Vertebrata Flashcards
Clade Vertebrata
Ancestral chordates likely resembled lancelets with the expression of Hox genes in vertebrate brain development
Defined by having a vertebral column that provides structural support and protects the nerve cord, allowing for more movement, complex body functions, and a larger body size
Vertebrata Shared Derived Traits
- Vertebral column
- Elaborate brain case from endoskeleton development and cephalization
- Two or mroe sets of Hox genes
- Neural crest cells to form different structures
- Dorsal, anal, and tail fins
- Possession of a modified complex circulatory system
Early Vertebrata
Lack jaws and vertebral columns
Hagfish and Lampreys
Hagfish
Vertebrata lacking jaws that have a cartilaginous cranium, reduced vertebrae, and a flexible rod of cartilage derived from the embryonic notochord
Marine, bottom-dwelling scavengers and filter feeders
Lampreys
Vertebrata lacking jaws with a cartilaginous skeleton, elaborate cranum, a gill basket, and rudimentary vertebral elements
No lateral fins, but have dorsal and tail fins.
Inhabit marine and freshwater habitats and are mostly parasitic
Early Vertebrate Evolution Evidence
Fossils from the Cambrian explosion
Conodonts were earliest vertebrates in fossil record with cartilaginous cranium, jawless, and vertebral column
Gnathostomes
A clade of vertebrates with jaws
Shared Derived Traits of Gnathostomes
- Opposing jaws
- Mineralization of skeleton with mineralized teeth
- Two pairs of lateral appendages
- Genome duplication
- Enlarged forebrain
- Lateral line system
Origin of Jaws and skeletal minerations
Earliest vertebrates had cartilage as skeletons and then mineralized skeletons started to replace it with e deposition of calcium phosphate
Gives increased structural support, enhanced protection of internal organs, and ability to support larger body sizes
Aligned with evolution of opposing jaws
Two Types of Vertebrate skeletal systems
- Endoskeleton derived from performed cartilage that supports the body, protects internal organs, and facilitates movement
- Dermal skeleton structures derived from intramembranous ossification that develop directly from skin with a cartilage template
Early Gnathostomes
Diverse array of extinct, jawed, vertebrate fish including placoderms and acanthodians
Placoderms: widespread giant predators
Acanthodians: primarily cartilaginous skeleton with fins supporting a wide, body base
Chondrichthyans
aka sharks
Cartilaginous skeletons with endoskeleton, bony teeth, and placoid scales
Primarily rely on ram ventilation
Digestive, urinary, and reproductive tracts all shared posterior orifice and cloaca
Three Modes Chondrichthyans Reproduction
Oviparous: laying fertilized eggs outside body
Ovoviviparous: embryo development in the uterus where embryo is nourished by an egg yolk
Viviparous: Embryo development in uterus nourished by placenta
