Practice question

Coho salmon are semelparous: adults migrate to freshwater, invest heavily in one spawning season, and die after reproduction. Their stored energy is spent on migration, competition, nest construction, gamete production, and defense rather than future survival. Loggerhead turtles and long-lived trees generally reproduce in multiple years, making them iteroparous. Selection can favor a large terminal effort when future survival is poor or when concentrating resources yields accelerating fecundity gains. Repeated breeding is favored when adults commonly survive and spreading reproduction buffers bad years. These predictions are conditional; a familiar species example illustrates a principle but does not define it for every environment. This reasoning also explains why field observations may be approximate even when the underlying textbook classification is useful. This interpretation connects individual-level processes with measurable changes in survival, reproduction, recruitment, or abundance across the population. Field evidence should therefore be compared with the model assumptions before extending the conclusion to every species, habitat, or time period.