Phylum Chordata Essay

All members of the phylum Chordata have, at some stage during their development, the following five characteristics:
- A notochord, which is a rod-like structure of cells which is ultimately replaced by vertebrae in most species.
- A dorsal tubular nerve cord which runs along the notochord, ultimately becoming the spinal cord.
- Pharyngeal pouches and slits. These may eventually become gills in fish and other aquatic vertebrates or structured such as Eustachian tubes and the middle ear cavities in certain terrestrial vertebrates.
- An endostyle which secretes mucus into the pharyngeal cavity to assist with filter feeding. In some vertebrates this may also develop into a thyroid gland.
- A post-anal tail.

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Sharks have various ways in which they find their prey through highly efficient sensory organs:
- Their olfactory organs are very sensitive (or to put it another way, they have a very keen sense of smell underwater). They are able to detect chemicals, even in small concentrations from up to 1km away.
- They have a lateral line system made up of neuromasts which can detect vibrations in the water, as well as changes in current and water pressure.
- The eyesight is very good and can track their

These microbes digest the cellulose and produce waste products in the form of fatty acids (fermentation). These fatty acids are absorbed through villi in the rumen. The rest of the food particles, including the protein and carbohydrates from the plant cells move to the reticulum, where they are softened by liquid; to the omasum, where they are compacted; and finally to the abomasums (which is the true stomach) where digestion with enzymes takes place. The waste products are then excreted. (Fermentation first, enzymatic digestion