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CAMPBELL
BIOLOGY
TENTH
EDITION
Reece • Urry • Cain • Wasserman • Minorsky • Jackson
33
An Introduction
to Invertebrates
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
© 2014 Pearson Education, Inc.
Figure 33.UN08
Phylum
Porifera (sponges)
Description
Lack true tissues; have choanocytes (collar
cells—flagellated cells that ingest bacteria and tiny
food particles)
Cnidaria (hydras, jellies, sea
anemones, corals)
Unique stinging structures (nematocytes) housed in
specialized cells (cnidocytes); diploblastic; radially
symmetrical; gastrovascular cavity (digestive
compartment with a single opening)
Dorsoventrally flattened acoelomates; gastrovascular
cavity or no digestive tract
Pseudocoelomates with alimentary canal (digestive
tube with mouth and anus); jaws (trophi); head with
ciliated crown
Coelomates with lophophores (feeding structures
bearing ciliated tentacles)
Platyhelminthes (flatworms)
Lophotrochozoa
Deuterostomia Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Rotifera (rotifers)
Lophophorates: Ectoprocta,
Brachiopoda
Mollusca (clams, snails, squids)
Annelida (segmented worms)
Coelomates with three main body parts (muscular foot,
visceral mass, mantle); coelom reduced; most have
hard shell made of calcium carbonate
Coelomates with segmented body wall and internal
organs (except digestive tract, which is unsegmented)
Nematoda (roundworms)
Cylindrical pseudocoelomates with tapered ends;
no circulatory system; undergo ecdysis
Arthropoda (spiders, centipedes,
crustaceans, and
insects)
Coelomates with segmented body, jointed appendages,
and exoskeleton made of protein and chitin
Echinodermata (sea stars,
sea urchins)
Coelomates with bilaterally symmetrical larvae and
five-part body organization as adults; unique water
vascular system; endoskeleton
Coelomates with notochord; dorsal, hollow nerve cord;
pharyngeal slits; post-anal tail (see Chapter 34)
Chordata (lancelets, tunicates,
vertebrates)
© 2014 Pearson Education, Inc.
Figure 33.2
Porifera
ANCESTRAL
PROTIST
Lophotrochozoa
Bilateria
© 2014 Pearson Education, Inc.
Eumetazoa
Common
ancestor of
all animals
Cnidaria
Ecdysozoa
Deuterostomia
Figure 33.UN03
Bilateria
Porifera
Cnidaria
Lophotrochozoa
Ecdysozoa
Deuterostomia
Bilaterian animals have bilateral symmetry
and triploblastic development
Most have a coelom and a digestive tract with
two openings
© 2014 Pearson Education, Inc.
Concept 33.3: Lophotrochozoans, a clade
identified by molecular data, have the widest
range of animal body forms
Some develop a lophophore for
feeding, others pass through a
trochophore larval stage, and a few
have neither feature
 The clade Lophotrochozoa was identified by molecular
data
 Lophotrochozoa includes the flatworms, rotifers,
ectoprocts, brachiopods, molluscs, and annelids
© 2014 Pearson Education, Inc.
Flatworms
 Members of phylum Platyhelminthes
live in marine, freshwater, and
damp terrestrial habitats
 Triploblastic, acoelomates
 Flatworms have a gastrovascular cavity with one opening
 Gas exchange takes place across the surface, and
protonephridia regulate the osmotic balance
 Their dorsoventrally flattened shape maximizes surface
area for gas exchange
© 2014 Pearson Education, Inc.
Figure 33.9
MAKE CONNECTIONS: Maximizing Surface Area
Folding
Flattening
SA: 6 (3 cm  3 cm) = 54 cm2
V: 3 cm  3 cm  3 cm = 27 cm3
1 µm
SA: 2 (3 cm  1 cm) + 2 (9 cm  1 cm)
+ 2 (3 cm  9 cm) = 78 cm2
V: 1 cm  3 cm  9 cm = 27 cm3
Diagrams comparing surface area (SA) for two
different shapes with the same volume (V)
Branching
© 2014 Pearson Education, Inc.
Projections
Thylakoid
 Flatworms are divided into two lineages
 Rhabditophora (Planarian) Free-living
 Planarians live in fresh water and prey on smaller
animals
 Planarians have light-sensitive eyespots and
centralized nerve nets
The planarian
nervous
system is more
complex and
centralized
than the nerve
nets of
cnidarians
© 2014 Pearson Education, Inc.
 Parasitic rhabditophorans live in or on other
animals
 Two important groups of parasitic rhabditophorans
are the trematodes and the tapeworms
parasites of vertebrates and
lack a digestive system
Tapeworms absorb nutrients
from the host’s intestine
© 2014 Pearson Education, Inc.
Rotifers
 Rotifers, phylum Rotifera, are tiny animals that
inhabit fresh water, the ocean, and damp soil
 Rotifers are smaller than many protists but are
truly multicellular and have specialized organ
systems
© 2014 Pearson Education, Inc.
Ectoprocts and Brachiopods
 Lophophorates have a lophophore, a crown of
ciliated tentacles around their mouth
 Lophophorates have a true coelom
© 2014 Pearson Education, Inc.
Figure 33.UN08
Phylum
Porifera (sponges)
Description
Lack true tissues; have choanocytes (collar
cells—flagellated cells that ingest bacteria and tiny
food particles)
Cnidaria (hydras, jellies, sea
anemones, corals)
Unique stinging structures (nematocytes) housed in
specialized cells (cnidocytes); diploblastic; radially
symmetrical; gastrovascular cavity (digestive
compartment with a single opening)
Dorsoventrally flattened acoelomates; gastrovascular
cavity or no digestive tract
Pseudocoelomates with alimentary canal (digestive
tube with mouth and anus); jaws (trophi); head with
ciliated crown
Coelomates with lophophores (feeding structures
bearing ciliated tentacles)
Platyhelminthes (flatworms)
Lophotrochozoa
Deuterostomia Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Rotifera (rotifers)
Lophophorates: Ectoprocta,
Brachiopoda
Mollusca (clams, snails, squids)
Annelida (segmented worms)
Coelomates with three main body parts (muscular foot,
visceral mass, mantle); coelom reduced; most have
hard shell made of calcium carbonate
Coelomates with segmented body wall and internal
organs (except digestive tract, which is unsegmented)
Nematoda (roundworms)
Cylindrical pseudocoelomates with tapered ends;
no circulatory system; undergo ecdysis
Arthropoda (spiders, centipedes,
crustaceans, and
insects)
Coelomates with segmented body, jointed appendages,
and exoskeleton made of protein and chitin
Echinodermata (sea stars,
sea urchins)
Coelomates with bilaterally symmetrical larvae and
five-part body organization as adults; unique water
vascular system; endoskeleton
Coelomates with notochord; dorsal, hollow nerve cord;
pharyngeal slits; post-anal tail (see Chapter 34)
Chordata (lancelets, tunicates,
vertebrates)
© 2014 Pearson Education, Inc.
Molluscs
 Phylum Mollusca includes snails and slugs,
oysters and clams, and octopuses and squids
 Mostly marine, soft-bodied animals but most are
protected by a hard shell
 Four of the major classes of molluscs are
 Polyplacophora (chitons)
 Gastropoda (snails and slugs)
 Bivalvia (clams, oysters, and other bivalves)
 Cephalopoda (squids, octopuses, cuttlefish, and chambered
nautiluses)
© 2014 Pearson Education, Inc.
 All molluscs have a similar body plan with three
main parts
 Muscular foot
 Visceral mass
 Mantle
 Many molluscs also have a water-filled mantle
cavity and feed using a rasplike radula
© 2014 Pearson Education, Inc.
Gastropods
 About three-quarters of all living species of
molluscs are gastropods
Gastropods move slowly
by a rippling motion of the
foot or by cilia
Most have a single, spiraled shell that functions in
protection from injury, dehydration, and predation
© 2014 Pearson Education, Inc.
Cephalopods
 Cephalopods are carnivores with beak-like jaws
surrounded by tentacles of their modified foot
Squids use their siphon to fire a
jet of water, which allows them
to swim very quickly
© 2014 Pearson Education, Inc.
Annelids
 Annelids are coelomates with bodies composed of
a series of fused rings
 The phylum Annelida was traditionally divided into
three clades
 Polychaeta (polychaetes)
 Oligochaeta (oligochaetes)
 Hirundinea (leeches)
 two major clades - Errantia - Sedentaria
© 2014 Pearson Education, Inc.
Sedentarians
 Sedentarians tend to be less mobile than
errantians
 Some species burrow into the substrate, while
others live in protective tubes
© 2014 Pearson Education, Inc.
Concept 33.4: Ecdysozoans are the most
species-rich animal group
 Ecdysozoans are covered by a tough coat called a
cuticle
 The cuticle is shed or molted through a process
called ecdysis
 The two largest phyla are nematodes and
arthropods
© 2014 Pearson Education, Inc.
Nematodes
 Nematodes, or roundworms, are found in most
aquatic habitats, in the soil, in moist tissues of
plants, and in body fluids and tissues of animals
Caenorhabditis elegans is a
model organism in research
Trichinella
spiralis can be
acquired by
humans from
undercooked
pork
© 2014 Pearson Education, Inc.
Arthropod
Two out of every three known species of
animals are arthropods
 The arthropod body plan consists of a segmented
body, hard exoskeleton, and jointed appendages
trilobite
© 2014 Pearson Education, Inc.
 Arthropod evolution is characterized by a
decrease in the number of segments and an
increase in appendage specialization
 These changes may have been caused by
changes in Hox gene sequence or regulation
© 2014 Pearson Education, Inc.
Figure 33.29
Experiment
Origin of Ubx and
abd-A Hox genes?
Other
ecdysozoans
Arthropods
Common
ancestor
Onychophorans
Results
Ant = antenna
J = jaws
L1–L15 = body segments
© 2014 Pearson Education, Inc.
General Characteristics of Arthropods
 The appendages of some living arthropods are modified for
functions such as walking, feeding, sensory reception,
reproduction, and defense
 These modified appendages are jointed and come in pairs
 Arthropod evolution is
characterized by a decrease in
the number of segments and an
increase in appendage
specialization
 These changes may have been
caused by changes in Hox
gene sequence or regulation
© 2014 Pearson Education, Inc.
 Morphological and molecular evidence suggests
that living arthropods consist of three major
lineages that diverged early in the phylum’s
evolution
 Chelicerates (sea spiders, horseshoe crabs,
scorpions, ticks, mites, and spiders)
 Myriapods (centipedes and millipedes)
 Pancrustaceans (lobsters and other crustaceans,
as well as insects and their relatives)
© 2014 Pearson Education, Inc.
Chelicerates
 Chelicerates, clade Chelicerata, are named for
clawlike feeding appendages called chelicerae
Most modern chelicerates are
arachnids, which include
spiders, scorpions, ticks, and
mites
© 2014 Pearson Education, Inc.
Myriapods
 The clade Myriapoda includes millipedes and
centipedes
 All living myriapods are terrestrial
 They have a pair of antennae and three pairs of
appendages modified as mouthparts
© 2014 Pearson Education, Inc.
Pancrustaceans
 Together, insects and crustaceans form the clade
Pancrustacea
Crustaceans
Crustaceans live in marine and
freshwater environments, have
highly specialized appendages
Planktonic crustaceans
copepod
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Insects
 Hexapoda is an enormous clade including insects and their
relatives, live in almost every terrestrial habitat and in fresh
water
 The internal anatomy of an insect includes several complex
organ systems
© 2014 Pearson Education, Inc.
 Insects diversified several times following the
evolution of flight, adaptation to feeding on
gymnosperms, and the expansion of angiosperms
 Insect and plant diversity declined during the
Cretaceous extinction, but has been increasing in
the 65 million years since
© 2014 Pearson Education, Inc.
 Flight is one key to the great success of insects
 An animal that can fly can escape predators, find
food, and disperse to new habitats much faster
than organisms that can only crawl
 Insect wings are an extension of the cuticle
© 2014 Pearson Education, Inc.
Figure 33.41
Archaeognatha (bristletails; 350 species)
Zygentoma (silverfish; 450 species)
Winged insects (many orders; six are shown below)
Complete metamorphosis
Coleoptera
(beetles; 350,000 species)
Diptera
(151,000 species)
Hymenoptera
(125,000 species)
Proboscis
© 2014 Pearson Education, Inc.
Lepidoptera
(120,000 species)
Incomplete metamorphosis
Hemiptera
(85,000 species)
Orthoptera
(13,000 species)
 Insects with complete metamorphosis have larval stages known by
such names as maggot, grub, or caterpillar
 The larval stage looks entirely different from the adult stage
In incomplete metamorphosis, the young, called
nymphs, resemble adults but are smaller and go
through a series of molts until they reach full size
© 2014 Pearson Education, Inc.