Explain why characteristics which helps an animal to live longer will generally tend to become more common in the population as a result of evolution by natural selection?

Characteristics that help an animal live longer, such as increased disease resistance or improved foraging abilities, allow that individual to survive and reproduce for a longer period, passing those beneficial traits on to the next generation. Over time, these advantageous characteristics become more common in the population because individuals with them are more likely to pass on their genes, increasing the overall fitness of the population.