Transcript Invertebrates

Invertebrates
Invertebrates
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Nearly all animals are invertebrates
(95%)
Invertebrates are animals that lack
backbones
Let’s take a survey of the major
phyla of animals! 
Chordates
Echinoderms
Major
Animal
Phyla
Arthropods
Annelids
Coelomate
Ancestry
Mollusks
Rotifers
Roundworms
Bilateral
Ancestry
Radial
Ancestry
Multicelled
Ancestry
Figure 25.2
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Flatworms
Cnidarians
Sponges
Single-celled, protistanlike ancestors
Symmetry
Radial
Bilateral
Figure 25.3
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The Gut
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Region where food is digested and
then absorbed
Saclike gut
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One opening for taking in food and
expelling waste
Complete digestive system
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Opening at both ends; mouth and anus
Body Cavities - Acoelomate
epidermis
gut cavity
no body cavity; region between gut
and body wall packed with organs
Figure 25.4a
Page 417
Body Cavities - Pseudocoel
epidermis
gut cavity
unlined body cavity
(pseudocoel) around gut
Figure 25.4b
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Body Cavities - Coelom
gut cavity
lined body cavity
(coelom)
peritoneum
Figure 25.4c
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Segmentation
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Repeating series of body units
Units may or may not be similar to
one another
Earthworms - segments appear
similar
Insects - segments may be fused
and/or have specialized functions
Animal Origins
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Originated during the Precambrian
(1.2 billion - 670 million years ago)
From what? Two hypotheses:
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Multinucleated ciliate became
compartmentalized
Cells in a colonial flagellate became
specialized
Phylum Porifera
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Representative organism: sponge
Have no true tissues (Parazoa)
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Sponges are sessile (nonmotile)
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Ancient Greeks believed them to be plants
Filter-feeders:
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Their cells are relatively unspecialized
Trap food from the
water that flows
through them
Most sponges are
hermaphrodites
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Each individual
produces both
sperm and eggs
Sponge Structure
water out
glasslike
structural
elements
amoeboid
cell
pore
semifluid
matrix
central
cavity
flattened
surface
cells
water in
Figure 25.7a
flagellum
microvilli
nucleus
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Phylum Cnidaria
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Have stinging
cells inside of
nematocysts
On tentacles
capsule’s lid
at free surface
of epidermal
cell
trigger
barbed
thread
inside
capsule
nematocyst
Figure 25.8
Page 420
Phylum Cnidaria
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Representative Organisms:
Jellyfish & Sea Anemones
Have true tissues and radial
symmetry
Body plan: sac with a central
digestive compartment known
as the gastrovascular cavity
(mouth & anus)
2 variations on the body plan:
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Polyp: sessile, mouth up,
waits for prey (sea anemone)
Medusa: floats, mouth down
(jellyfish)
Attack prey with tentacles
33-06b-JellySwimming-B.mov
Two Main Body Plans
outer epithelium
(epidermis)
mesoglea
(matrix)
Medusa
Figure 25.9 Page 420
inner epithelium
(gastrodermis)
Polyp
Obelia Life Cycle (Hydrozoan)
reproductive
polyp
male medusa
female medusa
ovum
sperm
zygote
feeding
polyp
polyp
forming
planula
Figure 25.10
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Phylum Platyhelminthes
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Representative
Organisms:
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Bilateral symmetry
Acoelomates –
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Tapeworms, flukes,
& planarians
no body cavity
enclosed by
mesoderm
Many are parasitic
Planarian Organ Systems
flame cell
nucleus
pharynx
cilia
protonephridia
opening of
tubule at
body surface
flame cell
fluid
filters
through
membrane
folds
Fig. 25.11a,b
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Planarian Organ Systems
brain
nerve cord
ovary
testis
oviduct
genital pore
penis
Fig. 25.11cd
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Flukes: Class Trematoda
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Parasitic worms
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Complicated life
cycle
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Larval stage
infects a
mollusk
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Adult infects a
Worms mate in
human host
Larvae bore
into human
skin
Larvae form,
leave snail
Fertilized egg
Asexual reproduction
in intermediate host
Ciliated larva
vertebrate
Southeast Asian blood fluke
Figure 25.14
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Tapeworms: Class Cestoda
Definitive host
Larvae
encysted in
muscle
tissue
Intermediate
host
Scolex attaches
to host
intestinal wall
Figure 25.15
Mature proglottid with fertilized eggs
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Phylum Nematoda
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Representative
organism:
roundworms
Pseudocoelomate
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have a body cavity,
but not encased by
mesoderm
Round worms with
tapered ends
Can be parasitic
(trichinosis)
Roundworms (Nematoda)
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pharynx
False coelom (pseudocoelomate)
Complete digestive system
intestine
false coelom
eggs in uterus
gonad
anus
muscularized body wall
Figure 25.13
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Two Coelomate Lineages
Protostomes
Deuterostomes
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Mollusks
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Echinoderms
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Annelids
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Chordates
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Arthropods
Cleavage Patterns
Protostome embryo
(spiral cleavage)
Blastopore becomes
mouth
Deuterostome embryo
(radial cleavage)
Blastopore becomes
anus
In-text figure
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Phylum Mollusca
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Representative
organisms:
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Coelomates
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snails, slugs, oysters,
clams, octopuses,
squids
Have a true coelom
Protostomes:
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Blastopore becomes
mouth
Phylum Mollusca
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Body plan has 3 main
parts:
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Muscular foot used for
movement
Visceral mass
covering the internal
organs
Mantle covers the
visceral mass (may
produce a protective
shell)
Cuttlefish Body Plan
Closed circulatory system with heart and
accessory heart
esophagus
digestive
kidney stomach
gland
Figure 25.22
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brain
arm
jaw
tentacle
mantle
reproductive internal
siphon
ink sac heart accessory organ
shell
radula
anus
gill
heart
Phylum Annelida
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Representative Organism:
earthworm
Annelids have segmented
bodies
Metanephridia (similar to
kidneys)
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Worms are hermaphrodites
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Remove wastes from the
blood
Produce both sperm and eggs
Setae provide traction for
burrowing in the soil
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Earthworms eat their way
through the soil
33-23-EarthwormLocomot-B.mov