Questions: What are the two primary forms of ecological succession?

The answer is the first one: primary and secondary succession.

Explanation for each option:

1. Primary and secondary succession: This is correct. Ecological succession is classified into two main types: primary succession, which occurs in lifeless areas where there is no soil, and secondary succession, which occurs in areas where a disturbance has destroyed an existing community but left the soil intact.
2. Initial and advanced succession: This is incorrect. These terms are not commonly used in the context of ecological succession.
3. Primary and tertiary succession: This is incorrect. Tertiary succession is not a recognized term in the context of ecological succession.

Summary: The two primary forms of ecological succession are primary and secondary succession.