20% is in the great lakes
Answer: Invasive species can harm both the natural resources in an ecosystem as well as threaten human use of these resources. An invasive species can be introduced to a new area via the ballast water of oceangoing ships, intentional and accidental releases of aquaculture species, aquarium specimens or bait, and other means.
Ruminant herbivores gain from the microflora in their gut through digestion of cellulose and in return, the microflora gets the nutrients from the ruminants. The shark doesn't benefit from the remora but the remora gets a free ride from the shark and it feeds on the leftovers from the shark's meal. The human host loses nutrients because the tapeworm gets to eat the food provided by the host. Cats provide shelter and food for the flea but the cat becomes anemic because of blood loss from its parasites.
The answer is mean!
mean is the average of a group of numbers; therefore, it is the most efficient and accurate!
Hope this helps!! :)
