Which statement about Type II survivorship curves is correct?

• A. They show mortality that decreases with age
• B. They show mortality that increases with age
• C. They show mortality that is highly variable with age
• D. They show a constant risk of death across ages

Answer: (D)

Type II survivorship curves show a constant risk of death across ages. In these populations, the chance of dying in any given time interval is roughly the same no matter how old the individual is. That leads to a steady decline in the number of survivors as age increases, rather than a sharp drop late in life or a large early loss. An everyday way to picture it is that about the same fraction dies in each year, so mortality is age-independent.

If mortality decreased with age, older individuals would be at lower risk than the young; if it increased with age, the risk would rise as individuals get older—these describe other survivorship patterns. If mortality is highly variable with age, there isn’t a consistent, age-independent hazard, which again doesn’t fit a Type II curve.