BIO 370 - Exam 1 - Gnathostomes Flashcards
Describe the traits of Cambrian vertebrates.
Evidence of a notochord marks these animals as chordates, and presence of a cranium and paired sensory structures mark them as vertebrates, because these structures form from neural crest and neurogenic placodes.These animals also had other vertebrate features: a dorsal fin and a ribbonlike ventral fin (but without fin rays); six or seven gill pouches with filamentous gills and a branchial skeleton; W-shaped myomeres, and segmental structures flanking the notochord interpreted as vertebral rudiments. Cambrian vertebrates lack bone and features that would convincingly unite them with either cyclostomes or gnathostomes.
Conodont animals features such as a notochord, myomeres, and large eyes, led to their interpretation as vertebrates.
Cambrian vertebrates and extant cyclostomes lack mineralized tissues.
Slide 6 - phylogenetic tree with Cambrian vertebrates
Head
Tripartite brain
Muscular pharynx
Neural arches
Determine if vertebrates evolved in marine or freshwater environments.
Evidence of Marine Origins
- The earliest vertebrate fossils are from marine sediments.
- Invertebrate deuterostomes are exclusively marine and have body fluids with approximately the same osmolal concentration as their surroundings.
- Hagfishes have concentrated body fluids like surrounding seawater (ocean water), and this probably represents the original vertebrate condition.
Slide 13 Describe the synapomorphies of cyclostomes.
Key features of cyclostomes that differentiate them from gnathostomes include:
- A single median nostril
- Gills supported by an unarticulated gill arch skeleton
- A membranous flap in the pharynx moved by muscles that pumps water over the gills
- Keratinous teeth on the tongue
- Trunk muscles that extend to the head near the eyes
- A primitive immune system
Describe the traits of hagfish.
Hagfish Synapomorphies
Slime glands
Barbels
Hagfish Systems
Skeletal System: keratinized teeth in longitudinal rows that open and close on a horizontal plane rather than vertical
Respiratory System: one nostril brings in both olfaction and water that pumps over gills, which are behind head for scavenging
Nervous System: thought to be rudimentary but great sense of smell
Osmoregulation: maintain chordate condition of body fluids same concentration as seawater
Reproduction: Skewed sex ratio (100:1 females)
Describe the traits of lamprey.
Lamprey Synapomorphies
Gill pouches that open to the outside in a slanted line
Round mouth with a buccal funnel for parasitizing other animals
Lamprey Systems
Skeletal System: teeth on tongue
Respiratory System: can’t ventilate gills so use tidal ventilation through gill openings
Nervous System: well-developed eyes with good color vision
Endocrine System: pineal eye
Digestive System: straight and simple digestive tube
Osmoregulation: well-developed kidneys allow them to live in a wide range of
salinities (now most common in freshwater
Reproduction: anadromous and semelparous
Describe the traits of osteognathostomes.
Dermal bone but no jaws
No well-formed vertebrae
Paired nostrils
Regionalization of the gut
Slide 27 - diversity of jawless osteognathostomes
Discuss why bone evolved.
to store minerals
Describe the synapomorphies of gnathostomes.
Gnathostome Traits
Joints in gill arches
Jaws with true teeth
Paired fins (dorsal, pelvic and pectoral)
Segmental W-shaped axial muscles
Gnathostome Skeletal Systems
Paired fins allow for more movement
Bones form in pectoral and pelvic fins
Jaws, of course
True vertebrae
Ribs provide anchor for muscles
Articulated gill arches allow for double-pump gill ventilation, in which water moves between muscularized chambers in the head
Gnathostome Systems
Muscular System: muscles differentiate and become more well-developed
Osmoregulation occurs
Digestive system: true teeth and an acid-secreting stomach
Circulatory: Small chamber anterior to ventricle of heart (conus arteriosus) that acts as a reservoir
Reproduction: specialized reproductive ducts and some offspring found with umbilical cords meaning that some had internal reproduction with pelvic claspers
Describe the origin of jaws.
open their mouths to pass O2 respiration
Slide 37 - Development and evolution of jaws.
Describe the origin of paired fins.
Balance
