A)sensory organs that provide information about the animal's environment.
B)internal digestive organs that break down food gradually.
C)an external skeleton that provides protection against predators.
D)a gastrovascular cavity that opens directly to the external environment.
E)filtration system that can change the composition of the interstitial and circulatory fluid.

A)a gastrovascular activity, a two-layered body, and a torpedo-like body shape.
B)an external respiratory surface, a small body size, and a two-cell-layered body.
C)a large body volume; a long, tubular body; and a set of wings.
D)complex internal structures, a small body size, and a large surface area.
E)an unbranched internal surface, a small body size, and thick covering.

A)there is a decrease in the surface-to-volume ratio.
B)reproduction becomes limited to terrestrial environments.
C)there is greater variability in metabolic rate.
D)migration to tropical areas becomes necessary for thermoregulation.
E)it becomes more difficult to conserve body warmth in cold environments.