1) humans bringing in and letting out a foreign species of fish into a nearby water way, resulting in the native species fighting for food and resources with the new species, or Invasive species.
2) human letting out a snake or exotic species into a forest, resulting, similarly to previous scenario, to the native species of the forest suffering the negative affects of the invasive species in regards to food, biodiversity, and the ecosystem of the area in which it was introduced buy the human.
