Final answer:
Large iguanas usually maintain body sizes above optimum because it provides them with advantages in their environment, such as better thermoregulation and increased survival and reproductive success.
Step-by-step explanation:
Large iguanas usually maintain body sizes above optimum because it provides them with advantages in their environment. One reason is that larger body sizes can help with thermoregulation, allowing them to better absorb and retain heat from the sun. This is important for their metabolism and overall activity levels.
Additionally, larger iguanas may have a better chance of defending themselves against predators or competing for resources like food and territory. By maintaining a larger body size, they increase their chances of survival and reproductive success.