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Phylum CHORDATA Subphylum VERTEBRATA Class MAMMALIA MAMMALS! Class Mammalia • Endotherms • 4-chambered heart • Produce milk for • Specialized teeth young • Modified limbs • Hair • Highly developed • Diaphragms brains MAMMALS! Hair is • made out of keratin (like feathers) • developed from scales (like feathers) • arrangement provides insulation / waterproofing • conserves body heat (endotherms) MAMMALS! Endotherms maintain constant body temperatures • panting (release heat) • sweating (release heat) • shivering (generate heat) • raising hair (conserving heat) MAMMALS! Mammals have several types of GLANDS • Scent • Saliva • Hormones • Milk • Digestive enzymes MAMMALS! Mammals nurse their young • Mammary glands – secrete milk that is rich in fats, sugars, proteins, vitamins, and minerals • This continues until offspring are able to eat and digest solid food MAMMALS! The diaphragm aids in breathing • muscle beneath the lungs, separating the THORACIC (chest) cavity from the ABDOMINAL cavity • Expands the chest cavity, bringing in air • Contracts and pushes air out MAMMALS! Mammals have a 4-chambered heart • Left and Right Atrium • Left and Right Ventricle Circulation removes • Oxygenated and waste and maintains HOMEOSTASIS deoxygenated blood are entirely separated. MAMMALS! Mammalogists love teeth! • you can tell what an animal eats based on its type of teeth • teeth are adapted to type of food eaten • teeth are hard and fossilize more often than other parts of the body MAMMALS! MAMMALS! This mole’s pointed incisors are used to grasp and hold small prey MAMMALS! A beaver’s incisors are modified for gnawing and can gnaw through almost anything. These teeth continue growing throughout the animal’s lifetime. MAMMALS! A lion’s sharp canines are perfect for slicing and tearing flesh. MAMMALS! Premolars and molars are used for slicing, shearing, crushing, and grinding. MAMMALS! Other characteristics include • modified limbs • complex behaviors – learning and remembering MAMMALS! Mammals have complex brains • Primates (including humans) are possibly most intelligent • use tools • communicate MAMMALS! 3 Orders of Mammals • Monotremes (platypus and echidnas) • Marsupials (kangaroos and oppossums) • Placental Mammals (Chiroptera- bats; Rodentia – rodents; Carnivora – weasels, skunks, bears, foxes; Cetacea- whales, dolphins; Primates- chimps, apes, monkeys, humans) MAMMALS! Monotremes • Eggs • Only 3 species alive today (1 platypus, 2 echidnas) • Found only in Australia and New Zealand Flat tail, duck beak, webbed feet Coarse brown hair, covered in spines MAMMALS! Marsupials • short period of development in mother’s body • period of development inside pouch • most are found in Australia – opossum is North American marsupial MAMMALS! Placental Mammals • Over 4000 species (mostly bats and rodents) • Young develop in the UTERUS • Nourished by a PLACENTA • Development inside the mother’s body ensures protection from predators and environment during development. MAMMALS! The placenta is derived from the same membranes that surround embryos in amniotic eggs (reptiles and birds) Marsupials also have PLACENTAE, but is short-lived MAMMALS! • smallest mammals are shrews and bats and weigh as little as 3 grams • largest is the blue whale – 160,000 kg! (352,739 lbs!) Origin of Mammals • The first placental mammals appeared in the fossils record about 125 million years ago. • Scientists trace the origins of placental mammals from a group of mouse-sized animals to a group of reptilian ancestors called therapsids. Origin of Mammals • Therapsids had features of both reptiles and mammals. • They existed between 270 and 180 million years ago. Origin of Mammals • The mass extinction of the dinosaurs at the end of the Mesozoic Era, along with the breaking apart of Pangaea and changes in climate, opened up new niches for early mammals to fill. • The Cenozoic Era (65 million years to present) is sometimes called the golden age of mammals because of the dramatic increase in their numbers and diversity.
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