Vertebrates Flashcards
Compare and contrast pharynx between vertebrate ancestor and amphioxus
feeding is no longer dependent on mucus, vertebrate ancestor engages in active feeding through a now muscularized pharynx. Respiratory tissue in the pharynx of vertebrates allows for diffusion of gases, and collagenous pharyngeal bars were replaced with bone/cartilage for added support and strength
What are the synapomorphies for vertebrates?
muscularized pharynx, neural crest, cranium, tripartite brain, closed circulatory system, endoskeleton of cartilage or bone paired appendages, ectodermal placode
what is the neural crest?
embryonic ectodermal tissue that gives rise to dentin, splanchnocranium (parts of the skull, jaw, gills), pigment cells, peripheral nerves, etc…
what is the ectodermal placode?
thickening of the ectoderm that gives rise to sensory structures
vertebrates active predacious lifestyle requires…
a sophisticated and cephalized nervous system
How did the pharynx evolve in the jawless agnathans?
they evolved a muscular pumping pharynx, drawing in more food allowing for increased size and a more active lifestyle
what were collagenous pharyngeal bars replaced with in vertebrates?
cartilaginous arches associated with capillary beds forming gills.
what did the evolution of jaws allow vertebrates to do?
inhale or grasp prey
what kind of scales did ostracoderms have?
dermal scales
what kind of features did primitive ostracoderms have?
extensive head shields (large bony plates), hypoceral tail
what kind of features did derived ostracoderms have?
pectoral fins, heterocercal tail, and partially ossified endoskeleton
what purpose did pharyngeal gill pouches serve in ostracoderms?
multiple pharyngeal gill pouches exclusively for respiration, exposed as external gill openings
What produced the dermal bony exoskeleton for ostracoderms?
the integuement
what function do bones serve in ostracoderms?
support, protection, muscle attachment, and mineral reservoir
hagfishes have __ semicircular canal(s)
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