Final answer:
Scientists bred fruit flies with DDT resistance which demonstrated that such traits could provide a selective advantage in environments with pesticide pressure.
Step-by-step explanation:
In a classic experiment to observe the effects of selection on fruit fly abdominal bristles, scientists selectively bred fruit flies that survived DDT exposure. These trials showed that DDT resistance in fruit flies gave them a higher evolutionary fitness compared to non-resistant ones. Due to the environmental pressure imposed by the widespread use of DDT, resistant fruit flies had a selective advantage, leading to changes in the population's genetic makeup. Moreover, research indicates that fruit flies allocate energy differently based on their mating status, with sperm-depleted males favoring larger, more fecund females. This behavior maximizes the chances of reproduction with limited resources.
Fruit flies exhibit different genetic expressions under varying conditions, such as cold temperatures, which can influence traits like fecundity. For instance, fruit flies adapted to cold are likely to have reduced early fecundity, potentially due to the energy costs of maintaining cold resistance. When studying the inheritance of traits like body color and eye pigmentation, we know from classical genetics that if all F1 progeny display a wild type phenotype after crossing certain true-breeding flies, the wild type alleles are dominant over the mutated alleles. Studies on how birds react to butterflies with or without eyespots help to illustrate how interspecies behaviors can drive natural selection.