Which of the following classes is
not a class of the vertebrata subphylum? (A) Amphibia, (B) Reptilia, (C)
Arthropoda, (D) Aves, or (E) Mammalia.
The kingdom Animalia can be divided
into vertebrata, animals with vertebral columns, sometimes called spinal columns or
backbones, and invertebrata, which are animals without vertebral columns. Let’s take a look through the
answer options to see whether these different classes are assigned into the
vertebrate or invertebrate group.
Amphibia is a class of vertebrates
called amphibians that live in wet environments and have soft, often slimy,
skin. As amphibians do have vertebral
columns, we can eliminate answer choice (A) as the question is asking for an option
that is not a class in the vertebrata subphylum.
Reptiles belong to class Reptilia
within the vertebrate subphylum and can be distinguished by their hard, dry,
keratin-based scales. As reptiles also have backbones, we
can eliminate answer choice (B) as well.
The class Aves is a group in the
vertebrata subphylum composed of birds. These are feathered animals that
tend to have beaks, lay eggs, and have a strong, lightweight skeleton. As this skeleton includes a
backbone, we can also eliminate answer (D).
Mammalia is a class of vertebrates
which includes organisms like humans that usually have hair or fur and whose
biological females tend to have mammary glands that produce milk for any offspring
they might produce. Mammals like us have backbones, so
answer option (E) is also incorrect.
The class Arthropoda consists of
organisms, like insects and crustaceans, that have segmented bodies and
exoskeletons, which are sometimes called external skeletons, rather than the
internal skeletons of the groups we have explored so far. As they do not have internal
skeletons, arthropods do not have a vertebral column either and so are classified
within the invertebrata subphylum. This means that we’ve found the
correct answer to this question. The class that is not in the
vertebrata subphylum is (C), Arthropoda.