Analysis:
To determine the relationship between the feature PAQ605 and the target variable (age group), we will compare the values of PAQ605 for the two target classes: Adult and Senior.

Based on the description of the feature, a value of 1 indicates that the respondent takes part in weekly moderate or vigorous-intensity physical activity, while a value of 2 represents that they do not engage in such activities.

Since the target variable is age group, we need to consider the different levels of physical activity typically associated with adults and seniors. Generally, adults are more likely to engage in regular physical activities, while seniors might have a lower proportion engaging in moderate or vigorous-intensity activities.

Let's calculate the relationship between the feature and the target variable by examining the PAQ605 values for the different age groups.

Dictionary:
Based on the analysis, the dictionary representing the relationship between the feature PAQ605 and the target classes, 'Adult' and 'Senior', will have the following format:

```json
{
	"Adult": [1.0, 1.0, 1.0, 1.0, 1.0],  
	"Senior": [1.0, 2.0, 2.0, 2.0, 2.0]  
}
```

Please note that the values provided in the dictionary are just examples and should not be considered as the actual values.