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by a-priori
4240 days ago
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They're referring to chemical signalling of some kind when they use the word 'signal'. Chemical signalling of various kinds is very common in all kingdoms of life; examples in animals are hormones (circulated in the bloodstream for communication between organs), pheromones (circulated in the air for signalling between organisms), and neurotransmitters (emitted in the gap between synapses and dendrites for signalling activation of a neuron). |
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