Which of these environments is a typical starting point for primary ecological succession?

Introduction / Context:
This ecology question checks whether you can distinguish primary succession from secondary succession. Succession describes the gradual changes in plant and animal communities over time in a particular area. Knowing where primary succession begins is important for understanding how life colonises new or drastically altered environments where soil initially does not exist.

Given Data / Assumptions:

• Primary succession starts on surfaces that initially lack soil and organic matter.
• Secondary succession starts where soil is already present but vegetation has been disturbed or removed.
• The options include environments with and without existing soil and living communities.

Concept / Approach:
Primary succession occurs in areas where life is just beginning to establish itself. Typical examples are bare rock exposed by retreating glaciers, newly formed volcanic islands, or lava flows that have cooled. In these places, there is no established soil profile, very little organic matter, and very few if any organisms at the start. Pioneer species such as lichens and mosses are the first colonisers. They slowly break down rock and contribute organic material, forming the first thin soil layer. Secondary succession, on the other hand, takes place in areas where a disturbance has removed vegetation but left the soil more or less intact, such as abandoned farmland, logged forests, or burned grasslands.

Step-by-Step Solution:

Verification / Alternative check:
You can verify this decision by recalling textbook diagrams of ecological succession. Often, these diagrams show primary succession beginning on bare rock after glacial retreat or volcanic activity. Lichens and mosses appear first, followed by grasses and shrubs, and eventually by larger plants and trees as soil depth and quality improve. In contrast, images of secondary succession show landscapes where some soil and seeds remain, such as an abandoned field that gradually develops shrubs and forest without needing to form soil from scratch.

Why Other Options Are Wrong:

A neglected yard in a city is incorrect because soil and many organisms already exist there. Succession in such a place would be secondary, not primary.

Abandoned farmland is incorrect because it still contains developed soil and often seed banks and root systems. The sequence of plant communities that follow is secondary succession.

An abandoned city with buildings and streets is incorrect because although some surfaces may be bare concrete, soil persists in cracks, parks, and margins. Plant colonisation in these places builds on existing organic matter, which fits better with secondary or urban succession rather than primary succession starting from bare rock everywhere.

Common Pitfalls:
Many learners confuse primary and secondary succession because both involve changes in communities over time. A common mistake is to label any abandoned or disturbed area as primary succession simply because it looks barren at first glance. The key is to check whether true soil has to form from rock or whether soil is already present. Remember that primary succession is slower and begins on substrates like lava flows and glacial rock, while secondary succession is faster and starts where soil remains after a disturbance.

Final Answer:
The typical starting environment for primary ecological succession among the options given is A surface of bare rock exposed by a retreating glacier.