BIOL108 Lecture Notes - Lecture 33: Bird Louse, Precocial, Cloaca

• School: University of Alberta
• Department: Biology (Biological Sciences)
• Course: BIOL108
• Professor: Lien Luong

Document Summary

Biol108, lecture 33, november 30, 2016 (origin of birds) Birds and crocodilians are the extant groups of archosaurs. Characteristics of modern birds: they have a four chambered heart (also in theropods and mammals). They have an aminiotic egg, and scales on their legs. They are endothermic, which is similar to carnivorous theropods. They use metabolic energy to maintain body temperature, and have a high rate of metabolism. Their feathers and layer of fat help retain body heat. They are homologous with scales, and are finely subdivided keratinous scales. They have a reduced number of forelimb digits, wings have only one main digit and two tiny digits, no claws on wing digits in extant species. Birds have horny beaks and lack teeth, which means that they swallow their food whole. They have a specialized structure called a gizzard, which is a muscular part of the stomach to during hard food.