Video Transcript
Which of the following
characteristics would help distinguish an arthropod from a mollusk? (A) The absence of a backbone. (B) A body divided into distinct
segments. (C) Having a single opening acting
as both the mouth and the anus. (D) Possessing extensions from the
body or appendages. Or (E) the absence of a complex
nervous system.
Arthropods and mollusks belong to
the phyla Arthropoda and Mollusca, respectively, which are both a part of the
invertebrate group of the animal kingdom. As invertebrates, they share some
characteristics. First and foremost, being
invertebrate means they have no backbone. Both arthropods and mollusks are
complex invertebrates, and so they have extensions or appendages attached to their
bodies. And they also have separate
openings for their mouth and anus. Therefore, we can eliminate answers
(A), (C), and (D), as these indicate characteristics that these two phyla have in
common.
What are the differences? Let’s first look at mollusks. Some common examples of mollusks
include snails, oysters, and octopus. All of these animals have a soft
fleshy body. They also have a muscular foot for
movement and a fold of tissues called a mantle, which secretes a hard shell. Some mollusks, such as the octopus,
have a complex nervous system, whereas others have a much simpler nervous
system.
Arthropods, on the other hand,
include organisms such as lobsters, spiders, and scorpions. These organisms have bodies that
are divided into segments and are covered by a hard exoskeleton. On the other hand, mollusks do not
have segmented bodies. So the correct answer is (B). A body divided into distinct
segments is a characteristic that could be used to distinguish between an arthropod
and a mollusk.
