Final answer:
Unequal sex ratios in a population can be caused by cultural factors, economic considerations, government policies, environmental factors like temperature-dependent sex determination in some species, mortality variations, nonrandom mating, and sexual selection.
Step-by-step explanation:
Unequal sex ratios in a population can be caused by a range of factors. For example, in some oil-producing countries in the Middle East, lopsided sex ratios favoring men are prevalent, often due to male-dominated migration for job opportunities, while the countries they leave from, such as ones in Southeast Asia, may subsequently have more women than men. Cultural factors like sexist attitudes and economic considerations also play a critical role. In parts of India, for example, the preference for male offspring can lead to a higher number of boys due to the dowry system. Similarly, government policies, such as the One-Child Policy in China, have created disbalances by exacerbating gender preferences.
Environmental factors can also influence sex ratios. Some species, like certain reptiles, have temperature-dependent sex determination (TSD), where the incubation temperature of eggs can determine the gender of the offspring. Additionally, variations in mortality rates due to diseases or violence, and nonrandom mating due to geographic separation, can also result in imbalanced sex ratios. Finally, sexual selection can lead to sexual dimorphism and differential reproductive success, influencing sex ratios within populations.