Worms!
Flatworms
Roundworms
Segmented worms
Types of Worms
 Flatworms (Phylum Platyhelminthes)
 Class Turbellaria (Planeria)
 Class Trematoda and Monogenea (Flukes)
 Class Cestoda (Tapeworms)
 Roundworms (Phylum Nematoda and Rotifera)
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Ascaris
Hookworms
Trichinella
Pinworms
Filarial worms
 Segmented worms (Phylum Annelida)
 Class Oligochaeta (Earthworms)
 Class Hirundea (Leeches)
Flatworms: Phylum
Platyhelminthes
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Flatworms are the simplest creatures with bilateral symmetery.
They develop from three germ layers.
They do not have a hollow body cavity.
Because they are flat, they can exchange oxygen and CO2 with the
environment through diffusion.
They have no circulatory or respiratory systems.
They have an incomplete digestive system consisting of a gut with
a single opening.
Nerves and sensory organs are located at one end. This is known as
cephalization.
Many flatworms are parasites, living on or in other creatures.
Some are not and are found in freshwaters, marine, and terrestrial
environments.
Flatworms: Phylum Platyhelminthes
 Class Turbellaria:
 Includes the Planarians, such as Dugesia species.
 Feed by scavenging bits of decaying plant and animal matter.
 Food is ingested through a muscular tube which is extended out
from the body.
 How do they get ride of excess water?
 Flame cells draw in excess water; water is transport through
tubules and excreted through pores.
 What are the cerebral ganglia, and what do they do?
 Simple brain; respond to stimuli and transmit signals to muscles
 Describe two way Planarians reproduce:
 Sexually
 Fertilize each other and lay eggs on rocks or debris
 Asexually
 Worms splits in two by attaching to solid surface
Flatworms: Phylum Platyhelminthes
Planaria
Flatworms: Phylum Platyhelminthes
 Class Trematoda and Monogenea
 Consists of parasitic flukes.
 They can live in the blood, intestines, lungs, liver, or other organs
and are called endoparasites.
 Ones that live on the outside of their host are called ectoparasites.
 How does a fluke stick to its host and what else does this structure
do?
 Anterior sucker and ventral sucker
 Most flukes are hermaphroditic and have a complex life cycle that
involves more than one host.
 Once disease caused by flukes includes Schistosomiasis which
affects more than 200 million people each year in Asia, Africa, and
South America.
Flatworms: Phylum Platyhelminthes
Flatworms: Phylum Platyhelminthes
 Class Cestoda
 Also known as tapeworms, which can live in the intestines of
almost all vertebrates.
 At the anterior end is a structure known as the scolex. What is
its structure and function?
 Has hooks and suckers that enable the worm to attach to its
host.
 Behind the scolex are the body segments called proglottids.
 What happens to these during reproduction?
 They grow in length; become fertilized from another either
from same individual or another individual.
 How can a human become infected with a taperworm?
 When they eat undercooked beef
Flatworms: Phylum Platyhelminthes
Tapeworm
Roundworms: Phylum Nematoda and
Rotifera
 Roundworms have bilaterally symmetrical bodies and a
fluid filled space to store eggs and sperm and for support.
 They have a complete digestive system, that is, one with two
openings, unlike cnidarians, ctenophores, and flatworms.
 They have separate sexes. The vast majority are free-living
on on land and in the water, and are parasites of plants and
animals.
Roundworms: Phylum Nematoda and
Rotifera
 Ascaris
 Live in intestines of humans as larvae, then move to bloodstream and
are carried to lungs and throat can block air passages and cause
bleeding.
 Hookworms
 Go through feet and travel through blood to lungs and throat
 If ingested, they will move to intestines and develop into adults
 Trichinella
 Live in intestines; larvale travel through blood stream to muscles and
form cysts, causing muscle pain and stiffness (trichinosis)
 Pinworms
 Live in intestines; tiny white threads in the lower intestines; females
come out at night and lay eggs on anus which spreads via scratching.
 Filarial worms
 Elephantitis infects lymphatic system and is spread by mosquito
Roundworms: Phylum Nematoda
Ascaris
Roundworms : Phylum Nematoda
Hookworms
Roundworms : Phylum Nematoda
Trichinella
Roundworms : Phylum Nematoda
Pinworms
Roundworms : Phylum Nematoda
Filarial worms
Segmented worms: Phylum Annelida
 Feather-duster worms, common earthworms and
leeches, are all members of this phylum.
 The phylum name means little rings.
 These organisms are bilaterally symmetrical and, like
mollusks, have a true coelom, a complete internal body
tube
 What does this structure allow to happen when the organism
moves?
 It allows the body to contract.
 Most have external bristles called setae.
 All organ systems are well-developed.
Segmented worms: Phylum Annelida
 Class Oligochaeta:
 The most familiar members of this class is the earthworm.
 Describe how it moves (and the structures involved):
 Thay have a fluid skeleton, and to move forward, they squeeze circular muscles of each
segment, to extend their body.
 They use their rough bristles to grip the surface of the ground at the front, then use
longitudinal muscles to pull their ends up to meet the front
 Complete or incomplete digestive tract? Explain.
 Complete two openings and one-way
 Open or closed circulatory system? Explain.
 Closedvia two main blood vessels, dorsal and ventral
 Oxygen and CO2 diffuse directly through the skin.
 The nervous system consists of a chain of ganglia connected by a ventral nerve cord.
 How do earthworms reproduce? Be sure to mention any special structures and their
functions
 Two press their ventral surfaces together with anterior ends pointing in opposite
directions
 They are held be setae and clitellum
 Exchange sperm with each other, ideally fertilizing each other (they are hermaphodites!)
Segmented worms: Phylum
Annelida- Earthworms
Segmented worms: Phylum Annelida
 Class Hirudinea
 Consists of about 500 species of leeches.
 They have no setae. At each end is a sucker that can attach to
surfaces.
 What two things do they secrete when they suck blood?
 Anaesthetic
 A substance that prevents blood from clotting
Segmented worms: Phylum
Annelida- Leeches