jimtrue.com : school : BSC2011L : Lab 06: Animalia I - Invertebrate Phyla Porifera through Mollusca

Posted by Jim True on October 12, 2004 2:24 PM. Last Updated October 22, 2006 9:23 PM

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Lab 06: Animalia I - Invertebrate Phyla Porifera through Mollusca

Objectives:

1. To learn the characteristics of representative animal phyla
2. To be able to separate phyla along the lines of: symmetry, body cavity type, germ layer development, grade of organization, skeletal type, and digestive tract and circulatory system structure.
3. To be able to classify organisms to appropriate phyla or classes within phyla.
4. To know distinguishing features of different phyla/classes.

Terms to Know:

• invertebrate - organisms without backbones
• alternation of generation - have one generation that reproduces asexually, and another generation that reproduces sexually.
• sessile - permanently attached to one location.
• asymmetry - having no balanced sides, a plane dividing the organism would never end up with mirror image halves.
• radial symmetry - any slice of an imaginary plane down the longitudinal axis would result in two mirror halves.
• bilateral symmetry - only a slice of an imaginary plane down the longitudinal axis from dorsal to ventral would result in left and right mirror images halves.
• GVC (gastrovascular cavity) - a structure of cnidarians that serves as digestive and circulatory system, distributing food around the body.
• metamerism - body divided into segments with repetition of many internal organ systems in each segment.
• hydrostatic skeleton - the body is given structure by the pressure of water or liquid within; there are no physically hard structures.
• exoskeleton - skeletal structure is OUTSIDE the body.
• endoskeleton - skeletal structure is INSIDE the body.
• diploblastic - having only two germ layers, ectoderm and endoderm.
• triploblastic - having all three germ layers, ectoderm, mesoderm and endoderm.
• cnidocytes - stinging cells of cnidarians
• pharynx - the mouth opening on Platyhelminthes
• pseudocoelom - having mesoderm present, but only coating ONE of the interior surfaces.
• spicules - diagnostic characteric of poriferans, three pronged structures
• nematocysts -
• scolex - the jaw like structure of the parasitic flatworms that the organism uses to attach itself to the intestinal tract.
• proglottid - body segments of the tapeworms that increase in size as they mature, primarily associated with reproduction.
• mantle - fold of tissue that secretes a calcium carbonate shell in mollusks.
• foot - muscular tissue that functions in locomotion in mollusks.
• radula - rasping tongue covered with teeth that tears away bits of food from a food source in mollusks.

Structures (& Functions) to Know from Dissections

From the female nematode:

• genital pore
• anus
• intestine
• excretory canal (lateral line)
• ovaries
• oviducts
• uterus
• vagina

From the clam:

• mantle
• incurrent and excurrent siphons (know which is which!)
• adductor muscles
• foot
• gills
• labial palps
• gonads and intestine (inside visceral mass)
• coelom
• heart and intestine (inside coelom)

Classification

• Phylum Porifera - sponges; have spicules.
• Phylum Cnidaria - have nematocysts (stinging cells)
• Class Hydrozoa - hydroids, man 'o war, e.g. Hydra, Physalia, Obelia
• Class Scyphozoa - jellyfishes, e.g. Aurelia
• Class Anthozoa - corals, anemones, e.g. Metridium
• Phylum Platyhelminthes - flatworms
• Class Turbellaria - all free-living, e.g. Planaria
• Class Trematoda - all parasitic flukes, e.g. Clonorchis (oral/posterior suckers)
• Class Cestoda - all parasitic tape worms, e.g. Taenia (scolex, proglottids)
• Phylum Nematoda - round worms, both parasitic, e.g. Ascaris and free-living, e.g. Turbatrix
• Phylum Mollusca - mantle (forms shell)
• Class Bivalvia - have two shells, clams (e.g. Anadonta), Oysters
• Class Gastropoda
• with shells, snails (terrestrial and fresh water), whelks and conch (marine)
• without shells, slugs (terrestrial), nudibranchs (marine)
• Class Cephalopoda - octopus, e.g., Octopus, squids, e.g. Loligo
• most highly advanced invertebrate

Notes

• Animalia is divided into 28-30 Phyla: There are distinct breaking points in the phylogenetic tree, that are the MAJOR branch points of the phylogeny (9 phylum). Some phylums will fall into major portions of these clades.
• Symmetry - Proportional ("mirror image" body halves produced by dividing the logitudinal axis of the body along an imaginary single plane.
• One phylum is asymmetrical; they lack everything. Sponges, Porifera. Parazoa (beside animals).
• Only phylum that expresses Radial Symmetry is Cnidaria (Echinoderms also have Radial symmetry as adults, but not as larvae.
• Most phlya are bilateral. Mid-sagital (right down the center longitudinal axis of the body.
• Platyhelminthes ("flat" "worms") - tapeworms, flukes.
• Nematoda (round worms)
• Mollusca (very robust, snails, slugs, squids & octupus (cephalapods), oysters, clams (bivalves)
• Body Construction:
• Germ Layers, during gastrulation (differentiation), we produce up to three germ layers. No germ layers in poriferan. Cnidaria form a ball with an inner and outer layer (ecto and endo); diploblastic (no mesoderm). Most phyla are triploblastic (ecto,endo and meso).
• Skelton - framework for muscle attachments.
• Hydrostatic skeleton (hydraulic systems); fluid pressure. (Cnidarians and Nematoda) Relies on internal fluid pressure against outer tissue structure to resist muscle contractions)
• Exoskeletons - outside
• Calcareous - calcium carbonate structure.
• Chitinous - less rigid, may have some calcium carbonate
• Endoskeleton (inside)
• Digestive tube (food dumped for digestion)
• Poriferans - none
• Cnindaria - incomplete (gastro vascular cavity); all digestion takes place in one place, waste leaves through the same location that food comes in.
• Respiratory
• Cutaneous respiration (across the skin); diffusion
• Phyla
• Poriferans - Collectively referred to as the sponges.
• Produce structures called spicules (prong like structures formed of CaCo3 or Si02 of varying shapes) provide protection and support to the tissues. (Shape is diagnostic significance)
• Cnidaria (3 Classes)
• Possess radial symmetry
• diploblastic body construction
• Tentacles, MUST be able to extend and contract along the entire length. (Octupus have zero tentacles, 8 arms)
• Cnidos (means nettle, to sting)
• Only phlum to include alternation of generations.
• Polymorphism - Polyp (tube with tentacles on top), Medusa, squashed upside down polyp, tentacles hang downward. Polyp is asexual; Medusa is sexual generation; reproduce by meiosis. Which generation dominates is of taxonomic importance.
• Cnidocytes (stinging cells, thread-like harpoons) nematocysts
• Three Classes:
1. Hydrozoa ("hydra") if alternation, polyp dominates
2. Scyphozoa ("jellyfish") if alternation, medusa is dominate
3. Anthozoa ('flower animal") - sea anemones, coral are polyps that secrete CaCo3 reef structure.
• Platyhelminthes
• "Flat"
• Dorsal-ventrally flattened (back to front)
• Worms - forms that have an elongate body form with no visible appendages

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