Today, plants and animals can typically travel around the world in hours or even days by plane or ship. Usually their presence is harmful, but some scientists believe they can actually be a catalyst for biodiversity! Invasive or exotic species have altered the Chesapeake Bay region; with both negative and positive impact. “Exotic species are plants, animals or microbes that have been transported from one geographic region to another. » (5) They are moved from an area where their evolutionary balance is defined, to an area where they can have no natural competitor. Invasive or exotic species can have a major impact on our environment. They can endanger ecosystems by altering an entire environment, replacing other native species in the environment, and even harming human activities such as fishing. (1) Once introduced into a new environment, invasive species disrupt the ecological balance of the area. They may have no natural predators and can outcompete natural organisms; giving them the opportunity for rapid growth throughout the environment! (The Nature Conservancy, 2004) In fact, invasive species are one of the main reasons why some of our endangered species are threatened. The graph on the left shows that approximately 50 percent of the affected threatened or endangered species were due to these exotic species! In the United States alone, many invasive and exotic species are already established! According to Exotics in the Chesapeake, “At least 4,500 species have established free-living populations in the United States” (3). These species have even appeared in the waters around us! I believe that these invasive and exotic species have even modified the Chesapeake Bay region and that these alterations are not always predictable! For example, oysters in the Chesapeake Bay have suffered since their parasites Dermo and MSX were introduced to the area as exotic species.(3) The fundamental role of oysters is to abolish algae in the water ; Yet with the decline of oysters, the bay's ecosystem is undergoing major destruction. (3) This not only affects the bay, it also affects the oyster fishery, causing many economic losses. (3) Other examples would include the mute swan; which acts aggressively towards other birds in the area. (2) Although these species have many disadvantages, many could bring good. The Hydrilla plant could take over and replace other native plants; but can also benefit the bay.