Multiple Choice
In an evolutionary tree depicting species 1 through 9, what does the common ancestor of all these species represent?
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1. Introduction to Biology
Introduction to Taxonomy
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A feature of bony fish not found in sharks is:
A
internal fertilization
B
cartilaginous skeleton
C
placoid scales
D
an operculum covering the gills
Verified step by step guidance1
Understand the key differences between bony fish (class Osteichthyes) and cartilaginous fish (class Chondrichthyes, which includes sharks). Bony fish have a skeleton made of bone, while sharks have a cartilaginous skeleton.
Review the term 'operculum.' The operculum is a bony flap that covers and protects the gills in bony fish. This structure is absent in sharks, which have exposed gill slits instead.
Eliminate the incorrect options: 'internal fertilization' is a reproductive feature found in some sharks, and 'placoid scales' are specific to sharks, not bony fish.
Recognize that the presence of an operculum is a distinguishing feature of bony fish, as it allows them to pump water over their gills for respiration even when stationary.
Conclude that the correct answer is 'an operculum covering the gills,' as this is a unique feature of bony fish not found in sharks.
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