Which species is commonly cited as an example of Type III survivorship?

• A. Humans
• B. Spiders
• C. Bears
• D. Elephants

Answer: (B)

Survivorship curves show how the chance of surviving changes as an organism ages. A Type III curve drops steeply early in life, meaning most offspring die soon after birth, but those that survive to adulthood live a long time. This pattern comes from organisms that produce many offspring with little parental care and high juvenile mortality.

Spiders fit this pattern well: they lay many eggs and provide little ongoing care, so a large fraction of the young die from predation, disease, or environmental hazards. Those that do reach maturity face fewer predators and can live for several years, giving a long lifespan once they survive the risky early period.

In contrast, species like humans, bears, and elephants invest heavily in their offspring and have higher juvenile survival, producing survivorship curves that are flatter early on (Type I or II).