Biology Chapter 14: Echinoderms Flashcards

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.

Test your knowledge of Echinoderms with these flashcards focused on chapter 14. Each card features a key term and its definition, enhancing your understanding of this fascinating group of marine animals. Perfect for studying and memorization.