Mammals Phylum: Chordata Class: Mammalia

1. Stina and Sam Mammals Phylum: Chordata Class: Mammalia

2. Mammals: Introduction • Mammals are among most active animals: • speed and endurance, in aquatic, aerial, and terrestrial habitats • Most biologically differentiating group in the animal kingdom. • exceedingly diverse size, shape, form, and function. • Humans cannot exist without other mammals.

4. Types of Skulls Anapsid Synapsid Diapsid

5. Origin and Evolution • Evolutionary descent of mammals= most fully documented transition in (vertebrate) history. • Synapsids:(mammals and ancestors) pair of temporal openings in skull associated with attachment of jaw muscles • Anapsids: characterized by solid skulls; includes some of earliest amniotes • Diapsids: two pairs of temporal openings in the skull; contain dinosaurs, lizards, snakes, crocodilians, and birds. • Turtles have skull with Anapsids morphology: thought to have evolved independently.

6. Origin CONT. • Pelycosaurs: earliest synapsids; radiated extensively into diverse herbivorous and carnivorous forms • Therapsids: the only synapsid group to survive beyond the Paleozoic         --see the erect gait with upright limbs positioned beneath the body, rather than out to the sides, like lizards and primitive pelycosaurs • Muscular coordination center of the brain (cerebellum) assumed an expanded role • Modifications in the morphology of therapsid skull and mandibular adductor muscles increased feeding efficiency --radiated into numerous herbivorous and carnivorous forms; most forms disappeared during the great extinction (end of Permian)

7. Origin CONT. "Mammal like reptiles" (pelycosaurs and Therapsids) • Cynodonts: survived mesozoic era; evolved several features that supported high metabolic rate; increased and specialized jaw musculature (permitting stronger bite), and several skeletal changes and supporting greater agility heterodont teeth, permitting better food processing and ability to eat diverse amount of foods. • Turbinate bones: in the nasal cavity, aides in retention of body heat, and a secondary bony palate, allowing animal to breathe while holding prey or in mouth, or chewing food. Secondary palate is more important to young, so they are able to breathe while suckling. • Loss of lumbar limbs is correlated to evolution of diaphragm, also may have provided greater dorsoventral flexibility in the spinal column

8. Origin CONT. Diphyodont (teeth replaced only once) Three middle ear bones, malleus, incus, and stapes help transmit sounds in mammals

9. Structural and Functional Adaptations of Mammals: Integument and Its Derivatives • Skin and Modifications distinguish mammals as a group • skin is strongly molded by animals' way of life • composed of dermis and epidermis • epidermis is thinner where protected by hair, but thick on palms and soles, and cornified with keratin (fibrous protein)

10. Hair • Characteristic of mammals; although humans have very little hair, and whales have only a few sensory bristles on the snout • Grows from follicle, originates in epidermis, sinks into dermis • grows continuously • Keratin: nails, claws, hooves, and feathers are made of this protein • True hair is composed of dead, keratin packed epidermal cells • Two types of hair forming Pelage (fur coat) • dense, soft under hair (insulation) and • coarse, longer, guard hair (protection against wear, and provide coloration.)

11. Hair CONT. • Consists of three layers: medulla or pith (center of hair), cortex (color pigment granules, next to medulla), and outer cuticle, composed of imbricated scales • Curly hair grows from curved follicles • Most mammals have two annual molts; one in spring and one in fall; North American Mammals have three annual molts             --White winter coat replaced with brownish gray summer coat, that coat is shed, revealing a grayer autumn coat. • Summer coats are thinner than winter coats

12. Hair CONT. • Somber colors help disguise them • Coloration/patterns allow camouflage in natural surroundings • Spots of leopards and fawns, stripes of tigers • Whiskers (vibrissae) are sensory hairs that provide sense to animals (send impulses to sensory nerve endings) • long in nocturnal and burrowing animals • Porcupines, hedgehogs, and echidnas developed spiny armor

13. Horns and Antlers • True Horns (found in Bovidae sheep and cattle) are hollowed sheaths of keratinized epidermis, arise from the skull, and true horns are not shed, but grow continuously in both males and females • Antlers (Deer family [Cervidae]) are branched, composed of solid bone when mature, only grow in mal                 (except for caribou) • develop during annual spring growth, under a covering of highly vascular soft skin called velvet • Just before fall breeding season blood vessels constrict and the stag will remove velvet by rubbing antlers against the trees

14. Horns CONT. • Antlers shed after breeding season; buds appear after a few months to herald next set of antlers; each year antlers are larger and more elaborate than years before • Annual growth strains mineral metabolism; older moose or elk must accumulate 50+ pounds of calcium salts from vegetable diet • Horns of Pronghorn Antelope (Antilocapridae family) similar to true horns, except keratinized portion is forked and shed annually; Giraffe horns similar to antlers, but retain covering and are not shed; Rhinoceros horns consist of hair like keratinized filaments that arise from dermal papillae cemented together, not attached to skull.

15. Glands • Mammals have greatest variety of glands; most fall under four classes: Sweat, Scent, Sebaceous, and Mammary • Sweat Glands: tubular, highly coiled, occur over much of the body surface (in most mammals) • not present in other vertebrates, two types: eccrine, apocrine • Eccrine: secrete watery fluid, if evaporated on surface draws heat away and cools skin; hairless regions--foot pads • Although in horses, and most primates, they are scattered over body, and reduced or absent in rodents, rabbits, and whales.

16. Glands CONT. • Apocrine Glands: larger than eccrine glands, have longer ducts secretory coil is in dermis, extending deep in to the hypodermis; always open into a hair follicle, or where a hair was • Develop near puberty and are restricted, in humans, to the axillae (armpits), mons pubis, breasts, prepuce, scrotum, and external auditory canals. • secretions are milky fluids, white or yellow, and dry on skin to form film. • Not involved in heat regulation.

17. Glands CONT. • Activity is correlated with reproduction function and signal cycle stage and receptivity (females) and degree maturity and relatedness of individuals within a species. • Scent Glands: location and functions vary in all mammals • used for communication within a species and for making territorial boundaries for warning and defense.

18. Glands CONT. • Sebaceous Glands: associated with hair follicles, some are free and open directly to the surface • Mammary Glands: only in females; develop by thickening of epidermis • increase in size during at maturity, becoming considerably large during pregnancy and subsequent nursing of young

19. Location of Scent Glands • Deer: orbital, metatarsal, and interdigital regions • Pica and Woodchuck: behind eyes and on cheek • Muskrats, Beavers, Many Canines: penis • Wolves and foxes: Base of tail (dromedary) • Skunks, Minks, and Weasels: Anal region • Secretions can be forcefully discharged for 2 to 3 meters • Many mammals give off strong scents for attracting the opposite sex during mating season.

20. Food and Feeding • Enormous variety of food sources among mammals • Food habits and physical structure are linked •  Adaptations for attack and defense, and specializations for finding, capturing, chewing, swallowing, and digesting food determines anatomy and habits • All mammals have teeth; modifications are correlated to mammals diet • evolved during Mesozoic; major changes occurred in teeth and jaw. • specialized, to preform specific functions (cutting, seizing, gnawing, tearing, grinding, and chewing.)

21. Food CONT. • Four Types of teeth: • Incisors: sharp edges, snipping/biting • Canines: piercing • Premolars and Molars: shearing, slicing, crushing or grinding •  Ancestral tooth formula (expresses number of each type of tooth) I 3/3, C 1/1, PM 4/4, M3/3=44;p shrews come closest to this pattern • Mammals do not continuously replace teeth throughout their life; 2 sets, Deciduous (milk teeth), and permanent set when skull is full grown, and large enough to accommodate a full set.

22. Feeding Specialization • Teeth, jaws, tongue, and alimentary canal are adapted to particular feeding habits • Insectivores digestive tracts are small, eat little fibrous vegetable matter • Herbivores: Browsers and Grazers • feed on grasses and other vegetation; ungulates [deer, horses, antelope, cattle, sheep, and goats. • Gnawers: rodents; rabbits and hares • Adaptations for cellulose, structural carbohydrate of plants; composed of long chains of glucose molecules • potentially nutritious food source • Ruminants (cattle, bison, buffalo, goats, goats, antelopes, sheep, deer, giraffes, and okapis) have four chambered stomachs

23. Feeding CONT. • Grass passes to the Rumen, digested by microorganisms; formed into cud, then is swallowed, returned to the rumen, fermentation is continued; • Pulp passes to reticulum • Then to the omasum, water, soluble food, and microbial products are absorbed. • Remainder passes to the abomasum ("true" acid stomach) and from there normal digestion occurs. • Carnivorous mammals feed mainly on herbivores • foxes, dogs, weasels, wolverines, fishers, and cats. • Equipped with biting, piercing teeth and clawed limbs • Digestive tract is short, and cecum small or nonexistent • Organize feeding into discrete meals, rather than continuous, much more leisure time.

24. Feeding CONT. • Carnivores are more active, and lead a "more interesting life" • must hunt and kill prey • Carnivores are intelligent, and noted for stealth and cunning. • Herbivores have are quick, agile, and have a keen sense of smell • Omnivorous mammals (pigs, raccoons, rodents, bears, and most primates [including humans]) eat a combination of plants and animals for food. • also eat fruits, berries, and grasses

25. Body Weight and Food Consumption • The smaller the mammal, the greater metabolic rate it has • Metabolic rate and food consumed varies on proportion to surface area rather than weight • Small mammals spend more time hunting and eating • Large carnivores can go with one meal for many days, and be fat and healthy.

26. Migration • Longest mammalian migrations are made by oceanic seals and whales. • Gray Whales migrate between Alaska, for summer, and Baja California, Mexico for winter. • annual migration of 11,250 miles • Female Northern Fur Seals travel as far as 1,740 miles, from California, to the Pribilofs • there, young are born within a few hours/days.

27. Flight and Echolocation • Gliding or flying evolved independently in several mammals; marsupials, rodents, flying lemurs, and bats. • Flying squirrels glide, using the patagium (gliding skin) extending from the sides • Bats are nocturnal, and use flight and capacity to navigate by echolocation • These adaptations allow bats to fly in the dark, and avoid obstacles, and also allow them to locate and catch insects • Research on Vespertilionidae (most common North American bats) has shown bats emit pulses 5 to 10 millisecond in duration, each pulse begins from 10,000 Hertz down to 30,000 Hertz • While searching for food, about 10 pulses are emitted per second

28. Flight CONT. • If prey is detected, pulses speed up to about 200 per second, in final phase of approach/capture. • External ears of bats are large, and shaped variously throughout the different species • Less is known about the inner ear, other than it receives ultrasonic sounds that are emitted • Some bats lack echolocation, although several species are diurnal. • these bats feed on fruit, flowers, and nectar • Use large eyes and olfaction to find this food.

29. Reproduction --Reproductive Cycles •  Definite mating seasons; usually summer/winter, so young are born during most favorable time of year • Males are capable of fertilizing any time of the year, females are restricted to specific time, during estrous cycle • How frequently a female in in estrous is diverse, and depends on the mammal • Monestrous: mammal having only one breeding season; dogs, foxes, and bats • polyestrous: recurring breeding season; field mice, and squirrels • Menstruation: endocrine (lining of uterus) is collapsed and discharged, mixed with blood, through the vagina; called the "menstrual cycle"

30. Reproduction CONT. --Reproductive Patterns • 3 different patterns among mammals: • Monotremes: egg laying (duck-billed platypus) • Marsupials: pouched (kangaroos) • Placental Mammals; eutherians: embryos remain in the uterus, nourished through food supplied by mother, through placenta; intimate connection between mother and young • Gestation of mice: 21 days • Gestation of rabbits and hares: 30-36 days • Gestation of cats and dogs: 60 days • Gestation of cattle: 280 days • Gestation of elephants: 22 months (longest) • Gestation of Baleen Whales: 12 months • Gestation of small bats: 4-5 months • Condition of young at birth also varies.

31. Territory and Home Range • Home range is a much larger foraging area, surrounding a defended territory, yet are not defended the same way as territories. Some may overlap, creating a "neutral zone" used for seeking food.

32. Mammalian Population • Populations are always lowest right before breeding season, and greatest after new additions arrive. • Also may fluctuate under influence of other causes. • Variations in climate; cold, hot or dry weather • Natural Catastrophes; fires, hailstorms, hurricanes • These are "Density Independent" factors, affect population, whether it is crowded or dispersed • "Density Dependent" factors, correlate with population crowding.

33. Humans and Mammals • Humans started domesticating mammals 10,000 years ago • Dogs were the first mammals to be domesticated • Domestication of cattle, buffalo, sheep and pigs came later • Horses, camels, oxen, and llamas probably were subdued by early nomadic peoples. • Elephants were never really domesticated because they seldom breed in captivity • Some activities can be conflicting to humans; damage of crops, and diseases. • bubonic plague; rodents such as brown rats and prairie dogs • rabbit fever; ticks carried by rabbits, woodchucks, muskrats, rodents. • rocky mountain spotted fever: dogs and ground squirrels

34. Humans CONT. • Lyme disease: ticks from white-tailed deer • Trichina and Tape worms: contracted through eating infected meat of infected hogs, cattle, etc.

35. Human Evolution --Evolutionary Radiation of Primates •  Humans are primates • Significant Characteristics: grasping fingers on all limbs, flat fingernails, instead of claws, forward pointing eyes, and great depth perception. • Two-Primate Lineage: Prosimians, and Simians (anthropoids) • Prosimians: lemurs, and lorises, with wet noses • Simians: Tarsiers, Monkeys, and Apes. •  Arboreal (tree-dwellers) • Highly developed sense organs, flexible limbs, precise timing, judgment of distance, and alertness • Diurnal, vision is dominant special sense, enhanced by color perception

36. Human CONT. • 3 Major simian clades • 1) New World Monkeys: South and Central America • 2) Old World Monkeys: Baboons • 3) Apes • Old World monkeys lack a grasping tail, have closed set nostrils, opposable, grasping thumbs, and more derived teeth. • Humans, orangutans, gorillas, and chimpanzees are recognized that belonging to one family, Hominidae; referred to as hominids

37. Human CONT --Early Humans •  Benefits of standing upright: better view of predators, free hands for using tools, defense, care for young, and gather food. • Transition to upright posture was enormous leap: required extensive redevelopment of skeleton and muscle attachments --Emergence of homo •  Many scientists argued over what the first form was; Homo habilis: fully erect, large, human like (shaped) brain, bulge represents Broca's motor speech area, suggests they were capable of rudimentary speech • First species to use simple stone tools • Oldest remains found: 2.4-1.8 Million years ago

38. Human CONT. --Homo sapiens: Modern Humans • Formed a single evolutionary lineage for the past 1.7 million years • Shown geographic differentiations • Neanderthals: 150,000 years ago; inhabited most of Europe and Middle East • Brain sixe similar to modern humans • Heavily muscled bodies helped them to survive cold climates --The Unique Human Position • Mutation, Isolation, Genetic Drift, and Natural selection (same processes that have affected all organisms)