Download 33_An Introduction to Invertebrates (a)

LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 33
An Introduction to Invertebrates
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
Overview: Life Without a Backbone
• Invertebrates are animals that lack a backbone
• They account for 95% of known animal species
• They are morphologically diverse
– For example, the Christmas tree worm
(Spirobranchus giganteus) has tentacles for gas
exchange and feeding
© 2011 Pearson Education, Inc.
Figure 33.1
Figure 33.2
Porifera
ANCESTRAL
PROTIST
Lophotrochozoa
Bilateria
Eumetazoa
Common
ancestor of
all animals
Cnidaria
Ecdysozoa
Deuterostomia
Figure 33.3a
Porifera (5,500 species)
Placozoa (1 species)
0.5 mm
A sponge
Cnidaria (10,000 species)
A placozoan (LM)
Ctenophora (100 species)
A jelly
Acoela (400 species)
1.5 mm
Acoel flatworms (LM)
A ctenophore, or comb jelly
Figure 33.3aa
A sponge
Figure 33.3ab
A jelly
Figure 33.3ac
1.5 mm
Acoel flatworms (LM)
Figure 33.3ad
0.5 mm
A placozoan (LM)
Figure 33.3ae
A ctenophore,
or comb jelly
Figure 33.3b
Platyhelminthes
(20,000 species)
Rotifera
(1,800 species)
0.1 mm
Ectoprocta
(4,500 species)
Ectoprocts
A marine flatworm
Acanthocephala
(1,100 species)
Nemertea
(900 species)
Brachiopoda
(335 species)
A brachiopod
A rotifer (LM)
Annelida
(16,500 species)
Cycliophora
(1 species)
Curved
hooks
100 m
An acanthocephalan (LM)
Mollusca
(93,000 species)
A ribbon worm
An octopus
A cycliophoran
(colorized SEM)
Lophotrochozoa
A marine annelid
Figure 33.3ba
A marine flatworm
Figure 33.3bb
Ectoprocts
0.1 mm
Figure 33.3bc
A rotifer (LM)
Figure 33.3bd
A brachiopod
Figure 33.3be
Curved
hooks
An acanthocephalan (LM)
Figure 33.3bf
A ribbon worm
Figure 33.3bg
100 m
A cycliophoran
(colorized SEM)
Figure 33.3bh
A marine annelid
Figure 33.3bi
An octopus
Figure 33.3c
Loricifera (10 species)
Priapula (16 species)
Onychophora (110 species)
50 m
A loriciferan (LM)
A priapulan
An onychophoran
Nematoda
(25,000 species)
Tardigrada
(800 species)
Arthropoda
(1,000,000 species)
100 m
A roundworm
(colored SEM)
Ecdysozoa
Tardigrades
(colorized SEM)
A scorpion (an arachnid)
Figure 33.3ca
50 m
A loriciferan (LM)
Figure 33.3cb
A priapulan
Figure 33.3cc
An onychophoran
Figure 33.3cd
A roundworm
(colored SEM)
Figure 33.3ce
100 m
Tardigrades
(colorized SEM)
Figure 33.3cf
A scorpion (an arachnid)
Figure 33.3d
Hemichordata
(85 species)
Chordata
(52,000 species)
A tunicate
Echinodermata (7,000 species)
An acorn worm
Deuterostomia
A sea urchin
Figure 33.3da
An acorn worm
Figure 33.3db
A tunicate
Figure 33.3dc
A sea urchin
Concept 33.1: Sponges are basal animals
that lack true tissues
• Animals in the phylum Porifera are known
informally as sponges
• They are sedentary and live in marine waters or
fresh water
© 2011 Pearson Education, Inc.
Figure 33.UN01
Porifera
Cnidaria
Lophotrochozoa
Ecdysozoa
Deuterostomia
• Sponges are suspension feeders, capturing food
particles suspended in the water that passes
through their body
• Water is drawn through pores into a cavity called
the spongocoel and out through an opening
called the osculum
• Sponges lack true tissues and organs
© 2011 Pearson Education, Inc.
Figure 33.4
Azure vase sponge
(Callyspongia
plicifera)
Food particles
in mucus
Flagellum
Choanocyte
Collar
Choanocyte
Osculum
Phagocytosis of
food particles
Amoebocyte
Spongocoel
Pore
Spicules
Epidermis
Mesohyl
Water
flow
Amoebocytes
Figure 33.4a
Azure vase sponge
(Callyspongia plicifera)
Figure 33.4b
Choanocyte
Osculum
Spongocoel
Pore
Spicules
Epidermis
Mesohyl
Water
flow
Amoebocytes
Figure 33.4c
Food particles
in mucus
Flagellum
Choanocyte
Collar
Phagocytosis of
food particles
Amoebocyte
• Choanocytes, flagellated collar cells, generate a
water current through the sponge and ingest
suspended food
• Sponges consist of a gelatinous noncellular
mesohyl layer between two cell layers
• Amoebocytes are found in the mesohyl and play
roles in digestion and structure
• Most sponges are hermaphrodites: Each
individual functions as both male and female
© 2011 Pearson Education, Inc.
Concept 33.2: Cnidarians are an ancient
phylum of eumetazoans
• All animals except sponges and a few other
groups belong to the clade Eumetazoa, animals
with true tissues
• Phylum Cnidaria is one of the oldest groups in this
clade
© 2011 Pearson Education, Inc.
Figure 33.UN02
Eumetazoa
Porifera
Cnidaria
Lophotrochozoa
Ecdysozoa
Deuterostomia
• Cnidarians have diversified into a wide range of
both sessile and motile forms including jellies,
corals, and hydras
• They exhibit a relatively simple diploblastic, radial
body plan
• The basic body plan of a cnidarian is a sac with a
central digestive compartment, the
gastrovascular cavity
• A single opening functions as mouth and anus
© 2011 Pearson Education, Inc.
• There are two variations on the body plan: the
sessile polyp and motile medusa
• A polyp adheres to the substrate by the aboral
end of its body
• A medusa has a bell-shaped body with its mouth
on the underside
• Medusae do not attach to the substate but move
freely
© 2011 Pearson Education, Inc.
Figure 33.5
Mouth/anus
Tentacle
Gastrovascular
cavity
Gastrodermis
Mesoglea
Body
stalk
Epidermis
Tentacle
Polyp
Mouth/anus
Medusa
• Cnidarians are carnivores that use tentacles to
capture prey
• The tentacles are armed with cnidocytes, unique
cells that function in defense and capture of prey
• Nematocysts are specialized organelles within
cnidocytes that eject a stinging thread
© 2011 Pearson Education, Inc.
Figure 33.6
Tentacle
Cuticle
of prey
Thread
Nematocyst
“Trigger”
Thread
discharges
Cnidocyte
Thread
(coiled)
• Phylum Cnidaria is divided into four major classes
–
–
–
–
Hydrozoa
Scyphozoa
Cubozoa
Anthozoa
© 2011 Pearson Education, Inc.
Figure 33.7
(b) Scyphozoa
(a) Hydrozoa
(c) Cubozoa
(d) Anthozoa
Figure 33.7a
(a) Hydrozoa
Figure 33.7b
(b) Scyphozoa
Figure 33.7c
(c) Cubozoa
Figure 33.7d
(d) Anthozoa
Hydrozoans
• Most hydrozoans alternate between polyp and
medusa forms
• Hydra, a freshwater cnidarian, exists only in polyp
form and reproduces asexually by budding
© 2011 Pearson Education, Inc.
Figure 33.8-1
Feeding
polyp
Reproductive
polyp
Medusa
bud
Gonad
Medusa
1 mm
Portion
of a
colony
of polyps
Key
Haploid (n)
Diploid (2n)
Figure 33.8-2
Feeding
polyp
Reproductive
polyp
Medusa
bud
MEIOSIS
Gonad
Medusa
Egg
Sperm
SEXUAL
REPRODUCTION
1 mm
Portion
of a
colony
of polyps
FERTILIZATION
Zygote
Key
Haploid (n)
Diploid (2n)
Figure 33.8-3
Feeding
polyp
Reproductive
polyp
Medusa
bud
MEIOSIS
Gonad
Medusa
Egg
ASEXUAL
REPRODUCTION
(BUDDING)
Portion
of a
colony
of polyps
SEXUAL
REPRODUCTION
FERTILIZATION
Developing
polyp
1 mm
Sperm
Mature
polyp
Zygote
Planula
(larva)
Key
Haploid (n)
Diploid (2n)
1 mm
Figure 33.8a
Scyphozoans
• In the class Scyphozoa, jellies (medusae) are the
prevalent form of the life cycle
© 2011 Pearson Education, Inc.
Cubozoans
• In the class Cubozoa, which includes box jellies
and sea wasps, the medusa is box-shaped and
has complex eyes
• Cubozoans often have highly toxic cnidocytes
© 2011 Pearson Education, Inc.
Anthozoans
• Class Anthozoa includes the corals and sea
anemones, and these cnidarians occur only as
polyps
• Corals often form symbioses with algae and
secrete a hard external skeleton
© 2011 Pearson Education, Inc.
Concept 33.3: Lophotrochozoans, a clade
identified by molecular data, have the widest
range of animal body forms
• Bilaterian animals have bilateral symmetry and
triploblastic development
• Most have a coelom and a digestive tract with two
openings
• The clade Bilateria contains Lophotrochozoa,
Ecdysozoa, and Deuterostomia
© 2011 Pearson Education, Inc.
Figure 33.UN03
Bilateria
Porifera
Cnidaria
Lophotrochozoa
Ecdysozoa
Deuterostomia
• The clade Lophotrochozoa was identified by
molecular data
• Some develop a lophophore for feeding, others
pass through a trochophore larval stage, and a
few have neither feature
• Lophotrochozoa includes the flatworms, rotifers,
ectoprocts, brachiopods, molluscs, and annelids
© 2011 Pearson Education, Inc.
Flatworms
• Members of phylum Platyhelminthes live in
marine, freshwater, and damp terrestrial habitats
• Although flatworms undergo triploblastic
development, they are acoelomates
• They are flattened dorsoventrally and have a
gastrovascular cavity with one opening
• Gas exchange takes place across the surface, and
protonephridia regulate the osmotic balance
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• Flatworms are divided into two lineages
– Catenulida, or “chain worms,” reproduce asexually
by budding
– Rhabditophora are more diverse and include both
free-living and parasitic species
© 2011 Pearson Education, Inc.
Figure 33.9
5 mm
Free-Living Species
• The best-known rhabditophorans are planarians
• Planarians live in fresh water and prey on smaller
animals
• Planarians have light-sensitive eyespots and
centralized nerve nets
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• The planarian nervous system is more complex
and centralized than the nerve nets of cnidarians
• Planarians are hermaphrodites and can reproduce
sexually, or asexually through fission
© 2011 Pearson Education, Inc.
Figure 33.10
Gastrovascular cavity
Pharynx
Gastrovascular
cavity
Mouth
Eyespots
Ventral nerve cords
Ganglia
Parasitic Species
• Parasitic rhabditophorans live in or on other
animals
• Two important groups of parasitic rhabditophorans
are the trematodes and the tapeworms
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Trematodes
• Trematodes parasitize a wide range of hosts, and
most have complex life cycles with alternating
sexual and asexual stages
• Trematodes that parasitize humans spend part of
their lives in snail hosts
• They produce surface proteins that mimic their
host and release molecules that manipulate the
host’s immune system
© 2011 Pearson Education, Inc.
Figure 33.11
Male
Human
host
Female
1 mm
Mature flukes
Ciliated
larva
Motile
larva
Snail host
Figure 33.11a
Male
Female
1 mm
Mature flukes
Tapeworms
• Tapeworms are parasites of vertebrates and
lack a digestive system
• Tapeworms absorb nutrients from the host’s
intestine
© 2011 Pearson Education, Inc.
• The scolex contains suckers and hooks for
attaching to the host
• Proglottids are units that contain sex organs and
form a ribbon behind the scolex
• Fertilized eggs, produced by sexual reproduction,
leave the host’s body in feces
© 2011 Pearson Education, Inc.
Figure 33.12
100 m
Hooks
Sucker
Proglottids with
reproductive
structures
Scolex
Figure 33.12a
100 m
Hooks
Sucker
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
© 2011 Pearson Education, Inc.
Figure 33.13
Jaws
Anus
Stomach
Crown
of cilia
0.1 mm
• Rotifers have an alimentary canal, a digestive
tube with a separate mouth and anus that lies
within a fluid-filled pseudocoelom
• Rotifers reproduce by parthenogenesis, in which
females produce offspring from unfertilized eggs
• Some species are unusual in that they lack males
entirely
© 2011 Pearson Education, Inc.
Lophophorates: Ectoprocts and Brachiopods
• Lophophorates have a lophophore, a crown of
ciliated tentacles around their mouth
• Lophophorates have a true coelom
• Lophophorates include two phyla: Ectoprocta and
Brachiopoda
© 2011 Pearson Education, Inc.
• Ectoprocts (also called bryozoans) are sessile
colonial animals that superficially resemble plants
• A hard exoskeleton encases the colony, and
some species are reef builders
© 2011 Pearson Education, Inc.
Figure 33.14
Lophophore
(a) Ectoprocts, colonial
lophophorates
Lophophore
(b) Lampshell,
a brachiopod
Figure 33.14a
Lophophore
(a) Ectoprocts, colonial
lophophorates
• Brachiopods superficially resemble clams and
other hinge-shelled molluscs, but the two halves of
the shell are dorsal and ventral rather than lateral
as in clams
• Brachiopods are marine and attach to the seafloor
by a stalk
© 2011 Pearson Education, Inc.
Figure 33.14b
Lophophore
(b) Lampshell,
a brachiopod
Molluscs
• Phylum Mollusca includes snails and slugs,
oysters and clams, and octopuses and squids
• Most molluscs are marine, though some inhabit
fresh water and some snails and slugs are
terrestrial
• Molluscs are soft-bodied animals, but most are
protected by a hard shell
© 2011 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
© 2011 Pearson Education, Inc.
Figure 33.15
Nephridium
Heart
Visceral mass
Coelom
Digestive tract
Intestine
Gonads
Mantle
Stomach
Shell
Radula
Mantle
cavity
Mouth
Anus
Gill
Foot
Nerve
cords
Esophagus
Mouth
Radula
• Most molluscs have separate sexes with gonads
located in the visceral mass, but many snails are
hermaphrodites
• The life cycle of many molluscs includes a ciliated
larval stage called a trochophore
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• 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)
© 2011 Pearson Education, Inc.
Chitons
• Chitons are oval-shaped marine animals encased
in an armor of eight dorsal plates
• They use their foot like a suction cup to grip rock,
and their radula to scrape algae off the rock
surface
© 2011 Pearson Education, Inc.
Figure 33.16
Gastropods
• About three-quarters of all living species of
molluscs are gastropods
© 2011 Pearson Education, Inc.
Figure 33.17
(a) A land snail
(b) A sea slug (nudibranch)
Figure 33.17a
(a) A land snail
Figure 33.17b
(b) A sea slug (nudibranch)
• Most gastropods are marine, but many are
freshwater and terrestrial species
• The most distinctive characteristic of gastropods is
torsion, which causes the animal’s anus and
mantle to end up above its head; torsion is
different from the coiling of a shell
• Most have a single, spiraled shell
• Slugs lack a shell or have a reduced shell
© 2011 Pearson Education, Inc.
Figure 33.18
Mantle
cavity
Anus
Mouth
Stomach
Intestine
Bivalves
• Bivalves are marine and include many species of
clams, oysters, mussels, and scallops
• They have a shell divided into two halves drawn
together by adductor muscles
• Some bivalves have eyes and sensory tentacles
along the edge of their mantle
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Figure 33.19
• The mantle cavity of a bivalve contains gills that
are used for feeding as well as gas exchange
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Figure 33.20
Mantle
Hinge area
Coelom
Gut
Heart
Digestive
gland
Adductor muscle
(one or two)
Anus
Mouth
Excurrent
siphon
Shell
Palp
Foot
Mantle
cavity
Gonad
Gill
Water
flow
Incurrent
siphon
Cephalopods
• Cephalopods are carnivores with beak-like jaws
surrounded by tentacles of their modified foot
• Most octopuses creep along the sea floor in
search of prey
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Figure 33.21
Squid
Octopus
Chambered
nautilus
Figure 33.21a
Squid
• Squids use their siphon to fire a jet of water, which
allows them to swim very quickly
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Figure 33.21b
Octopus
• One small group of shelled cephalopods, the
nautiluses, survives today
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Figure 33.21c
Chambered nautilus
• Cephalopods have a closed circulatory system,
well-developed sense organs, and a complex
brain
• Shelled cephalopods called ammonites were
common but went extinct at the end of the
Cretaceous 65.5 million years ago
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Protecting Freshwater and Terrestrial
Molluscs
• Molluscs are the animal group with the largest
number of recent extinctions
• The most threatened groups are
– Freshwater bivalves, including pearl mussels
– Terrestrial gastropods, including Pacific island
land snails
• These molluscs are threatened by habitat loss,
pollution, and non-native species
© 2011 Pearson Education, Inc.
Figure 33.22
Other invertebrates
Molluscs
Amphibians
Insects
Birds
Fishes
Mammals
An endangered Pacific
island land snail,
Partula suturalis
Recorded extinctions of animal
species (Data: International Union for
Reptiles
(excluding
birds)
Conservation of Nature, 2008)
Workers on a mound of pearl
mussels killed to make buttons
(ca. 1919)
Figure 33.22a
An endangered Pacific island land
snail, Partula suturalis
Figure 33.22b
Molluscs
Other invertebrates
Amphibians
Insects
Fishes
Mammals
Recorded extinctions of animal
species (Data: International Union for
Conservation of Nature, 2008)
Birds
Reptiles
(excluding
birds)
Figure 33.22c
Workers on a mound of pearl
mussels killed to make buttons
(ca. 1919)
Annelids
• Annelids have bodies composed of a series of
fused rings
• Annelids are coelomates
• The phylum Annelida is divided into two groups
– Polychaeta (polychaetes)
– Oligochaeta (earthworms and their relatives, and
leeches)
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Polychaetes
• Members of class Polychaetes have paddle-like
parapodia that work as gills and aid in locomotion
• Most polychaetes are marine
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Figure 33.23
Parapodia
Oligochaetes
• Oligochaetes (class Oligochaeta) are named for
relatively sparse chaetae, bristles made of chitin
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Earthworms
• Earthworms eat through soil, extracting nutrients
as the soil moves through the alimentary canal
• Earthworms are hermaphrodites but cross-fertilize
• Some reproduce asexually by fragmentation
© 2011 Pearson Education, Inc.
Figure 33.24
Cuticle
Coelom
Epidermis
Septum (partition
between segments)
Circular muscle
Metanephridium
Longitudinal muscle
Anus
Dorsal vessel
Chaetae
Intestine
Skin
Ventral vessel
Fused
nerve cords
Nephrostome
Metanephridium
Clitellum
Esophagus Crop
Pharynx
Intestine
Giant Australian earthworm
Gizzard
Cerebral
ganglia
Mouth
Subpharyngeal
ganglion
Circulatory
system vessels
Ventral nerve cords
with segmental
ganglia
Figure 33.24a
Giant Australian earthworm
Figure 33.24b
Cuticle
Epidermis
Circular muscle
Coelom
Septum (partition
between segments)
Metanephridium
Longitudinal muscle
Anus
Dorsal vessel
Chaetae
Intestine
Fused Ventral vessel
nerve cords
Nephrostome
Figure 33.24c
Anus
Skin
Metanephridium
Clitellum
Esophagus Crop
Pharynx
Gizzard
Cerebral
ganglia
Mouth
Intestine
Subpharyngeal Circulatory
ganglion
system vessels
Ventral nerve cords
with segmental
ganglia
Leeches
• Most species of leeches live in fresh water; some
are marine or terrestrial
• Leeches include predators of invertebrates, and
parasites that suck blood
• Leeches secrete a chemical called hirudin to
prevent blood from coagulating
© 2011 Pearson Education, Inc.