Production and productivity can be represented by `ul(x)` and `ul(y)` respectively.

Answer

### Step-by-Step Solution:

1. **Understanding Production**:
- Production refers to the total amount of output generated from a given set of inputs. It is the process of converting raw materials or resources into finished goods or services.
- In ecological terms, production can be measured in terms of biomass generated in a specific area over a specific time period.

2. **Representation of Production**:
- In this context, production is represented by `ul(x)`, where `x` signifies the total production.
- The unit of measurement for production is typically expressed in grams per square meter (g/m²).

3. **Understanding Productivity**:
- Productivity, on the other hand, measures how efficiently inputs are converted into outputs. It reflects the rate of production relative to the resources used.
- It is a time-related concept, indicating how much output is produced over a certain period.

4. **Representation of Productivity**:
- Productivity is represented by `ul(y)`, where `y` signifies productivity.
- The unit of measurement for productivity is usually expressed in grams per square meter per year (g/m²/year).

5. **Conclusion**:
- To summarize, `ul(x)` represents production (g/m²), and `ul(y)` represents productivity (g/m²/year). The distinction lies in the fact that production is a measure of total output, while productivity measures the efficiency of that output over time.