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Mammals Chapter 43 Monotreme species: Only 5 living: duck-billed platypus & 4 species of echidna (spiny anteaters). Placental mammals 4000 described species, mostly rodents and bats Marsupial mammals References: Holt biology text & materials http://www.ucmp.berkeley.edu/mammal/mammal.html Objectives for chapter 43 • Describe the major characteristics of mammals. • Compare the characteristics of early synapsids, early therapsids, and modern mammals. • Explain the advantage of endothermy in mammals. • Differentiate among the patterns of development in monotremes, marsupials, and placental mammals. • Recognize the various orders of mammals. – Mammalian characteristics All mammals have the following six major characteristics: 1. Endothermy 2. Hair 3. Completely divided heart 4. Milk/ mammary glands. 5. Single jawbone 6. Specialized teeth – Mammalian characteristics 1. Endothermy • All Mammals are endotherms which means they conserve and regulate body heat. • allows mammals to remain active in cold climates. • enables strenuous activities for extended periods. • Requires eating LOTS of food compared to cold blooded animals. – Mammalian characteristics 2. Hair • All mammals have hair- even aquatic ones. • Insulates against heat loss • Made of keratin protein filaments 3. Completely Divided Heart • 4 chambers (2 atria, 2 ventricles) • Efficient oxygen exchange- no deoxygenated blood pumped back into body Mammalian characteristics 4. Milk/ mammary glands. -All mammals produce milk, High in protein & sugar -only Monotremes do not have mammary glands but secrete milk like sweat. 5. Single jawbone. -lower jaw is 1 solid bone (reptiles have several bones) 6. Specialized teeth -teeth modified for different functions History of MammalsSynapsids & Therapsids Synapsids – were animals that were small and looked like modern lizards. Unlike most other reptiles, which have uniformly shaped teeth, these early synapsids had specialized teeth. Therapsids • A subset of synapsids, called therapsids, gave rise to mammals. • Therapsids appeared late in the Permian period and lived into the Jurassic period. – History of Mammals- History of Mammals • Mammals and dinosaurs – appeared during the Triassic period – coexisted for more than 150 million years. • Early mammals – about the size of mice – probably insectivores – active at night. – History of Mammals- Phylogenetic Diagram of Vertebrates Mammals have highly developed & efficient body systems: • Circulatory System • Respiratory System • Digestive System – note specialized teeth – Special Adaptations for Digesting Plants • Nervous System • Reproduction Circulatory System • 4 chambered heart • 2 atria, 2 ventricles – A septum completely separating the ventricles. – The complete septum is an adaptation that allows mammals’ bodies to use oxygen more efficiently. Respiratory System - efficient gas exchange. –larger surface area available for gas exchange –At rest, mammals breathe mostly with their diaphragm. Digestive System • TEETH: - size and shape of teeth reflect differences in diet in various species. – Incisors -Chisel-like cut. – Canines Pointed grip, puncture, and tear. – Premolars shear, shred, cut, or grind. – Molars grind, crush, or cut. • Carnivores have sharp incisors & long canines. • Baleen whales have baleen instead of teeth. Types of mammalian teeth: Special Adaptations for Digesting Plants • Herbivores have long digestive tracts • special organs w/ symbiotic microorganisms, which can break down cellulose. – Some have a rumen and are called ruminants. – Others have a cecum. Nervous System • Big Brains: – A mammals brain is at least 15X heavier than a similarly sized fish, amphibian or reptile. – Humans, other primates, and whales have the biggest brains cerebrum which is folded for max surface area. – due mostly to the size of the – The cerebrum evaluates input from the sense organs, controls movement, initiates and regulates behavior, and functions in memory and learning. • Senses: – Major senses include vision, hearing, smell, touch & taste. – Some animals are more developed in some senses: example Most bats, which are active at night, use echolocation to locate prey and other objects. There are 3 different kinds of mammals based on how they give birth: 1.Monotremes are oviparous, they lay eggs. 2. Marsupials are viviparous, they give birth to live young that further develop within a mother’s body. pouch on the 3. Placental mammals also viviparous, but the fetus typically develops within the mother’s reproductive system for a longer time & receives nourishment through blood-rich structure- the placenta. Mammalian orders: • Mammals are commonly classified into: –a single (1) order of Monotremes –7 orders of Marsupials –about 18 orders of Placental mammals Phylogenetic Diagram of Mammals Monotremes • Lay & incubate large eggs • Mom protects & feeds newborns until able to survive on their own. • The order Monotremata, (monotremes) is the only order in the subclass Prototheria. • Just 3 species exist today: – The duckbill platypus is adapted to life around rivers or streams in Australia. – Two echidna species live in dry woodlands or deserts in Australia and New Guinea. Marsupials • Embryo develops in the uterus, but when born, crawls into the mother’s pouch, attaches to a nipple to feed; develops in the pouch for several months. • Previously 1 order, but are now divided into at least 7 orders in the super order Marsupialia. • Most of 280 species live in Australia, • Virginia opossum is only marsupial native to USA • Theory: marsupials began to evolve in isolation when Australia drifted away from the other continents more than 40 million years ago. Placental Mammals • Placental mammals give birth to welldeveloped young after a long period of development inside the uterus. • During this period, the placenta provides nourishment and oxygen to developing offspring Your assignment: Read pages 868 to 874 in the textbook. Write down the following orders & give the main characteristics of each Plus at least 2 example organisms: • Monotremes • Superorder marsupialia • Placental mammals in super order Eutheria – Xenarthra – Lagomorpha – Rodentia – Primate – Chiroptera – Insectivora – Carnivora – Artiodactyla – Perissodactyla – Cetacea – Sirenia – Probscidea – Also the 5 orders in the table 43-1 Then- Answer questions 1-5 on page 874 18 orders of Placental Mammals Order Xenarthra • The order Xenarthra includes about 30 living species of anteaters, armadillos, and sloths living in the Americas. Order Lagomorpha • The order Lagomorpha, the lagomorphs, includes about 70 species of rabbits, hares, and pikas. 18 orders of Placental Mammals Order Rodentia • The order Rodentia, the rodents, is the largest mammalian order, which includes more than 1,800 species. • Rodents are adapted to a wide range of habitats worldwide. • Squirrels, marmots, porcupines, chipmunks, gophers, muskrats, mice, and rats are rodents. Order Primates • The order Primates is made up of 235 living species, including lemurs, tarsiers, lorises, monkeys, gibbons, apes, and humans. • They live in a variety of terrains; most are omnivores with complex behaviors. 18 orders of Placental Mammals Order Chiroptera • Chiroptera, the bats, are the only mammals that truly fly. • More than 900 species live throughout the world, except in polar environments. Order Insectivora • The order Insectivora includes about 390 species of shrews, hedgehogs, and moles. • Most members of this order are insectivores, but not all insectivores are members of the order Insectivora. 18 orders of Placental Mammals Order Carnivora • The 274 living species of the order Carnivora are distributed worldwide. • Dogs, cats, raccoons, bears, hyenas, otters, seals, and sea lions are some well-known carnivores. • Most members of this order eat meat. Most are skilled hunters. • Aquatic carnivores, known as pinnipeds, include the sea lions, seals, and walruses. Hoofed Mammals • • • Hoofed mammals are ungulates. Most are herbivores that run quickly. The two main groups of ungulates are characterized by their foot structure and by the presence of either a rumen or a cecum. Order Artiodactyla • • • Ungulates with an even number of toes are artiodactyls, in the order Artiodactyla. Most artiodactyls are ruminants, or animals that have a rumen. This order includes about 210 species of deer, cattle, giraffes, pigs, and camels. Order Perissodactyla • • • Ungulates with an odd number of toes are perissodactyls, in the order Perissodactyla. Perissodactyls have a cecum. This order includes about 17 living species, such as horses, zebras, rhinoceroses, and tapirs. Some Aquatic Mammals Order Cetacea • Closely related to Artiodactyla is the order Cetacea, the cetaceans. • Cetaceans include about 90 species of whales, dolphins, and porpoises worldwide. • Cetaceans are totally aquatic but evolved from land-dwelling mammals. Order Sirenia • Four species of manatees and dugongs make up the order Sirenia, the sirenians. • These herbivores live in tropical seas, estuaries, and rivers. • The similarities between whales and sirenians came about through convergent evolution. – More mammals Order Probscidea • Members of the order Proboscidea have a nose that is modified into a long, boneless trunk, or proboscis. • The only living species of this order are the Asian elephant and the African elephant, which is the largest living land mammal. • Mammoths and mastodons are extinct members of this order. • Elephants have long gestation periods, and can live to be 80 years old. And other orders making up less than 1% of mammals