Questions and Answers
What does 'ambulacrum' refer to?
What is the ambulacral groove?
A groove along each ambulacrum containing rows of tube feet.
What are tube feet used for?
Locomotion, clinging, food handling, and respiration.
What is the function of the radial nerve?
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What are pedicellariae?
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What is the role of papulae?
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What is a madreporite?
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What is the water-vascular system?
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What are Polian vesicles used for?
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What are ossicles?
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What are radial canals?
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What do lateral canals connect?
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What is the ampulla?
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What is the cardiac stomach?
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What is autotomy?
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What are pyloric ceca?
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What is the pyloric stomach?
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What are somatocoels?
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What is an axocoel?
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What is the hydrocoel?
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What is a bipinnaria?
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What are Ophiuroidea?
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Match the following descriptions with their corresponding terms:
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What are oral tentacles?
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What is a respiratory tree?
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What is a cloaca?
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What is an auricularia?
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What are Cuvierian tubules?
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What describes Holothuroidea?
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What defines Crinoidea?
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What is significant about Asteroidea?
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What does 'triploblastic' refer to?
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What is the Echinodermata?
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What is pentaradial symmetry?
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What type of symmetry do echinoderm larvae exhibit?
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What is a Deuterostome?
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What are dermal papulae?
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What is Aristotle's lantern?
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Study Notes
Echinoderms Overview
- Echinoderms belong to the phylum Echinodermata, characterized by their unique features and structures.
Unique Features
- Pentaradial symmetry: Adults exhibit this type of symmetry, while their larvae demonstrate bilateral symmetry.
- Triploblastic: Echinoderms develop from three germ layers during embryonic development.
- Deuterostome development: They exhibit deuterostomic cleavage patterns.
Key Anatomical Structures
- Ambulacrum: Radiating grooves with projecting podia from the water-vascular system.
- Ambulacral groove: Central groove of each ambulacrum containing tube feet flanked by movable spines.
- Tube feet: Serve multiple purposes including locomotion, adhesion, feeding, and respiration.
Water-Vascular System
- Madreporite: A sievelike structure serving as the entry point for the water-vascular system.
- Polian vesicles: Fluid reservoirs connected to the ring canal of the water-vascular system.
- Ossicles: Calcareous plates forming the body structure, often projecting spines.
Circulatory Elements
- Radial canal: Canals radiating from the ring canal along the ambulacra.
- Lateral canal: Connects radial canals to tube feet.
- Ampulla: Muscular vesicle above tube feet aiding in movement and function.
Digestive System
- Cardiac stomach: Can be everted for digestion and enzymatic breakdown of food.
- Pyloric stomach: Connected to digestive glands where extensive digestion occurs.
- Pyloric ceca: Digestive glands facilitating nutrient absorption.
Respiratory Structures
- Papulae: Projections aiding gas exchange by increasing respiratory surface area.
- Respiratory tree: Unique structure in some echinoderms for respiration, leading to the cloaca.
Defensive Mechanisms
- Autotomy: Ability to sever parts of their body for defense.
- Cuvierian tubules: Sticky, toxic structures expelled to deter predators.
Major Classes of Echinoderms
- Asteroidea (Sea Stars): Have variable arms, open ambulacral grooves with suckered tube feet, and can prey by everting their stomachs.
- Ophiuroidea (Brittle Stars): Characterized by a distinct central disc, autotomous limbs, and lack of suckers on tube feet.
- Echinoidea (Sea Urchins & Sand Dollars): No arms with fused ossicle plates forming a "test," equipped with moveable spines and suckered tube feet.
- Holothuroidea (Sea Cucumbers): Elongated body plan with no arms, utilized for respiration with a unique respiratory tree.
- Crinoidea (Sea Lilies & Feather Stars): Flower-shaped bodies with arms bearing food grooves and tube feet, anchored by flexible appendages called cirri.
Larval Forms
- Bipinnaria: Free-swimming, bilateral larva of asteroids.
- Auricularia: Free-swimming larva of Holothuroidea that develops into adult forms.
Additional Concepts
- Pedicellariae: Small pincher-like structures for defense and maintenance.
- Dermal papulae: Flesh-like projections acting in respiration.
- Aristotle's lantern: A specialized jaw mechanism found in Echinoidea for feeding.
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