Stomach the small intestine, where the extraction of nutrients begins. Depending on the quantity and contents of the meal, the stomach will digest the food into chyme within anywhere between forty minutes and a few hours. The average human stomach can comfortably hold about a litre of food. Gastric juice in the stomach also contains pepsinogen. Hydrochloric acid activates this inactive form of enzyme into the active form, pepsin. Pepsin breaks down proteins into polypeptides. Although the absorption in the human digestive system is mainly a function of the small intestine, some absorption of certain small molecules nevertheless does occur in
Fishing down the food web Ecopath model. Ecopath is a computerised ecosystem modelling system. The functioning of an ecosystem can be described using path analysis to track the direction and influence of the many factors controlling the ecosystem. The original Ecopath model was applied to a coral reef food web. Scientists tracked tiger sharks at the top of the food web and collected data on their feeding behaviour, what they ate and how much. Likewise, they collected feeding data on the other organisms in the food chains down to the primary producers, such as algae. This data was fed into an Ecopath model, which then