An ectotherm is any organism that needs to pull heat from their surroundings to keep a proper body temperature and maintain homeostasis. Pictured is an octopus, a species which has been identified as ectotherms. This means that in order to regulate their body temperature they need to live in specific parts of the ocean, or, in an aquarium, the water has to be monitored at a certain temperature to ensure that the octopus stays healthy.
20. Ectotherm
Haylee's Advanced Biology Blog 19-20 