Name ____________________________ Date ______________ Period ________
Biology
Unit 3 – Infectious Disease, Background Paper 3-6
Multicellular Parasite Infections
Three animal phyla account for the majority of multicellular parasite diseases.
Platyhelminthes – The Platyhelminthes are a diverse group of flat,
worm like organisms. Many are free living (class Turbellaria) and can
be found in most bodies of fresh water around the world. The parasitic
members of the phylum have adapted their life styles to successfully
live within another organism. They rarely kill their host as they absorb
nutrients from the host’s intestines or blood stream. The class Cestoda
includes a wide number of intestinal parasites collectively called
tapeworms1. The class Trematoda consists of parasites grouped under
the common name of flukes. Flukes affect many parts of the body
including the brain and blood.
Nematoda – The nematodes2, or non segmented roundworms, inhabit a wide
range of niches ( habitats). A shovel full of soil will contain a million or more of
these small worms. There are more than 30 species that exist as human parasites
and are present in all areas of the world. A few of the common infections include
hookworm, pinworm, guinea worm, trichina worm, and ascaris.
Arthropoda - The arthropods are the most numerous multicellular organisms
on earth, both in numbers of individuals and in number of species. The classes
that make up the phylum include
Insecta (insects), Crustacea (crabs
and lobsters), Arachnida (spiders), Diplopoda
(millipedes), and Chilopoda (centipedes). Those
arthropods that infect humans are primarily external
parasites. These include lice3, scabies, fleas, and ticks.
Mosquitoes and other biting insects are not normally
included since they do not remain on the host. They
do, however, play an important role in the transmission
of a number of infectious diseases since they transfer
Head Lice
blood from one animal to another.
1
Image public domain Center for Disease Control
Image public domain Center for Disease Control
3
Image CC BY SA Pediculosa
2
Background 3-6,Multicellular2012
Text 2012
Greg Ballog
Page 1
Name ____________________________ Date ______________ Period ________
Title of Reading: 3-6 Multicellular Parasites
Points Earned
1 2 3 4 5 6 7
Concept Map of Reading (3 points)
Main Idea
A) What one question do I have about this article?
1 Point
A&B
B) Show or describe the reading to a parent or guardian (Name ___________________).
What comments or questions did they have concerning the reading?
(Biology Homework Time __________)
Background 3-6,Multicellular2012
Text 2012
Greg Ballog
#
1
2
3
Answer
Page 2