Evolution of Individuality

EVOLUTION OF INDIVIDUALITY

As you have seen, there has been a shift in evolution toward greater complexity, particularly in multicellular organisms. The truth, however, is that this has not happened in all evolutionary lines and many organisms are still unicellular. Evolution has not actually been completely gradual. It has happened through a small number of major evolutionary transitions. Much of these transitions have involved the cooperation of different cells and organisms to form an entity that is more complex than prior entities.

One of the major transitions that has occurred is in the way DNA and other heritable information is stored and passed on to create progeny individuals. This involved organisms that were once able to replicate by themselves but later could only replicate as a group. It also involved a lack of conflict between the different cells that have come together so they can work toward the same goal.

How does this work? There is more than one step to this process. It takes first the formation of a more cooperative collection of organisms. It then takes cohesiveness within the group so it can be seen as a single organism. Lastly, it takes some type of division of labor within the group.

There are questions one must ask about how this transition occurs. For example, what conditions favor things like cooperative group formation, cooperation between the cells, division of labor, communication between the cells, and a reduction in conflict within the organism?

There needs to be some benefit to the cooperative process that directly affects those that cooperate versus those that do not cooperate. Some benefits include evasion of predators, the ability to make fruiting bodies that help in dispersal of young, and increased efficiency in the use of factors that individual cells secrete.

There is a phenomenon in evolution called kin selection. It means behaviors of one cell or organism that directly or indirectly benefits the organism that has the same DNA as the organism doing the behavior even if it does not directly benefit the individual itself. Bees do this type of behavior because there are many worker bees that ensure the survival of the species even if it doesn t ensure the survival of the worker bees. Cooperation can be directed at nonrelatives if it also benefits the cooperator. This is seen in ant colonies who benefit from each other.

There are certain conditions that favor the division of labor among the parts of an organism. Division of labor can be seen in certain algae that make small cells whose job it is to keep the colony floating because the cells make flagella for this purpose. Another case is seen in