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animal biology > week 10 - mammals > Flashcards

week 10 - mammals Flashcards

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1
Q

mammalian characteristics

A
  • Vertebrates ie. internal skeleton
  • Hair/fur (insulation)
  • Nails, hoofs, horns
  • Mammary glands – milk
  • Facial muscles: more muscle groups, externally placed (social creatures – communication)
  • Diaphragm: efficient breathing (metabolic rate etc)
  • High metabolic rate (also in birds): endothermy
  • Heterodonty: highly adapted teeth – usually a number of distinct types
  • Parasaggital (upright) gait
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2
Q

mammals
- Monoteremes

A

egg laying mammals
found in australia, new Guinea
have hair (fur)
endothermic (lower body temp than placental mammals ~ 32)
females produce milk but no nipples
- young lick milk from glands

two groups
- enchinas
- platypus

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3
Q

mammals
- Marsupials

A

now only found in Australiasia and the Americas
(once had global distribution)
characterized by young born at a very early stage of growth and the young must crawl to their mothers pouch where they complete their development

examples:
opossum (specifically a water opossum) found in the americas
marsupial moles (found in australia)

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4
Q

examples of convergent evolution between …

A

marsupials and placental (eutherian

Placental mammals diverged from marsupials at least 125 mya (million years ago).

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5
Q

eutherian (placental animals)

A
  • Closely related to marsupials (monotremes more distant)
  • Probally diverged from marsupials at least 125 Mya
  • Four main groups (clades)
    o Sources can differ
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6
Q

mammals overview
carnivores

A

Dogs, cats, bears, seals, weasels
25g to 1000kg
Pointed canines
Shearing molars (carnassial)
carnivorous

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7
Q

mammals overview
Perissodactyla

A
  • Odd toed ungulates:
    o Horses, zebras, tapirs, rhinos
  • Off toes hooves (digit III)
  • Herbivorous
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8
Q

mammals overview
Cetartiodactyla

A

Artiodactyls or even-toed ungulates
o Sheep, pig, cattle, deer, giraffes
- Even toes hooves (digits II and IV)
- Herbivores
Cetaceans:
o Whales, dolphins, porpoises
- Secondarily aquatic (moves into water then became very specialised
- Paddle-like forelimbs, hindlimbs absent, blubber
- Carnivorous
Closely related animals but very different

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9
Q

mammals overview
Chiroptera

A

Bats
- Wings made of skin-fold supported by elongated fingers
o Very specialised in mode of locomotion
- Carnviores and herbivores
o Diverse diets

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10
Q

mammals overview
Eulipotyphla

A
  • Hedgehogs, moles, shrews
  • Insectivores
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11
Q

mammals overview
Pholidota

A
  • Pangolins
  • Insectivores: ants and termites
  • Tend to get elongated snout (because of what they are eating)
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12
Q

when did mammals appear?

A

220 Mya (Triassic)

coexisted with dinosaurs in mesozonic

dominant, successful terrestial animals of the Cenozonic (last 63 years)

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13
Q

SPECIES NUMBERS

A
  • Birds: 91K species
  • Amphibians: 4.8K
  • Reptiles: 6.5K species (3K lizards, 2.5K snakes)
  • Mammals: 4.5K species (1.8K rodents)
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14
Q

SPECIES DIVERSITY

A
  • Largest terrestrial and aquatic vertebrates alive today
  • Most diverse vertebrate class
    o Although Mesozoic reptiles did at least as well
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15
Q

mammals
origins

A
  • Mammals separate from reptiles since before dinosaurs
  • Mammals branched from early reptiles at start of Mesozoic
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16
Q

mammals
lineages

A
  • Branch leading to mammals is the synapsids
  • Before dinosaurs some large, reptilian synapsids (Dimetrodon)
  • Then therapsids (mammal like reptiles)
  • Real mammal appeared during Mesozonic (180 Mya)
    o Small and probally nocturnal
  • After dinosaur extinction niches became available
  • In Cemozic mammals radiated higely into ‘empty’ niches
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17
Q

mammals
Dimetradon

A
  • Early Permian
  • Southwestern USA and Germany
  • Extinct BEFORE dinosaurs
  • ‘non-mammalian synapsid’
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18
Q

mammalian form: functional morphology
- early synapsids

A
  • Reptile like
  • Long tail
  • Sprawling gait with legs to the side (mammals have legs below)
  • Full set of ribs (protection
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19
Q

mammalian form: functional morphology
MANDIBLE AND DENTITION
- Teeth

A

Temporomandibular joint (TM)
- Flexible
- Simplified compared to reptiles
o Simplifying has allowed for diversification.
o The ears
- Significant lateral movement and hinge
o Chewing
Heterodont teeth
- Specialised according to function
- All fulfilling different functions
o Incisors
o Canines
o Pre-molars
o Molars
Teeth: carnivores
- Canines
o Killing
- Carnassial
o Slicing
- Specialised for function
Teeth: herbivores
- Grinding
- Diastema
- Protruding incisors or none
- Chewing animals

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20
Q

mammalian form: functional morphology
MANDIBLE AND DENTITION
- TMJ position and angle

A

How this can vary between carnivores (strong motion in one direction, none in the other) and herbivore (need motion in the other plane)
- So anatomy aids this
- Muscles also vital in anatomy
- Size difference in these tell us about function.
- Temporalis (straight down motion)
- Masseter (across plane motion)

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21
Q

mammalian form: functional morphology
STANCE ADAPTATION

A
  • Mammals
  • Legs held under body
  • Swing in vertical plane
  • Better for weight bearing
22
Q

mammalian form: functional morphology
STANCE ADAPTATION
- limb joint rotations

A
  • Socket rotates downwards
  • Upper limb head, ‘ball’, rotated medially (inwards)
    Adaptations that happened in order to become erect
    Needed to rotate the ball and socket joint.
23
Q

mammalian form: functional morphology
STANCE ADAPTATION
- Dorsi-ventral flexture of the spine

A
  • Spine flexes vertically
  • See in carnivores
  • Increased stride length
  • Maintains legs under body
    Evolving to be faster
    Cheater spine more flexible than most - spring motion can flex further therefore faster
    Moving legs underneath body allows this
24
Q

mammalian form: functional morphology
STANCE ADAPTATION
- hips in thorax only

A
  • Reptiles :
    o Compete set of ribs  dorsi-ventral flexion impossible
  • Mammals:
    o Thoracic ribs
    o Heart and lings protected
     Abdomen not
    o Lumbar spine bends
     Thoracic spine stiff
    o Balanced this out (other adaptations in behaviour because of this

so get a bend forwards

25
Q

mammalian form: functional morphology
STANCE ADAPTATION
FLIGHT

A
  • Pterosaurs:
    o Elongated metacarpal and phalange V (little finger)
  • Bats:
    o Elongated metacarpals and phalanges
  • Birds
    o Feathers are stiff so do not need to extend limb

Support wing with phalanges

26
Q

mammalian form: functional morphology
STANCE ADAPTATION
SWIMMING

A
  • Greatly reduced upper limb
    o Reduce drag
  • Flattened to form flipper
  • Simplified wrist
  • Extended phalanges
  • Digit reduction
27
Q

mammalian form: functional morphology
STANCE ADAPTATION
ABOREAL LOCOMOTION

A

PRIMATES
- Thumb rotated so can touch tips of other digits
- Results in power grip
o Can trace back to adaptation of climbing in trees
- Eventually allowed tool use
Lots of these traits make us highly successful as humans
Eyes at front
* Better to judge distances
* Jumping from tree to tree

28
Q

mammalian form: functional morphology
STANCE ADAPTATION
terrestrial locomotion-

A

Plantigrade:
o Power/digger
o No necessarily fast but need power in their feet
o E.g. hedgehog

Digitigrade:
o Speed (hunting)
o E.g. dog/cat
o Balance need for speed and other functions

Unguligrade:
o Speed (escape)
o E.g. deer

29
Q

mammalian form: functional morphology
STANCE ADAPTATION
terrestrial: femur length

A

unguligrade
- lower limb longer than upper limb
(speed)

digitigrade
- kinda even

Plantigrade
- lower limb shorter than upper limb
(power)

  • Difference in ratios (which limbs lengthen)
30
Q

mammalian form: functional morphology
STANCE ADAPTATION
terrestrial: tibia and fibula

A
  • Speed: tibia and fibula > femur
  • Power: tibia and fibula < femur
31
Q

mammalian form: functional morphology
STANCE ADAPTATION
terrestrial: foot

A
  • Speed: extended
32
Q

mammalian form: functional morphology
STANCE ADAPTATION
terrestrial: stand

A
  • Unguligrade:
    o fingertips (hooves)
  • Digitigrade
    o Finger (claws)
  • Plantigrade
    o Hand
33
Q

mammalian form: functional morphology
STANCE ADAPTATION
Unguligrade foot

A
  • Perissodactyl: odd-toed
  • Artiodactyl: even-toes
    From this changes (from ancestors - reptiles) has allows lots of diversification

Split in camel
- To do with sand environment
- Need a larger surface area

34
Q

mammals thermoregulation:
warm blooded

A
  • Mammals have colonised and exploited areas not available to reptiles and amphibians
  • This is primarily due to physiological specialisations, particularly temp, regulations
    o Can live in cold environments because have internal temperature regulation
35
Q

mammals thermoregulation:
types

A
  • Poikilothermy:
    o Body temp. varies e.g. in response to environmental change
  • Homeothermy:
    o Maintain a ‘constant ’body temp.
    o Humans
36
Q

mammals:
thermoregulatory mechanisms

A
  • Ectotherm:
    o Uses environmental heat sources to regulate body temp.
     E.g. solar radiation, hot and cold surfaces
  • Endotherm
    o Generates heat internally through high metabolic rate to maintain a high body temp
37
Q

Mammal thermoregulation:
- Endothermic homeotherms

A
  • Generate large amounts of internal heat
    o 10x that of an equivalent reptile
  • Fur/hair which provides insulation to limit heat loss
    o Or heat gain in very hot conditions
    Expensive to maintain –> need to generate a lot of internal heat –> this requires lots of energy
38
Q

mammals thermoregulation

A
  • Controlled by system of temp. sensors and thermostat to regulate generation of heat
  • Body temp (Tb) typically maintained at 37degreesC “set point”
  • Regulation usually very tight (<1degreesC varitation) but can be relaxed
    o E.g. hibernation or malfunction (fever)

negative feedback

39
Q

mammals: metabolism
metabolism and temperature

A
  • Maintaining constant body temp costs energy
    o All the reactions that need to take place
  • ‘cheapest’ when environmental temp is close to body temp (Tb)
  • Each species has a range of environmental temps. Over which it can maintain Tb at ‘low’ cost (thermal neutral zone TNZ)
  • When the environment goes above or below TNZ the cost of maintaining Tb goes up rapidly
40
Q

mammals: metabolism
metabolism and temperature
to maintain a stable body temp the animal must balance…

A

heat generation

heat loss to the environment

41
Q

mammals: metabolism and temperature
heat exchange with the environment can be expressed as:

A

H over T = C x (Tb - Ta)

T = rate of heat loss
H = change in heat
C = conductivity
(Tb - Ta): difference between body and environment temps

42
Q

mammals
living at low temperatures

A
  • For most mammals Ta<Tb so problem is heat loss to environment which can be tackled by:
    1. Insulation (reduce C)
    2. Avoidance:
    o Migrate
    o Seek shelter, exploit a microhabitat while Ta is very low
     Making use of outside temperature
    3. Heterothermy:
    o Relax control of Tb to reduce (Tb – Ta), either totally (hibernation/torpor) or locally
    4. Generate a lot of internal heat to balance a high
    This is all energy expensive!
  • Best to have a balance of all the above
43
Q

mammals:
reducing conductance size

A
  • When large your SA/vol ratio falls
    o Mass specific conductance (C/Kg) reduced
    o In extreme cold large animals tend to do better
    o In cold areas average size is greater (Eg. More fur so can trap more air)
     Bergmann’s Rule
44
Q

mammals:
Bergman’s rule

A

o In cold areas average size is greater (Eg. More fur so can trap more air)

e.g. largest moose at coldest altitudes

45
Q

mammals:
reducing conductance insulation

A
  • Mammal hair has excellent insulation
  • Size advantageous because increased carrying capacity
    o Fox about minimum size for effective insulation
  • Polar bears in winter experience almost no heat loss:
    o Blubber, fine insulating hair, guard hair
     Give off no detectable heat when sleeping
46
Q

mammals:
metabolism and temperature

A
  • So well insulated they easily overheat
  • Move slowly and rest often
  • Excess heat lost where fur is absent/blood vessels close to skin
    o Muzzle, nose, ears, inner things and shoulders)
  • Swim to cool down
  • Fur can moult
47
Q

mammals:
reducing temp. gradient: hibernation

A
  • Body temp relaxed
    o Reduced heat loss, reduced energy demand
  • Some level of control retained (brainstem) and many hibernators periodically ‘emerge’ (arousal)
  • Torpor is similar but dinural
    o Daily
    o E.g. colder nights
    o Not such a long time
  • Great to save energy
  • About not being able to eat enough to survive the cold
  • Burrow is warmer
  • Huge energy savings
48
Q

mammals:
reducing temp. gradient: regional heterothermy

A
  • Extremities (limbs, feet, even skin) cannot be maintained at core temp
  • Therefore relax body temp. in extremities by using a counter-current

this is very efficient

e.g. sled dogs and reindeer

49
Q

mammals:
increased heat generation: shivering and exercise

A
  • Generates extra heat
    o Direct muscular heat production
  • Exercise supresses shivering so cannot do both
  • In small animals exercise is inefficicent because:
    o Shivering stops
    o Insulative capacity of pelt is disturbed
    o Peripheral circulation increased (blood to muscles) leading to increased heat loss
50
Q

mammals:
increased heat generation: brown fat

A
  • Concentrated in strategic areas:
    o Neck
    o Thorax
    o Major blood vessels
  • Well vascularised to distribute heated blood
    o A lot of blood flow to it
  • An internal solution
51
Q

mammals:
why bother to maintain temperature

A
  • All this is very expensive (mammals eat 10x as much food as equivalent reptile) BUT allows:
    o Very high/continuous activity levels
    o Exploitation of tropic to poles
    o Current temps. “low” and this is hard for ectotherms
    o Mammals therefore are the most successful terrestrial vertebrate group
    A lot of this out for debate
  • Reproduction
    o Better adaption when in female (instead of a pouch)
  • Continuous activity levels (mammals can be in hot or cold)
    o Reptiles basking in heat and hibernate in cold
  • Evolution able to go in ways reptiles could not because of the different traits
52
Q
A

animal biology (16 decks)

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