The answer is natural selection.
In natural selection, genotype variations that will increase the chance
of survival and reproduction of some organism are preserved and will be
inherited. Red and green colors of butterflies increased the chance of their <span>survival and reproduction, so these traits will pass to the next generation.</span>
Our nervous system runs on chemical synapses ! that means we need chemical to transfer information from one neuron to another !
so when the signal reaches the synaptic knob of one neuron , it stimulates the neurotransmitters containing vacuoles to release the neurotransmitters !
the neurotransmitters may be dopamine, acetylcholine etc and after reaching the dendrites of other neuron, it stimulates signal in the other neuron and thus a signal travel from one part of body to other !
Darwin's theory of evolution by natural selection can explain how antibiotics are becoming defective because the bacteria that is trying to be fought off might have had a mutation making it more likely to survive. Once that surviving bacteria makes offspring most of the first generation will die from the antibiotic but soon all of their offspring will produce a resistance to that antibiotic.
Deep ocean floor would be your answer :)
