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Zoology > Class Mammalia > Flashcards

Class Mammalia Flashcards

1
Q

What kind of skull do they have ?

A

all mammals are synapsids

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2
Q

Why this type of morphology for the skull?

A
  • associated with attachment of mandibular muscles (important for chewing , biting)
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3
Q

Mammals have various skeletal changes

A

1) turbinate bones in nasal cavity (retain body heat)
2) bony secondary palate ( can breathe & chew at same time )
3) loss of lumbar ribs but evolution of diaphragm (more spinal flexibility)

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4
Q

Which lineage give rise to early mammals?

A

One cynodont lineage

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5
Q

What were early mammals like ?

A

-small & mouse-like but important adaptations nonetheless
- diphyodont dentition (teeth replaced only once)
former bones of jaw become incorporated into middle ear
-quadrate & articulate bones become malleus
& incus

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6
Q
  • what are the 3 major lineages by end of mesozoic
A

monotremes, marsupials and eutherians.

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7
Q

what characterize the modern mammal lineage ?

A

1) Mammary glands
2) Hair
3) Fat layer
4) 4 chambered heart
5 ) Usually shell-less embryo

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8
Q

mammary glands

A

milk (fat, sugar, proteins mineral vitamins)

relative composition varies

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9
Q

Fat layer

A

Under the skin
to retain heat
endothermic

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10
Q

4 chambered heart

A

everything separated .

  • dont mix oxygenated & non oxygenated blood.
  • support high metabolic rate
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11
Q

Shell less embryo

A

embryo avoid desiccation by developing inside mother.

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12
Q

Integumentary tissue

A
  • all vertebrates have dermis and epidermis

- but generally thicker skin in mammals with presence of hair & many glands.

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13
Q

Hair growth

A
  • hair grows from a hair follicle
  • epidermal cell but sunk into dermis
  • growth by cell proliferation in follicle – dead once out of follicle
  • hair shafts become filled with keratin (sound familiar?)
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14
Q

2 kinds of hair forming the pelage (fur coat)

A

underhair: dense & soft for insulation

guard hair: coarse & long for protection & colouration

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15
Q

Does it stop growing ?

A

Yes, hair typically stops growing once it reaches a certain length
- normally stays in follicle until a new growth starts – then falls out.

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16
Q

Molting

A

some only molt once/year (every summer)

most molt twice/year (spring & fall)

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17
Q

Hair isn’t just for isolation

A

camouflage or warning colouration

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18
Q

vibrissae

A

whiskers

modified as sensory structures

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19
Q

Horns or horn like structure

A
  • Mammals are the only animals that are able to grow it.
    -true horn are hollow sheaths of keratinized epidermis surrounding core of bone arising
    from skull
    both sexes, grow continuously, not branched,
    e.g. sheep, cattle
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20
Q

Antlers

A
  • antlers are composed of solid bone when mature
    -covered with vascularized soft skin (Velvet) during growth
    grown by males , shed annually after breeding season
    -only in deer family
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21
Q

Glands

A 
derivatives of epidermis 
separated into 4 types : 
1) sweat glands 
2) Scent glands 
3) Sebaceous glands 
4) mammary glands
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22
Q

Sweat glands

A

-tubular & coiled
- occur over much of body surface but absent in other vertebrates
-eccrine glands secrete watery fluid
-usually in hairless regions
function in evaporation cooling
-apocrine glands always open into a hair follicle in specific body regions
- fluids not involved in cooling
- correlated with reproductive cycle

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23
Q

Scent glands

A
  • locations & functions vary
  • communication, marking territory,attracting mates, defence
  • also in humans (but tend to dislike own scent!)
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24
Q

Sebaceous glands

A

-mostly associated with hair follicles
-gland cells discharged along with fatty mixture (sebum)
-keeps hair & skin pliable & glossy
very important for waterproofing in marine mammals.

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25
Q

Mammary glands

A
  • occur on all females & accompanied by adipose tissue
  • rudimentary on all males
  • monotremes have these glands but lack nipples
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26
Q

4 types of teeth

A

incisors
canines
premolar
moalrs

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27
Q

Incisors

A

simple crowns & sharp edges

- snipping / biting

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28
Q

canines

A

long, conical crowns

-piercing

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29
Q

premolars

A

compressed crowns, cusps, shearing, slicing, crushing, grinding

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30
Q

molars

A

same as premolars

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31
Q

Large masseter

A

large masseter for side-side movement

-articulation best for grinding motion

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32
Q

Diastema

A

gap to fit large tongue

in herbivores

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33
Q

Large temporalis

A
  • large temporals for up-down movement

- articulation best for providing strong downward force

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34
Q

grazers and browsers

A
  • ingest a lot of cellulose

- diets rich in carbon but low in protein

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35
Q

How do herbivore digest cellulose

A
  • lack enzyme needed to digest cellulose
  • depend on specialized bacteria & protozoa in digestive tracts
  • bacteria concentrate in foregut or hindgut
  • aerobic respiration replaced by fermentation converts sugars
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36
Q

What part of intestine is part in cellulose digestion ?

A

-digestion takes place less efficiently in
hindgut
-long intestinal tract slows food passage
-well-developed caecum to allow fermentation by mutualistic bacteria

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37
Q

Where is the cellulose most digested.

A
  • most digestion in foregut
38
Q

4 - compartment stomach

A

ruminants

39
Q

The rumen and reticulum are inhabited by what?

The function of it ?

A
  • inhabited by anaerobes and function as fermentation vats
40
Q

cud

A

regurgitate fermented material

41
Q

finer material (digestion of herbivore) enters…

A

the reticulum , then omasm and obomasum

42
Q

microorganism in rumen produce what?

A

produce fatty acids

43
Q

carnivores stomach

A

commonly large , expandable stomachs

44
Q

Why is it useful to have an expandable stomach ?

A
  • can’t be sure when next meal will be

- takes a lot of energy

45
Q

is the gut of carnivore long or short ? why?

A
  • carnivores have relatively short gut

- animal material easier to break down & assimilate

46
Q

Cecum present in carnivores ?

A

very reduce or absent

47
Q

Omnivores

A
  • omnivores ingest both plant & animal material
  • dependent upon season & needs
  • very opportunistic feeders
48
Q

longest migration are made by …

A

marine mammals (seal and whales)

49
Q

Migration is cause by…

A

temperature and other environmental factor with seasonal variations ( rain fall)

50
Q

Mammalian flight

A

-while bird & bat wings are homologous, flight evolved independently
-flight also evolved independently in several
groups of mammals
-but only bats capable of powered flight
-others actually glide , not fly

51
Q

How do bats stay competitive against the

much more dominant birds?

A

mostly nocturnal – occupy largely unoccupied niche

52
Q

success are attributable to 2 features in bats

A

flight and echolocation

53
Q

echolocation , how does it works

A
  • emit short sound pulses of very high frequency (ultrasonic)
  • spaced so receive echo of each before next emitted (prevent jamming)
  • pulse bounces off prey & is received back by ears
  • creates mental image of surroundings
54
Q

Other types of bats

A

dont use echolocation .
fruit bats
- vampire bats : secrete anticoagulant

55
Q

Mating season

A
  • Most mammals have definite mating seasons
  • birth & rearing of young during most conditions
  • seasonal reproduction in deer levels of hormone melatonin goes up as daylength goes down
  • stimulates reproductive hormones
56
Q

Fertility restrcited to

A

certain time of estrous cycle

- female only receptive to mating while in estrus ( heat)

57
Q

estrus

A

heat

58
Q

Subclass Prototheria

A

aka monotremes

  • egg-laying (oviparous)
  • embryos develop 10-12 days in uterus
  • thin, leathery shell secreted prior to laying eggs
  • hatch relatively undeveloped after ~12 days
  • feed on milk produced by mother’s mammary glands
59
Q

subclass theria

A

contain 2 subgroups
Both are viviparous ( no egg)
1) Metatheria
2) Eutheria

60
Q

Infraclass Metatheria

A

a.k.a marsupials
-most embryonic development completed in a pouch (not the uterus)
- only have a transient type of placenta (choriovitelline or placenta)
-early embryo floats freely in uterine fluid while encapsulated in shell membranes
- “hatch” from membranes but do not implant
- erode depressions in uterine wall to lie in & absorb nutrient secretions from yolk sac placenta
- brief gestation – birth to embryonic young
young crawl into pouch for prolonged period of lactation & parental care

61
Q

Infraclass Eutheria

A

a. k.a. true plancental mammals
- prolonged period of gestation
- yolk sac placenta replaced by chorioallantoic placenta
- highly vascularized with close connections between embryo & mother (diffusion of nutrients, wastes, respiratory gases)

62
Q

Why would a longer gestation

period confer an advantage?

A

eutherians have a longer gestation period but generally have to spend less time in total
caring for their young
-less time until next bout of mating – more offspring -more genes passed on
-but enormous variation among mammals in condition of young at birth (all are altricial but vary in how much)

63
Q

Subclass Prototheria

A

key traits: a.k.a. monotremes
-egg-laying (oviparous)
-members: only one order found in Australia, Tasmania & New Guinea
ex : platypus

64
Q 
Subclass Theria 
infraclass Metatheria
A 
key traits: 
-most embryonic 
- development completed in a pouch
 members: a.k.a. marsupials
 not just found in Australia! 
   (but most diversity &  largest   )
-marsupial lineage in Australia has been separated from eutherians for very long time
- much convergent  evolution – marsupials fill ecological niches usually held by eutherians elsewhere

ex: Kangaroo
Koala
North america = opossum

65
Q

Infraclass Eutheria (key traits)

A

key traits:

  • true placental mammals
  • members: distributed worldwide
  • greatest diversity
66
Q

Order Cetacea (trait)

A

Think about dolphin and whales

  • aquatic
  • no hind limbs (no pelvic fins like fish)
  • blowhole for gas exchange into lungs
  • produce sounds (echolocation)
  • lower jaw receives and transmit
  • conical teeth (dolphin)
67
Q

porpoises

A

no melon

Flat teeth

68
Q

whales

A

also communicate vocally & use echolocation (but no melon )
some have tooth
- others are filter feeders (toothless)

69
Q

whales are closely related to…

And share some characters with…

A

hoofed mammals t

- some characters with ungulates

70
Q

Order Rodentia (key traits)

A 
think mice & rats , beaver, squirrels
key traits: 
-2 prominent upper & lower incisors
 - grow continually
 -adapted for gnawing
 members: most numerous of 
  all mammals (number & 
  diversity)
71
Q

Order perissodactyla (traits)

A

key traits:

  • hoofed with an odd number of toes
  • 1 or 3 toes enclosed in keratinized hoof
  • all are herbivorous
    members: a.k.a. ungulates
    e. g. horses, zebras, rhinoceroses
72
Q

Order artiodactyla

A

key traits:

  • hoofed with an even # of toes
  • 2 or 4 toes enclosed in cornified hoof
  • many have horns or antlers
  • most are ruminant herbivores
  • members: many domesticated species
    e. g. pigs, cattle, sheep, goats, deer
73
Q

Order Carnivora

A 
key traits: 
-consumption of flesh prominent canine teeth – tearing
 members: mainly larger predators
 but vary in degree of carnivory
ex : cats, bears, wolves
74
Q

Order Primates

A 
many adaptation to life in trees
A. modified hand 
b. modified feet 
C. relatively large brains 
D. close -set eyes
75
Q

A. modified hands

A

mobile thumb that is fully opposable in monkeys & apes – 5 digits

  • allows for grasping
  • flat nails (instead of claws)
  • skin ridges on fingers (fingerprints)
76
Q

B. modified feet

A
  • opposable big toe
  • use like a grasping hand
  • humans are the exception
  • not good for bipedal lifestyle
77
Q

C. relatively large brain

A

also more folding

increases surface area

78
Q

D. close set eyes

A
  • binocular vision
  • brain takes information from each eye & unites into 1 picture
  • interprets slight differences between each view as depth
  • produces a 3-D picture (stereoscopic)
79
Q

Monkey and ape form a clade called

A

Anthropoidea

80
Q

Apes clade

A

Hominoids

81
Q

Old world monkey

A

-tail not used for gripping
-tree and ground dwelling
- nostrils open downwards
old world (africa and asia)

82
Q

New world monkeys

A

prehensile tail (grasp things)
- tree dwelling
- nostrils open to the sides
Ne world= South america

83
Q

Hominoids traits

A

non-human hominoids only in old world

  • all except gibbons are larger than monkeys
  • relatively long arms
  • short legs
  • no tail
  • larger brain in proportion to body size more complex behaviors
84
Q

Homo sapiens

A
  • relatively largest brain
  • bipedalism
  • reduced jawbones (flat face) and muscles , teeth
85
Q

Human evolution

A
  • humans descended from extinct hominoids more closely
  • related to humans than to chimps
  • earliest hominid fossils from 6-7 MYA
  • had some, but not all, derived characters of humans
    e. g. reduced canines, more upright & bipedal
86
Q

Mosaic evolution

A

different rates of evolution for different features . -characters did not evolve in tight unison
e.g. bipedalism while brains still relatively small

87
Q

Autralopiths

A
  • hominids from time of increased diversity 2-4 MYA
  • fossils indicate full bipedalism
  • “lucy”
  • brain size similar to chimpanzee long lower jaw
88
Q

Selective pressures towards bipedalism

A 
-changes in leg bones, pelvic structure,
  muscles
- long distances on 2 legs only 
 -more arid environment
- less energy for bipedal walking than on all fours
89
Q

Use of tools

A
  • earliest accepted evidence from 2.5 MYA
  • cut marks on animal bones
  • suggests stone tool use before large brains evolved
90
Q

Early members of genus Homo

A

substantially larger brain
brain shape suggests limited speech possible
more complex culture – used fire
-reduced sexual dimorphism
-perhaps more pair-bonding & biparental care

91
Q

Homo neanderthalensis

A
  • a.k.a. Neanderthals
  • once considered to be ancestors of H.sapiens in Europe
  • DNA analyses indicate Neanderthals form a clade while living Europeans more closely related to living Africans & Asians
  • migrating H. sapiens may have been superior competitors.
  • ancestor of all humans originated in africa.

Zoology (7 decks)

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