Transcript Feb 28 - University of San Diego

I.
Platyhelminthes
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Flatworms - Dorsoventrally flattened
Simplest bilaterally symmetrical organisms
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First organs and organ systems**
Central nervous system
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Simple “brain” coordinates muscle movements
Incomplete digestive system
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Mouth but no anus
Similar to Cnidaria and Ctenophora
Mesoderm**
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Cell layer between endoderm and ectoderm
Gives rise to muscles, reproductive system
I.
Platyhelminthes
A.
Turbellaria
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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)
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Most species (6000)
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Complex life cycles
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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)
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Parasitic
Live in vertebrate intestines
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Head attaches to intestine wall with suckers or hooks
Gutless – absorb nutrients through body wall
May reach 50 feet!! (sperm whales)
II.
Nemertea
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Ribbon worms
Cosmopolitan
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Complete digestive tract**
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Mouth and anus
Circulatory system**
Use long, fleshy proboscis to capture prey
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Most common in shallow, temperate regions
Feed on crustaceans and worms
May be cryptic or conspicuous
Can reach 30 m in length!!
III.
Lophophorates
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Three phyla – all animals possess lophophore
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Ciliated hollow tentacles arranged in a horseshoe
Suspension feeders
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Bilateral symmetry, coelom (body cavity), U-shaped gut
Ectoprocta – Bryozoans
A.
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Colonies consist of interconnected individual zooids
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Encrusting and lacy forms (CaCO3 tests)
Retractable lophophore
Phoronida – Phoronids, Horseshoe Worms
B.
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Worm-shaped
Agglutinated sediment tubes attached to hard substrate in
shallow water
Brachiopoda – Lamp Shells
C.
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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
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Three phyla – all animals possess lophophore
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Ciliated hollow tentacles arranged in a horseshoe
Suspension feeders
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Bilateral symmetry, coelom (body cavity), U-shaped gut
Ectoprocta – Bryozoans
A.
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Colonies consist of interconnected individual zooids
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Encrusting and lacy forms (CaCO3 tests)
Retractable lophophore
Phoronida – Phoronids, Horseshoe Worms
B.
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Worm-shaped
Agglutinated sediment tubes attached to hard substrate in
shallow water
Brachiopoda – Lamp Shells
C.
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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
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Three phyla – all animals possess lophophore
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Ciliated hollow tentacles arranged in a horseshoe
Suspension feeders
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Bilateral symmetry, coelom (body cavity), U-shaped gut
Ectoprocta – Bryozoans
A.
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Colonies consist of interconnected individual zooids
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Encrusting and lacy forms (CaCO3 tests)
Retractable lophophore
Phoronida – Phoronids, Horseshoe Worms
B.
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Worm-shaped
Agglutinated sediment tubes attached to hard substrate in
shallow water
Brachiopoda – Lamp Shells
C.
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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
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Phylum Cnidaria, Class Anthozoa (most)
Lack medusa stage
Hermatypic (reef building) corals produce
skeletons made of calcium carbonate
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Most contain mutualistic zooxanthellae (provide
nutrition; enhance calcium carbonate deposition)
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Many growth forms
IV. Corals
A.
Biology
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Reproduction
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Sexual: Most broadcast spawners; some brooders
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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
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Living reefs ~
600,000 km2
(0.17% of sea
floor)
Great Barrier
Reef = Largest
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>2000 km
long
Up to 145 km
wide
Visible from
space
V.
Coral Reefs
B.
Conditions
1.
Substrate
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2.
Primarily in areas with hard substrate
Light - Bright (Why?)
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3.
Rarely develop in water > 50 m deep
Continental shelves, around islands, tops of
seamounts
Temperature
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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
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Fig. 15-33
Too warm also problematic
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Can cause bleaching and eventually death
Bleaching events often occur during periods of
unusually warm water
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Extreme low tide
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El Niño event
Corals live near their upper thermal tolerance levels
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Corals from warmer waters have higher thermal
tolerance levels
V.
Coral Reefs
B.
Conditions
4.
Salinity
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5.
Reefs tend to be absent or poorly developed near
mouths of rivers
Sediments
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6.
Turbidity reduces light levels
Sediments can smother corals
Pollution
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7.
Corals sensitive to pesticides and other chemicals
Fertilizers support growth of algae that smother corals
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Most corals grow in areas with low nutrient levels
Tidal Regime
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Most corals intolerant of prolonged exposure