The answer is Pharyngeal Phase and Esophageal Phase stages of swallowing. In the pharyngeal phase, the bolus of food is pushed against the epiglottis, which closes the respiratory tract. The upper oesophageal sphincter relaxes and the bolus moves into the esophagus. In the oesophageal phase, the oesophageal sphincter closes when the bolus moves down and peristalsis action takes over to move the food down the oesophagus.
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.
