The model that assumes that evolution proceeds with a slow successive change in a given evolutionary line are referred to

a. the sympatric model.

b. the allopatric model.

c. successive descent model.

d. gradualism.

e. punctuated equilibrium

The correct answer is - d. gradualism.

Explanation:

Gradualism is a model of evolution that explains that the smaller variation in an individual organism that is occurring over a period of the time is to the betterment of the organism in their environment.

These changes or variations allow them to thrive and survive with a slow successive change in an evolutionary line or the whole population. It is a consistent process.

Thus, the correct answer is - D. gradualism.