1. Differentiate the three types of symbiosis
2. Describe the different ways to classify parasites
3. Discuss the costs and benefits of endo and ecto
4. Differentiate between parasite and parasitoid
6. Explain why small is good
Chicken body louse
Chicken feather louse
In this unit we will discuss insects that parasitize humans, mammals, and other
arthropods. You will first learn the difference in three symbiotic relationships, and
between parasite/parasitoid, parasitoid/predator, and you will learn about various
endo- and ectoparasites. Be prepared for some repugnant pictures that illustrate
some of the damage insect parasites can do to other animals.
textbook pages 328-348.
Symbiotic relationships refer to interactions between two different species. In fact,
when broken into its Greek roots, the word symbiotic means "life together."
means "together," and
means "life." In this unit you will first learn about three
different types of symbiotic relationships,
. The balance of the unit will then focus on different aspects of
parasitism. These terms are generally used to describe the relationship between
species but can also be used for interactions within a species, particularly humans.
relationships are those in which both species involved benefit. For
example, most friendships are a mutualistic relationship. As you can see in this
picture ants and aphids have a special mutualistic relationship. The aphids feed the
ants by secreting a sugary solution called honeydew through the tip of their
abdomen. The ants in return protect the aphid by attacking predators such as
Symbiotic Relationships Continued
relationships, one species benefits but the other neither profits
nor is harmed. In this picture, orchids are growing on the side of a tree. The
orchid needs the tree for support and protection, but the tree does not benefit
nor is it harmed by the orchid's presence.
Relationships in which one species benefits at the
expense of another is a
good example of this is a mosquito and human
relationship. As pictured here, this mosquito has
inserted her mouthpart into a human to draw out
blood. The human will have a nice itchy lump where
the mosquito has injected its poison, but the
mosquito will use the protein it got from the blood to
make her eggs.
Insects, more than any other arthropod class, practice parasitism. We humans are mostly aware
of the insect parasites that affect us. Mosquitoes seem to be everywhere we go. Your
household pets are commonly ailed by fleas, and schools often have to check for outbreaks of
lice among the students. Not only do insects harm us, but they also harm other mammals,
vertebrates, invertebrates and even members within their own class as depicted in the table