Practice question

Eurythermal species tolerate a broad range of environmental temperatures. Their proteins, membranes, metabolic regulation, stress responses, and behaviour remain functional across wider thermal limits than those of stenothermal species. This breadth allows survival through seasonal fluctuations, movement among contrasting microhabitats, or occupation of geographically variable environments. It does not mean performance is equally high at every temperature. A tolerance curve still contains an optimum, zones of stress, and lethal lower and upper boundaries; eurythermal simply means those boundaries are relatively far apart. Reproduction only in summer describes a seasonal schedule, not thermal breadth. Migration and hibernation are possible strategies for avoiding unfavourable conditions, but neither is required in a species that tolerates them directly. Acclimatization may shift thermal performance within an individual’s plastic capacity, while evolutionary adaptation can alter the population’s range over generations. Thermal tolerance can also differ among eggs, larvae, and adults, so the most sensitive stage may set distribution limits. A broad tolerance often aids widespread species and biological invaders, although dispersal, moisture, food, and biotic interactions still constrain where they actually occur.