What is the regular progression of species replacement known as

The regular progression of a species' replacement is known as ecological succession, or simply just succession.

Explanation: All ecosystems are not static, they change through time. All animals, plants, microorganisms, etc. (different species) create changes to their environments, but other factors such as climate change/weather, over-exploitation, human involvement, and other factors change an ecosystem.

b - the respond is innate and varies over time.

good luck!