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Lecture 18

Lecture 18 - Fishes.docx

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Biology (Sci)
BIOL 111
Suzanne Gray

November 1st Fishes Pharyngeal slits (pouches)  Located on lateral surface of head  Seem to be an ancestral trait in deuterostomes  Lost in echinoderms  In vertebrates, pharyngeal tissue supported by arches  Humans have a tail during fetus stage Function of Pharyngeal slits:  Filter feeding (Ex: Cephalochordate and Urochordate)  Respiration in vertebrates o Water coming in mouth passes through slits o O2 and CO2 can be exchanged across a respiratory surface = gills o Gills located between slits, supported by arches o Arches form the structure which allow respiration and the eventual evolution of jaws Gill slits and gill arches:  Pharyngeal slits = gill slits  Bars between the slits = gill arches o Bone or cartilage o Gill filaments are on the gill arches (INSERT PICTURE OF A) JAWLESS FISH!!) Bony fishes have 4 pairs of gill arches Each arch has pairs of gill filaments Bony fish also have a gill cover (operculum) Gill raker becomes smaller if the fish eats smaller food and vice versa The operculum is a hard structure, which enables the fish to protect its gills Respiratory surfaces? Must remain moist, are highly vascularized, are only 1-2 cells thick, have high surface area (Also important, maximize partial pressure gradients between respiratory media; water and blood) Larger surface area and more of them to transfer gases, athletes such as long distance runners have a larger lung capacity. Insert gill filament structure! Gill Filament structure:  Thin  Vascularized  High surface area  Blood vessels flow through arches  Capillary beds in gill filaments; gas exchange November 1t Fishes  Filament epithelium is one cell thick  Water and blood flow in opposing directions  water comes in with high oxyge
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