Z203/ Unit 6

Ch 28: Class Mammalia I. Diversity

A. Mammalogy - Study of mammals - Vertebrates with characteristics such as: homeothermic metabolism fur covered mammary glandular tissue four-chambered hearts complex nervous system majority are viviparous B. Overview

- Fur/hair is unique trait of most all mammals - amount varies from very little to lots - hair serves many functions:

protection, concealment, waterproofing, buoyancy, signaling, sensitive vibrissae & most importantly thermal insulation = endothermic homeotherms

- mammals have other key characteristic features: a. specialized placenta to feed embryo in most b. viviparous with internal fertilization c. nervous system most advanced d. mammary glands nourish newborns (modified sweat glands) e. 1 jaw bone w/ Heterodont Dentition f. 3 ear bones

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B. Diversity - about 4,800 living species known (compare to 9,700 birds, 28,000 fish, 1.1 million insects) - most highly differentiated group in animal kingdom - many domesticated for use as food, clothing, pets, labor & research - exotic introductions have usually disrupted ecology - habitat destruction is factor in 300 species & subspecies being considered endangered II. Origin & Evolution

A. History 1. earliest amniote ancestors well documented in fossils 2. over last 150-190 my, small, ectothermic, hairless ancestor

evolved into today’s endothermic, furry mammal 3. skull structures, especially teeth, provide abundant

evidence for evolutionary descent 4. skull roof separates amniotes into synapsids, anapsids, &

diapsids a. mammals derived from synapsids (paired openings in skull roof) b. synapsids 1st amniotes radiated widely

5. Therapsid lineage a. therapsids arose from early carnivorous synapsid, 1st to have efficient erect gait w/ upright limbs beneath body

c. reduced stability required expanded cerebellum d. most therapsids

disappeared in Permian extinction

e. last therapsid subgroup to evolve survived into Mesozoic

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6. Cynodonts – (transitional therapsid group) a. half reptile/ half mammalian characteristics b. high MR supported active life b. increased jaw musculature & skeletal changes for greater agility c. 2o bony palate allowed them to breathe while eating (young able to suckle & breathe)

d. heterodont teeth e. turbinate bones in nasal cavity (heat retention) f. ↑ # ribs, making spinal column more flexible g. small carnivorous group (Trithelodontids) resemble mammals h. extinct Late Triassic

7. Early Mammals of Triassic Period a. earliest mammals small & mouse-sized b. diphyodonts (teeth replaced only once as

deciduous and permanent teeth) c. evidence suggest endothermic

(cooler than modern mammals) d. hair essential & accompanied by sebaceous

& sweat glands e. mammary glands evolved before Triassic end f. young early mammals must have hatched

from eggs & relied on maternal milk g. all non-mammalian synapsids extinct when

dinosaurs became abundant

8. Cenozoic Radiation of Mammals a. "Adaptive Radiation" in Eocene ("mass extinctions") b. diversified to fill habitats by extinction of

amniote groups during Cretaceous (65mya) c. mammals were agile, endothermic, intelligent,

adaptable, & gave birth to protected young

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d. three groups emerged: 1. Protherian (oviparous mammals - platypuses and echidnas) 2. Metatherian (pouched mammals - marsupials) 3. Eutherian (placental mammals- )

III. Structural & Functional Adaptations A. Integument & Derivatives

1. Skin - generally thicker than other vertebrates - skin made of epidermis & dermis layers - dermis much thicker; thinner epidermis protected by hair - outer layers become thicker & cornified w/ keratin in areas

of high abrasion

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2. Hair

- reduced on humans; exists as a few bristles on whales - hair follicle is epidermal structure sunk into dermis - hair grows continuously by rapid proliferation of follicle cells - cells in hair shaft carried upward away from nutrients &

therefore die - dense keratin creates nails, claws, hooves

(same as feathers) - dense & soft underhair insulates by trapping air - coarse & longer guard hairs protect against wear & provide coloration - hair consists of 3 layers: 1. medulla or pith is center of hair 2. cortex w/ pigment granules next 3. outer cuticle composed of imbricated scales - different mammals have unique identifiable hair structure 1. brittle hairs in deer deficient in cortex 2. hollow air-filled hairs of polar bears &

wolverine deficient in medulla 3. rabbit hair scaled to interlock when pressed

together 4. sheep curly hair grows from curved follicles

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- keratinized cuticle covering makes it resistant & can be preserved in amber, tar, ice, etc (“fossil” hair can often be identified down to the species) - hair stops growing at certain length; remains in follicle

until new growth pushes it out - 3 Types of Hair: 1. Guard hairs – stiff, variable length 2. Underfur (vellus hair) – very short, fine hair 3. Vibrissae – long, highly sensitive & specifically located (whiskers) - periodic molts of entire coat common 1. foxes & seals shed every summer 2. most mammals molt twice (spring & fall)

making a heavier winter coat 3. dark coloration (Eumelanin) to pale coloration (Pheomelanin) possible in many species 4. northern & high elevation species have white

winter coats & brown summer coats 5. white winter fur is Leucism; not albinism

(have dark eyes, ear tips, noses, etc) - patterns include spots, stripes, salt/pepper etc are

disruptive & conceal animals - porcupine, hedgehog, echidna quills are barbed &

break off easy 3. Horns & Antlers - homologous to reptile scale

a. True horns = Hollow Sheath - found in ruminants (sheep, goats, muskox, bison & cattle) - hollow sheaths of keratinized epidermis - core of bone rising from skull - not usually shed or branched

(may be greatly curved) - grow continuously & found in both genders (except pronghorn)

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b. Antlers - formed in deer family - composed of solid bone when mature & forked - develop beneath annual spring covering of skin

“velvet” - only males produce antlers (except caribou) - BV constrict at end of growth period before

breeding season - antlers shed after breeding & new bud appears - each year, new pair of antlers grown, larger

than previous set & requires lots of Ca salts (moose or elk accumulate over 50lbs)

c. Rhinoceros Horn - hairlike keratinized filaments from dermis are

cemented together (epidermal cells) - structure not attached to skull 4. Glands (great variety but all epidermally derived)

a. sweat glands (only seen in mammals) - eccrine, apocrine, mammary glands - average 2-5 million, aid in temp regulation b. scent glands - variety of locations (anal, legs, feet, snout, cheeks, back, behind the eye) - important in communication c. sebaceous glands - “oil” glands, maintenance of skin & fur

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B. Digestion: Food and Feeding - exploit wide variety of food sources; some are specialists & some generalists - structures closely associated with adaptations for food finding, capturing & processing - teeth differentiation resulted in heterodont denitition 1. Incisors for snipping or biting 2. Canines for piercing 3. Premolars for shearing & slicing 4. Molars for crushing & grinding - Dental formula primitive mammal

3I:1C:4PM:3M

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(Diastema may be present) ♦ Human dental formula =

2I:1C:2PM:3M - mammals don’t continuously

replace teeth (2 sets) (deciduous/milk + permanent) = Diphydonty

- incisors, canines, & premolars usually deciduous; molars are single permanent set - some mammals lose their milk teeth in the development & are

born with permanent set

- secondary Palate (separate food and air) ♦ ↑ food processing (mouth): Mechanical & chemical - ↑ Digestive Efficiency

(specialized chambers) ♦ villi & microville (↑ SA) ♦ multichambered stomach ♦ cecum - Specializations: 1. Insectivores (shrew, mole, bats) - short digestive tract 2. Herbivores - browser/grazers deer, pronghorn, sheep - gnawers rodents, rabbit, hares - reduced or absent canines; molars broad/high crowned - chisel-shaped incisors grow cont in gnawers - fermentation chambers house anaerobic microorganisms to metabolize cellulose (4 chambers in ruminants) - side pockets/cecum/fecel consumption (increase digestion/absorption) - longer digestive systems in general 3. Carnivores - most feed on herbivores - short digestive tract (high protein) - highly digestible = more energy (don’t eat continuously) - capture prey using intelligence, stealth, and cunning tactics

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4. Omnivores - feed on both plant & animal tissues - pigs, racoons, rats, bears, primates - switch food items when scarce may require hibernation/migration - caching common - Body weight & food consumption 1. smaller body size, greater MR, eat more 2. amount of food a mammal or bird eats is about 0.7 power of body weight (3g mouse eats 5xs more food than does 10kg dog & 30xs more than 50,000kg elephant) 3. small 2g shrew must eat more than its body weight each day & will starve if w/out food for few hours 4. mountain lion may kill avg one deer/week C. Other Specializations

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1. Endothermic/Homeothermic

RESPIRATORY SYSTEM: - Lungs - ↑ surface area, end in Alveoli (air sacs) - Diaphragm contracts to create

negative pressure CIRCULATORY SYSTEM: - Double circuit closed system - 4 chambered heart - non-nucleated RBC's

2. Excretory - Kidneys

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nle

- two large kidneys with numerous nephrons

- metabolic waste converted to Urea (only 5x’s the energy to convert

compared to uric acid) - can be highly concentrated due to

long loops of He

3. Skeletal/ Muscle - overall skeleton designed for flexibility - full pelvic & pectoral girdles - limbs rotated beneath body - stout humerus/radius/ulna & femur/tibia/fibula - skull heavy (protection) - jaw bone reduced to one bone - ancestral reptilian jaw bones rotated into ear (3 ear bones) 4. Nervous System & Sensory - brain has significantly

increased ♦ neocortex of cerebrum ♦ cerebellum ♦ olfactory & optic lobe

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r snout w/ chemoreceptors)

p or-sharp incisors & anticoagulant saliva

) t

aja California to Pribilof Islands

spring produced, ↑ developmental stages)

earing

- ↑ smell (longe - ↑ hearing (external pinnae, 3 ear bones) - integration of senses greatly increased along with

memorization & problem solving 5. Communication - auditory (larynx w/ vocal cords) - visual & chemical (pheromone) 6. Echolocation - allows bats to navigate & find prey - use frequencies 30,000 to 100,000Hz (outside our range) - pulse 10 to 200 times then

receive echolocation via large ears - few moths detect ultrasonic

pulses - some bats use smell and

use sight (fruit eaters) - tro ical vampire bat has raz

D. Migration - fewer mammals then birds migrate (fur, lower MR - more in North America than any other continen - caribou migrate twice, spanning 160-1100km - gray whales migrate 18,000km between Alaska & B - fur seals journey from - most bats hibernate E.Reproduction (↓ # off - Reproductive cycles 1. mating seasons timed w/ favorable r 2. female receptivity known as estrous 3 estation period may be lengthened or de. g layed

. m ce a season) or polyestrous ng)

implantation to time birthing w/ season 4 onestrous (breed on (recurrent breedi

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. O

vered egg

p to 3 eggs

♦ young suck milk from mammary glands

. P r iparous mammals with a primitive

shell membrane

os ch

n e control:

erus) (can abort fetus if condition poor)

. P ians"

- Reproductive Patterns 1 viparous Monotremes "Protherians" - duck-billed platypus & echidnas lay eggs ♦ small 0.5 inch leathery co (similar to reptile) ♦ incubate egg (10 days), typically u ♦ no gestation, all nutrients in egg 2 ouched Marsupials "Metatherians"

- ma supials are viv “placenta”

- embryo 1st encapsulated by - “hatches” from membrane - brief gestation then give birth to tiny embry - long lactation & parental care w/in pou - ma y kangaroos have som embryonic diapause (delay develop of embryo inside ut 3 lacental Mammals "Euther - viviparous placental mammals - prolonged gestation & lactation

- membranes fuse to chorioallantoic placenta

- humans slower developing than any other mammal

. P

four calves during 50 yrs of life

nourishes embryo & removes waste - gestation longer the larger the mammal 4 atterns - ultimate number of young produced/year also depends on mortality & developmental rates REPRODUCTIVE SELECTIVE STRATEGIES: r-selective = max # young; high infant mortality k-selective = min # young; low infant mortality - small rodents produce more than one litter/season - meadow mice produce up to 17 litters of 4 to 9 young elephants produce

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ory

- size varies: several square miles in bear to a few meters in

- ho e extends further beyond defended territory and often shared

- all mammals live in ecological communities w/ other animals &

ther)

- lemmings have dramatic cycles of abundance forcing them to

- snowshoe hare cycles in response to predation/nutrients

mals

no ly subdued horses, camels,

xist as wild

F. Territory and Home Range - may use burrow or den as center of territ - territory marked usually w/ scent glands

ground squirrels - both or one gender maintains territory

me rang

G. Mammalian Populations - Population = group of individuals that potentially interbreed

plant species - populations kept in check by: density-independent factors (fire, wea density-dependent factors (diseases)

migrate IV. Humans and Mam A. Domesticated Animals - dogs probably 1st domesticated animal - domestic cat derived from an African race of wildcat - madic humans probab oxen, llamas & others - totally domesticated animals no longer e species (dromedary camel, llama)

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ependent to captive but not breeding (reindeer)

its) ation of predators

ks – squirrels, rodents)

- trichina & tapeworm (infects many mammals)

f Primates s:

) es

lorises)

increased intellect capacity (large cerebral cortex) ped vision & coordination

limbs

mya in Africa)

ids)

et umbs &

advanced teeth

- selective breeding yielded a variety of characteristics - animals range from fully d B. Mammals, crop damage, & human disease - major pests of crops & stored food (rodents, rabb - human monocultures & elimin compound the problem - many rodents carry disease - bubonic plague & typhus (rats & prairie dogs) - tularemia (wood ticks – rabbits & rodents) - rocky mtn spotted fever (tic - Lyme disease (ticks on deer) V. Human Evolution A. Evolutionary radiation o - Primate characteristic ♦ grasping fingers ♦ flat fingernails (shortened) ♦ eyes rotated medially (greater 3-D overlap - ancestral primates split into 2 major lineag ♦ Prosimians (lemurs, tarsiers, ♦ Simians (monkeys & apes) - both lineages probably arboreal, promoted: ♦ - highly develo ♦ grasping ♦ tool use - earliest Simians (fossils from 40 3 major simian groups: 1. New World Monkeys of S. America 2. Old World Monkeys (Cercopitheco (baboons, mandrill, colobus) lack grasping tail, have close-s nostrils, opposable th

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sister group to Old World monkeys

ica replaced forests (Miocene)

1. st d hands

2. Bipedal stance requires changes in skeleton & muscle

mya s afarensis

2mya, Hominid line branched to Homo

a)

Homo erectus (1.5mya to 300,000ya)

D. Ho dern Hominids - Nea

iens

odern humans may have out-competed

3. Anthropoid apes (apes & humans) apes 1st appeared 25mya B. First Hominids - 8mya, grasslands in Afr- Savannah Hypothesis:

anding upright provided better predator detection, freefor tool use, defense, parental care & food gathering

attachments 3. “near human” fossils evident 4 Australopithecu A. anamensis C. Emergence of Homo, True Humans species shared African habitat w/ Australopithecus Homo habilis (2mya to 500,000y

mo sapiens: Mo

nderthals early subculture of H. sap(130,000ya to 30,000ya) proficient hunters & tool users dominated Old World in late Pleistocene m

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n of Class Mammalia

Ornithodelphia Monotrema

oidea Homonidea

dea

Order Perissodactyla Order Artiodactyla

VII. Classificatio Subclass Prototheria Infraclass Order Subclass Theria Infraclass Metatheria Order Marsupialia Infraclass Eutheria Order Insectivora Order Macroscelidea Order Dermoptera Order Chiroptera Order Scandentia Order Primates suborder Prosimii superfamily Ceboidea superfamily Cercopithec superfamily suborder Anthropoi Order Xenartha Order Pholidota Order Lagomorpha Order Rodentia Order Cetacea Order Carnivora Order Pinnipedia Order Tubilidentata Order Proboscidea Order Hyracoidea Order Sirenia