What is sere ? It constitutes how many types of communities .

Explanation

### Step-by-Step Solution:

1. **Understanding Sere**:
- A sere is a term used in ecology to describe the sequence of changes in a community over time during ecological succession. It encompasses all the stages of development that an ecosystem goes through.

2. **Ecological Succession**:
- Ecological succession is the process through which ecosystems change and develop over time. It involves a series of stages where the composition and structure of a community change in response to environmental conditions.

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