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Lecture 20

BIO SCI 94 Lecture 20: Deuterosome Animals Part 1Premium


Department
Biological Sciences
Course Code
BIO SCI 94
Professor
Brad Hughes
Lecture
20

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2/20/19
Introduction
Deuterostomes- four phyla
Echinoderms
Includes sea stars, sea urchins
Hemichordates
Burrowing, deposit, suspension feeding acorn worms
Xenoturbella
Two wormlike species
Chordates
Includes vertebrates
Includes hagfish, lampreys, cartilaginous, bony fishes,
amphibians, mammals, reptiles
Non vertebrates- invertebrates
95% known species- invertebrates
Vertebrates dominate deuterostomes
What is an Echinoderm?
Echinoderms- named for spikes/spines
All marine animals
7000 species described
Very abundant, especially in deepwater environments
The Echinoderm Body Plan
Main traits synapomorphies, echinoderms monophyletic
Adults- radial symmetry
Calcium carbonate endoskeleton
Water vascular system
Larvae/deuterostomes bilaterally symmetric
Adults- pentaradial symmetry
Pentaradial came early in echinoderm evolution
Echinoderms- endoskeleton
Hard protective/supportive structures inside layer of epidermal tissue
During development, secretion of calcium carbonate plates inside skin→
endoskeleton
Some species, plate independent/flexible
Some species, plates fuse→ form rigid case
Tissue connect plates- stiff or flexible depending on conditions
Echinoderms defined by water vascular systems
Series of branching, fluid filled tubes and chambers→ form hydrostatic
skeleton
Important water vascular system feature- tube feet

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Elongated, fluid-filled appendages:
Ampulla on inside of body
Tube like podium projects on outside
How Do Echinoderms Feed?
Use most feeding methods: mass feeding, suspension feeding, deposit feeding
Tube feet important in obtaining food
Predatory species-sea stars
Use tube feet→ pry apart bivalve shells
Extrude stomach through opening
Secrete digestive enzymes
Absorb resulting molecules
Suspension feeders
Extend tube feet into water
Use tube to flick particles to cilia
Cilia sweep food into mouth
Deposit feeders
Use tube feet to secrete mucus
Sop up food material on substrate with mucus
Move food laden mucus into mouth with tube feet
Key Lineages: The Echinoderms
Most feather stars/sea lilies- sessile suspension feeders
Brittle stars/basket stars- five or more long arms; comes from small central disk
Use arm- suspension feeding, deposit feed, capture prey
Sea cucumbers- sausage shaped animals
Use tentacles- modified tube feet- for : suspension/deposit feed
Tentacles arranged in whorl around mouths
Echinodermata-Asteroidea (Sea Stars)
1900 known sea star species- live on hard/soft substrates along coast on every
ocean
Fully grown sea stars- range: less than 1 cm to 1 m meter across
Five or more long arms from central region
Central region contain mouth, stomach, anus
Arms not set off from central region by clear articulations
Sea stars
Predators or scavengers
Feed on animals like bivalves, sponges, barnacles, snails
Sexes separate, sexual reproduction predominates
Reproductive organs at one or more arms
Produce many gametes
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