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Questions and Answers
What does the suffix '-zoic' denote in geological periods?
What does the suffix '-zoic' denote in geological periods?
The genus Homo appeared during the Pleistocene epoch.
The genus Homo appeared during the Pleistocene epoch.
True
What features distinguished the early vertebrate called Haikouella?
What features distinguished the early vertebrate called Haikouella?
Dorsal nerve cord, notochord, pharynx, paired eyes, enlarged brain
Which of the following traits is NOT found in Cyclostomes?
Which of the following traits is NOT found in Cyclostomes?
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The ________ is considered a possible sister group to Vertebrata.
The ________ is considered a possible sister group to Vertebrata.
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Hagfishes and lampreys both have complex reproductive structures.
Hagfishes and lampreys both have complex reproductive structures.
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Match the geological periods with their corresponding characteristics:
Match the geological periods with their corresponding characteristics:
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What is the primary feeding strategy of adult parasitic lampreys?
What is the primary feeding strategy of adult parasitic lampreys?
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What is one of the two lines of evidence supporting a marine origin hypothesis for vertebrates?
What is one of the two lines of evidence supporting a marine origin hypothesis for vertebrates?
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The larval stage of lampreys is known as ________.
The larval stage of lampreys is known as ________.
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Conodonts are considered early vertebrates due to their complex dental structures.
Conodonts are considered early vertebrates due to their complex dental structures.
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Match the following groups of lampreys with their characteristics:
Match the following groups of lampreys with their characteristics:
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What are myomeres?
What are myomeres?
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How do free-living adult lampreys feed?
How do free-living adult lampreys feed?
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Lampreys generally have more males than females in their populations.
Lampreys generally have more males than females in their populations.
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In what type of waters do adult lampreys typically spawn?
In what type of waters do adult lampreys typically spawn?
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What impact did lampreys have on Lake Trout fisheries by 1950?
What impact did lampreys have on Lake Trout fisheries by 1950?
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Ostracoderms are characterized by having jaws and teeth.
Ostracoderms are characterized by having jaws and teeth.
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What evolutionary advantage do Gnathostomata have over jawless vertebrates?
What evolutionary advantage do Gnathostomata have over jawless vertebrates?
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The structure formed by the mandibular arch in Gnathostomes is known as the __________.
The structure formed by the mandibular arch in Gnathostomes is known as the __________.
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Match the following features with their respective groups:
Match the following features with their respective groups:
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What evolutionary development allowed for more complex structures like jaws?
What evolutionary development allowed for more complex structures like jaws?
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Both myelin sheaths and specialized muscles are absent in the nerve fibers of Gnathostomata.
Both myelin sheaths and specialized muscles are absent in the nerve fibers of Gnathostomata.
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What feature do most bony fishes exhibit regarding their teeth?
What feature do most bony fishes exhibit regarding their teeth?
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Study Notes
Agnathans and Gnathostomes
- Agnathans are jawless fish.
- Gnathostomes are jawed vertebrates.
- Evolution of jaws is a crucial step.
Geologic Time and Fossil Record
- Earth formed millions of years ago
- Periods and epochs are defined by changes – landmasses, organisms, or asteroid impacts
- "-zoic" in a name indicates an interval dominated by animal life.
- Major time periods (with associated events)
- Ordovician, Silurian, and Devonian eras: "Age of the Fishes"
- Permian, Triassic, Jurassic, and Cretaceous periods: "Age of the Dinosaurs"
- Tertiary era: mammals begin to appear.
- Quaternary era: genus Homo appears (Pleistocene -> Cavemen, Holocene -> Modern man).
What Did the Earliest Vertebrates Look Like?
- Fossils of Pikaia (from Burgess Shale) display key features of early chordates, like a notochord and V-shaped muscle blocks, which indicate placement within the chordate lineage.
- Pikaia is possibly a cephalochordate.
Early Vertebrate Evidence
- Haikouella, a small fish-like animal from the early Cambrian beds in China, exhibited chordate synapomorphies (dorsal nerve cord, notochord, pharynx) and even some vertebrate features like pharyngeal muscles, paired eyes, and an enlarged brain.
- However, Haikouella lacked a cranium and distinct forebrain.
- Possibly a sister group to the vertebrates.
Conodonts
- Odd tooth-like fossils found in Paleozoic marine sediments.
- Later discoveries of whole fossils confirmed their possession of myomeres, teeth, paired eyes, and notochord.
- Almost certainly members of the Vertebrata clade but their precise position is uncertain.
Environment of Early Vertebrate Evolution
- Earliest vertebrate fossils found in marine sediment suggesting a marine origin.
- Nonvertebrate chordates and deuterostome invertebrates show similar body fluid concentrations to the surrounding marine water, suggesting a marine origin.
- Hagfishes, with concentrated body fluids, might represent the original vertebrate condition.
Simplified Phylogeny of Early Vertebrates
- A cladogram depicting the evolutionary relationships among early vertebrates, showing extinct and extant groups.
- Displays key derived character features like distinct heads, cartilage (in cyclostomes), jaws (in gnathostomes), bone, paired fins, complete cartilaginous craniums (in gnathostomes).
- Extinct groups are marked with daggers (+), current groups with stars (*).
Cyclostomes - Extant Jawless Fish
- Agnatha (Jawless) includes hagfish and lampreys.
- Lack internal ossification, paired fins, scales, jaws, and complex reproductive structures.
- Possess a single nostril.
- Have a velum "pump" in their pharynx.
- Have rudimentary vertebral precursors (arcualia).
- Have single circulation.
- Muscular tongue with keratinous teeth.
Myxiniformes - Hagfishes
- ~75 species; ~0.5 m long
- Marine, cold-water scavengers.
- Slime glands.
- Single opening for mouth, intake, water, and gill ventilation (posterior gill openings).
- Females outnumber males 100:1
Petromyzontida - Lampreys
- ~40 species, both freshwater and marine.
- Free-living and parasitic species; 10 cm to 1 m long
- Temperate waters.
Lamprey Spawning Cycle
- Adults migrate from lakes or ocean to streams (anadromous).
- Fertilization is external.
- Eggs hatch in ~2 weeks, releasing ammocoetes larvae.
- Ammocoetes remain in nests; (~3-7 years) metamorphosis to adults.
- Free-living species don't feed as adults, die after spawning.
- Parasitic species migrate back to lakes or oceans.
Humans vs. Lampreys
- Sea lampreys ( Petromyzon marinus) invaded the Great Lakes via the canals.
- This caused a severe collapse of the Lake Trout fisheries by the 1950s.
- Control measures were implemented due to species negative impact on the food web.
Ostracoderms
- First unambiguous vertebrate fossils.
- Jawless, possession of true bone.
- Median fins (dorsal, anal, caudal).
- Heavy armor-plating.
Gnathostome Derived Characters
- Jaws (teeth): firm grasp, greater food resources.
- Paired limbs (pectoral and pelvic): improved movement.
- Jointed gill arches: double-pump ventilation.
- Vertebral column (segmented vertebrae): support and structure.
- Nerve fibers (myelin sheaths): faster impulses.
- Muscles (epaxial and hypaxial): more complex movement.
- Heart (conus arteriosus): improved circulation.
Gnathostome Body Plan
- Horizontal septum divides trunk muscles (dorsal epaxial and ventral hypaxial).
- Three semicircular canals in inner ear (addition of horizontal canal).
- Two olfactory tracts, lead to two nostrils.
- Jaws with teeth.
Extant Gnathostome Teeth
- Chondrichthyans - tooth whorl (rests on jawbone -- not embedded).
- Some bony fishes, modern amphibians, and lizards – teeth set within a shelf of the inside jawbone.
- Most bony fishes and some reptiles - teeth are fused to the jawbone.
- Mammals - teeth are set in sockets and attached by periodontal ligaments.
Origin of Jaws
- Gnathostome jaws formed from the mandibular arch.
- Jaw supports are formed from the hyoid arch.
- HOX gene duplication led to more complex structures.
Cyclostome vs. Gnathostome Gill Placement
- Cyclostomes - gills are located in a pouch-like structure.
- Gnathostomes - gills are located in arch-supported rows.
Vertebrate Nose
- Cyclostomes have a single nostril (monorhiny).
- Gnathostomes have two nostrils (diplorhiny).
- Nasal capsules (olfactory) close to the forebrain in cyclostomes; more anterior in gnathostomes.
Origin of Paired Appendages
- Pectoral fins were the first paired appendages.
- Fish swim by flexing their bodies and tails back-and-forth.
- Gnathostomes have a distinct head region between head and neck.
Advantages of Fins
- Caudal fins: propulsion.
- Other fins: steering.
- Unpaired dorsal and anal fins prevent body rotation.
- Paired pectoral and pelvic fins control pitch, act as brakes.
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Description
Test your knowledge on vertebrate evolution and geological time periods with this quiz. Explore key concepts like the features of early vertebrates and the characteristics of different geological epochs. Perfect for students studying biology or paleontology.
