Which organism is considered a tertiary consumer? 

A)  jellyfish 
B)  zooplankton 
C)  phytoplankton 
D)  osprey

Tertiary consumers are organisms that obtain energy by eating secondary consumers, which in turn eat primary consumers. Ospreys are birds of prey that feed primarily on fish, which are secondary consumers that feed on primary consumers such as zooplankton and smaller fish. Therefore, ospreys are considered tertiary consumers in this food chain. Jellyfish and phytoplankton are both primary producers and do not eat other organisms, while zooplankton are primary consumers that eat phytoplankton, making them secondary consumers themselves.