When an object rests on a surface, such as a table, for example, the downward force it applies to the surface is counteracted by an equal but upwards force, or reaction, applied by the surface. See more at Newton's laws of motion. A response to a stimulus, such as a reflex.
Background. The northern snakehead fish (Channa argus) has been identified as an invasive aquatic fish across the country. Snakehead fish got their name because of their long, cylindrical body plan and large scales on their head that give them a snake-like appearance.
An invasive species can be any kind of living organismâan amphibian (like the cane toad pictured left), plant, insect, fish, fungus, bacteria, or even an organismâs seeds or eggsâthat is not native to an ecosystem and which causes harm. They can harm the environment, the economy or even, human health.nvasive species are primarily spread by human activities, often unintentionally. People, and the goods we use, travel around the world very quickly, and they often carry uninvited species with them. 1  Ships: Ships can carry aquatic organisms in their ballast water.