The principle characteristic distinguishing marine and freshwater ecosystems is a. temperature. b. presence of corals. c. presence of fish. d. dissolved salt.

The answer is D. Marine water has a high amount of dissolved salts than freshwater. For every liter of marine water, there is an average of 35 grams of dissolved salts which are over 200 times that of freshwater. Therefore, the organisms in marine water have to adapt to the high osmotic pressure of the waters while those in freshwater to the low osmotic pressure.

it will increase due to the time span

the sphincter muscles at the end of the digestive tract is the anus.