To find out how many students are in the Environmental Club, we need to calculate 25% of the total number of students, which is 200.
First, we convert 25% into a decimal: \[ 25% = \frac{25}{100} = 0.25 \]
Next, we multiply the total number of students by 0.25: \[ 0.25 \times 200 = 50 \]
Therefore, the number of students in the Environmental Club is \( \boxed{50} \).