Video Transcript
Organisms belonging to the class
Osteichthyes are more commonly known as bony fishes; an example is pictured. Which of the following is not a
characteristic of an organism in the class Osteichthyes? (A) Their skeletons are formed from
bones. (B) They possess an air bladder to
help them swim or float. (C) Their bodies are covered in
skin. Or (D) they have paired fins.
Osteichthyes are one of three
classes of organisms that are commonly referred to as fish. Organisms within this class have
many characteristics in common, and the question is asking us to find out which of
these answers is not one of the shared traits. Organisms, like the one pictured,
belonging to class Osteichthyes have skeletons made out of bone tissue, which
explains the common name of this group, bony fish. This can be contrasted with
organisms like sharks that belong to a different class of fish, Chondrichthyes,
which have skeletons made out of cartilage.
As answer option (A) states that
their skeletons are formed of bones, and we are looking for an answer that is not a
feature of organisms in the class Osteichthyes, this cannot be the correct answer to
our question.
A distinguishing feature of fish in
the class Osteichthyes is that they possess a structure called a gas bladder,
sometimes called an air bladder or swim bladder, which helps the fish to remain
buoyant and a float at a fairly constant water depth without expending excess
energy. As a result of finding out this
information, we can eliminate answer option (B).
All fish belonging to class
Osteichthyes have paired fins either side of a line of symmetry along their body to
help them move, stop, and turn in water. This means that answer option (D)
is also incorrect.
Fish in this class tend to be
covered with scales that are flat, translucent, and smooth. This means the answer option (C),
their bodies are covered in skin, is not a characteristic of an organism in class
Osteichthyes.
From this, we can deduce that the
correct answer to this question is (C). The feature that is not a
characteristic of an organism in the class Osteichthyes is that their bodies are
covered in skin.
