Scientists use fossils to study earth history by identifying the fossil and what era it came from. By knowing what era the fossil came from and what location it was found, scientists can make assumptions about the earth formation at that time.
The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism. Later, when pollution was reduced, the light-coloured form again predominated. Industrial melanism in the peppered moth was an early test of Charles Darwin's natural selection in action, and remains as a classic example in the teaching of evolution. Sewall Wright described it as "the clearest case in which a conspicuous evolutionary process has actually been observed."
<span>Myelination enhances the speed of action potential propagation.
The difference between myelinated and unmyelinated axons are in the propagation of action potential. In unmyelinated axons, the action potential travels continuously through the axons. On the other hand, among the myelinated nerve fibres, transmembrane currents can only occur at the nodes of Ranvier where the axonal membrane is exposed, so the excitation of the axonal membrane jumps from node to node. This propagation is called saltatory conduction and this movement of depolarization wave is much faster than in unmyelinated fibres.</span>
