Video Transcript
What am I? I have six jointed legs. I have two pairs of wings. I collect nectar from flowers. (A) Housefly, (B) spider, (C) ant,
(D) scorpion, or (E) bee.
This question is asking you to
identify an animal from some of its structures, which involves the process of
classification. So, let’s review some key facts we
need to know about the classification of animals so we can come up with the correct
answer.
Classification is the arrangement
of organisms into taxonomic groups according to their observed similarities. We start with large groups of
organisms and break these down into smaller and smaller groups of organisms, which
have more and more similar features. If we look at the animal kingdom,
it can be split into vertebrates and invertebrates. Vertebrates have a backbone, and
invertebrates do not.
Looking at the question, all the
answer options are organisms without backbones. So, we will now look at the
invertebrates more closely. Although invertebrates do not have
an internal skeleton, also known as an endoskeleton, many of them have a rigid
external covering, called an exoskeleton. If we look at the first parts of
these names, endo- means “inside,” and exo- means “outside.” Both endo- and exoskeletons provide
structural support and protection to the internal organs and tissues of the
animal.
The invertebrates can then be split
down into smaller groups, one of which is the arthropods. An arthropod is an invertebrate
animal with an exoskeleton, segmented body, and jointed appendages. Appendages are parts that stick
out, such as legs and antennae. Arthropods can be further divided
into subgroups, largely according to the number of legs they have. These subgroups include the
arachnids, myriapods, and insects. So, let’s look at the differences
between them.
Arachnids are a group that includes
spiders and scorpions. They have a body made up of two
segments: the front one called the cephalothorax and the rear one, the abdomen. They have eight legs attached to
the cephalothorax, but no wings. If we look at the question, it is
asking for an organism with six legs. Spiders and scorpions are arachnids
with four pairs of legs. Therefore, we can rule out options
(B) and (D) from our possible answers.
So, what about myriapods? These have a body made up of many
segments, and they have a pair of legs attached to nearly all of them, meaning they
have lots of pairs of legs. The name “myriapod” comes from the
Latin for “many feet.” Some examples of myriapods are
centipedes and millipedes, which have varying numbers of legs, from 30 to 750!
Lastly, we come to the insects. Insects have three clear segments
to their body, called the head, thorax, and abdomen. Attached to the thorax, they have
three pairs of jointed legs and often one or two pairs of wings. Examples include bees, ants, and
houseflies, all of which are mentioned in the answer options. We therefore cannot eliminate any
of these options on leg number.
So, how about wing number? Houseflies, bees, and some ants
have wings. The worker ants do not have
wings. It is normally just the males and
queen ants that do, and they have two pairs. You tend to only see flying ants
during their reproductive season, when they are looking for a mate. Houseflies have one pair of
wings. What used to be a second pair has
evolved over millions of years to become a pair of small structures called halters,
which help the flies balance when they are in the air. This means we can rule out option
(A) housefly, as we are looking for an animal with two pairs of wings.
Bees have two sets of wings: the
large forewings and the smaller hindwings. When flying, these pairs of wings
hook together to form a set of large wings, which is why you may be mistaken that
they only have one pair. Both the housefly and bee have a
long, tonguelike structure called the proboscis, which acts as a straw to suck up
their food. Bees use the proboscis to suck up
nectar from flowers, a substance rich in sugars.
Ants have chewing mouthparts,
called mandibles, to break their food apart. We can therefore rule out ants from
the possible correct answer as they have the wrong mouth parts to collect nectar
from flowers.
We now know that the correct answer
to our question is option (E). The animal that has six jointed
legs, two pairs of wings and collects nectar from flowers is a bee.
