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Mammals. Chapter 28. I. Diversity. Only 4600 living species but most highly differentiated of all animal groups Many domesticated to use as food, clothing, pets, beasts of burden, and in research Habitat destruction is the cause of 300 species and subspecies being listed as endangered.

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Mammals

Mammals

Chapter 28


I diversity
I. Diversity

  • Only 4600 living species but most highly differentiated of all animal groups

  • Many domesticated to use as food, clothing, pets, beasts of burden, and in research

  • Habitat destruction is the cause of 300 species and subspecies being listed as endangered


Ii origin a synapsids
II. Origin A. Synapsids

  • First amniotes to radiate into fully terrestrial habitats

  • Pair of openings in skull roof

  • Over 150 million years small, hairless ectothermic ancestors evolved into today’s furry endotherms

  • Herbivorous and carnivorous pelycosaurs


B therapsids
B. Therapsids

  • Arose from carnivorous synapsid lineage

  • Only synapsid group to survive beyond Paleozoic

  • Efficient erect gait with limbs beneath body

  • Cerebellum expanded to coordinate more muscles

  • Most died out in Permian extinction


C cynodonts
C. Cynodonts

  • Therapsid subgroup that survived into Mesozoic

  • Higher metabolic rate to support more active lifestyle

  • Skeletal changes improved flexibility, agility, and muscle attachment

  • Developed secondary palate that allowed animal to breathe while eating prey; important innovation that allowed later mammals to breathe while suckling


D diphyodonts
D. Diphyodonts

  • Early mammals evolved in Triassic, small and shrewlike and nocturnal

  • Diphyodonts means teeth replaced once with permanent teeth

  • Endothermic but cooler than placental mammals

  • Hair with sebaceous and sweat glands

  • Hatched from eggs and relied on mammary milk

  • Radiated in Eocene after extinction of many amniote groups at end of Cretaceous


Iii general characteristics
III. General Characteristics

  • Hair; even in aquatic forms may be few but present

  • Mammary glands to nourish young

  • Most specialized placenta to feed embryo

  • More advanced nervous system


Iv skin
IV. Skin

  • Thick

  • Dermis much thicker than epidermis

  • Thin epidermis protected by hair


V hair a structure
V. Hair A. Structure

  • Hair follicle sunk in dermis of skin

  • Cells divide in follicle; as they grow away from source of nourishment, they die, forming hair shaft

  • Made of protein keratin

  • Three layers: pith center surrounded by cortex of pigment, then outer cuticle made of scales


B function
B. Function

  • Protection against wear or attack (quills)

  • Concealment—spots , stripes, salt-and-pepper disrupt coloration

  • Waterproofing

  • Buoyancy

  • Signaling & sensing--coarse long guard hairs and whiskers

  • Thermal insulation--dense soft underhair



C molting
C. Molting

  • Usually twice in spring and fall

  • Some have winter coat which is heavier and may be white for camouflage; condition called leukemism which also includes dark eyes, dark ear tips, noses , etc


Vi horns antlers a horns
VI. Horns & Antlers A. Horns

  • Found in ruminants such as sheep and cattle

  • Hollow sheaths of epidermis surrounding a core of bone from skull

  • Not shed or branched, but may be greatly curved

  • Found in both sexes and grow continuously


B antlers
B. Antlers

  • Deer family, males only

  • When, mature composed of solid bone

  • Covered in spring by highly vascular skin called “velvet’

  • Before breeding velvet drops off; after breeding antlers drop off

  • New set bigger than last


Vii glands a sweat
VII. Glands A. Sweat

  • 1. Eccrine

  • Watery fluid evaporates heat from surface of skin

  • Found in hairless areas

  • Absent in rodents, rabbits, and whales


2 apocrine
2. Apocrine

  • Larger than eccrine and open onto hair follicle

  • Forms film on skin

  • Related to reproductive cycle

  • In humans, develop at puberty in armpits, groin, ear canals


B scent
B. Scent

  • Found in all mammals though vary in location

  • Used for communication, warning, defense, and marking territory

  • Stronger during breeding season to attract mates

  • Skunks, minks, and weasels have very strong glands near anus


C sebaceous
C. Sebaceous

  • Associated with hair follicles but some open directly onto skin; all over body

  • Fats and oils that keep skin soft, and hair flexible and glossy


D mammary
D. Mammary

  • Modified apocrine glands

  • Rudimentary in males; occur on all females

  • Swelling when pregnant or nursing

  • Humans, develop at puberty with fat; further development at pregnancy


Viii teeth a general
VIII. Teeth A. General

  • Heterodont (diphodont) dentition—differentiation of teeth for cutting, seizing, gnawing etc

  • Structure reveals life habits of animals; some are specialists and others generalists

  • Primitive mammal arrangement—3 incisors, 1 canine, 4 premolars, 3 molars

  • 1 baby set and 1 adult set of teeth; generally molars only appear in adult set



B types
B. Types

  • Incisors—sharp edges for snipping, biting

  • Canines—piercing

  • Premolars—compressed crowns with 1-2 cusps for shearing, slicing

  • Molars—large bodies, variable cusp arrangements for crushing, grinding


Feeding specializations a insectivores
Feeding SpecializationsA. Insectivores

  • Shrews, moles, anteaters, bats

  • Short digestive tract because eat few plants

  • Other mammals may eat insects but not exclusively


B herbivores
B. Herbivores

  • Browsers, grazers-- horses, deer, antelope, cattle, sheep, goats, camelids; Gnawers– rabbits, rodents

  • Reduced or absent canines; molars broad and high crowned

  • Rodents have chisel-shaped incisors that growth throughout life

  • Long digestive tracts; ceca add additional absorptive area

  • Fermentation chambers in stomach to aid in digestion of cellulose

  • Ruminants 4-chambered stomachs; food regurgitated and passed back through

  • Rodents eat fecal pellets to add to fermentation

  • Some use size and defensive behaviors to avoid predation; others keen senses and escape behavior


C carnivores
C. Carnivores

  • Feed mainly on herbivores; some switch to fruits, berries when food scarce

  • Many specializations to kill prey; more intelligence, stealth, and cunning used

  • Short digestive tract

  • More leisure time because do not have to continuously graze

  • Humans have exterminated many carnivores from areas; led to more crop pests in these areas


D omnivores
D. Omnivores

  • Eat plant and animal tissue—pigs, raccoons, rats, bears, primates

  • Migration, hibernation, food caching used in temperate areas where food supplies become scarce during certain seasons


X metabolism
X. Metabolism

  • Smaller the animal, greater metabolic rate and more must eat per unit size

  • Small animals end up spending more time hunting and eating than larger animals

  • Small shrews weighing 2 g. must eat more than this each day; if deprived of food for a few hours will die

  • Mountain lions need to eat an average of 1 deer a week


Xi migration
XI. Migration

  • Most remain in a home range, but some migrate and most located in North America

  • Caribou migrate100-700 miles; gray whales 11, 250 miles


Xii flight
XII. Flight

  • Bats fly; some mammals glide

  • All bats nocturnal so use echolacation to find food

  • Echolocation uses high frequency sounds in pulses that bounce off objects

  • Large ears help collect “echos and bat forms mental image of object

  • Some moths have coevolved to have ultrasonic detectors to avoid bats


Reproduction a cycles
ReproductionA. Cycles

  • Mating seasons timed to coincide with favorable time to rear young

  • Estrous Cycle—mating restricted to fertile period in females (estrous or heat) when ovulation occurs; 1 mating/year (monoestrous); multiple (polyestrous)

  • Sometimes blastocyst remains dormant for implantation until a more favorable season—delayed gestation

  • Menstrual Cycle—old world monkeys and humans; cycle terminated by menstruation when uterine lining is shed


B patterns
B. Patterns

  • Egg-laying—montremes only; egg fertilization and formation similar to birds but eggs are leathery; laid once a year in burrow and incubated; young hatch and nursed from milk

  • Pouched—marsupials only; short gestation with early birth of embryos; mother usually immediately becomes pregnant with suckling young still in pouch but development of embryos arrested (embryonic diapause); long lactation period

  • Placental—long gestation, short lactation period; embryo in uterus nourished by placenta; humans slowest developing animal



Humans mammals a domestication
Humans & MammalsA. Domestication

  • Dogs were probably first; derived from wolves

  • Cats from African wildcat

  • Subdued horses, oxen, reindeer, camels, elephants, and llamas

  • Wild versions of llamas and dromedary camels no longer exist

  • Traits have been modified through selective breeding


B pests
B. Pests

  • Rodents and rabbits major pests of crops; elimination of natural predators has heightened problem

  • Diseases such as Tularemia, Lyme disease, and Rocky Mountain spotted fever transmitted by ticks on animals such as rodents, dogs, and deer

  • Tapeworms and trachina worms transmitted by eating infected meat


Human evolution a evolutionary groups
Human EvolutionA. Evolutionary Groups

  • Primates—grasping fingers, flat fingernails, forward facing eyes; split into prosimians & simians

  • Prosimians—dental comb, more projecting face; lemurs, tarsiers, lorises

  • Simians—opposable thumb, some tool use, large cerebrum; split into monkeys and apes

  • Monkeys—Old World located in Africa & Asia, close set nostrils, advanced dentition (baboon, mandrill, colobus); New World located in South America, grasping tail

  • Apes--tailless

  • Hominids—bipedal, larger cranium, speech



B first hominids
B. First Hominids

  • Grasslands and drought appeared about 8 mya; thought to be selective pressure that pushed apes out of trees.

  • Ardipithecus ramidus—appears about 4.4 mya with combination of ape/hominid traits

  • Australopithecus afarensis—appears about 4 mya; short bipedal hominid; brain size and facial features similar to chimp

  • Australopithicus africanus—appears about 2.2 mya; maybe descendant of A. afarensis and ancestor to Homo


A. afarensis

H. habilis and A.africanus

H. erectus


C emergence of homo
C. Emergence of Homo

  • Found in Africa

  • Homo habilis—first fully erect hominid that used stone and bone tools; appeared 2 mya and disappeared 1.5 mya

  • Homo erectus– appeared 1.5 mya; larger head and height; spread throughout Africa, Europe, and Asia; complex culture;disappeared about 300,000 years ago


D homo sapiens
D. Homo sapiens

  • Homo erectus disappeared about 300,000 years ago

  • H.neanderthalensis—some consider it a subspecies; emerged about 130,000 years ago; proficient hunters and tool users; large nose, big brow ridges, sloping head; big bones; disappeared about 30,000 years ago

  • H. sapiens—appear about 100,000 years ago; more tool using culture; rounded head, finer features; current people today





A order monotremata
A. Order Monotremata

  • Duck billed platypus, spiny anteater; Australia, New Guinea & Tasmania

  • Egg laying mammals

  • Oviparous


B order marsupiala
B. Order Marsupiala

  • Viviparous

  • Pouched (marsupium)

  • Young nourished by yolk-sac placenta

  • Short gestation

  • Australia and North America

  • 260 species


C order insectivora
C. Order Insectivora

  • Insect eaters

  • Pointy snout

  • Live part of time underground

  • Shrews, hedgehogs, tenrecs, and moles

  • All over except Australia and New Zealand

  • 419 species


D order chiroptera
D. Order Chiroptera

  • Flying with modified forelimbs with membrane between elongated fingers

  • Bats

  • Worldwide

  • 925 species


E order primates
E. Order Primates

  • Large cerebrum

  • Most arboreal

  • 5 digits with flat nails on fore- and hindlimbs; fore- used for grasping

  • Prosimians, monkeys, apes, humans

  • Worldwide

  • 223 species


F order xenarthra
F. Order Xenarthra

  • Toothless or simple peg teeth

  • Anteateaters, armadillos, sloths

  • South and Central America

  • 29 species


G order lagomorpha
G. Order Lagomorpha

  • Long constantly growing incisors

  • Additional pair of peglike incisors growing behind 1st set

  • Herbivores

  • Hares, rabbits, pikas

  • Worldwide

  • 80 species


H order rodentia
H. Order Rodentia

  • 2 pairs of incisors used for gnawing which also grow constantly

  • Extremely adaptable; fast reproduces

  • Comprise 40 % of all mammals

  • Squirrels, rats, mice, woodchucks, beavers, porcupines, gophers

  • 1935 species


I order cetacea
I. Order Cetacea

  • Forelimbs modified into broad flippers

  • Posterior limbs absent

  • Tail divided into flukes; dorsal fin sometimes present

  • Nostrils modified into blowhole on top

  • No hair except some hairs around mouth

  • Mammary glands only

  • Whales, dolphins, porpoises

  • 78 species


J order carnivora
J. Order Carnivora

  • Teeth modified for eating flesh

  • Dogs, cats, bears, weasels, seals

  • Worldwide except Australia

  • 280 species


K order proboscidea
K. Order Proboscidea

  • Proboscis (long nose)

  • Elongated incisors forming tusks

  • Elephants

  • Asia and Africa

  • 2 species


L order perissodactyla
L. Order Perissodactyla

  • Odd-toed hoofed mammals (1 or 3)

  • Ungulate

  • Teeth adapted for chewing

  • Horses,asses, zebras, tapirs, rhinoceroses

  • 18 species


M order artiodactyla
M. Order Artiodactyla

  • Even-toed hoofed mammals (2 or 4)

  • Toe sheathed in hoof

  • Ruminants

  • Herbivorous

  • Swine, camels, deer, hippos, antelope, cattle, sheep, goats


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