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Questions and Answers
What is the primary function of the water-vascular system (W-VS) in echinoderms?
What is the primary function of the water-vascular system (W-VS) in echinoderms?
How does water travel through the water-vascular system in echinoderms?
How does water travel through the water-vascular system in echinoderms?
What role do Tiedemann bodies serve in the water-vascular system?
What role do Tiedemann bodies serve in the water-vascular system?
What is a common characteristic of the madreporite in echinoderms?
What is a common characteristic of the madreporite in echinoderms?
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Which of the following statements about the water-vascular system is true?
Which of the following statements about the water-vascular system is true?
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Which structures are involved in the fluid storage for the water-vascular system?
Which structures are involved in the fluid storage for the water-vascular system?
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In terms of body structure, how do echinoderms typically appear?
In terms of body structure, how do echinoderms typically appear?
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What is the role of the madreporite in maintaining the water-vascular system?
What is the role of the madreporite in maintaining the water-vascular system?
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What structures make up the circulatory system of molluscs?
What structures make up the circulatory system of molluscs?
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Which of the following best describes the function of the radula in molluscs?
Which of the following best describes the function of the radula in molluscs?
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In molluscan reproduction, what type of larval stages are produced from a fertilized egg?
In molluscan reproduction, what type of larval stages are produced from a fertilized egg?
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What is the primary mode of locomotion in cephalopods?
What is the primary mode of locomotion in cephalopods?
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Which organ is NOT typically found in the mantle cavity of molluscs?
Which organ is NOT typically found in the mantle cavity of molluscs?
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Which of the following best describes the function of nephridia in molluscs?
Which of the following best describes the function of nephridia in molluscs?
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What characterizes the body plan of coelomate organisms such as molluscs?
What characterizes the body plan of coelomate organisms such as molluscs?
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What is a common feature of the nervous system in molluscs?
What is a common feature of the nervous system in molluscs?
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What characteristic distinguishes echinoderms from other animal groups within the deuterostome lineage?
What characteristic distinguishes echinoderms from other animal groups within the deuterostome lineage?
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Which class of echinoderms is characterized by being sessile and usually possessing a stalk?
Which class of echinoderms is characterized by being sessile and usually possessing a stalk?
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What is the significance of the coelom in echinoderm development?
What is the significance of the coelom in echinoderm development?
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Which characterizes the evolutionary history of echinoderms?
Which characterizes the evolutionary history of echinoderms?
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Which echinoderm is known for a star-shaped, free-living form typically found in marine environments?
Which echinoderm is known for a star-shaped, free-living form typically found in marine environments?
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What does the term 'echinoderm' signify based on its Greek roots?
What does the term 'echinoderm' signify based on its Greek roots?
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What type of cleavage development is associated with the deuterostome lineage to which echinoderms belong?
What type of cleavage development is associated with the deuterostome lineage to which echinoderms belong?
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What is a common feature of the Echinodermata phylum regarding body symmetry?
What is a common feature of the Echinodermata phylum regarding body symmetry?
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Which characteristic is NOT associated with arachnids?
Which characteristic is NOT associated with arachnids?
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Which of the following classes does NOT belong to the phylum Arthropoda?
Which of the following classes does NOT belong to the phylum Arthropoda?
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What is the primary environment for most myriapods?
What is the primary environment for most myriapods?
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Which feature is characteristic of the class Insecta?
Which feature is characteristic of the class Insecta?
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What distinguishes Decapoda within the subphylum Crustacea?
What distinguishes Decapoda within the subphylum Crustacea?
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Which of the following accurately describes the life cycles of insects?
Which of the following accurately describes the life cycles of insects?
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Which distinguishing feature do all arachnids share?
Which distinguishing feature do all arachnids share?
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What is the primary method of excretion in arachnids?
What is the primary method of excretion in arachnids?
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Which characteristic is unique to Ctenophora compared to Anthozoa?
Which characteristic is unique to Ctenophora compared to Anthozoa?
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What structure in Anthozoa facilitates water movement into the gastrovascular cavity?
What structure in Anthozoa facilitates water movement into the gastrovascular cavity?
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Which statement correctly describes a feature of Ctenophora?
Which statement correctly describes a feature of Ctenophora?
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What is a primary function of the mesoglea in Ctenophora?
What is a primary function of the mesoglea in Ctenophora?
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What distinguishes the larval stage of Ctenophora from that of Anthozoa?
What distinguishes the larval stage of Ctenophora from that of Anthozoa?
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In which way do Ctenophora capture their prey differently from Anthozoa?
In which way do Ctenophora capture their prey differently from Anthozoa?
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Which anatomical feature is common between both Ctenophora and Anthozoa?
Which anatomical feature is common between both Ctenophora and Anthozoa?
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What is the main difference in symmetry between Ctenophora and other acoelomate animals?
What is the main difference in symmetry between Ctenophora and other acoelomate animals?
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Study Notes
Phylum Cnidaria
- Strong swimmers and predators with elaborate eyes for maneuvering obstacles.
- Some species (e.g., Chironex) have lethal stings for humans.
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Anthozoa (Sea anemones and coral)
- Polyp with limited mobility.
- Oral end expands into an oral disc with tentacles surrounding a slit-like mouth.
- Gastrovascular cavity has compartments divided by mesenteries.
- Mesenteries contain cnidocytes and gonads.
- Mesoglea contains amoeboid mesenchyme cells.
- Mouth leads to a pharynx.
- Siphonoglyph at one or both ends of the mouth moves water into the gastrovascular cavity.
Phylum Ctenophora
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Comb Jellies, Sea Walnut, Sea Goose, Sea Berry
- Biradially symmetrical, transparent, fragile, acoelomate, luminescent marine animals.
- Eight bands of cilia resembling combs between the oral and aboral poles.
- Stotocyst coordinates cilia beating for movement through water.
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Mnemiopsis
- Largest animals moving by cilia.
- Have gelatinous mesenchyme for muscle development.
- Monomorphic with no attached sessile life stage.
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Pleurobrachia
- Hermaphroditic with a cydippid larval stage.
- Complete gut with a pharynx leading to branching gastrovascular canals ending in anal pores.
- Tentacles have adhesive glue cells (colloblasts) that trap prey with sticky threads.
- Ingestion occurs as tentacles wipe across the mouth.
Similarities with Cnidaria
- Radial symmetry.
- Feeding tentacles.
- Gelatinous medusa-like form.
- Acoelomate.
- Simple nerve net.
Distinctions from Cnidaria
- No stinging nematocysts.
- Mouth for food intake and two anal pores for waste excretion.
Phylum Echinodermata
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Introduction:
- Derived from Greek words: "echinos" (spiny) and "derma" (skin), "ata" (to bear).
- Deuterostome lineage.
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Characteristics:
- Anus develops from or near the blastopore, mouth develops elsewhere.
- Coelom budded off from the archenteron.
- Radial and regulative cleavage development.
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Classification:
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Crinozoa: Sessile, stalked echinoderms with anus near the mouth.
- Crinoidea (Feather stars and sea lilies): Antedon neocrinus.
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Asterozoa: Free-living, star-shaped echinoderms without stalks.
- Asteroidea (Starfish or sea stars): Asterias, Astropecten.
- Ophiuroidea (Bristle stars and basket stars): Ophiothrix, Ophiura, Amphiura.
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Echinoidea: Spherical or disc-shaped, free-living echinoderms.
- Echinoidea (Sea urchins, sand dollars, heart urchins):
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Crinozoa: Sessile, stalked echinoderms with anus near the mouth.
Circulation and Coelom
- Water-Vascular System (W-VS) functions as a hydrostatic skeleton.
- System includes water-filled canals that extend from the body surface forming podia or tube feet.
- W-VS originates in embryogenic development as a modified coelom and is ciliated internally.
- Pentameric array with an oral ring and radial canals bearing the tube feet.
Functioning of W-VS
- Provides water pressure for operating tube feet.
- Water moves from the madreporite into the ring canal, then radial canals, and finally to tube feet.
- Canals act as a network of water pipes connected to tube feet.
- Water exits the body via the madreporite.
Body Plan
- Unsegmented with round, cylindrical, or star-shaped body with radiating areas (ambulacra).
- Ring canal opens to the outside or body cavity via a stone canal and a madreporite.
- Madreporite can be a sieve-like plate (sea stars) or a simple opening (other echinoderms).
- Madreporite replenishes water lost from the W-VS and balances pressure.
Associated Structures
- Tiedemann bodies: Swellings on the ring canal, produce phagocytic cells (coelomocytes) for defense.
- Polian vesicles: Structures associated with the ring canal for fluid storage in the W-VS.
Circulation
- Three systems are involved in circulation:
- W-VS
- General body cavity
- Non-metamerically symmetrical coelomates.
Phylum Mollusca
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Characteristics:
- Unsegmented body with a head, foot, visceral mass, and shell.
- Mantle cavity with gills (ctenidia), hypobranchial gland, anus, kidney opening, and oesphradium.
- Buccal cavity with a unique radula (toothed belt) for feeding.
- Coelom reduced to cavities of the gonads, kidneys, and perivisceral space.
- Perivisceral space is hemocoelic.
Biology of Mollusca
- Circulatory system: Heart with two auricles and one ventricle, blood vessels.
- Excretory system: Nephridia (tubular or branched structures) for excretion.
- Nervous system: Circum-pharyngeal ring, buccal, cerebral, pleural, pedal, parietal, and visceral ganglia.
- Locomotion: Diverse; gliding, jumping, swimming (sea angels, cephalopods).
- Reproduction: Sexual reproduction (simple or complex).
- Larvae: Trochophore larva and veliger larva are typical.
Feeding
- Use radula to scrape algae and diatoms from rocks.
- Mucus molds scraped particles before transport to the stomach.
- Partial digestion occurs extracellularly in the stomach.
- Intracellular digestion occurs in digestive diverticular tubules (DDT).
Classification
- Class Aplacophora: Worm-like, without plates.
- Class Monoplacophora: Primarily benthic marine habitats with one plate.
Phylum Arthropoda
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Introduction:
- Includes insects, arachnids, crustaceans, and myriapods.
- Diverse with over one million described species.
- Characterized by a segmented body, exoskeleton, and jointed appendages.
Class Arachnida
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Spiders, scorpions, ticks, mites
- Most extant arachnids are terrestrial, some live in freshwater and marine environments.
- Over 100,000 named species.
- Predacious, capture and poison prey.
- External digestion with suctorial stomachs.
Characteristics
- Prosoma (cephalothorax): Head and thorax fused.
- Opisthosoma (abdomen): Posterior body region.
- Chelicerae: First pair of appendages (jaws).
- Pedipalps: Second pair of appendages (sensory and feeding).
- Four pairs of legs: For walking and movement.
Excretion and Reproduction
- Excretion via Malpighian tubules and coxal glands.
- Excretes guanine.
- Sexual reproduction with courtship and mating.
Subphylum Crustacea
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Characteristics:
- Over 26,000 known species.
- Two or three body segments.
- Multiple pairs of antennae.
- Marine, freshwater, and terrestrial (primarily aquatic).
- Free-floating nauplius larval stage.
- Five pairs of walking legs in decapods.
Examples
- Anostraca: Fairy shrimp and brine shrimp.
- Phyllopoda: Water fleas.
- Malacostraca: Shrimps, crabs, lobsters, crayfishes.
- Copepoda: Planktonic herbivores, Daphnia.
- Cirripedia: Lepas and barnacles.
Subphylum Myriapoda
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Characteristics:
- Millipedes, centipedes, pauropods, and symphylans.
- Over 13,000 species.
- Most are terrestrial.
- Range from 750 to 10 legs (many pairs).
- Moist forest habitats, some in grasslands, semi-arid, or deserts.
Class Insecta
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Characteristics:
- Chitinous exoskeleton.
- Three-part body: head, thorax, abdomen.
- Three pairs of jointed legs.
- Compound eyes and a pair of antennae.
- Highly diverse.
- More than a million described pterygotes and apterygotes.
- Ubiquitous, few ocean dwellers.
Life Cycles
- Complete metamorphosis: Egg, larva, pupa, adult.
- Incomplete metamorphosis: Egg, nymph, adult.
Phylum Annelida
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Introduction:
- Called segmented worms.
- Name originated from annulus meaning "little ring".
- Examples include ringworms, ragworms, lugworms, and leeches.
Classification
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Class Polychaeta:
- Most numerous species.
- Marine species.
- Examples:
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Description
Explore the fascinating characteristics and anatomy of Phylum Cnidaria and Phylum Ctenophora. Learn about their unique features, such as the deadly stings of certain jellyfish and the distinct structures of sea anemones. This quiz will test your understanding of these intriguing marine organisms.
