Cambrian Explosion: best illustrated guide (Introduction)

by David Turell , Tuesday, April 19, 2016, 16:56 (3140 days ago) @ dhw

DAVID: One cannot tell the difference in our two approaches from the history of evolution, just as one cannot tell the difference in a beautifully programmed bacteria from one that has some independent decision-making ability.
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> dhw: Agreed. And so when eminent scientists inform us that bacteria are cognitive, sentient, cooperative, decision-making beings, one should perhaps take their findings seriously. - The appearance of cognitive ability, interpreted as primary initiative responses in bacteria by a few enthusiastic scientists who overstate the case for emphasis, does not negate the fact that it is their personal interpretation of a phenomenon which has two equally possible interpretations. - This article shows the automaticity: - https://en.wikipedia.org/wiki/Autoinducer - "In the most simplified quorum sensing systems, bacteria only need two components to make use of autoinducers. They need a way to produce a signal and a way to respond to that signal. These cellular processes are often tightly coordinated and involve changes in gene expression. The production of autoinducers generally increases as bacterial cell densities increase. Most signals are produced intracellularly and are subsequently secreted in the extracellular environment. Detection of autoinducers often involves diffusion back into cells and binding to specific receptors. Usually, binding of autoinducers to receptors does not occur until a threshold concentration of autoinducers is achieved. Once this has occurred, bound receptors alter gene expression either directly or indirectly. Some receptors are transcription factors themselves, while others relay signals to downstream transcription factors. In many cases, autoinducers participate in forward feedback loops, whereby a small initial concentration of an autoinducer amplifies the production of that same chemical signal to much higher levels." (my bold) - Comment: Note controls by a feedback loop, automatic.