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CHAPTER 33
THE
INVERTEBRATES
Prepared by
Brenda Leady, University of Toledo
Copyright (c) The McGraw-Hill
Companies, Inc. Permission required
for reproduction or display.
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Parazoa – Phylum Porifera
Sponges
 Loosely organized and lack…
 Multicellular with several types of cells
 __________ species mostly marine



Adults sessile, larvae free-swimming
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
Water drawn through…
Flows out through _________
 ____________ line _____________

 Trap
and eat small particles and plankton
Reproduce …
 Most __________________ producing
eggs and sperm

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Radiata – Phylums _________
and _______________



Mostly …
Only 2 embryonic germ layers – ____________
 Ectoderm



and endoderm
_____________ connects 2 layers
_____________ cavity for extracellular digestion
True nerve cells arranged in nerve net
 No
central control organ
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Phylum Cnidaria

2 different body forms
 ______________–
tubular body with tentacles
surrounding opening (mouth and anus)
 ______________– umbrella-shaped body
with a mouth on the underside surrounded by
tentacles

____________ contain ______________
 Hairlike trigger – cnidocil
 Some sticky while other sting

Simple muscles and nerves
 Not
true muscles with mesoderm
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Phylum Ctenophora

Less than 100 species- all marine and look
like jellyfish
 Eight rows of ______ on surface beat for
propulsion
 2 long tentacles ________ stinging cells
 Colloblasts secrete sticky substance
 First _____________– mouth and anus
 Hermaphroditic


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Lophotrochozoa


Traditionally, bilaterally symmetrical animals split
into acoelomate platyhelminthes,
pseudocoleomate nematodes and rotifers and
remaining coelomate phlya
Molecular data suggests a different grouping
with the deuterostomates separate and the
protostomates divided into the Lophotrochozoa
(Platyhelminthes, Rotifera, Lophophorata,
Mollusca and Annelida) and the Ecdysozoa
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Phylum Platyhelminthes




Lack a specialized respiratory or circulatory system
to transport gases
Respire by …
Among first animals with active predatory lifestyle




First with 3 embryonic germ layers – ___________
Mesoderm key innovation – led to more
sophisticated organs
___________________ – lacking fluid-filled cavity
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Digestive system…
 Distinct excretory system with

Light sensitive eyespots or ocelli
 Cerebral ganglia receive input
 Retain nerve net with beginning of more
centralized nervous system
 Sexual or asexual reproduction

 Most

…
4 classes –
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______________ – Free-living, Planaria
 ______________ – Fish flukes
 ______________ – Tapeworms, parasitic



2 separate host species in life cycle
______________ – Flukes, parasitic
 More
complex life cycle with multiple hosts
 Chinese liver fluke, Clonorchis sinensis
 Blood flukes, Schistosoma spp., most
common parasitic trematode infecting humans
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http://www.puristat.com/parasites/index.asp
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Phylum Rotifera






Named for ciliated crown or corona
1800 species – mostly freshwater
Digestive tract with mouth and anus – mastax
Pseudocoelom
Protonephridia with flame bulbs
Reproduction unique
– amictic eggs – unfertilized diploid
eggs develop into females
 Mictic eggs – unfertilized haploid eggs become
degenerate males that live long enough to produce
sperm
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 Parthenogenesis
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Phoronida, Bryozoa, Brachiopoda

All possess a
__________ – ciliary
feeding device that
also functions in
respiration


Phylum _________
 Elongated,
tubedwelling marine worms
 About 15 species
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
Phylum ___________

 Look
like plants
 About 4,000 species
 Animal secretes and
lives inside _________

Phylum ___________
 Marine
with 2 shells

 About
300 species
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Phylum Mollusca



Over 100,000 species
Soft body with, in many species, protective
external shell
Body has 3 parts





Coelom confined to small area around …
Open circulatory system
Metanephridia
__________ – unique tongue-like organ
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 Most
shells complex 3 layered and
secreted by …
 Separate sexes although some
hermaphroditic
 ______________– some internal (key
to snails colonizing land)
 _______________develops into
veliger with rudimentary foot, shell
and mantle
 8 classes with 4 common

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Polyplacophorans –
 ___________________ – snails, slugs
and nudibranchs

 Largest
class, shells can be reduced or lost,
most marine or freshwater but some
colonized land
_____________ – clams, mussels, oysters
 _____________ – octopuses, squids,
nautiluses

 Most
morphologically complex, fast-swimming
marine predators, closed circulatory system
 Beaklike jaw, only nautilus has external shell,
some have foot modified into ____________
for propulsion
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Fiorito and Scotto’s Experiments Showed
Invertebrates Can Exhibit Sophisticated
Observational Learning Behavior
Octopuses trained to attack red or white ball
using reward and punishment
 Classical conditioning
 Color blind so must see relative brightness
of balls
 Observer octopuses watched trained
octopuses attack ball

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Phylum _________________


Rings are distinct __________ separated
by a _________
Segmentation has advantages
1.
Coelom acts as hydrostatic skeleton
3. Permits …
2.

Double transport system

_____________ and _____________carries
nutrients, wastes and respiratory gases
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Digestive system ___________ and
unsegmented
 Sexual reproduction involves 2 individuals
(sometimes separate sexes other
hermaphroditic) with internal fertilization
 Asexual reproduction by …
 15,000 species
 All annelids except leeches have
________ on each segment
 3 classes –
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
_____________ – marine worms
 Most

_____________ – terrestrial and
freshwater worms (earthworms)
 Role

species rich, many long setae
in conditioning soil through castings
_____________ – leeches
 Primarily
freshwater, __________
(anticoagulant), may be used in reattachment
surgeries, generally external parasites
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Ecdysozoa

Separation from Lophotrochozoa
supported by molecular data and
morphological characteristic

All ecdysozoans possess a ________ for
support and protection
 Developmental options – metamorphosis

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Phylum Nematoda

In nearly all habitats from poles to tropics
 Over 100,000 species
 Tough cuticle covers body
 ______________ but not circular muscles
 ______________ acts as hydrostatic
skeleton and circulatory system


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 Reproduction
usually sexual with
separate males and females
 Internal fertilization
 Caenorhabditis elegans as model
organism
 Large number of species parasitic in
humans and other vertebrates
Ascaris
lumbricoides
Necator americanus
Enterobius vermicularis
Wuchereria bancrofti
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Phylum Arthropoda
Perhaps most successful phylum
 ____ of all described living species
 Success related to body plan of all major
biomes
 Exoskeleton made of …

 Can
be extremely tough or soft and flexible
 Relatively impermeable to _________
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
Tagmata –
 Extensive ________________

 Well
developed organs for sight, touch, smell,
hearing and balance
 Compound eyes – ommatidia

Sophisticated brain with 2 or 3 ganglia
connected to several smaller ventral nerve
ganglia
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________ circulatory system
 Gas exchange –

Complex digestive system
 Excretion – metanephridia or …
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6 main classes – Trilobita, Arachnida,
Diplopoda, Chilopoda, Insecta and
Crustacea
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 Extinct
early arthropods, bottom feeders, little
specialization of body segments

 Spiders,
scorpions, ticks and mites
 2 tagmata-
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
_____________ – millipedes
2

pairs of legs per segment, herbivorous
_____________ – centipedes
1
pair of legs per segment, carnivorous
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 More
species of insects than all other animal
species combined
 ________ crucial to success – outgrowths of
body wall
 35 orders – differences in …
 Separate
sexes with internal fertilization
 Metamorphosis
__________ – 4 stages with adult and larval
stages very different
 __________ – 3 stages with young resembling
miniature adults

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 Crabs,
lobsters, barnacles and shrimp
 Marine, fresh water and terrestrial
 Unique __________ of antennae

 __________________
 Cuticle
covering head extends over
_______________
 Nauplius larvae very different from adult
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Insect Diversity May Be Explained by the
Appearance of the _________________
More species found in class Insecta, over 1
million, than in any other class
 Over half a million species of beetle, Order
Coleoptera
 Appearance of angiosperms led to increased
richness of insects in general and leaf-eating
beetles in particular
 Lineages that fed on angiosperms have
become much more diverse that those that
fed on _________________

Deuterostomia:

Phylum ______________
 Modified
______________ – 5 parts

 Cephalization
________
 No brain – simple nervous system
 _______________ covered with spines and
_________
 ________________________ with tube feet
functions in …
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No excretory organs – respiration and
excretion by _____________
 Autotomy – intentionally detach body part
that will later regenerate
 Reproduce sexually with separate sexes
 External fertilization
 5 main classes –
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Phylum _______________

4 key distinguishing innovations
1.
2.
3.
4.

All chordates exhibit these at some time
during development
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Subphylum Urochordata
3,000 marine species
 Adult _________with only pharyngeal slits
 Larvae tadpole-like exhibiting all 4
hallmarks
 Filter feeders with …

Whole animal enclosed in _______
 Rudimentary circulatory system
 Simple nervous system
 Mostly hermaphroditic

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Subphylum Cephalochordata
26 species
 All marine _____________
 Have 4 hallmarks
 Gas exchange across body surface
 Usually sessile but can leave burrow and
swim

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