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Defense against infections

Last update 1-11-2008

Evolution of the defense against infections

This part of the site provides an overview of the defense mechanisms against infection from an evolutionary perspective. The intention is to provide an insight why all these different defense mechanisms exist.

Behind each summarized stage a more extensive story is told. Please click through.

The major stages in the development of the defense against infections
Time Layer Story Defense mechanism
2 bilion years ago Innate First heterotrophic bacteria like life forms developed Plenty of space and food - no attack nor defense needed. Life forms adapt to fill available nices
500 milion years ago Innate Multiple single celled life forms existed in abundance Space and food are scarce (locally) - chemical warfare and defense (resistance) commence using bacteriocins
1.6 - 2.1 billion years ago Innate Simple procaryotic life forms developed into more complex eukaryote life forms ??
??? years ago Innate Some life forms started eating each other The advent of predator - prey relationship
??? years ago Innate Multiple celled life forms developed They had an 'outside' and an 'inside' and therefore a new vulnerability
??? years ago Innate Multiple celled life forms developed a barrier to separate inside and outside Microorganisms were kept out, but some soon learned to pass the barrier
??? years ago Innate Multiple single celled life forms started to develop a gut The war on food and space moved into the organisms, inside the gut
??? milion years ago Innate Partnerships for defense Multi-celled species with a gut learned to tolerate 'friendly' species as part of the defense works
??? milion years ago Innate Complex life forms developed specialized defense mechanisms Forming symbiontic relations with some microorganisms require not-attacking them. This led to the development of specific immunity