Lecture 21 Flashcards
Vertebrata
chordates with vertebrae, previously called Craniata, includes largest animals
6 vertebrate character states
- vertebral column
- 2 or more sets of Hox genes
- neural crest cells
- endoskeleton and pronounced cephalization
- modifications to circulatory system
- pharyngeal clefts function as gill slits ancestrally (in aquatic)
vertebral column
chain of skeletal elements (cartilage or bone) surrounding and protecting nerve cord, replaces
notochord in rigidity, provides attachment sites for muscles and other skeletal elements
Hox genes in vertebrates
2 or more sets, result of ancestral mutation that duplicated the set of genes (non-vertebrate chordates have only 1 set)
neural crest cells
clusters of embryonic cells that form near dorsal margins
of closing neural tube, contribute to formation of bones and cartilages of cranium and other structures
cranium
brain encased in protective plates
vertebrate modifications to circulatory system
- closed circulatory system with a pumping heart
- haemoglobin in red blood cells
- oxygenated by passing close to gills or lungs
Pikaia
from Burgess Shale, vertebrate from Cambrian, but no obvious cranium or clear vertebrae
Haikouichthys
Cambrian fossil with braincase and definite eyes, no clear vertebrae
agnathans
jawless vertebrates, no paired fins
2 classes of agnathans
- myxini
2. petromyzontida
myxini
hagfish, very small cartiaginous vertebral elements, cartilaginous cranium and other skeletal elements, protect themselves by exuding slime, some overfished for skin
myxini feeding
- grip flesh using keratinous plates in mouth
- tie body into knot
- slide knot forwards until braced against
flesh - pull off chunk
petromyzontida
lampreys, notochord surrounded by cartilaginous tube, primitive vertebral column, eyes with lenses, no jaws, larval lampreys like cephalochordates (suspension feeders), adults are parasites of fish,
gnathostomes
vertebrates with jaws, 2 pairs of fins, 4 clusters of Hox genes
origin of jaws
modifications of 2 pairs of skeletal rods that supported anterior pharyngeal slits, posterior slits became specialized for gas exchange (gill slits)
chondrichthyes
sharks, rays, chimeras, endoskeleton made of cartilage, bony teeth, called cartilaginous fishes, ancestors with bony skeleton
fish
paraphyletic group including any completely aquatic vertebrate that uses gills for respiration (includes jawless fishes, cartilaginous fishes, and bony fishes)
cartilaginous skeletons
during development of most vertebrates, skeleton is
first cartilaginous and then becomes ossified (replacement of cartilage by calcium phosphate), chondrichthyans skip this developmental step
sharks
pectoral fins add lift, gain buoyancy by storing oil in liver, teeth homologous to jagged scales on rough skin, teeth continuously replaced, detect changes in electrical fields generated by muscular movement via pores around head, detect vibrations in water via lateral line, cloaca
shark reproduction
sperm transfer through copulation (males have pelvic fins modified as claspers), oviparous species protect eggs in leathery case, viviparous species nourish young through placenta, milk-like secretions, or eating other eggs, two feed on zooplankton
cloaca
reproductive tract, excretory system, and digestive
system all exit through same opening
rays and skates
swim by flapping large pectoral fins (rather than tail propulsion), flat plate-like teeth for grinding prey
chimeras
flat tooth plates for crushing shelled prey, called ‘chimeras’ because they look like they were constructed by putting together bits of other fishes
sharks as entertainment and food
shark watching, dorsal fin removal, low reproductive rate makes overfishing a concern
