Mode Of Digestion Lab Report

As evolution of digestion has occurred, the ways organisms gain their energy from food has also evolved into much more complex processes. From the intracellular digestion process of single-celled organisms to multicellular organisms, such as humans, morphing into extracellular digestion, digestive systems have had to evolve with us so that our bodies allow us to easily absorb nutrients from our food.
The simplest digestive system takes place in the subkingdom Protozoa, where organisms are made up of only a single cell. The mode of digestion is always intracellular, meaning that food particles or liquid foods are ingested into a cell by Phagocytosis and Pinocytosis processes respectively, because it is not possible to undergo digestion outside …show more content…
There are, however, some exceptions to this rule of digestion amongst Protozoans. Euglena, a single celled organism that we viewed in the lab, is a Protozoan, though it does not undergo this type of digestion. Digestion of food materials is not required for autotrophic organisms, organisms having chlorophyll, because they do not need to produce simple food after breaking down complex food. In our lab, Chlamydomonas, Volvox, and Euglena were all autotrophs, so they do not digest in the same way as other organisms. In the figure, these three organisms would all fit body plan B, as they have chloroplasts that aid them in photosynthesizing. Euglena’s cell membrane, the pellicle, is responsible for permitting absorption of nutrients when the organism does not have sunlight to photosynthesize. However, when sunlight is present, the Euglena is able to produce carbohydrates from carbon dioxide in water and absorb nutrients through this process, a relatively simple digestive process compared to more advanced organisms. In addition Euglena, Paramecium is also a Protozoan. Digestion of a Paramecium begins when food enters its open mouth from an oral groove, and soon after, the gullet, …show more content…
These organisms are no longer single-celled, which can be seen due to their larger sizes. Because the organisms have evolved to a larger size, their digestive systems have evolved with it to become more complex and fit the needs of the organism’s enlarging bodies. A well formed canal system is present in their body, in which a water current is produced by the organism’s flagellum, a thread-like structure that is present in Poriferans. This water current bears food particles to be passed into their bodies through numerous small openings known as Ostia. The food materials are taken from the water current by collar cells, which later digest the materials through an intracellular process. Once the Poriferans have finished digesting, the undigested materials are removed from a large pore known as Osculum. Earthworms, one of the organisms from our lab, is a Poriferan. Although earthworms do not have the exact same digestive system as other Poriferans, scientists still classify them in this subkingdom. Earthworms first begin digestion by drawing food into their open mouth through the rhythmic contractions of the pharyngeal muscles. From the mouth, food goes into a small buccal cavity that opens into a large pharynx. The pharynx opens into the earthworm’s esophagus, which has numerous calciferous glands attached to it that bind