1. Most endotherms (animals that maintain high body
temperatures by internal heat production) are either
birds or mammals (almost all of which are quite large
as organisms go), though a few very large fish are
endotherms (e.g. tuna), and a few large insects are
endotherms at least some of the time (e.g. bumblebees
and some large moths).
a. What are some of the costs and benefits of being
endothermic?
b. Why is endothermy almost completely absent
from most small organisms?
c. Why are most aquatic endotherms extremely
large (e.g. tuna fish and whales)?
2. Most endotherms (animals that use internal heat
production to maintain body temperatures) are
homeotherms (have constant body temperatures), and
most ectotherms (body temperature depends on
temperature of external environment) are poikilotherms
(have variable body temperatures).
a. Under what circumstances might it be useful for
an endotherm to be poikilothermic? Give examples.
b. Under what circumstances might en ectotherm be
homeothermic? How could an ectotherm achieve this?
