Characteristics of Mammals Hair – composed of keratin for insulation, sensation, appearance, and protection. (other keratinized structures – horns, antlers, etc.) Mammary Glands – modified sweat gland that, in females, produce milk to nourish their offspring. 3 Middle Ear Bones – malleus, incus, and stapes (hammer, anvil, and stirrup); the first two derived from the ancestral jaw.
Question Hair is made out of a protein called A. lactose. B. keratin. C. mammalin. D. hemoglobin. Other mammal structures made of keratin:
Characteristics of Mammals Highly differentiated teeth 2 sets of teeth Single lower jaw bone 4 chambered heart Secondary palate Muscular diaphragm Highly developed brain Endothermy and homeothermy Separate sexes (XX or XY) Internal fertilization
Question Which of the following is NOT a characteristic of mammals? A. 4-chambered heart B. Internal fertilization C. Muscular diaphragm D. Multiple lower jaw bones Although mammals have only one lower jaw bone, they have three inner ear bones. The three mammalian ear bones were originally jaw bones, but have changed in size and function. The reduction in number of lower jaw bones is easily traced through fish, amphibian and reptile.
Mammalian Teeth Heterodont teeth – different types of teeth 2 sets of teeth - Diphyodont Dental Formula – shorthand way of describing teeth Diastema – toothless gap Carnassial apparatus 1.Incisors chisel shaped for gnawing and nipping (1 root) 2.Canines long conical for catching, killing, and tearing (1 root) 3.Premolars and Molars broad for chewing (1-2 or 2-3 roots)
Question Mammals have diphyodont teeth. What does this mean? A. They have two sets of teeth. B. They have different types of teeth. C. They have a toothless gap in their teeth. D. They have more than two sets of teeth. All mammals are born with a temporary set of teeth that are lost and replaced by a permanent set as they mature into adults.
Mammalian Glands Glands are an epidermal tissue that secrete substances. 1.Sudoriferous – sweat for evaporative cooling and elimination of waste. 2.Sebaceous – secrete oil for waterproofing of hair. 3.Scent – secrete pheromones for defense, sex recognition, and territorial behavior.
Cold Weather Adaptations Endothermy – the generation of internal heat Homeothermy – the maintenance of constant temperature Winter Sleep – the organism is less active, alert, and easily aroused (Bears and raccoons) Hibernation – the organism slows metabolism, and heart and respiratory rates (monotremes, and some insectivora, rodentia, and chiroptera)
Question True or False Bears hibernate in the winter. Hibernation involves a slowing of heartbeat and respiration and usually a significant drop in body temperature. In contrast, bears enter a state of sedation referred to as torpor. Their metabolism slows down during the long winter sleep so that they do not need to eat, drink, urinate, or defecate until they emerge from their dens.
Mammalian Classification 1. Prototheria (Monotremes): oviparous (egg-laying). 2. Metatheria (Marsupials): viviparous with a short gestation, further development occurring in a pouch. 3. Eutheria (Placentals): viviparous with a long gestation.
Question Which group of mammals is oviparous? A. Monotremes B. Marsupials C. Placentals D. All of the above Monotreme is from the Greek monos meaning single & trema meaning hole. This refers to the fact that they possess a cloaca, through which a single egg is laid.
Terrestrial Placental Orders 1. Order Artiodactyla 2. Order Perissodactyla 3. Order Carnivora 4. Order Insectivora 5. Order Lagomorpha 6. Order Rodentia 7. Order Chiroptera 8. Order Primates 9. Order Xenartha 10. Order Proboscidea
Order Artiodactyla (Even-Toed Ungulates) Specialized for distance running with long hoofed legs Number of teeth is variable but they all have a diastema Chambered stomachs for microorganisms to decompose cellulose into digestible components Males often sport antlers or horns Include deer, sheep, antelope, cows, hippopotamuses, camels, & giraffes
Order Perissodactyla (Odd-Toed Ungulates) Simple stomachs Middle toe is larger than the others Horses, Rhinos, Tapirs
Order Carnivora Although not all current carnivora are carnivorous, the ancestors were meat eaters Recognizable carnassial apparatus for shearing meat and tendons Keen senses and large brains 3 upper and 3 lower incisors Dogs, cats, bears, raccoons, mustelids
Order Insectivora Third largest order of mammals and possibly the most primitive group of placental mammals Insectivorous Taxonomy is currently being revised Moles, shrews, and hedgehogs
Order Lagomorpha Resemble large rodents with short tails Flaps of skin can close behind the incisors so that chewing can happen with the mouth closed Flaps of skin can also close the nostrils 2 upper incisors, one behind the other Produce two types of fecal material, one that is wet and eaten again for further nutrient absorption, and one that is dry and discarded Rabbits
Order Rodentia Largest mammalian order (40% of species) Individual upper and lower incisors that are rootless and grow throughout life for a gnawing life style Squirrels, chipmunks, rats, mice, beavers, and porcupines
Order Chiroptera Second largest mammalian order (20% of species) Bat wings are modified forelimbs with the flight surface covered with skin and supported by four fingers The flight membrane usually extends down the sides of the body and attaches to the hind legs Bats
Order Primates Originally adapted as tree-dwellers Shortened nose and forwardly directed eyes, associated with stereoscopic vision Most live in the tropics or subtropics Lemurs, Tarsiers, Monkeys, Gibbons, and Apes
Order Xenarthra Incisors and canines absent Xenarthra means "strange joints", and was chosen because their vertebral joints are unlike those of any other mammals Placed in a separate group from all other eutherians Anteaters, sloths, and armadillos
Order Proboscidea Have a long, muscular trunk that functions almost as a fifth limb Have a pair of huge tusks derived from upper incisors Their cheek teeth are uniquely adapted to their highly abrasive diet Elephants
Question Which group of placental mammals has a name that literally means strange joints? A. Primates B. Xenarthra C. Proboscidea D. Artiodactyla Their vertebral joints have extra articulations and are unlike those of any other mammals.
Aquatic Placental Orders 1. Order Carnivora – Otters, Weasels, Seals, Walruses, Sea Lions 2. Order Cetacea – Whales, Dolphins, Porpoises 3. Order Sirenia – Manatees, Sea Cows