Question

Imagine that a species of fish used to be a broadcast spawner (producing many eggs that then get no subsequent parental care) but has evolved to be a mouth brooder (holding the eggs in the parent's mouth until they hatch and then caring for the young for a while). We would expect the survivorship curve of this species to:

A. Shift from Type I to Type II or III.
B. Shift from Type II to Type I.
C. Shift from Type III to Type I or II.
D. Shift from Type II to Type III.
E. Vary unpredictably.

Answer 1

The survivorship curve of this species would shift from Type III to Type II or Type I.

Step-by-step explanation:

The survivorship curve of a species that has evolved from being a broadcast spawner to a mouth brooder would be expected to shift from Type III to Type II or Type I.

A Type III survivorship curve is characterized by high mortality in the early stages of life, with low mortality for those that survive to advanced years. This is typical of organisms that produce many offspring but provide little parental care.

However, as the species evolves to become mouth brooders, where the parent cares for the eggs and young for a period of time, the mortality rate in the early stages of life would decrease, resulting in a shift towards Type II or even Type I survivorship curves, which are characterized by lower mortality in the early and middle years.