To determine the birthrate of a population, we use the formula:
[tex]\[ \text{Birthrate} = \frac{\text{Number of New Individuals}}{\text{Original Population Size}} \][/tex]
In this scenario:
- The original population size is 1000 individuals.
- The number of new individuals born over the period of 1 year is 300.
Substituting these values into the formula, we get:
[tex]\[ \text{Birthrate} = \frac{300}{1000} \][/tex]
After performing the division, we obtain:
[tex]\[ \frac{300}{1000} = 0.3 \][/tex]
Therefore, the equation that correctly shows how to calculate the birthrate of this population is:
[tex]\[ D. \frac{300}{1000} = 0.3 \][/tex]
So, the correct answer is:
[tex]\[ \boxed{D} \][/tex]