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Mammals

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Title: Mammals


1
Mammals
  • Chapter 28

2
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

3
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 todays furry
    endotherms
  • Herbivorous and carnivorous pelycosaurs

4
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

5
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

6
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

7
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

8
IV. Skin
  • Thick
  • Dermis much thicker than epidermis
  • Thin epidermis protected by hair

9
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

10
B. Function
  • Protection against wear or attack (quills)
  • Concealmentspots , stripes, salt-and-pepper
    disrupt coloration
  • Waterproofing
  • Buoyancy
  • Signaling sensing--coarse long guard hairs and
    whiskers
  • Thermal insulation--dense soft underhair

11
Hair
12
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

13
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

14
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

15
VII. Glands A. Sweat
  • 1. Eccrine
  • Watery fluid evaporates heat from surface of skin
  • Found in hairless areas
  • Absent in rodents, rabbits, and whales

16
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

17
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

18
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

19
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

20
VIII. Teeth A.
General
  • Heterodont (diphodont) dentitiondifferentiation
    of teeth for cutting, seizing, gnawing etc
  • Structure reveals life habits of animals some
    are specialists and others generalists
  • Primitive mammal arrangement3 incisors, 1
    canine, 4 premolars, 3 molars
  • 1 baby set and 1 adult set of teeth generally
    molars only appear in adult set

21
Primary Teeth
22
B. Types
  • Incisorssharp edges for snipping, biting
  • Caninespiercing
  • Premolarscompressed crowns with 1-2 cusps for
    shearing, slicing
  • Molarslarge bodies, variable cusp arrangements
    for crushing, grinding

23
Feeding SpecializationsA. Insectivores
  • Shrews, moles, anteaters, bats
  • Short digestive tract because eat few plants
  • Other mammals may eat insects but not exclusively

24
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

25
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

26
D. Omnivores
  • Eat plant and animal tissuepigs, raccoons, rats,
    bears, primates
  • Migration, hibernation, food caching used in
    temperate areas where food supplies become scarce
    during certain seasons

27
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

28
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

29
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

30
ReproductionA. Cycles
  • Mating seasons timed to coincide with favorable
    time to rear young
  • Estrous Cyclemating 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
    seasondelayed gestation
  • Menstrual Cycleold world monkeys and humans
    cycle terminated by menstruation when uterine
    lining is shed

31
B. Patterns
  • Egg-layingmontremes 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
  • Pouchedmarsupials 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
  • Placentallong gestation, short lactation period
    embryo in uterus nourished by placenta humans
    slowest developing animal

32
Forms of Reproduction
33
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

34
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

35
Human EvolutionA. Evolutionary Groups
  • Primatesgrasping fingers, flat fingernails,
    forward facing eyes split into prosimians
    simians
  • Prosimiansdental comb, more projecting face
    lemurs, tarsiers, lorises
  • Simiansopposable thumb, some tool use, large
    cerebrum split into monkeys and apes
  • MonkeysOld World located in Africa Asia, close
    set nostrils, advanced dentition (baboon,
    mandrill, colobus) New World located in South
    America, grasping tail
  • Apes--tailless
  • Hominidsbipedal, larger cranium, speech

36
Primates
37
B. First Hominids
  • Grasslands and drought appeared about 8 mya
    thought to be selective pressure that pushed apes
    out of trees.
  • Ardipithecus ramidusappears about 4.4 mya with
    combination of ape/hominid traits
  • Australopithecus afarensisappears about 4 mya
    short bipedal hominid brain size and facial
    features similar to chimp
  • Australopithicus africanusappears about 2.2 mya
    maybe descendant of A. afarensis and ancestor to
    Homo

38
A. afarensis
H. habilis and A.africanus
H. erectus
39
C. Emergence of Homo
  • Found in Africa
  • Homo habilisfirst 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 culturedisappeared about 300,000
    years ago

40
D. Homo sapiens
  • Homo erectus disappeared about 300,000 years ago
  • H. neanderthalensissome 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. sapiensappear about 100,000 years ago more
    tool using culture rounded head, finer features
    current people today

41
H. Erectus and H. sapiens
42
Neanderthal Man
43
XIV. Class Mammalia
44
A. Order Monotremata
  • Duck billed platypus, spiny anteater Australia,
    New Guinea Tasmania
  • Egg laying mammals
  • Oviparous

45
B. Order Marsupiala
  • Viviparous
  • Pouched (marsupium)
  • Young nourished by yolk-sac placenta
  • Short gestation
  • Australia and North America
  • 260 species

46
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

47
D. Order Chiroptera
  • Flying with modified forelimbs with membrane
    between elongated fingers
  • Bats
  • Worldwide
  • 925 species

48
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

49
F. Order Xenarthra
  • Toothless or simple peg teeth
  • Anteateaters, armadillos, sloths
  • South and Central America
  • 29 species

50
G. Order Lagomorpha
  • Long constantly growing incisors
  • Additional pair of peglike incisors growing
    behind 1st set
  • Herbivores
  • Hares, rabbits, pikas
  • Worldwide
  • 80 species

51
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

52
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

53
J. Order Carnivora
  • Teeth modified for eating flesh
  • Dogs, cats, bears, weasels, seals
  • Worldwide except Australia
  • 280 species

54
K. Order Proboscidea
  • Proboscis (long nose)
  • Elongated incisors forming tusks
  • Elephants
  • Asia and Africa
  • 2 species

55
L. Order Perissodactyla
  • Odd-toed hoofed mammals (1 or 3)
  • Ungulate
  • Teeth adapted for chewing
  • Horses,asses, zebras, tapirs, rhinoceroses
  • 18 species

56
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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