BSC 116 Lecture Notes - Lecture 19: Platypus, Simian, Homo Sapiens
4 Jun 2016
School
Department
Course
Professor
Document Summary
Mammals are named for their distinctive mammary glands, which provides milk for the offspring. Mammals are endothermic, and most have a high metabolic rate. Hair, another mammalian characteristic, and a fat layer under the skin help the body retain heat. Efficient respiratory and circulatory system (including four chambered heart) supports a mammal"s metabolism, a sheet of muscle called the diaphragm helps ventilate the lungs. Mammals belong to a group of amniotes known as synapsids. Early non- mammalian synapsids lacked hair, had a sprawling gait, laid eggs, and a single temporal fenestra; a hole behind the eye socket on each side of the skull. Permian-triassic extinction nearly wiped out the early non-mammal synapsids and increasing number of mammal like synapsids emerged. Are found only in australia and new guinea and are represented by one species of platypus and four species of echidnas. Have hair and produce milk, but lack nipples. After hatching, the baby sucks the milk from the mother"s fur.
