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Class Mammalia mammals. Class Mammalia. Origins and Relationships Therapsids- in early Mesozoic (approx. 230 mya) Reptiles with mammal-like characteristics limbs directly under body not lateral; provided speed Cerebellum- became expanded and took on greater role; muscular coordination
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Class Mammalia • Origins and Relationships • Therapsids- in early Mesozoic (approx. 230 mya) • Reptiles with mammal-like characteristics • limbs directly under body not lateral; provided speed • Cerebellum- became expanded and took on greater role; • muscular coordination • separation of food and air passages; • made possible prolonged chewing; • animal could hold food in mouth and still breathe • developed hair • developed mammary glands
Class Mammalia • When dinosaurs vanished mammals suddenly expanded • Lack of competition allowed for mammal expansion • about 70 mya (beginning of Cenozoic) marks beginning of the age of mammals • About 55 to 30 mya mammals reached their peak
Class Mammalia Characteristics • Body covered with hair (function is to conserve body heat) • may be reduced in some species • Integument (skin) with a variety of glands: • Sweat • Scent • Sebaceous • lacrimal, • mammary glands
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Glands • Sweat Glands • keep organism cool • Two Types • Eccrine Glands – Watery Sweat • Apocrine Glands –Milk like sweat (attracting mates – pheromones) • Scent Glands- • used for attraction of mates • and to warn of possible enemies, • to set territories • Sebaceous Glands- Oil glands; • used to keep skin soft • and hair flexible • Mammary Glands • modified sweat glands; • rudimentary in males • used to feed young
Class Mammaliacharacteristics • Important skeletal features include: • two occipital condyles • head held up off ground • seven cervical vertebrae • ribs attached to thoracic vertebrae • often with elongated tail • limbs under body • body held off ground
Class Mammaliacharacteristics • Teeth • Mouth with heterodont teeth (differentiated for different functions); • have diphyodont teeth (i.e., two sets-baby and adult); • lower jaw a single enlarged bone-dentary • Teeth absent in baleen whales
Class Mammaliacharacteristics • Moveable eyelids and fleshy outer ears • four limbs (tetrapod) • Four chambered heart; Has lungs and voice box; • separation of food and air passages; • muscular diaphragm separates thoracic and abdominal cavities, • improves efficiency of breathing • Metanephritic kidney that usually opens to a bladder
Class Mammaliacharacteristics • Brain highly developed; • 12 pairs of cranial nerves
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Integument (epidermis and dermis) and its derivatives • Hair; characteristic feature of all mammals; in some it is reduced (humans, whales) • two kinds of hair forming pelage or fur • under hair- provides insulation • guard hair- provides protection and coloration
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Horns and Antlers • true horns- found in ruminants (sheep and cattle) • hollow sheaths of keratin anchored to core of bone on skull • not normally shed or branched • found in both sexes
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Antlers- in the deer family are entirely of bone material • develop beneath a covering of highly vascular tissue called "velvet" • growth stops during breeding season and male tears off velvet against tree • antlers dropped after breeding season, and a new set starts to develop each year getting bigger • in large species this represents as much as 50 lbs of calcium salts that is gotten from diet
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Rhinoceros horn • third kind of horn • from hairlike horny fibers from dermis that are cemented together
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Feeding Specializations • Herbivores- two groups; teeth specialized for shredding, grinding • all have to deal with cellulose • ruminants deal with it with four chambered stomach • • rumen• reticulum• omasum• obomasum • Carnivores- teeth modified for ripping and tearing • Omnivores- teeth modified to handle both animal and plant food • Insectivores- • Filter Feeders- Baleen Whales
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Migration found in some species not all • Harder for most mammals than birds • primarily because of locomotion on land • Prime example is the caribou- migrates about 700 miles twice annually; • summer range further north where calving takes place; • winter range to the south where food is, not so cold • longest mammal migrations done by seals and whales- easier time of it than land mammals
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Flight • Bats only mammals that can fly • wings of bats and birds homologous • some others may glide- such as flying squirrel, not true flight;
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Echolocation (bats & marine mammals) • Bats capable of echolocation; • emission of sounds that bounce off things as they echo back bats able to pick them up • allows them to locate objects without actually seeing them
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Reproduction- most have definite breeding season • males capable of fertile copulation anytime • females mating function of periodic cycle called estrus cycle; • receptive to male only during estrus or heat
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Frequency of estrus species specific • Monestrus • one estrus cycle per year • dogs, foxes, bats • Polyestrus • have several estrus cycles per year • mice, squirrels and many tropical mammals • Menstrual Cycle - typical of old world monkeys and humans; • Follows lunar cycle • postovulation period results in mentruation -discharge of lining of uterus
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Patterns of Reproduction • Monotremes • Egg laying • found in Australia • ex. duck billed platypus; • eggs fertilized then shell is put around them and they are buried; • after hatching mother feeds them with milk
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Patterns of Reproduction • Marsupials- • eggs fertilized • and early development in uterus (33 days); • then fetus leaves uterus and travels to pouch and hooks onto nipple and continues development there (200+ days)
Class MammaliaSTRUCTURAL AND FUNCTIONAL ADAPTATIONS OF MAMMALS • Patterns of Reproduction • Placentals- (Eutheria) • most successful mammal groups; • fertilization, development in uterus; • gestation period varies with species; • ex. mice 21 days, cattle 280 days, elephants 22 months; • generally gestation longer in bigger animals; • exception are the whales- gestation about 12 month
Class Mammaliahigher classification • Subclass Protheria • Order Monotremata • Subclass Theria • Infraclass Metetheria (Marsupials) • Infraclass Eutheria (Placentals)
