Subkingdom Metazoa: Characteristics and Classification
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Questions and Answers

What is the name of the subkingdom that includes the Cnidarians?

  • Metazoa (correct)
  • Bilateria
  • Porifera
  • Cnidaria

    • What is the main characteristic of the Cnidarians' body structure?

  • Radial or biradial symmetry (correct)
  • Cellular grade of organization
  • Tissue grade of organization
  • Bilaterial symmetry

    • What is the function of the cnidocytes in Cnidarians?

  • To aid in locomotion
  • To digest food
  • To defend against predators
  • To capture prey (correct)

    • What is the name of the larvae stage in Cnidarians?

    <p>Planula</p> Signup and view all the answers

    What is the name of the class that includes Hydra and Obelia?

    <p>Hydrozoa</p> Signup and view all the answers

    What is the function of the gastrovascular system in Cnidarians?

    <p>To digest food and eliminate waste</p> Signup and view all the answers

    What is the name of the process by which Cnidarians reproduce asexually?

    <p>Budding</p> Signup and view all the answers

    What is the name of the symbiotic algae that live inside the tissues of some Cnidarians?

    <p>Zooxanthellae</p> Signup and view all the answers

    How many classes are Cnidarians grouped into?

    <p>4</p> Signup and view all the answers

    What is the name of the phylum that includes the Cnidarians?

    <p>Cnidaria</p> Signup and view all the answers

    What is the function of the reproductive polyps in the life cycle of Obelia?

    <p>To release medusa into the water</p> Signup and view all the answers

    What is the result of the fertilization of an egg by sperm in the life cycle of Obelia?

    <p>A zygote is created</p> Signup and view all the answers

    What is the stage that develops into a free-swimming plantula larva?

    <p>Blastula</p> Signup and view all the answers

    What is the final stage of the life cycle of Obelia?

    <p>Asexually budding colony</p> Signup and view all the answers

    What is the role of medusa in the life cycle of Obelia?

    <p>To release sperm and eggs into water for fertilization</p> Signup and view all the answers

    What is the name of the fire coral?

    <p>Millepora</p> Signup and view all the answers

    What is the term for the feeding polyps of the Portuguese man-of-war?

    <p>Gastrozooids</p> Signup and view all the answers

    What is the name of the class that includes sea wasps and box jellyfish?

    <p>Cubozoa</p> Signup and view all the answers

    What is the term for the larval stage of jellyfish?

    <p>Planula</p> Signup and view all the answers

    What is the name of the class that includes sea anemones and corals?

    <p>Anthozoa</p> Signup and view all the answers

    What is the name of the Portuguese man-of-war?

    <p>Physalia physalis</p> Signup and view all the answers

    What is the term for the adult stage of jellyfish?

    <p>Medusa</p> Signup and view all the answers

    What is the name of the class that includes true jellyfish?

    <p>Scyphozoa</p> Signup and view all the answers

    What is the term for the stinging cells of jellyfish?

    <p>Nematocysts</p> Signup and view all the answers

    What is the name of the species of box jellyfish that is known for its potent venom?

    <p>Chironex fleckeri</p> Signup and view all the answers

    Study Notes

    Hydrozoans and Coral

    • Millepora, known as fire coral, comprises significant coral species with both hydrozoan and coralline characteristics.
    • The term "Millepora" translates to "many pores," indicating its distinctive structure.
    • Fire corals possess specialized polyps known as dactylozooids for defense, and gastrozoids responsible for feeding.

    Portuguese Man o' War

    • Physalia physalis, commonly referred to as the Portuguese Man o' War, is a colonial organism made up of a multitude of specialized polyps.
    • Unlike jellyfish, it cannot survive independently due to its colony structure.
    • The gas-filled bladder allows it to float and move with ocean currents, while containing a mixture of gases similar to compositions found in the atmosphere.

    True Jellyfish (Class Scyphozoa)

    • Scyphozoans are traditional jellyfish that can be differentiated by their unique medusa form.
    • Examples include Aurelia, Chrysaora, Pelagia, and Cyanea capillata, some of which can be venomous to humans.
    • Aurelia's life cycle consists of several stages: polyp (gonangium) produces medusa, which release gametes for fertilization, leading to the planula stage.

    Environmental Impacts

    • Some jellyfish species, like Aurelia aurita and the Australian box jellyfish, negatively affect marine ecosystems by depleting fish eggs and larvae.
    • These invasive jellyfish threaten local fisheries and marine biodiversity through competition for food resources.

    Box Jellyfish (Class Cubozoa)

    • Known as sea wasps, box jellyfish have a cube-shaped bell and possess complex nervous systems.
    • Species like Chironex fleckeri are notorious for their potent venom.
    • They can swim rapidly, achieving speeds of up to six meters per minute, facilitated by specialized structures for propulsion.
    • Box jellyfish possess true eyes allowing them not only to detect light but also to see specific points of illumination.

    Sea Anemones and Hard Corals (Class Anthozoa)

    • Anthozoa exclusively exist in the polyp form, including sea anemones and stony corals.
    • Their body cavity is partitioned by mesenteries; they may exist solitarily or in colonies.
    • Two subclasses: Hexacorallia (with six or multiple tentacles, e.g., sea anemones and corals) and Octocorallia (with eight tentacles, e.g., soft corals).

    Characteristics of Cnidarians (Phylum Cnidaria)

    • Derived from the Greek word "cnidos," referring to stinging threads known as nematocysts.
    • Distinctive body symmetry categorized as radial or biradial.
    • Organized into two main categories: diploblastic (two tissue layers) and triploblastic (three tissue layers).

    Reproduction and Life Cycle

    • Cnidarians reproduce both sexually and asexually; polyps usually reproduce sexually, while medusa do so sexually to produce free-swimming larvae.
    • External fertilization occurs in aquatic environments, yielding zygotes that develop into planulae before settling and forming polyps.

    Nutritional and Respiratory Processes

    • Cnidarians exhibit a gastrovascular cavity that serves both digestive and excretory functions.
    • Two-way digestive system: Food and waste exit through the same opening.
    • Respiration occurs through diffusion across body surfaces, emphasizing their reliance on water for oxygen uptake.

    Unique Adaptations and Ecology

    • Some Cnidarians form symbiotic relationships with zooxanthellae, facilitating photosynthesis and enhancing energy acquisition.
    • The presence of antioxidants aids in protecting against cellular damage within the marine environment.
    • Regeneration capabilities allow for recovery of lost body parts, crucial for survival in dynamic ecosystems.

    Classification Overview

    • Cnidarians encompass approximately 9,200 species within four main classes: Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa.

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    Description

    Learn about the subkingdom Metazoa, its characteristics, and classification into two main groups. Understand the importance of Metazoa in the animal kingdom.

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