Final answer:
Life expectancy refers to the average lifespan of people in a population and is influenced by various factors such as nutrition, healthcare, and lifestyle. In the United States, females tend to have higher life expectancy than males. Aging and death can be caused by programmed factors and damage-related factors.
Step-by-step explanation:
Life expectancy is the statistical measure that represents the average lifespan of people in a given population or country. It is influenced by various factors such as nutrition, healthcare, sanitation, and lifestyle. In the United States, the life expectancy in 2015 was 77 years for males and 82 years for females. The maximum human lifespan is estimated to be around 115 years, with a limit of 125 years. Aging and ultimately death can be attributed to programmed factors like telomere shortening and damage-related factors like DNA mutations.