Question

Refer to this portion of a dichotomous key for fish identification to answer the question.

1. (a) Has a single dorsal fin ® 5
(b) Has a double dorsal fin ® 2
5. (a) Has small fin on back near tail ® 6
(b) Has no fin on back near tail ® 7
6. (a) Has barbs near the mouth ® Catfish
(b) Does not have barbs near the mouth ® 10

What do the numbers after the arrows represent?