What is the main characteristic of Type II survivorship curves?

Type II survivorship curves are characterized by a constant mortality rate across all ages. This means that the likelihood of dying is relatively uniform throughout the lifespan of the organism. In other words, individuals face the same risk of death regardless of their age.

This pattern is often associated with certain species that experience a consistent level of predation or environmental hazards throughout their life, rather than being critically affected by early-life mortality risks or other age-specific factors. Species that exhibit this type of survivorship might include some birds or small mammals, where the chances of survival decrease steadily rather than sharply at specific ages.

In contrast, other options describe different survivorship patterns. High mortality at young ages pertains to Type III curves, low mortality in early life relates to Type I curves where most individuals survive into old age, and variable mortality rates among age groups also align with Type I or Type III curves, but not Type II. These alternative survivorship curves illustrate how different species adapt to their environments and life histories, focusing on protection during specific life stages versus overall consistent risk.