Final answer:
A survivorship curve with uniform death rates over time describes a Type II survivorship curve, where death is equally likely to occur at any age, typical of many bird populations.
Step-by-step explanation:
Survivorship curves are important tools for population ecologists to understand the different survival strategies of species. A survivorship curve with uniform death rates over time describes a situation in which individuals are equally likely to die at any age.
This pattern is characterized by a Type II survivorship curve. An example of this would be many bird populations, which have relatively constant mortality rates throughout their lifespans. As a comparison, a Type I survivorship curve would show low mortality in early and middle life, with high mortality in older ages—common in humans and many mammals.
In contrast, a Type III survivorship curve would show high mortality at younger ages and lower mortality once a certain age is reached, which is often seen in trees and certain marine invertebrates. As such, the correct answer to the question is:
b. by a Type II survivorship curve because the number of survivors decreases uniformly over time, reflecting a constant probability of dying at any age.