Final answer:
Ectotherms rely on external heat sources for body heat, while endotherms generate and maintain body temperature internally.
Step-by-step explanation:
Ectotherms and endotherms have different strategies for generating and maintaining body heat. Ectotherms are more dependent on the environment for body heat because they rely on external heat sources to regulate their body temperature. On the other hand, endotherms can generate and maintain their body temperature internally through metabolically generated heat. This allows them to regulate their body temperature within a wider range. While ectotherms harmonize with external rhythms, endotherms uphold a consistent, albeit energy-intensive, internal equilibrium, affording them a wider thermal tolerance and enhancing their resilience across ecological niches.