Vertebrates 1 - Lecture notes 1 PDF

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Basic background on early vertebrates and how they evolved. These notes are from Dr. Kershner's lessons. ...

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Subphylum vertebrata Jawless fish- class Agnatha (“natha”=jaw, “ag”=without) ● Includes lampreys and hagfish Cartilaginous fishes- class Chondrichthyes ● Includes rays, sharks, skates, etc Bony fishes- class Osteichthyes ● Includes sunfish, clownfish, many other well recognised fishes Amphibians- class Amphibia ● Includes salamanders, newts, frogs, toads, etc Reptiles - class Reptilia ● Includes, lizards, snakes, crocs., alligators, turtles Birds- class Aves ● Birds… obviously Mammals- class Mammalia ● Canines, felines, rodents, ungulates, etc Extinct classes: ● Class acanthodii- fishes ● Class placodermi- fishes Characteristics of Vertebrates (unique, shared characteristics) 1. Bony/mineralized vertebrae assoc. w/ vertebral column a. Enhances body structure and mobility b. Not present in a major way in agnatha, no evidence in hagfish, remnants in adult lampreys i. Secondarily lost during the course of evolution ii. Possess complex calcium homeostasis system c. Over time vertebrae formed around the notochord, and the neural tube thickened. Blood vessels also developed, and later the vertebrae encased the neural tube as well. 2. A cranium of some kind→ bony, cartilaginous, fibrous, etc a. Vertebrates formerly known as the “craniata” b. Structure surrounds/protects brain and is associated with sensory systems i. Allowed for expanse of sensory centres and complexity of the brain structure 1. Greatly increase capacity to respond to environment 2. Reducing likelihood of damage→ increased range of habitat and activities 3. & 4. Ontogenetic characteristics→ effects organism during development a. (3) duplication and expansion of HOX gene complex (homeotic, master, etc) i. Genes associated with body plan/development/formation ii. Encode transcription factors→ turns genes on and off during devo. 1. Limb devo. head/cephalic region, articulation on limbs (hands/feet) iii. Tetrapods have 4 copies (~35-50 genes)

iv. Fish have 3-13 copies (~39-110 genes) v. Changes in structure of individual HOX genes b. (4) neural crest cells i. Cells that form when neural plate (sheet of ectoderm) sinks into embryo to form dorsal hollow nerve tube (DHNT) 1. NCC change form, migrate around developing embryo, differentiate into diff. Cell types ii. NCC associated with a range of neuron diversity, cartilage, bone (craniofacial region), peripheral nervous system, range of connective tissues, endocrine system, sensory system iii. Coupling HOX genes and NCC 1. Responsible for massive elaboration of vert. Plan a. Major driver of diversity form/function...