Name: _________________________________
Pd. ______
Date: __________________
Section 27-1 Notes: Flatworms
What is a flatworm?
 Phylum Platyhelminthes
 No more than a few ___________________
thick
 Have _________________ and internal ________________
systems
 Have bilateral __________________ and ___________________
 Known as acoelomates (“without coelem,” which is a fluid
filled ______________________)
Form and Function in Flatworms
Feeding
 Digestive cavity with a single opening through which both
___________ and _______________ pass
 Parasitic worms obtain _________________ from foods that have
already been ___________________ by their hosts
Respiration, Circulation, and Excretion
 Rely on diffusion to:
 Transport _______________ and _________________ to internal tissues
 Remove __________________________ and other wastes from their bodies
 Have no gills or respiratory organs, ____________, blood vessels, or blood
 Some have flame cells – remove excess water and _________________________
from the body
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Response
 A head encloses several ganglia (groups of _______________________) that
control the nervous system
 Have eyespots that look like eyes, but are groups of cells that can detect
changes in the _________________________________ in their environment
Movement
 Two means of movement:
 ____________ to help glide through water
 Muscle cells allow them to __________________________
Reproduction
 Most are hermaphrodites that reproduce __________________
 A hermaphrodite is an individual that has both _________ and
__________________ reproductive organs
 Asexual reproduction takes place by fission, in which an organism
____________________________
Groups of Flatworms
 Three main groups of Flatworms
 Turbellarians
 ______________
 Tapeworms
 Most turbellarians are _______________________
 Most other flatworm species are ___________________
Turbellarians
 Free-living flatworms
 Live in _____________ or freshwater
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Flukes
 Class Trematoda
 Parasitic __________________
 Infect the ______________________________ of
their host
Tapeworms
 Class Cestoda
 Long, ________, parasitic worms
 Adapted to life inside the
__________________ of their host
 No ___________________ tract
 Absorb already _________________
nutrients from host
Review Questions:
1. What is an acoelomate?
2. What do flatworms rely on diffusion for?
3. What are two ways that flatworms move?
4. What are the three main groups of flatworms?
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Notes 27-2: Roundworms
What is a Flatworm?
 Phylum ___________________
 Slender, ________________________ worms with tapering ends
 Range in size from _______________________ to a meter
 Most are free-living, inhabiting _________ and
____________
 Others are _________________
 Have a pseudocoelom (“false ______________”)
 Have a digestive tract with two openings – a
______________ and an __________
Form and Function in Flatworms
 Have specialized ________________ and organ systems
 Body systems of free-living flatworms are more _______________ than parasitic
ones
Feeding

Predators that use grasping mouthparts to catch and eat _____________________
Respiration, Circulation, and Excretion
 Exchange _____________ and excrete metabolic ____________ through their body
walls
 Depend on _________________ to carry nutrients and waste through their bodies
Response

Simple __________________ systems

Have several types of ________________ organs
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Movement

______________ extend the length of their bodies
Reproduction

Reproduce _________________, and most have separate sexes
Roundworms and Human Disease
 Parasitic roundworms include:
 Trichinosis-causing worms
 _______________ worms
 Ascarid worms
 __________________
Trichinosis-Causing Worms
 Trichinosis – terrible _______________ caused by the roundworm Trichinella
 Adult worms live and mate in the __________________ of their hosts
 Humans usually get the disease from eating ________________________ pork
Filarial Worms
 Threadlike worms that live in ___________ of birds
and mammals
 Causes _______________________
Ascarid Worms
 Serious parasite of ___________________ animals
 Causes malnutrition in more than ___________________ people worldwide
 Absorbs ___________________ food from the host’s small intestine
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Hookworms
 25% of people in the ____________ are affected with hookworms
 Live in host’s ___________________
 Feed on blood, causing ____________________ and poor growth
Review Questions:
1. What is a pseudocoelom?
2. Name 2 things roundworms rely on diffusion for.
3. How do flatworms reproduce?
4. Name 3 parasitic roundworms that cause human disease.
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27-3: Annelids
What is an Annelid?
 Phylum ____________________
 Worms with _____________________ bodies
 Each segment is separated by a septum
 Have a true __________________
Form and Function in Annelids
 Feeding and Digestion
 Many get their food using a ___________________
 Food moves from the pharynx, into the _____________________, the
crop, the gizzard, and then to the _____________________
 Others obtain food by ______________ feeding
 Circulation
 Closed circulatory system – blood is contained within a _________________
of blood vessels
 Respiration
 Aquatic annelids often breath through ___________
 Land-dwelling annelids take in _______________ and give off carbon
dioxide through their moist __________
 Excretion
 Digestive wastes pass through the anus at the end of the
__________________ tract
 Cellular waste is _________________ through nephridia (excretory organs)
 Response
 Well developed nervous system consisting of a ____________ and several
___________ cords
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 Movement
 Two groups of muscles that work together as part of a
______________________ skeleton
 Reproduction
 Most reproduce _________________
 Some have _____________________ sexes, others are hermaphrodites
Groups of Annelids
 Three classes of Annelids
 Oligochaetes
 ____________
 Polychaetes
Oligochaeta
 Class Oligochaeta
 Contains ______________________ and their relatives
 Streamlined bodies
 Relatively _________ setae
 Most live in soil or _____________________
Leeches
 Class Hirudinea
 External __________________ that suck the
blood and body fluids of their host
Polychaetes
 Class ___________________
 Contains ____________________, blood worms, and relatives
 Marine annelids that have _____________, paddlelike appendages tipped with
setae (brushlike structures)
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Ecology of Annelids
 Earthworms and many other annelids spend their lives ____________________
through soil, ________________ and mixing it
 Earthworms help plant matter _____________________
 Earthworm castings are rich in _________________, phosphorus, potassium,
micronutrients, and beneficial _________________
Review Questions:
1. Name two ways that annelids get food.
2. What is a closed circulatory system?
3. Name the three classes of Annelids.
4. How are earthworms beneficial to life?
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Notes 27-4: Mollusks
What is a Mollusk?
 Soft-bodied animals
 Usually have an internal or external
______________
 Free-swimming _________________
stage called a trocophore
Form and Function in Mollusks
 True ________________
 Complex, interrelated ______________ systems
Body Plan
 Variation on four main parts:
 ___________ – takes many forms
 Mantle – layer of ___________________ that covers the mollusk’s body
 Shell – made by ______________ in the mantle
 Visceral mass – consists of _______________ organs
Feeding

Can be herbivores, ___________________, filter feeders, detritivores, or
__________________

Snails and slugs feed using a
________________________ structure called a radula

Clams, oysters, and scallops use ___________

Food enters through a siphon – _________________
structure through which water enters and leaves the
body
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Respiration
 Aquatic mollusks breathe using ___________ inside their mantle cavity
 Land snails and ___________ respire through the moist _______________ of their
skin
Circulation
 Some have ______________ circulatory systems – works well for __________moving mollusks (snails and clams)
 Others have ________________ circulatory systems – works best for ___________
moving mollusks (octopi and squid)
Excretion
 Nephridia remove wastes from the ____________ and release it
__________________ the body
Response
 Two-shelled mollusks have ______________ nervous systems
 Octopi and relatives have the most ________________________ nervous systems
of all invertebrates
Movement
 Move in a variety of ways
 Snails secrete ________________ and move over surfaces using the ________
 Octopi use a form a jet _________________
Reproduction
 Reproduce in a variety of ways
 Snails and two-shelled mollusks: __________________ fertilization (sexually)
 Tentacled mollusks and some snails: __________________ fertilization (sexually)
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Groups of Mollusks
 Three major classes:
 Gastropods
 Bivalves
 Cephalopods
Gastropods
 Class Gastropoda
 Shell-less or _______________-shelled
 Move using ________________ foot on ventral side
 Includes: pond snails, __________________, sea
butterflies, sea hares, limpets, and nudibranchs
Bivalves
 Class Bivalvia
 Have ____________________ held together by
one or two powerful muscles
 Include: clams, _________________, mussels, and
scallops
Cephalopods
 Class Cephalopoda
 _________-bodied
 Head is attached to a _____________ foot
 Foot is divided into __________________ or
arms
 Includes: octopi, squids, cuttlefishes, and
nautiluses
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Ecology of Mollusks
 Mollusks play many different roles in living systems:
 Feed on _____________
 Prey on _______________
 Filter ____________ out of the water
 Eat detritus
 Some mollusks are hosts to symbiotic algae or to parasites; others are
themselves _________________
 Mollusks are food for many organisms
Review Questions:
1. What are the four main parts of a mollusk’s body?
2. How do aquatic and land mollusks respire?
3. Name two examples of gastropods.
4. Name 2 ways mollusks affect living systems.
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