Can the dorsal blood vessel of a worm be seen from the worm's exterior?

Are substances released into the environment that in excess amounts cause damage

What word is used to describe differences of individual organisms

What kind of seafood would you expect to have the highest levels of mercury and why? kelp, because they use the sun to photosynthesize on the bottom trophic level. oysters, because they filter feed on plankton on a lower trophic level. small fish, because they eat plankton on a higher trophic level. sharks, because they feed on organisms on a higher trophic level.