Download A parasite is an organism that lives in or on the living tissue of a host

Beware - Parasites!!
A parasite is an organism that lives in or on the living tissue of a host organism at the expense of that host. The biological
interaction between the host and the parasite is called parasitism. Parasitism is a type of symbiosis.
Parasites are generally smaller than their hosts, absorbing nutrients from the host's body fluids, but this is far from a
universal strategy. Organisms whose life cycle guarantees the death of the host are not called parasites, but are
parasitoids. A few parasites have hosts which are themselves parasites. These are called hyperparasites.
Parasitism is an interaction between two organisms, in which one organism (the parasite) benefits and the other (the
host) is harmed. Parasitism can be considered a special case of predation since their effects on the host are similarly,
though not equivalently, detrimental. Parasites that live inside the body of the host are called endoparasites (e.g.,
hookworms that live in the host gut) and those that live on the outside are called ectoparasites (e.g., mosquitos). A
parasite that kills its host is called a parasitoid. Some parasites are social parasites, taking advantage of interactions
between members of a social host species such as ants or termites to their detriment. Kleptoparasitism involves the
parasite stealing food that the host has caught or otherwise prepared.
Many endoparasites acquire hosts by passive mechanisms, such as the nematode Ascaris lumbricoides, an endoparasite of
the human intestine. A. lumbricoides produces large numbers of eggs which are passed from the host's digestive tract
into the external environment, relying on other humans to inadvertently ingest them in places without good sanitation.
Ectoparasites, on the other hand, often have elaborate mechanisms and strategies for finding hosts. Some aquatic
leeches, for example, locate hosts by sensing movement and then confirm their identity through skin temperature and
chemical cues before attaching.
The hosts of parasites often evolve elaborate defensive mechanisms as well. Plants often produce toxins, for example,
which deter both parasitic fungi and bacteria as well as herbivores. Vertebrate immune systems can target most parasites
through contact with bodily fluids. Many parasites, particularly microorganisms, evolve adaptations to a particular host
species; in such specific interactions the two species generally coevolve into a relatively stable relationship that does not
kill the host quickly or at all.
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Examples of Ectoparasites (ecto = outside; parasites that live on but not within their hosts, for example, attached to their skin)
o Plants
 Cuscuta
 Mistletoe
 Toothwort
 The woodrose, Dactylanthus taylorii
o Animals
 Hirudinea (some leeches)
 Phthiraptera (Lice)
 Siphonaptera (Fleas)
 Acarina (Ticks)
Endoparasites (endo = within; parasites that live inside their hosts)
o Plants
 Rafflesia
o Animals
 Candiru (Vampire fish of Brazil)
Hookworm
 Clonorchis sinensis (the Chinese liver fluke)
 Dracunculiasis (Guinea Worm Disease)
o Fungi (such as ringworm)
 Gymnosporangium and other rusts
o Protists (Protozoa)
 Malaria (a common blood disease caused by plasmodium)
 Giardia lamblia (the most common intestinal protozoan in the United States)
Name:
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Date:
Parasites
1) What is a parasite?
Lice
2) How does a parasite get nutrition?
3) What is a hyperparasite?
4) What is the difference between an ectoparasite and an endoparasite?
5) Name two (2) ectoparasites and two (2) endoparasites.
Leech