Video Transcript
Which of the following is a
defining feature of an animal belonging to the vertebrate subphylum? (A) The animal develops an external
skeleton. (B) The animal develops a backbone
or spine. (C) The animal uses the environment
to regulate their own temperature. Or (D) the animal has a segmented
body.
The kingdom Animalia can be divided
into two subphyla: vertebrates and invertebrates. What distinguishes these two
groups? A key feature of animals belonging
to the vertebrate subphylum is the presence of a vertebral column, which is also
known as a spine or backbone. Invertebrates, on the other hand,
do not have a vertebral column. Instead, many invertebrates, such
as crustaceans like lobsters, have external skeletons to support and protect their
inner tissues and organs, while other invertebrates, like jellyfish, have no
skeleton at all.
As external skeletons are only
found in invertebrates and not vertebrates, which is the group that this question
concerns, option (A) cannot be the correct answer.
The use of the environment to
regulate body temperature is a feature of ectothermic animals. For example, many reptiles, like
lizards, bask in the Sun, using the heat it radiates to warm up their bodies. While all invertebrates are
ectothermic, only some vertebrates are. Ectothermy is therefore not a
defining feature of all vertebrates, as some, like us humans, are endotherms. Endotherms internally regulate
their own body temperature through mechanisms like sweating or shivering without
utilizing the external environment. This means that answer option (C)
can be eliminated as it does not appropriately describe all animals belonging to the
vertebrate subphylum.
While vertebrates do have
segmentation in their backbones, this feature is not exclusive to this subphylum as
some invertebrates, such as lobsters, also have segmented bodies. As a result, we can eliminate
answer option (D) too.
This leaves us with answer option
(B), which appropriately describes a defining feature of an animal belonging to the
vertebrate subphylum. The animal develops a backbone or
spine.
