Final answer:
Survivorship curves are graphs showing the number of individuals alive at each age for a population, used by ecologists to study survival patterns. There are three main types: Type I (low early mortality, high in old age, e.g., humans), Type II (constant mortality rate, e.g., birds), and Type III (high early mortality, low after certain age, e.g., trees).
Step-by-step explanation:
Graphs that illustrate the number of individuals of a population that are still alive at any given age are known as survivorship curves. Survivorship curves are useful tools for population ecologists to depict and analyze the survival patterns of different species over time. There are three main types of survivorship curves:
- Type I survivorship curve: Characterized by low mortality during early and middle life with mortality increasing in older age groups. Humans and many mammals exhibit this pattern.
- Type II survivorship curve: Mortality is relatively constant across all ages. Birds are often cited as examples demonstrating this pattern.
- Type III survivorship curve: High mortality rates in early life with a steep decline in mortality for those that survive past a certain age. Many trees, marine invertebrates, and fishes exhibit this type of curve.
Each curve represents a different strategy species use to adapt to their environments and provide insights into the reproductive strategies and life histories of organisms.