In ecotoxicology studies, ED-50 is ________ 

The correct answer is the dose that affects 50% of the population or observed subjects.

 Key Points

• The ED-50 is the dose required to achieve 50% of the desired response in 50% of the population.
• It is thus calculated from a dose-response curve by dropping a line on the dose axis where 50% of the desired response is seen. 
• The ED-50 of any toxicant varies depending on the effect measured.
• In general, the less severe the effect measured, the lower the ED-50 for that particular effect.
• Toxicants are not tested in humans in such a fashion.
• Instead, animals are used to predict the toxicity that may occur in humans. 

​Therefore, the correct answer is the dose that affects 50% of the population or observed subjects.