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Radiate animals – phyla? Name means? Movement? Easy meal? Germ layers? Layer names? Major innovation?
- Phylum Cnidaria and phylum Ctenophora make up the radiate animals
- Radiate means that they can be cut longitudinally in any direction and both halves are alike (unlike humans with bilateral symmetry)
- Most are sessile
- They make easy meals for other animals (unlike sponges)
- Diploblastic (ectoderm and endoderm), If they have a mesoderm it was derived from ectoderm
- Epidermis formed from ectoderm, gastrodermis formed from endoderm
- Gastrodermis cells are located in gastrovascular cavity
- Simplest animals with nerve cells (unmyelinated)
Phylum Cnidaria – examples? Classified how? Habitat? Forms? Digestive system? Reproduction? Special cells/structures?
- Include Hydroids, sea anemones, jellyfish, and horny corals
- Classified into phylum based on presence of cnidocytes
- All aquatic (mostly marine and a few freshwater)
- Two forms of life: polyp (sedentary) and medusa (mobile)
- Medusa has thicker, more defined mesoglea
- Majority have mouth, but no anus (waste exits through mouth area – incomplete digestive system)
- Asexual and sexual reproduction
- Epitheliomuscular: epithelial cells are attached to muscle fibers (actin/myosin). DO NOT HAVE MUSCLE CELLS.
- If they have an exoskeleton/endoskeleton it is made of chitin, calcium carbonate, or protein
- Have gastrovascular cavity
- Ciliated, mobile, larva called planula
- Have a nerve net (unmyelinated nerve cells, neurotransmitters, and neuromuscular system. No brain.)
What are the classes within phylum Cnidaria? List specific genera associated with each class.
- Hydrozoa: Obelia, Hydra, Gonionemus, Physalia, Polyorchis
- Scyphozoa: Aurelia
- Cubozoa: Carybdea marsupialis
- Anthozoa: Metridium, coral
Contrast polyp and medusa stage in Cnidarians
- Polyp: sedentary, tubular, has aboral end (point of attachment) and oral end (mouth), some form colonies – gonozoite (reproduction), dactylozoite (defense), and gastrozoite (feeding), large gastrovascular cavity
- Medusa: mobile, bell shape/umbrella shape, mouth is in center of animal, mesoglea is thicker than polyp stage, aboral end (top of umbrella), oral end (mouth), small gastrovascular cavity
Describe the anatomy and physiology of the Cnidocyte. What are the three types of nematocysts?
- Cnidocyte houses the nematocyst (weapon) internally, like an organelle
- Cnidocil: small nub at tip of cnidocyte, causes operculum to open when stimulated by nerve.
- Operculum: flap/lid of nematocyst capsule, when operculum opens the filament is released
- Filament: can have various functions, based on the type of nematocyst…
- Pentrants: penetrate and inject poison
- Volvents: entangle prey, and bring prey to mouth for digestion
- Glutinants: release adhesive substance used for locomotion and attachment
Where are interstitial cells found and what is their function?
Interstitial cells are found in Cnidarians, are pluripotent, and give the Cnidarians regenerative abilities. Interstitial cells can differentiate into spermatozoa, cnidocytes, or nerve cells, but CANNOT differentiate into epitheliomuscular cells.
Class Hydrozoa – genera? Stages? Habitat? Special cells/structures?
- Genera include Obelia, Hydra, Gonionemus, and Physalia
- Some have medusa, polyp, or both
- Mostly marine, but freshwater Hydra
- Colonial (Obelia, Physalia)
- Have velum (a membrane on the subumbrella surface of medusa) which allows swimming, only found in Hydrozoans
What are the differences between Hydra and the rest of Hydrozoa?
- Only polyp stage
- freshwater (not marine)
- solitary (not colonial)
- multiply sexual AND asexually
- small size
- sedentary (not mobile)
Hydra – habitat? Reproduction? Layer names? Mouth? Special cells/structures? Stages?
- Asexual reproduction by budding
- Testis and ovaries for sexual reproduction (monecious)
- Epidermis, Gastrodermis, and mesoglea (3 layers)
- Mouth opens to gastrovascular cavity
- Interstitial cells (regenerative abilities)
- Polyp only
Gonionemus – habitat? Stages? Reproduction
- Medusa is mature (reproduces in this stage)
- Gonads attach to radial canal
- External fertilization (in environment)
- Polyp stage may undergo asexual reproduction (budding) or may form medusa.
- Forms medusa from strobila (like Aurelia)
Obelia – habitat? Stages? Special cells/structures? Lifecycle?
- Sexual stage is free-swimming medusa
- Medusa similar to Gonionemus, but smaller
- Colonial (gastrozoite, gonozoite, and dachtylozoite)
- Hydrocaulus: main stalk/trunk of polyp stage
- Perisarc: dead material, found on periphery of hydrocaulus. Made of chitin (glucose molecule w/ N attached)
- Coenosarc: living material, found in center of hydrocaulus
- Medusa buds are released from gonozoite, and become mature medusa. Medusa sexually reproduce through external fertilization, which results in ciliated, free-swimming, planula (larval stage). Planula attaches to sea floor and becomes immature polyp. Polyp becomes mature polyp with colonies.
Physalia – common name? Stages? Special cells/structures?
- Common name – Portuguese Man-of-War
- Polymorphism: has many shapes (essentially colonial)
- Looks like a single animal, but is made up of gastrozoite, gonozoite, and dachtylozoite
- A single animal has both polyp and medusa
- Float: entire top portion of animal
- Crest: line on float, usually at top
Class Scyphozoa – Genera? Common name? Habitat? Stages? Reproduction? Life cycle? Special cells/structures?
- Genera include Aurelia
- Commonly called “true jellyfish”
- All marine
- Most large jellyfish belong to this class (polyp is absent or reduced)
- Sexes are separate, gametes released to gastrovascular cavity
- Internal fertilization
- Zygote on oral arms of medusa, then in sea water
- Ciliated planula (larva) -> scyphistoma (polyp-like stage) -> strobila (stack of 11-12 ephyra) -> ephyra (immature medusa) -> medusa
- No velum in medusa, but still able to move
- One order is sessile
Class Cubozoa – Genera? Common name? Name means? Special cells/structures? Other?
- Species include Carybdea marsupialis
- Commonly called “sea wasps”
- Umbrella looks like a cube
- Have velarium (similar function to velum of Hydrozoa)
- Polyp is small
- Metamorphosis directly to medusa stage (no ephyra, polyp, strobila, etc)
- Stinging is dangerous to human, can kill (textbook says most venomous animal on planet)
Class Anthozoa – Examples? Common name? Habitat? Stages? Special cells/structures? Reproduction? Other?
- Metridium, thorny corals
- Commonly called “flower animals” due to vibrant colors in tentacles
- All marine
- Polyps only, medusa absent
- Pharynx or gullet present (mouth)
- Gastrovascular cavity has 6 complete septa, several incomplete septa
- Mesoglea has amoeboid cells
- Use nematocysts for defense/hunting
- Asexually reproduce by pedal laceration and lateral fission
- Coral reefs created when corals absorb/deposit calcium carbonate from ocean around themselves. When the animal dies, coral reef remains.
Phylum Ctenophora – common name? genera? How do they resemble Cnidarians? How do they differ?
- Commonly called “comb jellyfish”
- Genera include Pleurobrachia
- Resemble Cnidarians: radial symmetry, aboral-oral axis, well developed mesoglea, no coelomic cavity, nerve plexus, lack of organ system, no respiratory system
- Differences: No nematocysts, have distinct muscle cells, have comb plates (can generate electricity, generate light), no polymorphism (only one stage), never colonial, have anal pore (on aboral end), smaller amount of species
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