Mammals. Early Mammals. First mammalian fossil found in Mesozoic era (hair, single jawbone, specialized teeth, & endothermic) Early mammals were small, shrew like, insect eaters that had large eye sockets making them probably nocturnal
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Early Mammals • First mammalian fossil found in Mesozoic era (hair, single jawbone, specialized teeth, & endothermic) • Early mammals were small, shrew like, insect eaters that had large eye sockets making them probably nocturnal • When dinosaurs became extinct, new habitats & food supplies opened up for mammals • "Age of mammals" occurred during Cenozoic era
Main Characteristics of mammals • Endothermic - maintain high, constant body temperature through their metabolism
Main Characteristics of mammals • hair or fur made of protein called keratin covering all or part of the body • The primary function of hair is insulation. The hair of some mammals helps them blend in with their surroundings. In some mammals, specialized hairs serve a sensory function
Main Characteristics of mammals • Single jawbone • Specialized teeth for biting, cutting, & chewing • Mammals have only two sets of teeth throughout their lives: baby teeth or milk teeth, then permanent teeth. • Mammals have four kinds of teeth: incisors, canines, premolars, and molars.
Mammary glands in females are modified sweat glands that make milk containing sugars, proteins, & fats to nourish young Young mammals are nourished on milk from birth until weaning, the time when the mother stops nursing them.
Respiratory • Mammalian lungs are more efficient at obtaining oxygen than are reptilian and amphibian lungs. • Mammalian lungs contain alveoli, small chambers that provide a very large surface area. • Diaphragm - muscle below lungs that aids respiration
Highly developed brain (large cerebrum) • Four chambered heart ( two atria & two ventricles) keep oxygenated & deoxygenated blood from mixing; double circulation
Reproduction • All mammals reproduce by internal fertilization. • Mammals are divided into three groups based on differences in how and where the fertilized egg develops.
Mammals that lay eggs • Monotremes are mammals that have a cloaca and lay hard-shelled amniote eggs. • In Greek it means single hole/opening • comes from the fact that their urinary, defecatory, and reproductive systems all open into a single duct, the cloaca. • Examples: duckbill platypus and spiny anteater of Australia.
Mammals that lay eggs • Female duckbill platypus lays her eggs in a burrow in the ground where she incubates them. • After hatching, young lick milk seeping from modified sweat glands on abdomen of males and females
Mammals that lay eggs • Spiny anteater has a pouch formed by swollen mammary glands and muscle; egg moves from cloaca to pouch and hatches; young remain for 53 days and live in burrow where mother feeds them
Mammals That Have Pouches • Marsupials begin development inside mother's body but are then born in a very immature state. • include kangaroos, koalas, wallaby, wombats, Tasmanian devils, and opossums. • Newborns crawl up into a pouch on their mother's abdomen. • Inside a pouch they attach to nipples of mother's mammary glands and continue to develop
Mammals That Have Pouches • New borns are called joeys • It will not re-emerge for several months, during which time it develops fully. • After this period, the joey begins to spend increasing lengths of time out of the pouch, feeding and learning survival skills. • Joeys stay in the pouch for up to a year in some species, or until the next joey is born.
Mammals That Have Placentas • Placental mammals use a placenta, an organ of exchange between maternal and fetal blood. • Placenta supplies nutrients to and removes wastes from blood of developing offspring. • Placenta also allows mother to move about while offspring develop. • Placenta enables young to be born in a relatively advanced stage of development.
Mammals That Have Placentas • Placental mammals are very active animals; possess acute senses and a relatively large brain. • Brains of placental animals have cerebral hemispheres proportionately larger than other animals. • Young go through a long period of dependency on parents after birth.
Mammals That Have Placentas • Placental mammals populate all continents except Antarctica. • Most are terrestrial, but some are aquatic, and bats can fly. • There are 19 orders of placental mammals, which include more than 90 percent of all mammal species. • The vast majority of mammal species are found within 12 orders.
Order Rodentia • About 40 percent of all mammal species are rodents. Rodents have teeth that are specialized for gnawing. • Most rodents are small in size. Rodents have a rapid rate of reproduction.
Order Chiroptera • This order is composed of bats, the only mammals capable of true flight. Most bats live in groups and are active only at night. • Most bats eat insects, using echolocation to catch insects while in flight.
Order Insectivora • This order consists of small mammals, such as the shrew, mole, and hedgehog that eat mainly insects.
Order Carnivora • Most species in this order are flesh-eating hunters. • Carnivores consist of lions, cats, dogs, foxes, wolves, bears, raccoons, otters, skunks, weasels, and more… • Carnivores have excellent senses of smell, vision, and hearing.
Suborder Pinnipedia • This suborder of marine carnivores includes seals and sea lions. • All four limbs of pinnipeds are modified as flippers for swimming. Their bodies are streamlined for rapid movement through the water.
Order Primates • Humans belong to the order Primates. • Other members of this order include the prosimians, monkeys, and apes. • Most nonhuman primates are tree-dwellers.
Order Artiodactyla • mammals with hooves. They have an even number of toes. • Includes pigs, hippopotamuses, camels, llamas, deer, giraffes, antelope, sheep, goats, and cattle. • Many artiodactyls have a stomach with a storage chamber called a rumen. Mammals with a rumen regurgitate partially digested food, called cud, rechew it, and swallow it again for further digestion
Order Perissodactyla • They have an odd number of toes within their hooves • includes horses, zebras, and rhinoceroses. • They lack a rumen and do not chew their cud.
Order Cetacea • It is divided into two groups: the predatory toothed whales, dolphins, and porpoises, and the filter-feeding baleen whales.
Order Lagomorpha • This order is composed of rabbits and hares. • They have long, continually growing incisors. • They also have another pair of incisors that grow behind the first pair. • Rabbits and hares have long hind legs and are specialized for hopping.
Order Sirenia • They include dugongs and manatees, barrel-shaped marine animals that eat aquatic plants. • They have front limbs modified as flippers. • Sirenians are closely related to elephants and are often called sea cows.
Order Proboscidea • There are two living species in this order, the African elephant and the Asian elephant. • These animals are the largest land animals alive today