Unit 10 – Flatworm, Roundworm and Segmented Worms
Flatworms
Characteristics of Flatworms
Flatworms (phylum ______________________________) are a step “up” the ladder of
evolution being ________________________________________________________.
Flatworms have a _____________________________. This body plan means they have
___________________________________________________________________________
__________________________. However, _______________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________.
These specialized systems are exemplified by the Planaria which is a heterotrophic free-living
flatworm.
There are three Classes of flatworms.
Class Turbellaria – example Planaria free living, incomplete gut, no suckers or
hooks.
Class Trematoda – example flukes parasitic, incomplete gut, _____________
_________________________________.
Class Cestodae – example tapeworms parasitic, no gut, ___________________
_________________________________
_________________________________.
Body Plan Summary
- Both primitive and advance characteristics
- ____________________________________________.
- ______________________________________
- ______________________ - concentration of sensory
organ and nervous tissue at anterior end of body
- ________________________________________
___________________________________________ (germ layers).
- Ectoderm – forms outer epidermis.
- Mesoderm - forms muscle tissue and reproductive, and excretory organs.
- Endoderm – forms inner gut.
- ____________________________________________
Movement
Some larval stages move using cilia while adults move using muscle contractions.
Class Turbellaria
Planaria __________________________________________________________________
___________________________. The __________________________________________
___________________________________________________ on the end of a muscular
___________________________________________________________________________
___________________________________________________________________________
to the body. Indigestible wastes leave the same way they came in through mouth.
There are approximately 4,500 species that live in the ________________. Some live in
________________________
Planaria Digestive System
The digestive system in Planaria is similar to that of the cnidarians. It consists of a _________
_____________________________. A pharynx extends from the underside of the flatworm
and sucks up food through the mouth. The food is then ______________________________
___________________________.
Wastes are expelled through the
same opening. Nutrients can be
carried through the organism
efficiently by ________________
because the flatworm is so thin.
Label Planaria Digestive System
Planaria Excretory System
Excretion is the expulsion of excess water and wastes. These wastes differ from those
expelled from the gastrovascular cavity in
that wastes excreted by the excretory
system were first digested and entered
the body of the flatworm. Planarians have
specialized cells called
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
Planaria Reproductive System
Planarians are ___________________________, meaning they
are ______________________________________, but they
______________________________________ between
organisms. Adjacent flatworms will align themselves so that they
will simultaneously fertilize each other. Planaria also have
amazing _________________________________________. If a
planaria is cut lengthwise, it will grow into two separate animals.
And, if a planarian is cut down the center, but not completely, it
will develop two heads.
Label Planaria Reproductive System
Planaria Nervous System
The nervous system of the planarian consists of
______________________________________
______________________________________
______________________________. This type
of nervous system is referred to as a
___________________________. The
cephalization consists of a brain, chemosensitive
organs, and two eyespots. The chemosensitive
organs guide the flatworm toward food and the
eyespots are sensitive to light. Planaria will move
away from light probably to avoid predation. The
nervous system also controls muscles used for movement.
Other Systems in Planaria
CIRCULATORY and RESPIRATORY SYSTEMS – not true systems
- part of the gastrovascular cavity.
- ____________________________________________________________________
_______________________________________________.
MUSCULAR SYSTEM – a true system.
-controlled by longitudinal, circular, and oblique layers of muscle
sometimes assisted by secreting a layer of mucus.
SKELETAL SYSTEM – NONE
Class Trematoda
There are an estimated 9000 species of Trematoda. Many of these are ______________
(liver, lung, heart, intestine).
Flukes are _________________________. Flukes have _____________________________
___________________________________________________________________________
___________________________. They absorb nutrients through the gastrovascular cavity.
They have ___________________________ for excretion. Nerve cords and anterior ganglia
make up the nervous system. They are _______________________________. Flukes have a
_______________________________________ with numerous larval stages that infect a
number of hosts.
The entire external surface of a fluke is covered by a continuous sheet of fused cells called the
____________________________. The ________________________ consists of a layer of
protein and carbohydrates that __________________________________________________
______________________________________________________.
Liver Fluke Life Cycle
Class Cestoda
There are an estimated 5000 species of Cestoda. An example is tapeworms.
Tapeworms are ________________ animals
and are specialized for living within a host.
Most body systems have been lost as they are
not required as the host provides nutrients.
There are ___________________
___________________________________
__________________________. Tapeworms
____________________________________
__________________ through their skin. The
____________________________________
____________________________________
This adult tapeworm has a _____________________________________________________
___________________________________________________________________ While the
tapeworm grows in the host's intestine, ___________________________________________
__________________________________________________________________________.
This species occurs most often in rabbits, cats and rodents, but sometimes humans, causing
diarrhea, weight loss and abdominal discomfort. Adult tapeworms may grow 5-10 meters in
length.
Proglottids are body segments
specialized for reproduction
Tapeworms have a Scolex with hooks and
suckers used to attach to the inside wall of
the host intestine
Tapeworm Life Cycle
Tapeworm Reproduction Summary
- Carried out by ______________________
______________________________.
- Tapeworms are ____________________ contain both ovaries and testes and ______
___________________________________.
- Zygotes are passed out of host’s body with
feces.
- Larvae hatch in water and in grass.
- Larvae are eaten by a herbivore
(________________________________)
and the larvae then burrows through the wall
of the intestine and into the blood stream.
Intermediate hosts contain tapeworm cysts
(__________________________________________________________________________
___________________________________________________________________________
______________________________________________________.
MMmmm Tapeworms
As part of a University of Salford experiment to develop a diagnostic test for beef tapeworm,
biologist Mike Leahy volunteered to grow this gruesome parasite inside his own gut. Mike
swallowed the immature tapeworm cyst with a glass of red wine and the worm started to grow
at an initial rate of four centimetres a week. Twelve weeks later he had to call a halt to the
unusual experiment because he was getting married! After a dose of anti-worm pill Mike
passed out an intact tapeworm three metres long.
Parasitic Flatworms
Flatworms that are parasitic on humans fall into two categories, _______________________
_________________. Due to the fact that they live in the gut of a host animal these flatworms
have an anatomy __________________________________________. Generally, _________
___________________________________________________________________________
________________________. Parasitic flatworms will usually have hooks on the scolex
(anterior region) to attach it to the wall of the gut and they have an ______________________
______________________________________________ When a flatworm reproduces, the
eggs are passed out with the feces. When consumed by another host the life cycle continues.
Flukes and tapeworms can infect many different animal hosts. _________________________
___________________________________________. One host when sexually mature called
the primary host and a secondary host in which the eggs mature to larvae.
Roundworms
General Characteristics Roundworms
Roundworms belong to the Phylum ______________________________ (also called
___________________________).
Nematodes are the most speciose phylum after the arthropods.
They occur in nearly every habitat including ________________
___________________________________________________
______________________ (they don't like dry places however).
One species is known that can live in old vinegar (Turbatrix aceti)
and another that has only been found in German beer mats.
Though only about 80 000 species have been described some
scientists estimate there may be as many as a million species all
told. They can occur in very dense numbers in the soil and rotting
vegetation, as many as 90 000 have been found in a single rotting apple, while millions occur
in the top 3cm (1 inch) of a square metre of good quality soil.
While there are a huge number of ______________________ Nematodes there are also a
large number of __________________________________, many of which cause diseases to
man and other animals as well as to plants, nearly every living organism has been found to be
parasitised by one species of nematode or another.
Most nematodes are reasonably small, they range in size from 100 micrometres in length
(1/10th of a mm or 1/250th of an in) to the female Giant Nematode Dioctophyme renale which
may be up to 1 metre, or 3 ft long.
Body Systems in Roundworms
Roundworms (phylum ____________)
have a _________________________
_______________________________.
This body plan is more advanced than
the Platyhelminthes and Cnidarians
which, you should recall from previous
units, have a single opening functioning
as a mouth and anus called a sac plan.
Nematodes _____________________
_______________________________.
This design allows for ____________
______________________________
______________________. At the
anterior (head) end there is a mouth which has 3 lips behind which predatory species possess
a few teeth, this leads to a ___________________. The pharynx of Nematodes is an efficient
pump and forces food into the intestines as it can be used to suck liquid food into the mouth.
________________________________________________________________________.
Digestive System
Roundworms have a __________________________________________. It is a long tube
shaped digestive tract with _____________________________________________________
___________________________________________________________________________.
As food is pushed through digestive tract it is digested and ____________________________
_________________________ into the cells of the body. Undigested remains continue on
through tract and are _________________________________________________________
_________________________.
Free living round worms are often _______________________________________________
___________________________________________________________________________
___________________________________________________________________________.
They excrete metabolic waste through their body walls by __________________.
Circulatory and Respiratory Systems
Roundworms have __________________________
_____________________________________. They
breathe and excrete waste through their body walls.
They do not have an internal transport (circulatory)
system and rely on ________________________.
The _____________________________ is filled with
fluid and it distributes digested foods and dissolved
oxygen to the body. It also acts as
___________________________________.
Excretory System
In roundworms, ____________________________________________________________
_______________________________________________________________________.
Nervous System
Nematodes, especially free living forms generally have a reasonably well developed nervous
system. This is comprised of a circum-pharyngeal nerve ring and longitudinal nerves that
extend down through the body to the various parts of the gut and the reproductive organs.
___________________________________________________________________________
___________________________________________________________________________.
They have simple sense organs.
Reproduction
Nematodes are copiously reproductive and most of their body cavity, which is a
_________________________________, is filled with paired sets of reproductive organs,
either ovaries or testes. _______________________________________________________
_____________________________________. The female has long coiled ovaries that
produce thousands of eggs every day. Eggs are stored in a uterus. The vagina leads to an
external opening. ____________________________________________________________
_____________________________________________. Sperm cells pass through the sperm
duct though an opening at the posterior end of the worm. During copulation sperm is released
into the vagina resulting in internal fertilization. After fertilization, _______________________
______________________________________. The females lay eggs over a prolonged time
period, thus a female Ascaris lumbricoides may lay her eggs at the rate of 200,000 per day
and have had a total 27 million eggs within her at the start of her reproductive career.
Summary
Primitive Characteristics :
- ___________________________.
- No circulatory System.
- No skeletal system.
- ________________________________________________
Advanced Characteristics:
- ______________________________________________.
- Cylindrical shape (round worms).
- _____________________________________________.
Ectoderm – produces tough cuticle.
Mesoderm – muscle and various organs.
Endoderm – digestive tract.
- ____________________________________________________ – mouth to anus!
- ___________________________ - between the mesoderm and the gut is a fluid filled
space.
Ascaris
Ascaris is usually diagrammed to typify roundworm anatomy. Ascaris is a roundworm that is
___________________________. The entire life cycle can take place in the human body and
the eggs can be passed out with feces. Eggs in food or water are _____________________
_____________________________, the eggs hatch in the small intestine, larvae enter the
blood vessels and are carried to the lungs, larvae then travel to the throat and are swallowed.
Adult ascaris worms live in the small intestine with eggs leaving the host in the feces.
With a longitudinal cross section the tube within a tube design can be observed. It can also be
observed that the digestive system is not very well developed as the length of the gut after the
pharynx is unchanged and reproductive organs are quite large in comparison to the body. This
is a characteristic of an internal parasite to have a simple digestive system and well developed
sex organs.
Ascariasis is the human disease caused by ____________________ with as many as
______________________________________________________. It is common in tropical
regions, regions with poor sanitation, poor personal hygiene, and places where human feces
are used as fertilizer. Intake of food or drink contaminated with Ascaris eggs causes the
infection.
The symptoms of Ascariasis are listed below.
Passing worms in stool.
Vomiting up worms.
Worms exiting through the nose or mouth.
Low-grade fever.
Cough.
Bloody sputum.
Wheezing.
Shortness of breath.
Skin rash.
Vomiting.
Stomach pain.
Note: There may be no symptoms.
Label Ascaris
Other Parasitic Roundworms
Even though ________________________________________________________________
____________________________________ are typically enough to ward off roundworm
infection many roundworm diseases are common worldwide including some in North America.
_________________________________ are common in North America, while more serious
infections such as ______________________________________ are common in Africa and
are rarely seen here.
Trichina worm causes
Trichinosis when the
host eats __________
____________________
____________________
____________________.
Trichinosis forms cysts in
the muscles of its victims
and causes symptoms
such as pain, blisters,
muscular weakness, and anemia. The images below show a
trichina worm and a cyst formed in muscle around a worm.
......
Pinworms are tiny pin-shaped nematodes known
as Enterobius vermicularis to the medical and
zoology communities. Also called seatworms or
threadworms these small, whitish roundworms
are responsible for contagious intestinal _______
_______________________________________
_______________________________________
_______________________________________
____________________________________________
Although adult pinworms inhabit the large intestine, the
eggs are laid outside of the anus during the night
creating a severe itching sensation. Other symptoms
include disturbed sleep, decreased appetite and weight
loss. Spread from person to person usually occurs with
____________________________________________
____________________________________________
____________________________________________
The eggs can also drift through the air where they are
inhaled or swallowed. Once they enter the new host the
eggs hatch in the small intestine and travel down to the large intestine for maturation.
_________________
_________________
_________________
_________________
_________________
_________________
_________________
_________________
_________________
Filaria worms __________________
_____________________________
_____________________________
_____________________________.
Elephantiasis is transferred by
mosquitoes and blocks lymph
vessels as the worms increase in
size. Lymph vessels return fluid to
the bloodstream from the tissues so
when the vessels are blocked the
limbs increase greatly in size.
Loiasis, called eye worm or loa
loa, is endemic to the rainforests
of central and western Africa
where mango flies of the
Chrysops species serve as both
intermediate host and the parasite
vector. About 13 million people
are currently infected.
This map shows the distribution of
eye worm infections.
Guinea worms, also known as the stick worm,
form ulcerating blisters in human skin. People
get infected when they drink standing water
containing a tiny water flea that is infected with
the even tinier larvae of the Guinea worm. Over
the course of a year in the human body, the
immature worms pierce the intestinal wall, grow
to adulthood, and mate. The males die, and the
females make their way through the body,
maturing to a length of as much as 3 feet, and
ending up near the surface of the skin, usually in
the lower limbs. The worms cause
____________________________
__________________________________
__________________. To soothe the burning,
sufferers tend to go into the water, where the
blisters burst, allowing the ______________
___________________________________
___________________________________. In
the water, the larvae are swallowed by small water
fleas, and the cycle begins again. These parasites
can cause long-term suffering and sometimes
crippling after-effects. The worms are slowly
removed from the body by winding them slowly
around a stick to pull them out.
Segmented Worms
General Characteristics of Annelids
The annelids or _____________________________________________________________
___________________________________________________________________________
____________________________________. The general characteristics of an Annelid are
similar to those of a roundworm. They are _________________________________________
___________________________________________________________________________
___________________________. However, an Annelid also has a _____________________
___________________________. Both the coelom and segmentaion allow for greater
specification of body parts. _____________________________________________________
and allow structural support by creating a hydroelastic skeleton. ________________________
___________________________________________________________________________
which will be discussed in the anatomy of the earthworm later in this lesson. The ___________
___________________________________________________________________________
__________________ (filtering organ) in each segment. The Annelid moves by alternating
contractions of circular and longitudinal muscles. The circular muscles encompass the body
wall and therefore contractions cause the body to become long and thin. The longitudinal
muscles run the length of the body and cause the body to shorten and fatten.
The Phylum name Annelida means "Ringed in Form". _______________________________
______________________________________________________________ within the
animal for different purposes. The coelom is divided into separate compartments (septa) by
partitions. These septa enable different compartments to contract or expand independently.
Duplication of some of the organ systems in each segment provides insurance against injury.
There are three Classes of Annelids that we will discuss in this book.
1. Class Polychaeta meaning "____________________________".
2. Class Oligochaeta which _________________________________________.
3. Class Hirudinea which ____________________________________.
Marine Worms
Class Polycaeta are so named because they have many _______
on their segments. These _______________________________
____________________________________________________
____________________________________________________.
In some marine worms they are arranged like a paddle and are
called _______________________________________________
___________________________________ because Annelids
breath through their body wall by _________________ and
parapodia expand the surface area of the animal. Some marine
worms such as Nereis have a more noticeable cephalization.
Nereis has an invertible pharynx that exposes chitinous (made of
chitin - a strong complex carbohydrate common to fungi cell walls
and some animals) jaws, eyes, and other sense organs. Some
marine worms have bristles to aid in defense. Nereis seen below is an example of a free living
predatory marine worm.
Predatory worms also have ____________________________________________________.
Other marine worms live in tubes that may be made of calcium, silica (sand) or protein. These
tube worms are filter feeders. Here's what these worms look like when retracted.
Earthworms
Segmented worms of the class ___________
___________ (maximum 20 setae per segment)
and are exemplified by the common
____________________, Lumbricus terrestris.
Earthworms do not have cephalization as
advanced as marine worms such as Nereis, but
they do _____________
___________________________________
______________________________. They do
not have eyes, but are capable of detecting and avoiding
water without actually coming in contact with it. Earthworms
live in soil and freshwater while some types are found in the
ocean. Earthworms act as ______________________,
maintain the fertility of soil, release nutrients into the soil,
loosen and ________________
________________________________________. Some
segmented worms such as the Tubifex (sludgeworm) seen in
the third picture can survive in polluted sediments and areas
with little oxygen.
Earthworm Digestion
The digestive system of the earthworm and other annelids is
quite advanced. In the earthworm, ______________________________________________
as they burrow ____________________________________________. From the pharynx food
moves through the ___________________________________________________________
____________________________. It ____________________________________________
___________________________________________________________________________.
The _______________________________________________________________________
________________________________________________________. The intestines have a
typhlosole, which is a fold that increases surface area for absorption. ____________________
_________________________ (castings that are good for the garden) __________________
_____________________________.
Here's an image showing Oligochaeta digestive system.
Earthworm Circulation
The circulatory system of an Earthworm consists of a ________________________________
___________________________________________________________________________
_______________________ that connect the two vessels together behind the head region.
The branches _______________________________________________________________
___________________________________________________________________________
_______________________________________________. Due to the pulsating action of the
branches, which is similar to the action of hearts, they are termed "hearts" or pseudohearts.
The purpose of this ___________________________________________________ is to
transport oxygen, carbon dioxide, nutrients and wastes throughout the body of the earthworm.
Earthworms have _____________________________________________________________
___________________________________________________________________________
and into small blood vessels when the skin is moist.
Earthworm Excretion
As stated in the general characteristics,
____________________________________
________________________. In earthworms,
____________________________________
____________________________________
___________________________________.
The cellular wastes and excess water are
eliminated through these nephridia. Each
segment of the earthworm except the first
three and last one have nephridia.
Earthworm Nervous System
The nervous system of an Earthworm is ____________
____________________________________________
______________________. Most body segments have a
single ganglion. These worms also have an __________
_____________________________________________
and can respond to light, touch, chemicals, moisture,
temperature, and vibrations.
Movement in these worms is made possible by
segmentation. ________________________________
____________________________________________
______________________. To move,______________
____________________________________________
and contracts circular muscles in front of these segments. Hydrostatic fluid in the coelom
increases pressure and elongates the worm. Then longitudinal muscles pull posterior
segments forward as they contract and shorten.
Earthworm Reproduction
Earthworms are ____________________________________________________________
__________________________________________________________________________.
The clitellum is the relatively large band around the earth worm. _______________________
________________________________________ (an individual worm cannot fertilize its own
eggs) by aligning head regions with clitellums. Two earthworms press their ventral surfaces
together with the anterior ends pointing in opposite directions. _________________________
___________________________________________________________________________
_________________________ as it transfers. Each earthworm injects sperm into the mucus
which moves into a pouchlike seminal receptacle of each worm. After several days each worm
secretes a tube of mucus and chitin (thick carbohydrate) which picks up the worms eggs and
stored sperm. The sperm and
egg are then expelled through
a slime tube and fertilization
takes place. The tube closes
up to form a protective case
for 2-3 weeks until the young
worms hatch.
Leeches
Class ________________________________________
_____________________________________________
with approximately 300 species. Although ___________
____________________________________________,
many leeches are annelids which are ______________
________________________________________________
_________________________________________. They
________________________________________________
________________________________________________
_____________________________________. They also
________________________________________________
________________________________________________
________________________. If undisturbed, a leech can
ingest 10 times its own weight in blood. A leech will drop off
once finished eating and will not need to eat again for up to a
year.
Leeches are used in medicine________________________
_________________________ in amputated digits (fingers or toes) that have been surgically
reattached.
Body Plan comparison in the Worms
This lesson compares the body plan of the three classes of worms discussed in this unit. The
diagrams below are keyed as follows.
Ectoderm: blue
Endoderm: yellow
Mesoderm: red
_________________________ ________________________
_________________________ ________________________
Body cavity filled with
Body cavity partially lined with
mesoderm.
mesoderm.
________________________
________________________
Body cavity entirely lined with
mesoderm.