Thermoregulation in Animals Part 5: There are two ways that different types of animals control their body temperature, or thermoregulate: ectothermy ("cold bloodedness") where the organism doesn't spend any of its energy on maintaining its body temperature, and endothermy ("warm-bloodedness") where the organism uses some of its energy to keep its body temperature constant. Birds and mammals, including humans, are endotherms. Sea urchins are an example of an ectotherm. Observe the figures at the right. Explain the difference in the reaction to environmental temperature between endotherms and ectotherms.