beginning to learn how that works. A major aspect of that is the vital problem of reproduction, which itself has many meanings. Similarly, many if not most organisms are able to maintain viable states by responding to changes in their environment. We will describe general aspects of development as well as genes and the regulation of their expression that makes this responsiveness possible.
An important point is that within an organism communication largely involves specific signals that are received by cells specifically looking for them. Another problem of dealing with the internal world actually derives from the external. Organisms are always subject to being invaded by microorganisms that could do them harm. They have developed a variety of ways to cope.
Genetics and the Logic of Evolution, by Kenneth M. Weiss and Anne V. Buchanan. ISBN 0-471-23805-8 Copyright © 2004 John Wiley & Sons, Inc.
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