Question

what is Book gill and what is Book lung?
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Answer 1

Answer:

It is believed that book lungs evolved from book gills. Although they have a similar book-like structure, book gills are external, while book lungs are internal. ... Book gills are flap-like appendages that effect gas exchange within water and seem to have their origin as modified legs.

Answer 2

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It is believed that book lungs evolved from book gills. Although they have a similar book-like structure, book gills are external, while book lungs are internal. ... Book gills are flap-like appendages that effect gas exchange within water and seem to have their origin as modified legs.