Mate choice may be based on the traits of potential mates or by some other criterion, such as territory quality. Male parental care evolves when males can be sure of paternity and when they can increase their RS more by caring for offspring than by mating with additional females. Sexual selection may lead to sexual dimorphism and exaggerated secondary sexual characteristics in males. Organisms may be solitary or live in social groups. Asexual reproduction enables the greatest reproductive rates but produces little or no genetic variability.
Sexual reproduction lowers the maximum reproductive rate but produces genetic variability.
Individuals of some species change sex to maximize their reproductive success. Differences in parental investment lead to the sexes having different strategies to maximize reproductive success. Mate choice may be based on the traits of potential mates or by some other criterion, such as territory quality. Organisms allocate limited energy supplies to different needs, including the maintenance of homeostasis. In temperate and polar zones, day length is more reliable than weather as an indicator for seasonal cycles.