Video Transcript
The figure shows a member of the
animal kingdom. To which arthropod subgroup does it
belong?
This question is asking us to
identify the subgroup of arthropods that this animal belongs to. To answer this question correctly,
let’s review some key features of arthropods and how they are further split down
into smaller groups.
Taxonomy is the science of
classifying organisms into hierarchical groups according to their shared
characteristics. Hierarchical grouping means that we
start with larger groups, such as the kingdoms. Here, we will start with the animal
kingdom. Animals are then split into
vertebrates, those with a backbone, and invertebrates, those without a backbone. The invertebrates and vertebrates
then break up into smaller groups, which then break down into smaller groups, and so
on, until we end up with a very small groups called species.
The arthropods is the largest group
of invertebrates. Arthropods have an exoskeleton, a
body made up of segments and jointed appendages. Appendages are parts that stick
out, such as legs and antennae. An exoskeleton is a rigid covering
found on the exterior of some animals. It provides structural support and
also protects the tissues and organs underneath. The arthropods can be split down
further into smaller subgroups. The number of legs the arthropod
has helps determine which subgroup they belong to. Insects, for example, have six legs
and a body made up of three segments, called the head, thorax, and abdomen. The legs, and usually one or two
pairs of wings, are attached to the middle section, the thorax.
Another subgroup is the
arachnids. These have four pairs of legs. Their body is split into two
segments: the cephalothorax, to which the legs are attached, and the abdomen. The arachnids include spiders and
scorpions. Myriapods have a body made up of
many segments, and they have a pair of legs on most of these. This means they can have an awful
lot of legs. Centipedes and millipedes belong to
this subgroup. Centipedes have between 34 and 354
legs, and millipedes have up to 750.
If we look at the picture in the
question, which is a picture of a scorpion, we can count the number of legs it
has. This is the easiest way to
determine which subgroup it belongs to. We can only count down one side of
it, but this will give us the number of pairs of legs it has. We can see this animal has four
pairs of legs. Therefore, the correct answer to
this question is, the arthropod subgroup that this animal belongs to is the
arachnids.
