phylum echinodermata
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Q: What does "Echinodermata" mean?
A: "Spiny skin"
Q: What is the habitat of all echinoderms?
A: Marine (ocean/saltwater) - all echinoderms are marine animals
Q: How many living species of echinoderms are there?
A: Approximately 6,000 living species
Q: Is Phylum Echinodermata an ancient or recent group?
A: Ancient group of animals
Q: What type of developmental pattern do echinoderms have?
A: Deuterostome development
Q: What type of skeleton do echinoderms have?
A: Endoskeleton (internal skeleton)
Q: What are the two key characteristics that define echinoderms?
A: 1) Deuterostome development and 2) Endoskeleton
Q: Do echinoderms have an exoskeleton or endoskeleton?
A: Endoskeleton (internal skeleton, unlike arthropods which have exoskeletons)
Q: What type of symmetry do echinoderm larvae have?
A: Bilateral symmetry
Q: What type of symmetry do adult echinoderms have?
A: Pentaradial symmetry (five-part radial symmetry)
Q: Describe the fundamental shift in echinoderm body plan during development.
A: Larvae have bilateral symmetry, but adults undergo a shift to pentaradial symmetry
Q: What does "pentaradial symmetry" mean?
A: Five-part radial symmetry (body parts arranged in fives around a central axis)
Q: What type of ancestor are echinoderms thought to have evolved from?
A: A bilateral ancestor
Q: What is the oral surface of an echinoderm?
A: The surface where the mouth is located
Q: What is the oral/aboral axis in echinoderms?
A: The axis that runs from the mouth (oral surface) to the opposite side (aboral surface)
Q: How is echinoderm body structure described?
A: In reference to their mouths, which define the oral surface (oral/aboral axis)
Q: What is the aboral surface?
A: The surface opposite the mouth (the "top" or upper surface)
Q: Why is the larval bilateral symmetry of echinoderms significant?
A: It provides evidence that echinoderms evolved from a bilateral ancestor, even though adults are radially symmetrical
Q: Where is the echinoderm endoskeleton located?
A: Internal to (underneath) a delicate epidermis
Q: What does the echinoderm epidermis contain?
A: Thousands of neurosensory cells
Q: What type of nervous system do echinoderms have?
A: A nerve ring (no brain)
Q: Do echinoderms have a brain?
A: No, they have a nerve ring but no brain
Q: What are ossicles?
A: Hard calcium carbonate plates that make up the echinoderm endoskeleton
Q: What is the endoskeleton composed of?
A: Calcium carbonate plates called ossicles
Q: What are the two types of ossicles in echinoderms?
A: Movable ossicles or fixed ossicles
Q: Which echinoderms have movable ossicles?
A: Starfish (sea stars) and sea cucumbers
Q: Which echinoderms have fixed ossicles?
A: Sea urchins and sand dollars
Q: Why are the ossicles perforated with pores?
A: To allow extension of tube feet
Q: What is mutable collagenous tissue?
A: Tissue in the endoskeleton that can rapidly change from rigid to flexible, allowing echinoderms to autotomize (self-amputate) body parts
Q: What does "autotomize" mean in echinoderms?
A: The ability to voluntarily break off or shed body parts (self-amputation)
Q: What is regeneration in echinoderms?
A: The ability to regrow lost body parts
Q: Which echinoderms are known for regeneration?
A: Starfish (sea stars) and brittle stars
Q: What is evisceration in sea cucumbers?
A: The ability to expel internal organs as a defense mechanism (they can regenerate them later)
Q: What are three abilities provided by mutable collagenous tissue?
A: 1) Autotomize body parts,
2) Regeneration,
3) Evisceration
Q: How can a starfish regenerate?
A: If a starfish loses an arm, it can regrow it; some species can even regenerate an entire new starfish from a single arm with part of the central disk
Q: What is an ampulla?
A: A muscular sac for tube feet control (controls water pressure to extend and retract tube feet)
Q: How do ampullae control tube feet?
A: Ampullae are muscular sacs that contract to force water into tube feet (extending them) or relax to allow water out (retracting them)
Q: What is the relationship between ampullae and tube feet?
A: Each tube foot has an ampulla above it that acts like a squeeze bulb to control the tube foot's extension and retraction
Q: How does the hydraulic system in tube feet work?
A: When the ampulla contracts, water is forced into the tube foot, causing it to extend; when the ampulla relaxes, the tube foot retracts
Q: What are the main components of the water-vascular system (in order)?
A: Madreporite → stone canal → ring canal → radial canals → ampullae → tube feet
Q: What happens when an ampulla contracts?
A: Water is forced into the tube foot, causing the tube foot to extend
Q: What causes a tube foot to extend?
A: The ampulla contracts, forcing water into the tube foot
Q: What are longitudinal muscles in tube feet?
A: Muscles that run lengthwise along the tube foot and control its bending and retraction
Q: What happens when longitudinal muscles contract unilaterally (on one side)?
A: The tube foot bends to that side
Q: What happens when all longitudinal muscles contract while the ampulla is relaxed?
A: Water is forced back into the ampulla, causing the tube foot to retract
Q: What causes a tube foot to retract?
A: All longitudinal muscles contract while the ampulla is relaxed, forcing water back into the ampulla
Q: How does a tube foot bend in a specific direction?
A: Unilateral contraction (contraction on one side only) of the longitudinal muscles bends the tube foot in that direction
Q: Describe the complete tube foot extension and retraction cycle.
A: Extension: ampulla contracts → water forced into tube foot. Retraction: longitudinal muscles contract + ampulla relaxes → water forced back into ampulla
Q: How do echinoderms perform respiration (gas exchange)?
A: Through the body wall and tube feet
Q: What type of circulatory system do echinoderms have?
A: Open circulatory system
Q: Do echinoderms have an excretory system?
A: No, echinoderms have no excretory system
Q: How do echinoderms dispose of nitrogenous waste?
A: By diffusion through tube feet
Q: What type of digestive system do echinoderms have?
A: Complete digestive system (with mouth and anus)
Q: What type of digestion occurs in echinoderms?
A: Extracellular digestion (digestion occurs outside cells, in the gut cavity)
Q: What are the two respiratory surfaces in echinoderms?
A: Body wall and tube feet
Q: Why can echinoderms lack a dedicated excretory system?
A: Because they can dispose of nitrogenous waste through diffusion across their tube feet and body surfaces (they're aquatic, so waste can diffuse into surrounding water)
Q: What type of fertilization occurs in echinoderms?
A: External fertilization
Q: Are echinoderms gonochoric or hermaphroditic?
A: Gonochoric (separate sexes - males and females are different individuals)
Q: What type of symmetry do echinoderm larvae have?
A: Bilateral symmetry (free-swimming bilateral larvae)
Q: Where do echinoderm larvae develop?
A: In the plankton (floating in open water)
Q: What happens to echinoderm larvae as they mature?
A: They metamorphose (transform) into sedentary adults
Q: What type of lifestyle do adult echinoderms have?
A: Sedentary (relatively stationary, slow-moving, or attached to surfaces)
Q: Can echinoderms reproduce asexually?
A: Yes, some echinoderms can reproduce asexually by splitting
Q: What is the complete life cycle symmetry pattern in echinoderms?
A: Bilateral larvae → metamorphosis → pentaradial adults
Q: Describe the typical echinoderm reproductive process.
A: Gonochoric individuals release gametes into water (external fertilization) → free-swimming bilateral larvae develop in plankton → metamorphose into sedentary pentaradial adults
Q: What type of asexual reproduction can occur in some echinoderms?
A: Splitting (fission) - the animal divides into two parts, each regenerating missing structures
Q: How many extinct classes of echinoderms are there?
A: More than 20 extinct classes
Q: How many extant (living) classes of echinoderms are there?
A: Five extant classes
Q: What type of symmetry do all five extant echinoderm classes share?
A: Pentaradial symmetry (five-part radial symmetry)
Q: What is Class Asteroidea?
A: Sea stars (starfish) and sea daisies
Q: What is Class Crinoidea?
A: Sea lilies and feather stars
Q: What is Class Echinoidea?
A: Sea urchins and sand dollars
Q: What is Class Holothuroidea?
A: Sea cucumbers
Q: What is Class Ophiuroidea?
A: Brittle stars (and basket stars)
What is the typical habitat/feeding role of Asteroidea?
A: Predators in the intertidal zone.
Q: How many arms do most sea stars have?
A: 5 arms (or multiples of 5).
Q: What do Echinoidea mainly feed on?
A: Mostly algae.
Q: Do Echinoidea have arms?
A: No, they have no arms.
Q: How are tube feet arranged in Echinoidea?
A: In 5 double rows.
Q: What protects Echinoidea?
A: Movable protective spines.
Q: What is the feeding strategy of Ophiuroidea?
A: Detritivores.
Q: How many arms do brittle stars have?
A: 5 arms.
Q: What is unique about their tube feet?
A: Tube feet lack ampullae and are used for feeding, not locomotion.
Q: Do Ophiuroidea have an anus?
A: No, they have no anus.