What is the sigmoid and peak phenomena and what's the difference?

In sigmoid phenomenon, the population of a species do not reaches to its highest extent as compared to a peak phenomenon.

Explanation:

In a sigmoid phenomenon of Population growth the population of a species grows when there is abundant food and habitat. With the depletion of resources and impact of some external environmental factors , the population of the species reduces to a level where it get stabilized. This phenomenon follows a sigmoid path and the species are referred to as K – related species

While in the peak phenomenon, when the food resources are abundant, the population of the dependent species grows up to its highest extent and then start reducing suddenly. This process of rising and falling population continues in a cyclical pattern. The species are referred to as r – related species