Final answer:
Baker and Bellis posited that human sperm competition involves physiological and behavioral changes in response to perceived competition, with the aim of increasing reproductive success. Examples include increasing sperm count and selecting more fecund mates. These adaptions may lead to the preferential passing of such advantageous genes.
Step-by-step explanation:
The theories of human sperm competition by Baker and Bellis suggest that when a male suspects the presence of sperm from other males within the female's reproductive tract, the male's body shows physiological responses aimed at maximizing the chance of successful fertilization with his sperm. They describe forms of sperm competition in humans which include increasing the number of sperm ejaculated, altering the quality of sperm, and modifying sexual behavior based on the male's perception of sperm competition.
One example of behavior change is seen in fruit flies, where sperm-depleted males, lacking a full load of reproductive cells, choose more fecund females to increase their chances of successful reproduction. This behavioral shift demonstrates the role of energy expenditure and resource allocation in reproductive strategies, as discussed in behavioral biology or ethology.
Further theories in this field, such as the Fisherian runaway model and the good genes hypothesis, provide additional frameworks for understanding the complexities of sexual selection and reproductive behavior. The adaptive behaviors of sperm-depleted males choosing larger, more fecund females for mating could be seen as a form of natural selection, where the genes that prompt such advantageous behaviors are more likely to be passed on to the next generation.