Ecological Succession

Step 1: Understanding the Concept:
The question asks for the correct sequence of seral stages in a primary succession on bare rock, also known as a xerosere or lithosere. This process involves the gradual development of soil and plant communities over time.

Step 3: Detailed Explanation:
The sequence of succession on bare rock is as follows:
1. (D) Crustose-lichens stage: These are the pioneer species. Crustose lichens are flat and encrusting, capable of growing directly on the bare rock surface. They begin the process of soil formation by weathering the rock and trapping dust.
2. (B) Foliose-lichens stage: Once a thin layer of soil is formed, larger, leaf-like (foliose) and shrubby (fruticose) lichens can establish themselves. They further contribute to soil formation.
3. (A) Moss stage: As soil deepens, mosses, which require more soil and moisture, start to grow, outcompeting the lichens.
4. (C) Herbaceous stage: With more developed soil, grasses, herbs, and other herbaceous plants can take root.
5. (E) Shrub stage: As the soil continues to improve, larger plants like shrubs can establish, shading out the herbaceous plants.
This is eventually followed by a climax forest community.

Step 4: Final Answer:
The correct chronological order of the stages is (D) Crustose-lichens stage (B) Foliose-lichens stage (A) Moss stage (C) Herbaceous stage (E) Shrub stage.

Step 1: Understanding the Concept:
The question asks for the ecological term for the first organisms to colonize a previously uninhabited or disturbed environment. This is a concept from the study of ecological succession.

Step 3: Detailed Explanation:
Ecological succession is the process of change in the species structure of an ecological community over time.

Step 4: Final Answer:
The species that first invades a bare area is referred to as a pioneer species.