Chapter 22: Specialized Teeth, Hair, Endothermy, and Viviparity

1
Mammals

• Chapter 22 Specialized Teeth, Hair, Endothermy,
  and Viviparity

2
Major Concept 1

• 1. Mammalian characteristics evolved gradually
  over a 200-million-year period in the synapsid
  lineage.

3
Major Concept 2

• 2. Two subclasses of mammals evolved during
  the Mesozoic era---the Prototheria and the
  Theria. Modern Mammals include monotremes,
  marsupial mammals, and placental mammals.

Placental Mammals
Monotremes
Marsupial
4
Major Concept 3

• 3. The skin of mammals is thick and protective
  and has an insulation covering of hair.

5
Major Concept 4

• 4. Adaptations of teeth and digestive tract
  allows mammals to exploit a wide variety of food
  resources.

Siberian Brown Bear - Teeth
Beaver Teeth
Orca teeth
6
Major Concept 5

• 5. Efficient systems for circulation and gas
  exchange support the high metabolic rate
  associated with mammalian endothermy.

7
Major Concept 6

• 6. The brain of mammals has an expanded cerebral
  cortex that processes information from various
  sensory structures.

8
Major Concept 7

• 7. Metanephric kidneys permit mammals to excrete
  urea without excessive water loss.

9
Major Concept 8

• 8. Complex behavior patterns enhance mammalian
  survival.

http//www.msnbc.msn.com/id/15487308/ns/technology
_and_science-science/ Article about self
recognition in elephants.
10
Major Concept 9

• 9. Most mammals are viviparous and have
  reproductive cycles that help ensure internal
  fertilization and successful development.

11
Major Concept 10

• 10. Primate evolution included the evolution of
  the apes and humans. Human evolution is
  documented by evidence from the fossil record,
  molecular biology, and numerous other sources.

12
Classification - Class Mammalia

• Mammary glands hair diaphragm three middle-ear
  ossicles herodont dentiton sweat, sebaceous,
  and scent glands four-chambered heart large
  cerebral cortex.

13
Classification Subclass Prototheria

• This subclass formerly contained the monotremes.
  Monotremes have recently been reclassified, and
  this subclass now contains only extinct species.

Pseudotribos
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Classification - Subclass Theria

• Technical characteristics of the skull
  distinguish members of this subclass.

Therapsid
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Classification Infraclass Ornithodelphia

• Technical characteristics of the skull
  distinguish members of this infraclass.
  Monotremes.

Platypus
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Classification Infraclass Metatheria

• Viviparous primitive placenta young are born
  early and often are carried in a marsupial pouch
  on the females belly. Marsupials.

Koalas
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Classification Infraclass Eutheria

• Complex placenta young develop to advanced stage
  prior to birth. Placentals.

Bengal Tiger
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Classification Superorder Laurasiatheria

• Order Insectivora- Diverse group of small,
  primitive mammals third-largest mammalian order.
  Hedgehogs, tenrecs, moles, shrews.

Shrew
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Classification Order Chiroptera
Gray Bat

• Cosmopolitan, but especially abundant in the
  tropics bones of the arm and hand are elongate
  and slender flight membranes extend from the
  body, between digits of forelimbs, to the hind
  limbs most are insectivorous, but some are fruit
  eaters, fish eaters, and blood feeders
  second-largest mammalian order. Bats

20
Classification Order Carnivora
Bullmastiff Rottweiler Mix

• Predatory mammals usually have a highly
  developed sense of smell and a large braincase
  premolars and molars modified into carnassial
  apparatus three pairs of upper and lower
  incisors usually present, and canines are well
  developed. Dogs, cats, bears, raccoons, minks,
  sea lions, seals, walruses, otters.

21
Classification-Order Perissodactyla

• Hoofed axis of support passes through the third
  digit. Skull usually elongate, large molars and
  premolars primarily grazers.( the Artiodactyla
  also have hoofs. Artiodactyls and perissondactyls
  are, therefore, called ungulates) (L. ungula,
  hoof). Odd-toed ungulates horses, rhinoceroses,
  zebras, tapirs.

Tapirs
22
Classification- Order Artiodactyla

• Hoofed axis of support passes between third and
  fourth digits digits one, two and five reduced
  or lost primarily grazing and browsing animals(
  pigs are an obvious exception). Even-toed
  ungulates pigs, hippopotamuses, camels,
  antelope, deer, sheep, giraffes, cattle

Giraffe.
23
Classification-Order Cetacea

• Streamlined, nearly hairless, and insulated by
  thick layers of fat (blubber) no sebaceous
  glands forelimbs modified into paddlelike
  flippers for swimming hindlimbs reduced and not
  visible externally tail fins (flukes) flattened
  horizontally external naris (blowhole) on top
  skull.

Dolphin
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Classification-Order Cetacea cont.

• Toothed whales (beaked whales, narwhals, sperm
  whales, dolphins, porpoises, killer whales)
  toothless, filter-feeding baleen whales (right
  whales, gray whales, blue whales, and humpback
  whales).

Killer Whale
25
Classification-Order Superorder Xenartha

• (ze nar-thra) (this name is also used as the
  common order name)
• Incisors and canines absent cheek teeth, when
  present, lack enamel brain case is long and
  cylindrical hindfoot is four toed, forefoot has
  two or three prominent toes with large claws
  limbs, are specialized for climbing or digging
  xanthrous lumbar vertebrae. Anteaters, tree
  sloths, armadillos

26
Classification-Order Lagomorpha

• Two pairs of upper incisors one pair of lower
  incisors incisors are ever-growing and slowly
  worn down by feeding on vegetation. Rabbits,
  pikas.

Pika
27
Classification-Order Rodentia

• Largest mammalian order upper and lower jaws
  bear a single pair of ever-growing incisors.
  Squirrels, chipmunks, rats, mice beavers,
  porcupines, woodchucks, lemmings.

Squirrel
28
Classification-Order Primates

• Adaptations of primates reflect adaptations for
  increased agility in arboreal ( tree-dwelling)
  habitats omnivorous diets unspecialized teeth
  grasping digits freely movable limbs nails on
  digits reduced nasal freely movable limbs nails
  on digits reduced nasal cavity enlarged
  stereoscopic eyes and cerebral hemispheres.

Great Ape.
29
Classification-Order Primates cont.

• Lemurs( Madagascar and the Comoro Islands ),
  tarsiers ( jungles of Sumatra and the East
  indies), monkeys, gibbons, great apes ( apes and
  humans)

Gibbons
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Classification-Order Proboscidea

• Long, muscular proboscis (trunk) with one or two
  finger-like processes at the tip short skull
  with the second incisor on each side of the upper
  jaw modified into tucks six cheek teeth are
  present in each half of each jaw teeth erupt (
  grow into place) in sequence from front to rear,
  so that one tooth in each jaw is functional.
  African and Indian elephants.

African Elephant
31
Classification-Order Sirenia

• Large, aquatic herbivores that weigh in excess of
  600 kg nearly hairless, with thick , wrinkled
  skin heavy skeleton forelimb is flipperlike,
  and hindlimb is vestigial horizontal tail fluke
  is present horizontally oriented diaphragm
  teeth lack enamel. Manatees ( coastal rivers of
  the of the Americas and Africa) , dugongs (
  western Pacific and Indian Oceans)

Dugong
32
Evolutionary Perspective

• The fossil record that documents the origin of
  the mammals from ancient reptilian ancestors is
  very complete and relatively uncontroversial.
• Confirmed many macroevolutionary theories
• age of mammals began 70mya

Therapsid
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Evolutionary Perspective

• Mammals evolved from a group of synapsids called
  the Therapsids.

34
Evolutionary Perspective

• Members of the Subclass Synapsida
• Cynognathus was a mammal-like reptile that
  probably foraged for small animals, much like a
  badger today.
• Order Therapsida the stock from which mammals
  arose during the mid-Triassic period.

Cynognathus
35
Evolutionary Perspective

• http//www.youtube.com/watch?vSyFBQmThEPk
• Introduction to the Ultimate Mammal Family Tree

36
Evolutionary Perspective
Eomaia

• First Mammals
• Small (less than 10cm long)
• Mammals from the Jurassic and Cretaceous periods
  were mostly predators that fed on other
  vertebrates and arthropods
• A few were herbivores
• Others were omnivores
• First evidence of hair was 60mya from fossil
  record, however, evidence suggests that hair
  arose 130mya

37
Evolutionary Perspective

• First mammals
• Structures important to hearing and olfactory
  senses were important to the evolution of
  mammals.
• May indicate that first mammals were nocturnal
• This nocturnal trait may have lead to endothermy

http//www.sciencedaily.com/releases/2006/10/06101
2184910.htm This article references the genes
that help with nocturnal sight
38
Evolutionary Perspective

• http//www.youtube.com/watch?vAXcYXRFQ_DEfeature
  fvst
• The development of the inner ear in mammals

39
Evolutionary Perspective

• Subclass Theria
• Diverged into three infraclasses
• Infraclass Ornithodelphia monotremes
• Infraclass Metatheria marsupials
• Infraclass Eutheria Placental mammals

Monotremes Duckbill Platypus
Marsupials Grey Kangaroo
Placental African Lion
Eggs
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Infraclass Ornithodelphia - Monotremes

• http//www.youtube.com/watch?vOVneqhu9oZk
• Watch Studies on the Northern and Southern
  Duckbill Platypus

41
Infraclass Metatheria - Marsupials

• http//www.youtube.com/watch?v2lCKc8tURtc
• Kangaroo Birth

42
Infraclass Eutheria Placental Mammals

• http//www.youtube.com/watch?vO71VjOmFFm0
• Lab Puppy Birth Turn the Music Down it is
  annoying Quick Video
• http//www.youtube.com/watch?v_vLXVe1QOEI
• White Lion Birth (Long Video) (530 to see the
  birth of the cubs) very interesting and
  informative.

43
Evolutionary Pressures-External Structure and
Locomotion

• Skin has epidermal and dermal layers
• Functions to provide
• Protection
• From mechanical injury
• From invasion by microorganisms
• From suns ultraviolet light
• Temperature Regulation
• Sensory perception
• In excretion
• In water regulation

44
Evolutionary Pressures-External Structure and
Locomotion

• Hair is uniquely mammalian
• Functions
• Sensory Perception
• Temperature Regulation
• Communication
• 2 kinds of Hair
• Long guard hairs
• Shorter insulating under hair

45
Evolutionary Pressures-External Structure and
Locomotion

• Hair because hair is composed largely of dead
  cells it must be periodically molted
• Humans gradually
• Arctic Fox Winter pelage is white spring molt
  pelage is grey and yellow. The pictures below
  show winter, molt, then summer.

46
Evolutionary Pressures-External Structure and
Locomotion

• Hair is important for the sense of touch
• Mechanical displacement of the hair stimulates
  nerve cells
• Guard hairs
• Thick found around legs, nose, mouth, and eyes

47
Evolutionary Pressures-External Structure and
Locomotion

• Hair as protection
• Air spaces in shaft and between hairs provide an
  effective insulating layer
• Arrector Pili muscles contracts lifting hair
  increases the amount of air trapped and improves
  insulation. This muscle also operates in the
  fight-or-flight response to provide the
  appearance of increased size and strength.

48
Evolutionary Pressures-External Structure and
Locomotion

• Hair Color depends on the amount of pigment
  (melanin) deposited in it and the quantity of air
  in the hair shaft.
• Most mammals pelage is dark above and light below
  to be conspicuous
• Some advertise their defenses ex. Skunk

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Evolutionary Pressures-External Structure and
Locomotion

• Pelage is reduced in large mammals from hot
  climates or aquatic mammals

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Evolutionary Pressures-External Structure and
Locomotion

• Claws are present in all amniote classes

51
Evolutionary Pressures-External Structure and
Locomotion

• Glands Develop from the Epidermis of the Skin.
• Sebaceous (oil) glands oily secretion
  lubricates and waterproofs
• Sudoriferous (sweat) glands 2 types
• Eccrine glands watery secretions used in
  evaporative cooling
• Apocrine glands secrete a mixture of salt,
  urea, and water that microorganisms convert to
  odor

52
Evolutionary Pressures-External Structure and
Locomotion
53
Evolutionary Pressures-External Structure and
Locomotion

• Sent or Musk Glands found around face, feet, or
  anus
• Secret pheromones
• Used in defense
• Used in species and
• sex recognition
• Used in territorial behavior

A male tiger spraying to mark his territory
54
Evolutionary Pressures-External Structure and
Locomotion

• Mammary Gland functional in female mammals and
  are present, but nonfunctional, in males
• Milk secreted contains water, carbohydrates
  (sugar lactose), fat, protein, minerals, and
  antibodies.

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Evolutionary Pressures-External Structure and
Locomotion

• Evolution of Mammary Glands
• Derived from apocrine glands and usually contain
  substantial fatty deposits
• Apocrine glands secret lipids and other complex
  organic molecules

56
Evolutionary Pressures-External Structure and
Locomotion

• Early synapsids probably had a mammary area
  similar to that found in monotremes
• Monotreme young suck milk from mammary hairs
  following hatching, the glands discharge milk
  into depressions on the belly, where the young
  lap it up.
• In other mammals, mammary glands open via nipples
  or teats, and the young suckle for their
  nourishment.

57
Evolutionary Pressures-External Structure and
Locomotion

• The Skull and Teeth
• Jaw Bone Single bone of the lower jaw
  articulates the mammalian jaw (Mandible)
• Secondary Palate Soft Palate allows mammals to
  breath while chewing, breathing stops briefly
  while swallowing.

58
Evolutionary Pressures-External Structure and
Locomotion

• Mammals Teeth are Heterodont, meaning teeth are
  specialized for different functions.
• Mammals have teeth set inside the sockets of the
  jaw
• Most mammals have two sets of teeth in life
• Milk teeth Deciduous teeth
• Permanent Teeth

59
Evolutionary Pressures-External Structure and
Locomotion
60
Evolutionary Pressures-External Structure and
Locomotion

• Types of Teeth
• Incisors used for gnawing and nipping
• Canines used for catching killing and tearing
  prey.
• Premolars used for chewing
• Molars used for used for chewing

61
Evolutionary Pressures-External Structure and
Locomotion

• Zoologist use a dental formula to characterize
  taxa

62
Evolutionary Pressures-External Structure and
Locomotion

• The Vertebral Column
• Seven cervical vertebra (even in giraffes and
  whales)
• First two vertebra are the atlas and axis
• Five cervical vertebra follow
• Trunk divided into thoracic and lumbar region
• Thoracic contains the rib cage
• Lumbar have interlocking process that give
  support, but little freedom of movement

63
Evolutionary Pressures-External Structure and
Locomotion
64
Evolutionary Pressures-External Structure and
Locomotion

• http//www.youtube.com/watch?vTUlx0LVzeP0
• Inside Natures Giants Episode 4 The Giraffe Part
  1/5 HQ
• Giraffe Dissection of the neck
• About a 10 min. video very informative and
  interesting
• http//www.youtube.com/watch?v_5JVxtR89Gs
• Short Giraffe video animal planet

65
Evolutionary Pressures-External Structure and
Locomotion

• Appendicular Skeleton
• The Appendicular skeleton of mammals rotates
  under the body so that the appendages are usually
  directly beneath the body.
• Bones of the pelvic girdle are fused, which is
  advantageous for locomotion.
• The pubic symphysis loosens in females before
  birth allowing the pelvis to spread during birth

66
Evolutionary Pressures-External Structure and
Locomotion

• Muscles Because the appendages are beneath the
  bodies of most mammals the skeleton bears the
  weight of the body. Muscle mass is concentrated
  in the upper appendages and girdles.

67
Evolutionary Pressures-External Structure and
Locomotion
68
Nutrition and the Digestive System

• The digestive tract of mammals is similar to that
  of other vertebrates but has many specializations
  for different feeding habits.
• Cecum is a fermentation pouch where
  microorganisms aid in cellulose digestion
• Horses, rodents and rabbits have an enlarged
  cecum
• Ruminants have stomachs divided into 4 parts
  three are fermentation chambers (deer, cattle
  and sheep)

69
Nutrition and the Digestive System
70
Circulation, Gas Exchange, and Temperature
Regulation

• Heart Four chambered, keep blood in systemic
  and pulmonary circuits separate
• Shows Convergent evolution with the hearts of
  birds, both are adapted for active life styles

71
Circulation, Gas Exchange, and Temperature
Regulation

• Most important adaptation is the exchange of
  nutrients, gases, and wastes that simply diffuse
  between fetal and maternal blood supply, no blood
  actually mixes.

72
Circulation, Gas Exchange, and Temperature
Regulation

• High metabolic rates require adaptations for
  efficient gas exchange.
• Mammals have
• Separate oral and nasal cavities
• Warming and moistening air
• Respiratory passages are highly branched
• Increase surface area
• Lungs resemble a sponge versus a sac

73
Circulation, Gas Exchange, and Temperature
Regulation

• Diaphragm Muscle that separates the thoracic
  and abdominal cavities.
• Inspiration causes the diaphragm to contract and
  expand the rib cage this allows air to enter.
• Expiration is normally by elastic recoil of the
  lungs

74
Circulation, Gas Exchange, and Temperature
Regulation
75
Circulation, Gas Exchange, and Temperature
Regulation

• Two Catagories of heat producing mechanisms
• Shivering thermogenesis muscular activity
  generates large amounts of heat, and little
  movement
• Non-shivering thermogenesis produces heat
  through general cellular metabolism and
  metabolism of brown fat.

76
Circulation, Gas Exchange, and Temperature
Regulation

• Thermoregulation
• Mammals are insulated by
• Pelage
• Fat Deposits
• Which are also a source of energy to sustain high
  metabolic rates

77
Circulation, Gas Exchange, and Temperature
Regulation

• Example Walrus
• In cold temperatures has a surface temp of 0 C
  with a body temp. of 35 C.
• When out of icy water Walruses will increase
  peripheral blood flow quickly warming skin.

78
Circulation, Gas Exchange, and Temperature
Regulation

• Countercurrent heat-exchange systems
• This system allows heat to be returned to the
  body due to the close association of arteries and
  veins, heat from the blood in arteries is
  transferred to the blood in the veins to conserve
  heat returning to the body.

79
Circulation, Gas Exchange, and Temperature
Regulation

• Hot, dry environments present far greater
  problems, because of evaporative cooling may
  upset water balances.
• Jackrabbits and Elephant use big ears to radiate
  heat.

80
Winter Sleep and Hibernation

• Winter sleep less active but are still
  relatively alert and easily aroused (bears and
  raccoons)
• Hibernation - a period of winter inactivity in
  which the hypothalamus of the brain slows the
  metabolic, heart and respiratory rates. (Echidna,
  moles, chipmunks and bats)

Bears in winter sleep
Chipmunk Hibernation
81
Nervous and Sensory Functions

• Enlarged Cerebral Cortex Due to Active lifestyle

82
Nervous and Sensory Functions

• Sense of Touch well developed, when hair is
  displaced then stimulus is detected

83
Nervous and Sensory Functions

• Olfactory Mammals can perceive olfactory
  stimuli over long distances during either the day
  or night to locate food, recognize members of the
  same species, and avoid predators.

84
Nervous and Sensory Functions

• Auditory
• Adapatations
• Ear Flap (the Pinna)
• External canal leading to the tympanum
• The Middle Ear
• Three ear ossicles that conduct sound to inner
  ear
• Inner Ear
• Cochlea Structure provides more surface area
  for receptor cells and gives mammals greater
  sensitivity to pitch and volume

85
Nervous and Sensory Functions

• Vision
• Color Vision is less well developed than in birds
  and reptiles
• Rods dominate the retinas of most mammals,
  supporting the hypothesis that most early mammals
  were nocturnal.
• Primates, squirrels and a few other mammals have
  well developed color vision.

86
Excretion and Osmoregulation

• Metanephric Kidney Excrete Urea Less toxic
  than ammonia and does not require large amounts
  of water. Water is lost because urea is water
  soluble and cannot be excreted as a semisolid.
  Leading to water loss.

87
Excretion and Osmoregulation

• Development of the Kidney from embryo to adult

88
Excretion and Osmoregulation

• Function of the nephron of the kidney is to
  filter fluids and small solids from the blood
  through a group of capillary systems called the
  glomerulus.
• The main adaptation in mammals is in the loop of
  the nephron where water and Na/Cl- is reabsorbed.

89
Excretion and Osmoregulation

• Water can be lost through activity, physiological
  state, environmental temperatures, in urine and
  feces, in evaporation of sweat glands,
  respiratory surfaces and during nursing.
• Adaptations to prevent water loss include
• Kangaroo Rat survives without drinking water
• Nocturnal
• Feces are almost dry
• The loop of the nephron reabsorbs water
• Eats seeds high in fats and carbohydrates that
  when metabolized produce water

90
Behavior

• Mammals have complex behaviors to enhance
  survival
• Bristled fur, arched back, and open mouth cats
  communicate message to potential threat.
• Tail-wagging dog wants to play or is happy
• Wolf on back giving up in a fight with other
  wolves or avoiding a fight with other wolves

91
Behavior
Tiger Spraying to claim territory.

• Pheromones
• Recognize members of the same species
• Recognize members of the opposite sex
• Recognize the reproductive state of a member of
  the opposite sex
• Induce sexual behavior
• Help establish and recognize territories
• Ward off Predators
• Recognize young or parents

92
Behavior

• Auditory-
• Herd animals stay together as long as familiar
  sounds are around them (bellowing, hooves on
  grass, ruminating stomach sounds). If disrupted
  sounds they will flee.
• Vocalizations and Tactile
• Pre-copulatory nosing that occurs in many
  animals
• Grooming

Elk pre-mating behavior
93
Territoriality

• Cats rub their faces against objects and people
  to claim them, they are rubbing their scent
  glands from their faces.

94
Territoriality

• Male California Sea Lions Establish Territories
  and defend them for breeding season. Females
  swim to shore and choose a birth site this is
  also the site of the father of next years young.
  
• Embryonic Diapause Mating in California Sea
  Lions occurs 2 weeks after birth of pervious
  years young. The embryo is paused in birth and
  mothers carry their unborn for 12 months instead
  of nine months.

95
Reproduction and Development

• Mammalian Viviparity requires a large expenditure
  of energy on the part of the female during
  development and on the part of one or both
  parents caring for young after they are born.
• Advantages
• Mother can roam and find food or proper climate,
  not tied to a nest
• Evolution of the Uterus allows for viviparity

96
Reproduction and Development

• Estrus Cycle a time during which the female is
  behaviorally and physiologically receptive to the
  male.
• Hormonal changes stimulate the development of the
  ova in the ovary and induce ovulation

Human Estrus Cycle
97
Reproduction and Development

• Most Mammals do not bleed or slough the uterine
  lining if fertilization does not occur
• Monestrus have only one yearly cycle (wild
  dogs, bears, sea lions)
• Diestrus domestic dogs cycle twice a year
• Polyestrus rats and mice every 4-6 weeks
• Humans, Apes and monkeys similar and if
  fertilization does not occur then menses the
  sloughing of the uterine lining occurs

98
Reproduction and Development

• Usual Fertilization
• Occurs in upper third of the oviduct within hours
  of copulation
• Delayed Fertilization Females can store sperm
  for periods of up to two months.
• Bats are different copulation in fall and
  fertilization in spring

Human Fertilization
99
Reproduction and Development

• Modes of Development
• Oviparous Monotremes lay eggs that are
  incubated
• Marsupials gestation period is short due to the
  inability to maintain the hormones needed to
  support uterine lining. Gestation period is 8-40
  days. Baby Crawls into pouch and attaches to the
  nipple for 60-270 days

Long Beaked Echidna Egg laying monotreme
100
Reproduction and Development

• Gestation Period the length of time the young
  develop in the mothers reproductive tract
• Eutherian mammals Embryo implants deep in the
  uterine wall - maternal and fetal blood never
  mix but nutrients, gases and wastes diffuse
  between the two blood streams. Gestation periods
  range from 20days rodents to 19months African
  Elephants.
• Elephant Birth http//www.youtube.com/watch?vF4M
  zcpX3viY

101
Interesting Videos

• Whale Evolution
• http//www.youtube.com/watch?vxCx-nwkj8fUfeature
  fvwrel
• How did whales move from land to water

102
Interesting Video

• See how many evolutionary features you can
  isolate in the video
• http//www.youtube.com/watch?vCvrmZLGWfFsfeature
  related
• Evolution in 5 min. There are some missing gaps
  between Cynognathus and Australopithecus

103
Interesting Video

• http//www.youtube.com/watch?vTMCf7SNUb-Qfeature
  related
• Dolphin making bubble rings

104
Resources

• http//www.biologyjunction.com/mammals20notes20b
  i.htm
• http//www.biologycorner.com/APbiology/evolution/c
  h19.html
• http//prehistoricanimal.blogspot.com/2010_07_01_a
  rchive.html
• http//amazingdata.com/mother-earth-mammals-the-un
  derdogs-triumph/
• http//palaeo.gly.bris.ac.uk/palaeofiles/fossilgro
  ups/marsupia/monochar
• http//animals.nationalgeographic.com/animals/mamm
  als/gray-kangaroo/
• http//www.becci.com/Safari05.htm
• http//biology.wsc.ma.edu/mammals/monotremes/
• http//www.animalpicturesarchive.com/view.php?tid
  3did25659
• http//kidsresearchexpress-5.blogspot.com/2008/08/
  skin.html
• http//www.keratin.com/aa/aa007.shtml
• http//bioweb.uwlax.edu/bio203/s2008/olson_alex/ad
  aptation.htm
• http//m.amp.avai.com/Home/Page/262?pageid271
• http//www.flickr.com/photos/12319981_at_N02/33860009
  59/
• http//www.hairtx.com/hair-growth/hair-anatomy/
• http//chemistry.about.com/b/2010/08/01/oxiclean-t
  o-remove-skunk-odor.htm
• http//www.thesharkguys.com/lists/top-7-killer-wha
  le-attacks/
• http//www.ci.cedar-park.tx.us/cp/squirrels.aspx
• http//www.theanimalfiles.com/mammals/elephants/af
  rican_elephant.html

105
Resources

• http//www.scientificamerican.com/article.cfm?idh
  ow-zoos-kill-elephants
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