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 according to this dichotomous key, any catfish must have a double dorsal fin, a small fin on the back near the tail, and barbs near the mouth. a single dorsal fin, no small fin on the back near the tail, and barbs near the mouth. a double dorsal fin, a small fin on the back near the tail, and no barbs near the mouth. a single dorsal fin, a small fin on the back near the tail, and barbs near the mouth.

Explanation:

To identify the traits of a Catfish using the dichotomous key:

1. Catfish is reached via step 6(a). Step 6 is linked from 5(a), which is linked from 1(a).
2. Step 1(a) = single dorsal fin; step 5(a) = small fin on back near tail; step 6(a) = barbs near mouth.

Answer:

a single dorsal fin, a small fin on the back near the tail, and barbs near the mouth.