Which would be a pair of ecological equivalents?

Question

zooplankton andsea anemone
salmon and seagull
rattlesnake and desert rat
elephant and hyena
zebra and wild horse

Answer 1

Remembering that ecological equivalents must resemble each other in some way, there's only one logical answer.

http://www.encyclopedia.com/doc/1O6-ecologicalequivalents.html

Answer 2

is it zooplankton and sea anemone?

if not, my second guess is zebra and wild horse

Answer 3

Then is it zooplankton and sea anemone?

Answer 4

I lean toward zebra and wild horse because they are similar.