81) You have been working with a marine biologist on a trip from Baltimore through the Chesapeake Bay, to the open ocean, and back to test salinity levels and the kinds of plankton that live in each sampled area. The marine biologist is very nearsighted and she cannot see more than a few feet without the eyeglasses she lost two days ago when out on the open ocean. She arises one morning late in the trip, with no idea where the ship is. But after an hour of hearing you report salinity readings that vary by as much as 1 percent, she says, “So, we’re in the Chesapeake Bay?” How did she (correctly) make that conclusion based on the information provided?

82) From studying ecosystems and biomes, it may seem as if there is complete “bottom up” control, that the producers determine the life and success of the ecosystem. Yet closer examination shows “top down” control by the third trophic level is essential as well. Evaluate why this is so, citing at least one good example.

83) Many animal rights activists and “Hunger Watch” groups have claimed that if beef cattle and other sources of meat were eliminated, more people could be fed. What is the ecological theory behind the argument that humans should eat a greater proportion of their food “lower in the food chain”? Also speculate about a situation in which this principle may be less applicable.