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I.
Platyhelminthes
•
•
Flatworms - Dorsoventrally flattened
Simplest bilaterally symmetrical organisms
•
•
First organs and organ systems**
Central nervous system
•
•
Simple “brain” coordinates muscle movements
Incomplete digestive system
•
•
•
Mouth but no anus
Similar to Cnidaria and Ctenophora
Mesoderm**
•
•
Cell layer between endoderm and ectoderm
Gives rise to muscles, reproductive system
I.
Platyhelminthes
A.
Turbellaria
•
•
•
Mostly free-living carnivorous species
Most commonly seen (Why?)
Some live as commensal animals inside other
invertebrates (oysters, crabs, etc.)
I.
Platyhelminthes
B.
Trematoda (Flukes)
•
Most species (6000)
•
•
Complex life cycles
•
•
•
C.
Parasitic – Feed on tissues, blood, gut contents
Adults live in vertebrate host (fish, whale, bird)
Larvae may inhabit invertebrates (intermediate hosts)
Vertebrate eats intermediate host (clam, snail, etc.)
Cestoda (Tapeworms)
•
•
Parasitic
Live in vertebrate intestines
•
•
•
Head attaches to intestine wall with suckers or hooks
Gutless – absorb nutrients through body wall
May reach 50 feet!! (sperm whales)
II.
Nemertea
•
•
Ribbon worms
Cosmopolitan
•
•
Complete digestive tract**
•
•
•
Mouth and anus
Circulatory system**
Use long, fleshy proboscis to capture prey
•
•
•
Most common in shallow, temperate regions
Feed on crustaceans and worms
May be cryptic or conspicuous
Can reach 30 m in length!!
III.
Lophophorates
•
Three phyla – all animals possess lophophore
•
•
Ciliated hollow tentacles arranged in a horseshoe
Suspension feeders
•
Bilateral symmetry, coelom (body cavity), U-shaped gut
Ectoprocta – Bryozoans
A.
•
Colonies consist of interconnected individual zooids
•
•
Encrusting and lacy forms (CaCO3 tests)
Retractable lophophore
Phoronida – Phoronids, Horseshoe Worms
B.
•
•
Worm-shaped
Agglutinated sediment tubes attached to hard substrate in
shallow water
Brachiopoda – Lamp Shells
C.
•
•
•
Abundant in fossil record
Superficially resemble clams, but shells are dorsal-ventral, not
left-right as in mollusks
Many attached to substrate with pedicle (short stalk)
Bryozoans
III.
Lophophorates
•
Three phyla – all animals possess lophophore
•
•
Ciliated hollow tentacles arranged in a horseshoe
Suspension feeders
•
Bilateral symmetry, coelom (body cavity), U-shaped gut
Ectoprocta – Bryozoans
A.
•
Colonies consist of interconnected individual zooids
•
•
Encrusting and lacy forms (CaCO3 tests)
Retractable lophophore
Phoronida – Phoronids, Horseshoe Worms
B.
•
•
Worm-shaped
Agglutinated sediment tubes attached to hard substrate in
shallow water
Brachiopoda – Lamp Shells
C.
•
•
•
Abundant in fossil record
Superficially resemble clams, but shells are dorsal-ventral, not
left-right as in mollusks
Many attached to substrate with pedicle (short stalk)
III.
Lophophorates
•
Three phyla – all animals possess lophophore
•
•
Ciliated hollow tentacles arranged in a horseshoe
Suspension feeders
•
Bilateral symmetry, coelom (body cavity), U-shaped gut
Ectoprocta – Bryozoans
A.
•
Colonies consist of interconnected individual zooids
•
•
Encrusting and lacy forms (CaCO3 tests)
Retractable lophophore
Phoronida – Phoronids, Horseshoe Worms
B.
•
•
Worm-shaped
Agglutinated sediment tubes attached to hard substrate in
shallow water
Brachiopoda – Lamp Shells
C.
•
•
•
Abundant in fossil record
Superficially resemble clams, but shells are dorsal-ventral, not
left-right as in mollusks
Many attached to substrate with pedicle (short stalk)
IV. Corals
A.
Biology
•
•
•
Phylum Cnidaria, Class Anthozoa (most)
Lack medusa stage
Hermatypic (reef building) corals produce
skeletons made of calcium carbonate
•
Most contain mutualistic zooxanthellae (provide
nutrition; enhance calcium carbonate deposition)
•
Many growth forms
IV. Corals
A.
Biology
•
Reproduction
•
•
•
Sexual: Most broadcast spawners; some brooders
•
Polyp  Planula (planktonic larva)  Polyp
Asexual: Fragmentation (can be *very* important)
All polyps in a colony genetically identical
Fig. 15-4
V.
Coral Reefs
A.
Distribution
•
Living reefs ~
600,000 km2
(0.17% of sea
floor)
Great Barrier
Reef = Largest
•
•
•
•
>2000 km
long
Up to 145 km
wide
Visible from
space
V.
Coral Reefs
B.
Conditions
1.
Substrate
•
2.
Primarily in areas with hard substrate
Light - Bright (Why?)
•
•
3.
Rarely develop in water > 50 m deep
Continental shelves, around islands, tops of
seamounts
Temperature
•
•
Mean annual water temperature > 20 oC
Best development at 23-25 oC
Distribution of Coral Reefs
Fig. 15-14
V.
Coral Reefs
B.
Conditions
3.
Temperature
•
•
•
Fig. 15-33
Too warm also problematic
•
Can cause bleaching and eventually death
Bleaching events often occur during periods of
unusually warm water
•
Extreme low tide
•
El Niño event
Corals live near their upper thermal tolerance levels
•
Corals from warmer waters have higher thermal
tolerance levels
V.
Coral Reefs
B.
Conditions
4.
Salinity
•
5.
Reefs tend to be absent or poorly developed near
mouths of rivers
Sediments
•
•
6.
Turbidity reduces light levels
Sediments can smother corals
Pollution
•
•
7.
Corals sensitive to pesticides and other chemicals
Fertilizers support growth of algae that smother corals
•
Most corals grow in areas with low nutrient levels
Tidal Regime
•
Most corals intolerant of prolonged exposure