BIOL 111 Lecture Notes - Lecture 19: Thoracic Cavity, External Fertilization, Parental Investment

• School: McGill University
• Department: Biology (Sci)
• Course: BIOL 111
• Professor: Rudiger Krahe

Document Summary

2 groups of bony fish: ray-finned fishes (actinopterygians, the majority of fishes. Coelacanth (actinistia: fossils going back 410 million years, thought to be extinct (65 mya, 1938. Found at south african fish market: 1998. Walk on lobe fins: tetrapod motion, breathe through gills and primitive lungs, estivate or dormant in mud during droughts. Why move on land: devonian droughts (~400 mya) shallow inland seas, swamps, ponds low dissolved o2 increased competition in water crowding in small pools new food resources on land e. g. , arthropods, plants no vertebrate predators on land. Differences between land and water as relevant to life availability of water/moisture density of medium amount of oxygen stability of temperature amount of uv radiation. Advantages of terrestrial respiration: air has higher concentration of oxygen than water, gases diffuse faster in air than water. 2-chambered heart: blood oxygenated in gills, single circuit circulation, relatively low pressure required.