Planarians lack dedicated respiratory and circulatory systems. this deficiency does not cause a problem because planarians lack dedicated respiratory and circulatory systems. this deficiency does not cause a problem because they lack mesoderm as embryos and, therefore, lack the adult tissues derived from mesoderm their body cavity, a pseudocoelom, carries out these functions their flame bulbs can carry out respiratory and circulatory functions none of their cells are far removed from the gastrovascular cavity or from the external environment

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 2. (a) one fin is spiny, the other is smooth ® 3 (b) one fin is not spiny or smooth ® 4 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 7. (a) tail is asymmetrical ® 8 (b) tail is symmetrical ® 9 10. (a) scales are small ® trout (b) scales are large ® whitefish what is the next step to complete to identify a fish that has a single dorsal fin, no fin on the back near the tail, and no barbs near the mouth? step 2 step 5 step 7 step 10