111. Osmoconforming animals, such as the spider crab, that live in the open ocean show little ability to
withstand large variations in salinity, while coastal animals, such as the closely related fiddler crab,
show great ability to withstand large salinity changes. Explain why this is the case, considering the
relevant abiotic features of both habitats.
112. Barnacles and mussels compete with each other for space on the rocky intertidal. What type of
interaction exists between these two species? If you knew that mussels are capable of occupying all
available space in the rocky intertidal then what would happen to the barnacles? What keeps mussels
from crowding out barnacles throughout the entire intertidal zone?
113. What is the difference between the rocky intertidal community and the rocky intertidal ecosystem?
114. Explain why the number of trophic levels in a given ecosystem is limited.