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VertsLab2 - The Vertebrates Structure Function and...

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The Vertebrates: Structure, Function and Evolution (BIOEE 2740) Lab 2 – Invertebrate relatives of the vertebrates and the jawless craniates Goals for this lab: 1. Learn what morphological features define the major deuterostome groups, and how these groups are related to each other. 2. Explore the diversity, structure and function of the invertebrate relatives of the vertebrates, the Hemichordates (acorn worms and pterobranchs), Urochordates (tunicates) and Cephalochordates (lancelets) . 3. Explore the diversity, structure and function of jawless craniates, the Myxiniformes ( hagfish ) and the Petromyzontiformes ( lamprey ). 4. Become familiar with the internal anatomy of the lamprey through dissection of Petromyzon marinus , the sea lamprey. Station 1: Synapomorphies Familiarize yourself with the synapomorphies of the major groups in the Deuterostomata , the division of bilateral animals that includes the vertebrates . Remember that synapomorphies need only be present at some point in the lifetime of the animal, not retained through the entire life cycle. Chordates include the Urochordates (= tunicates) , the Cephalochordates (= lancelets, amphioxus) and the Craniata . Morphological synapomorphies of the Chordata are: 1. Dorsal, fluid-filled nerve cord – a fluid-filled bundle of nerve fibers that runs along the dorsal portion of the organism. 2. Notochord – a cartilaginous structure that supports the nerve cord. 3. Postanal tail – the body extends past the anal opening, forming a muscular tail. 4. Endostyle – a groove in the pharynx filled with cilia and mucus that aids in gathering food particles. The thyroid gland of vertebrates is derived from the endostyle. Craniates are the group comprised of the Myxiniformes (= hagfish) + Vertebrata (= lamprey + jawed vertebrates). Some morphological synapomorphies of the Craniata are: 1. Cranium the skull, the protective box around the brain. 2. Tripartite brain – the brain is divided into three segments, the forebrain, midbrain and hindbrain, associated respectively with smell, vision and balance. 3. Cephalized sense organs – complex sense organs, concentrated in the head. 4. Two-chambered heart – the heart has at least two chambers, the atrium and the ventricle.
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5. Muscular pharynx – muscular control of the pharynx. This allowed the diversification of feeding styles, and allowed for more efficient procurement of food, and therefore increases in body size and complexity. 6. Neural crest – the embryonic tissue that gives rise to nerve cells during development. Vertebrates include the Petromyzontiformes (= lamprey) + Gnathostomata (= jawed vertebrates). Some morphological synapomorphies of the Vertebrata are: 1. At least 2 semicircular canals – the fluid-filled canals in the inner ear which allow detection of movement and balance.
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