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Intro to Chordates and Fish

3 Pages

Biology (Sci)
Course Code
BIOL 111
Irene Gregory- Eaves

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01/11/11 Chordates: ~ 53000 speices = very diverse - Include the vertebrates - Deuterostomes - Coelomates - Bilateral symmetry 3 unique characteristics: 1. Dorsal hollow nerve cord 2. Notochord: supportive rod internally (highly reduced in vertebrates, replaced by spine) 3. Post-anal tail Other characteristics: 1. Pharyngeal slits: found in chordates but not unique to them: seen first in deuterostomes 2. Hollow dorsal nerve cord and segmentation is formed by neurulation 3. Central heart 4. Reduced segmentation 5. Segmented musculature - myomeres Deuterostomes include chordates Pharyngeal slits: - Pouches in human embryo - Located on lateral surface of head - In all vertebrates, ancestral trait in deuterostomes - In vertebrates: are supported by arches: what become jaws and are important for gas exchange - For Filter feeding - For respiration in vertebrates: water coming in mouth passes through slits - O2 and CO2 can be exchanged across a respiratory surface = gills - Supported by gill arches Gills: bars in between the slits = gill arches - made of bone or cartilage - gill filaments on gill arches: respiratory exchange takes place - In boney fishes: 4 pairs of gill arches - Pairs of filaments down the filaments - Gill raker: strained food, prevents food from exiting mouth through gills - Covered by operculum, protects gills - Gills full of vascular tissue - Filament structure: = thin, vascularized, high surface area, moist, maintain partial pressure 01/11/11 - facilitate gas exchange - Lamella are small exchange surfaces - blood flows through gill arches - capillary bed in gill filaments/gas exchange - filament epithelium is one cell thick - water and blood flow in opposing directions = counter current exchange, maintains concentration gradients, achieves maximum exchange of gases (O2/CO2) Vertebrate circulation: - Closed circulatory system: blood in vessels - Heart = strong, muscular pump - Maintains blood flow - 2+ chambers (atrium/ventricle)  2 in fish - one way valves inside - Pulmonary circuit/systemic circuit: - heart  lungs  heart  body
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