WJEC Biology for AS: Study and Rev Guide

Pointer Fish die out of water because the gills collapse and the filaments stick together greatly reducing the surface area for absorption of oxygen. Pointer Due to the efficiency of counter-current flow, more carbon dioxide diffuses from the blood into the water in bony fish than cartilaginous fish. QUI QUI e Fill in the missing words. Gas exchange in cartilaginous fish is …………. effective than in bony fish. Water and blood flow in the …………. direction, which is known as ………………. flow. Gas exchange occurs over ……… of the gill lamellae so …………………. is reached, and ……………. oxygen is absorbed compared to counter- current flow. Bony fish can ……………their gills by lowering and raising the …………. of the mouth or buccal cavity. Cartilaginous fish can only ventilate their gills by continuously …………… Ventilation mechanism in bony fish Bony fish have an internal bony skeleton and a flap covering the gills called the operculum. Ventilation mechanism in bony fish Human respiratory system Human respiratory system The trachea, which is supported by 20 incomplete cartilaginous rings, branches into two bronchi, each entering a lung. Bronchi branch into finer tubes called bronchioles, finally ending in alveoli where gas exchange takes place. Water intake Water expulsion (1) Mouth open (2) Floor of buccal cavity LOWERS Water rushes in X X Water forced out over gills (2) Floor of buccal cavity RISES (3) Opercular valve CLOSED (3) Opercular valve OPEN (4) Volume INCREASES pressure DROPS (4) Volume DECREASES pressure INCREASES (1) Mouth closed 81 2.2 Adaptations for gas exchange