14.7. Vespula pensylvanica: Yellowjacket Wasp http://www.ck12.org
instance, red blood cells are shaped with a pocket that encloses oxygen, and carries it to other body cells. Then there
are nerve cells, which are long and stringy, so that they can form a line of communication with other nerve cells, like
a wire. Because of their shape, they can quickly send signals. Cells are shaped in ways that help them do their tasks.
Yellowjackets are multicellular organisms and have many types of specialized cells in them.
Evolution
The yellowjacket wasp didn’t evolve from honey bees, even though it has been said before. The reason that’s
been said before is because honey bees and yellow jackets do have a similar ancestor in their background. But
they’re neither a bee nor ant. Yellowjackets evolved several traits before vertebrates (animals characterized by a
segmented spinal column and a differentiated head) even appeared. These traits are found in most animals. The first
yellowjacket trait to evolve was “multicellularity”, a highly adaptive change. Many cells can do different jobs. They
can make special changes that enable them to do their work very well. However, the first invertebrates still needed
tissues. Sponges are the first organism at the multicellular stage of invertebrate evolution.
Living cnidarians (invertebrate animals of the phylum Cnidaria) like jellyfish, are the next part of invertebrate
evolution. This was the first step in the evolution of organs and organ systems. At first, invertebrates created
tissues from just two embryonic cell layers. There was an outer cell layer called “ectoderm” and an inner cell called
“endoderm”. Both cell layers allow different kinds of tissue to form.
A trait that evolved very early is symmetry. A sponge doesn’t have symmetry. This means that it can’t be cut in two
identical halves. The coral polyp and the beetle have symmetry. The coral polyp has radial symmetry, which was
the first type of symmetry to evolve. The coral has a distinct top, as well as bottom, but not distinct ends. It can be
split into equal halves like a pie, but not in right and left halves. Animals that have radial symmetry have no sense
of direction, which makes controlled movement impossible.
Flatworms are the next level of invertebrate evolution. They evolved cephalization, which is adaptive and gives
control of the whole organism. Cephalization was the first part in the evolution of a brain.
Cephalization created bilateral symmetry. This allows the animal to tell the difference between different movements,
which is of course it needs to control its direction.
Ancestors of the flatworms also evolved a mesoderm. The mesoderm is the last layer of cells that are in middle of
the ectoderm and the endoderm. The evolution of this new cell layer lets animals make new tissues such as muscle.
Early invertebrates didn’t have a digestive system. There was only one opening for the mouth and anus. The first
roundworms were the start of animals developing a complete digestive system. They had a separate mouth and anus,
which allowed food to go through the body in a single direction. This all made up the evolution of the digestive
system.
The first roundworms evolved a pseudocoelom. This is a body cavity that is full of liquids. It gives space for the
inner organs to develop.
Segmentation evolved next. This is the body breaking up into many parts. The earthworm and the ant both have
segmented bodies, which gives them more flexibility. This also gives them better movement. All arthropods also
evolved jointed appendages. For example, they evolved jointed legs for walking, and antennas.
Ecology
These types of wasps mainly feed on other insects, and a common favorite is flies. Yellowjacket wasps eat spiders
and insects, as well as human food. The human food diet includes meats, sweets, picnic trash, bird feeder seeds,
sodas, and fruits. Many adults eat nectar, and larvae feed on pre-chewed food. They look for sources of food within
a mile of the nest. They don’t leave stingers in skin, unlike bees. The stinger goes in smoothly, so they can sting a
person multiple times. The yellow jacket’s nest is very easy to see if you’re outside, and hard to see if you’re inside.
You can sometimes hear them in the walls of complexes, if they have built a nest there. Yellow jackets are attracted