What is growth?

Explanation

### Step-by-Step Text Solution

1. **Definition of Growth**: Growth can be defined as an increase in size, mass, or number of cells in an organism. It is a fundamental characteristic of living organisms.

2. **Irreversibility**: One of the key aspects of growth is that it is irreversible. Once an organism or a cell has grown, it cannot return to its previous size. This distinguishes growth from other processes that may involve temporary changes.

3. **Levels of Biological Organization**: Growth occurs at various levels of biological organization:
- **Cell Level**: The basic unit of life is the cell. When a cell increases in size, it contributes to the overall growth of the organism.
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