BIOL 111 Lecture Notes - Lecture 18: Actinistia, Aestivation, Endoskeleton

• School: McGill University
• Department: Biology (Sci)
• Course: BIOL 111
• Professor: Rajinder Dhindsa

Document Summary

Biol 111-lecture 18-amphibians: key innovation sin the evolution of vertebrates, early ordovician bony exoskeleton, early silurian jaws, early devonian body endoskeleton, late devonian limbs capable of moving on land, mid carboniferous amniotic egg, bony fishes (continue, coelacanth (actinistia, lungfish (dipnoi) -estivate in mud during drought: why move on land, devonian drought. -low dissolved o2: increased competition in water, new food resources on land. -e. g. arthropods, plants: no vertebrate predators on land, terrestrial respiration, advantages. -used as supplemental respiratory device: problems on land, desiccation. -water required for fertilization & larval development: air is less dense than water. -higher pressure required in circulatory system: air temperature is more variable. -double circuit of blood flow pulmocutaneous & systemic circuit (single circuit in fish, relatively low pressure required) *advantage blood under higher pressure disadvantage mixed blood: tail used for balance, primary respiratory organ lungs, uv radiation more intense.