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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 33.3b
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 33.3c
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 33.3d
Hemichordata
(85 species)
Chordata
(52,000 species)
A tunicate
Echinodermata (7,000 species)
An acorn worm
Deuterostomia
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.
• 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 33.4b
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
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.
• 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.
Figure 33.5
Mouth/anus
Tentacle
Gastrovascular
cavity
Gastrodermis
Mesoglea
Body
stalk
Epidermis
Tentacle
Polyp
Mouth/anus
Medusa
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
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.
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http://www.pnas.org/
http://www.plosone.org/home.action
http://www.ncbi.nlm.nih.gov/
http://rspb.royalsocietypublishing.org/
http://jeb.biologists.org/
Reaction+Research+Reflection Paper
at least 1 page, intermediate paper
Consider the following questions in writing your
paper:
1. What are coral reefs?
2. How are coral reefs formed?
3. Why are coral reefs important?
4. What are the different threats to coral reefs?
5. What is coral bleaching?
6. What is the state of the coral reefs in the
world? in the Philippines?