Q. Which of the following is the correct sequence of phases of biotic succession?

Correct Answer: d) Migration – Ecesis – Reaction – Stabilisation

Explanation:

Biotic succession refers to the natural process by which ecosystems develop and change over time, eventually reaching a stable climax community. The correct sequence of phases in biotic succession is as follows:

1. Migration: This is the initial phase where propagules (seeds, spores, or other reproductive units) of species arrive at a new area through dispersal mechanisms like wind, water, or animals.

2. Ecesis: After migration, the propagules establish themselves in the new environment. This involves germination, growth, and adaptation to the local conditions.

3. Reaction: As the organisms grow and interact with the environment, they modify it (e.g., altering soil composition, light availability, or nutrient cycles). These changes can make the environment more suitable for other species and less suitable for the pioneer species.

4. Stabilisation: This is the final phase where a relatively stable climax community is established. The ecosystem reaches equilibrium, and significant changes in species composition cease.

Thus, the correct sequence is Migration → Ecesis → Reaction → Stabilisation, making option d the correct answer.