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Mammalia

1Approximately 5400 living species Among the most highly differentiated groups in animal kingdomDomesticated for use as food, clothing, pets, beasts of burden, and in researchExotic mammal introductions have usually disrupted the ecologyIn 2007, 512 species were listed as critically endangered or endangeredDiversity

Classification : Class MammaliaPhylum ChordataClass Mammalia (26 Orders)Monotremata: egg laying mammals.(Platypus, Echidnas)Marsupials: Pouched mammals (kangaroo)Eutherians: Placentals mammals (whales, tigers, humans)

Synapsid3

What makes a Mammal?

Hair : Protection, concealment, waterproofing and buoyancy, signaling, sensory function, and thermal insulationMost are placentalSpecialized teeth and jaws for processing diverse foods in mostNervous system more advanced than in other animal groupsMammary glands nourish the newbornMamma (L.)= breast Diaphragm for efficient ventilation of the lungsConvoluted turbinate bones in the nasal cavity :Provide a high surface area for warming and moistening inspired air and for reducing moisture loss during exhalation

Integument and Its DerivativesMammals skin generally thicker than in other vertebratesComposed of an epidermis and dermis Dermis thicker than the epidermisIn regions subject to abrasion, outer layers of epidermis become thicker and cornified with keratin

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Integument FunctionsMechanical protection againstabrasionwater lossbacterial invasiondamaging UV light effectsEndothermic animals -temperature regulationExcretory and sometimes respiratory functionsPigmentation may assist in camouflage and signalingSecretes molecules that may play role in mate attractionContains sensory receptors

NOT EXACTLY ROCKET SCIENCE:

The Worst Places To Get Stung By A Bee: Nostril, Lip, PenisbyEd YongIts when a honeybee flew upMichael Smithsshorts and stung him in the testicles.Smith is a graduate student at Cornell University, who studies the behaviour and evolution of honeybees. In this line of work, stings are a common and inevitable hazard. If youre wearing shorts and doing bee work, a bee can get up there easily, he says. But I was really surprised that it didnt hurt as much as I thought it would.That got him thinking: Wheres the worst place onthe body to get stung?http://phenomena.nationalgeographic.com/2014/04/03/the-worst-places-to-get-stung-by-a-bee-nostril-lip-penis/

Ed YongHairdistinctive keratinized derivative of mammalian skin

slender keratinous filaments

shaft embedded in a hair follicle

follicle wall composed of epidermal cells

base enlarged to form a root, into which a conical hair papilla growsHair grows for the root. Once leave follicle, cells die and filled with keratin.

8Hairconsists of three layersMedulla is in the center of the hairCortex with pigment granules lies outside medullaCuticle is outermost layer and composed of imbricated scalesArrangementa complete coverage of hair is termed a pelage (fur coat)outer guard hairs; coarse and longunderhair; dense and soft

Hair Structure

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1. InsulationUnderhair traps a layer of insulating airGuard hair forms a protective blanket over underhairInsulative value related to guard hair length & underhair density2. CommunicationRaised hair can communicate warnings of anger or fear3. SensationVibrissae (whiskers) provide tactile information from surroundingsOften particularly long in nocturnal and burrowing mammals4. DefenseSpines of porcupines, hedgehogs etc. protection against predation5. CamouflageSnowshoe hares, arctic foxes etc.molt according to seasonHair Functions

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Glandsmammals have the greatest variety of integumentary glandsall are derivatives of the epidermis and fall into 4 categories

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GlandsSweat GlandsEccrine glands not associated with hair folliclesfunction before pubertysecrete a watery fluidinvolved in evaporative coolingfound in hairless regions of most mammals (e.g. foot pads)(ii) Apocrine glands associated with hair follicles begin to function at onset of sexual maturity secrete a viscous fluid appear to be functional in chemical communicationin armpits, on and around genitalia, ears.

12Glands2. Sebaceous GlandsAssociated with hair follicles and found over entire body surfaceProduce an oily secretion, sebum, that waterproofs & lubricates hair and skin

3. Scent glandsModified sebaceous glands or apocrine glandsUsed for communication (marking territory, warning, defense)Locations vary greatly:Deer: face, chin, belly, interdigitalDromedary: back of headWolves and Foxes: base of tailSkunks: anal region

134. Mammary Glandsoccur in all female mammals and in males in a rudimentary formproduce and release milk to a suckling (lactation)composed of numerous lobules, each a cluster of milk secretingAlveolialveoli open into a duct that either opens (a) directly to the surface(b) into a chamber (cistern) or(c) through raised epidermal papilla

Glands14Integument SpecializationsNails, Claws and Hoovesnail/claw (unguis), tightly compacted keratinized regions on the surface of fingers and toesmatrix cells produce new unguis continuously, pushing existing nail outwardnails unique to primatesclaws found in numerous vertebrate groupshooves are enlarged keratinized plates on the tips of ungulate digits

15Horns and Antlersboth formed by bony outgrowths of frontal bones of skullAntlersbranched and composed of solid bone when mature April May Late Summerantlers grown & shed annually, typically found in males onlyfunctional in social recognition, sexual display and joustingbone surrounded by a vascularized skin (velvet)

Integument Specializations16True Hornshollow keratinized sheaths of epidermis surrounding a core of bone and germinal epidermal layernever shed or branch and grow continuouslyfound in both males and females

True Horns AntlersIntegument Specializations

17Feeding SpecializationsFood and Feeding Mammals exploit a wide variety of food sourcesspecialistsgeneralistsTeeth Structure of teeth reveal the habits of a mammalDifferentiation of teeth for cutting, seizing (heterodont)Reptiles have homodont dentition or uniform tooth patterns

Mammals have only 2 sets of teeth (diphylodont teeth).Fishes and Reptiles, polyphylodont. Continually replaced.

18Insectivores: Due to limited ingestion of fibrous vegetable matter, digestive tract is shortHerbivores: generally have long digestive tracts for the prolonged time needed to digest fiber. A side pocket or cecum may also serve as a fermentation chamber and absorptive area.Carnivores: High protein diet is easily digestible and, therefore, the digestive tract is shorterOmnivores: intermediate between herbivores and carnivoresFeeding Specializations - Digestive Tract

19The smaller the animal, the greater is its metabolic rateRequires more food per unit sizeAmount of food varies more closely in proportion to the body surface area rather than the body weightBody Weight & Food Consumption

Surface area is proportional to about 0.7 power of body weight.Amount of food a mammal or bird eats is also about 0.7 power of body weight.Shew eats it body weight each day and may die within hours.Mountain lion eats once a week.

Few terrestrial mammals make regular seasonal migrationsMost remain in a home rangeMore migratory animals in North America than any other continentCaribou migrates twice each year, spanning 1601100 kilometers (100700 miles)Migration

Reproductive CyclesEstrous CycleMost mammals have mating seasons timed to coincide with most favorable time to give birth and rear youngFemale usually restrict mating to a fertile period during the estrus cycleCommonly called heat or estrus Animals with only one breeding season a year are monestrousRecurrent breeding is polyestrous

Reproduction

Reproductive Patterns Egg-Laying monotremesMonotremes, such as the duck-billed platypus, lay eggs with one breeding season per yearEggs are fertilized in oviduct before albumin and a thin, leathery shell are addedEggs are laid in a burrow nest and incubated for 12 daysNo gestation period and egg provides all nutrientsAfter hatching, young nourished by milk lapped off mothers fur near mammary glandsReproduction

Pouched, viviparous mammalsMarsupials do have a primitive choriovitelline placentaEmbryo is first encapsulated by shell membranes and floats free in uterus for several days

Pouched Marsupials

After hatching from shell membranes, embryo erodes a shallow depression in the uterine wall and absorbs nutrient secretions by a vascularized yolk sacGestation is brief and marsupials give birth to tiny young that are still embryosEarly birth is followed by a prolonged interval of lactation and parental care in mothers pouchEutherians are viviparous placental mammalsEmbryo nourished in uterus through a placentaGestation is longer than in marsupials and is much longer for large mammalsGestation and body size are loosely correlated due to variation in maturity at birthHumans have slower developmental period than any other mammal Placental Mammals

Humans and MammalsDomesticated Animals Dogs were probably the first domesticated animals, being an adaptable offspring of social wolvesThe domestic cat is probably derived from an African race of wildcatNomadic people probably subdued horses, camels, oxen, and llamasSome totally domesticated animals no longer exist as wild species (e.g., dromedary camel, llama) Many have been selectively bred to yield characteristics desirable for human purposes

Characteristics : Class MammaliaBody mostly covered with hair, but reduced in someIntegument with sweat, scent, sebaceous, and mammary glands, underlain with thick layer of fatSkull with two occipital condyles and secondary palate; jaw joint between squamosal and dentary bones, middle ear with three bones (malleus, incus, stapes); Pelvic bones fusedMouth with diphyodont teeth (milk, or deciduous, teeth replaced by permanent set); teeth heterodont in most (varying in structure and function); lower jaw a single enlarged bone (dentary)Moveable eyelids and fleshy external ears (pinnae)

27Circulatory system of four-chambered heart (two atria and two ventricles); persistent left aortic arch, and nonnucleated, biconcave red blood cellsRespiratory system of lungs with alveoli, and larynx; secondary palate (anterior bony plate and posterior continuation of soft tissue, the soft palate) separates air and food passages; muscular diaphragm for air exchange separates thoracic and abdominal cavities; convoluted turbinate bones in the nasal cavity for warming and moistening inspired airExcretory system of metanephric kidney with ureters that usually open into a bladder. Loop of Henle for concentration of urine. Urea as nitrogenous waste.Brain highly developed, especially cerebral cortex; 12 pairs of cranial nerves; olfactory sense highly developedEndothermic and homeothermic.Characteristics : Class Mammalia28Cloaca present only in monotremes (present but shallow in marsupials)Sexes separate; reproductive organs of a penis, testes (usually in scrotum), ovaries, oviduct and uterus; sex determination by chromosomes (male heterogametic)Internal fertilization; embryos develop in a uterus with placental attachment (except in monotremes); fetal membranes (amnion, chorion, allantois)Young nourished by milk from mammary glandsCharacteristics : Class Mammalia