Final answer:
Natural selection favored traits in Texas longhorns that made them well-adapted to survive in the wild. As a result of living in a harsh environment for many years, longhorns developed genetic traits that helped them survive, such as strong immune systems and efficient use of resources.
Step-by-step explanation:
Natural selection's effect on the Texas longhorn population was to favor traits that made them well-adapted to survive in the wild. As a result of living in a harsh environment for many years, longhorns developed genetic traits that helped them survive, such as strong immune systems and efficient use of resources. Over time, individuals with these favorable traits were more likely to survive and reproduce, passing down their advantageous genes to future generations.