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Mammals and evolution > week 3 > Flashcards

week 3 Flashcards

1
Q

Much of the Palaeozoic climate is characterised by what? which in turn affects what 2 things?

A

fluctuating ice sheets

affecting global temperatures and sea level

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2
Q

What was gondwana like during the Paleozoic?

A

ice sheets covered it for most the time causing wide variation in regional climate

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3
Q

during the paleozoic vertebrates were restricted to where?

A

equatorial regions

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4
Q

continental coalescence altered ____ ____ and influenced climate

A

ocean currents

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5
Q

What are believed to be the predecessors of land tetrapods?

A

lobe finned fish (including lung fish and coelocanths

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6
Q

the first amphibians appeared during which period? fossil name?

A

devonian 350mya

Ichthyostega

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7
Q

the first amphibians resembled what now a days?

A

big newts

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8
Q

Nature article on the Coelacanth genome says what about the closest relative to tetrapods? Amemiya et al 2013

A

a phylogenetic tree of a broad selection of jawed vertebrates shows that lungfish, not coelacanth is the closest relative of tetrapods

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9
Q

another well known fossil of the first tetrapods also from greenland?

A

Acanthostega

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10
Q

the first tetrapods had what sort of life style?

A

aquatic had gills and a lateral line, flexible spine but modifications were evident

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11
Q

what is the current thinking of the first tetrapods?

A

that these stem tetrapods were aquatic living in shallow rivers

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12
Q

what was a highly significant find in 2006 that was an intermediate between lobe finned fish and Ichthyostega?

A

Tiktaalik roseae

fishapod

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13
Q

The early tetrapod radiations:

during the carboniferous there were about ___ families.

A

40

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14
Q

How many groups of early tetrapods are classically recognised?

A

three
Temnospondyls (larger forms)
Leptospondyli (smaller forms)
Lissamphibia (extant amphibians)

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15
Q

what are the 4 physiological adaptations for life on land?

A

sensory (olfaction replaces lateral line)
respiration
water balance
reproduction

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16
Q

what are the 4 physical adaptions for life on land?

A

increased support of body
limb joints and limb girdles
digits
skin/scales

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17
Q

The tetrapod morphology changes when they adapted to land life. What becomes more pronounced and why?

A

Zygopophyses
these prevent the spine from twisting and bending, making it much stiffer, this means the spine can act in a supporting fashion like a suspension bridge to bear the weight of the viscera slung underneath.
The spine interlocks and becomes rigid

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18
Q

What happens to the tetrapods that have reinvaded the aquatic niche?

A

secondarily lost the zygapophyses as the spine no longer bears weight

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19
Q

In the carboniferous period what appears?

A

early amniotes

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20
Q

in the carboniferous what was the flora like?

A

tropical conditions around equatorial land masses
damp forests of tall trees and lush undergrowth
coal is formed from decaying undergrowth
more oxygen allows for giant invertebrates

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21
Q

the large early tetrapods dominated the late carboniferous but the earliest amniotes are on the scene by _____

A

mid-carboniferous

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22
Q

what are extant amniotes?

A

birds mammals reptiles

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23
Q

what define the groups within amniota?

A

the amniotic egg and skull fenestrations

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24
Q

What are the earliest amniotes?

A

Hylonomus and Paleothyris

small slender lizard like

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25
Q

What happens to the jaw strength over basal tetrapods?

A

increased

the pterygoideus muscle supplementing the adductors in pulling up the jaw

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26
Q

what are the 4 types of skull fenestration?

A

anapsids
diapsids
synapsids
euryapsids

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27
Q

define synapsid?

A

one fenestrae in lower position

28
Q

define diapsid

A

two fenestra

29
Q

define eryapsid

A

one fenestrae in upper position

30
Q

define anapsid

A

no fenestra

31
Q

The diapsids occur in which animals?

A

birds, dinos, reptiles

32
Q

what are the 5 different types of diapsids?

A 
Primitive diapsid condition
Lizard condition
Snake condition
Primitive archosaur condition
Derived avian archosaur condition
33
Q

explain the 5 different diapsid conditions

A

Primitive diapsid - tuatara - both upper and lower fenestra present

lizard condition - lower temporal bar lost

snake condition - upper and lower temporal bars lost

primitive archosaur - thecodonts, most dino, antorbital foramen and mandibular foramen have been added to the basic diapsid pattern

derived avian archosaur - convergently with the condition in mammals the orbit has become merged with the temporal opening s and the brain case is enclosed in dermal bone

34
Q

the synapsid is the linneage giving rise to what?

A

mammals

35
Q

what is the derived mammalian synapsid condition?

A

the orbit has become merged with the temporal opening, and dermal bone has grown down from the skull roof to surround the braincase

36
Q

What is the euryapsids supposed to characterise?

A

marine reptiles

we now know this so called euryapsid condition is merely a modified diapsid one

37
Q

evolution of the temporal fenestrae had several benefits? (4)

A

more space for muscle attachment
lighter skull
stronger bite
saving of calcium

38
Q

What does the phylogenetic pattern suggest about the acquisition of fenestrae?

A

that the condition arose independently in the synapsid and diapsid lineage, because more primitive sauropsids than diapsids lack holes entirely.

39
Q

Temporal fenestrae provide room for what?

A

muscles to bulge

40
Q

In general amniotes have larger and more differentiated __ ___ than non amniotes.

A

jaw muscles

41
Q

what was the preferred evolutionary explanation for temporal fenestrae?

A

room for bulging

42
Q

what is a flaw in the preferred evolutionary explanation?

A

this cannot be why they started to evolve since a small initial hole provides no room for muscles and why does no non-amniote develop temporal fenestrae

43
Q

What did Frazzetta 1968 suggest was key to the evolution of temporal fenestrae?

A

lies in the changes in the complexity and orientation of the jaw muscles

44
Q

In fishes and non-amniote tetrapods the jaw muscles are a simple, little differentiated mass and the feeding movements consist of a simple snap. what does the more domed skull of the amniotes allow?

A

muscles to originate directly from underside of the skull roof and to run vertically down to the jaw

45
Q

what does the new orietnation of one portion of the jaw adductor complex allow?

A

the animal to apply static pressure between the teeth when the jaws are closed

46
Q

what does the other portion of the original adductor complex become?

A

now the pterygoideus muscle, originating from the pterygoid flange on the palate, a new feature in amniotes

47
Q

why is the skull of non amniotes flat and shallow?

A

because they use their head for the buccal pumping mode of lung ventilation and a flat skull does not allow this orientation of the muscles

48
Q

what would happen to a muscle in the same position seen on amniotes in a non amniote skull?

A

would be too short to allow the jaw to open very far as muscles can be stretched only 1/3 their resting length

49
Q

what would allow for more complex jaw movements and ultimately permitting greater diversity of feeding types?

A

increased differentiation of the adductor muscle mass in amniotes

50
Q

What happens to the basal tetrapods in the permian period?

A

they are replaced as dominant land vertebrates by amniotes : reptiles and mammal like reptiles

51
Q

What do the climate changes do to the flora? permian period

A

altered so lush tropical forests go and club mosses and horsetails die out - seed plants favoured

52
Q

what dominate in the hot arid conditions of the northern hemisphere? permian period

A

conifers

53
Q

what dominate in the cold temperate south in the permian period?

A

glossopterids

54
Q

what were the first synapsids?

A

Pelycosaurs

55
Q

when did the Pelycosaurs appear?

A

late carboniferous

56
Q

how many families were there in the Pelycosaurs?

A

6

57
Q

what is special about the Pelycosaurs and until when did they dominate?

A

Most diverse group of tetrapods in the early permian (70% of genera)
mid permian

58
Q

what is a pelycosaur?

A

dimetrodon

59
Q

why is the reflected laminar of angular important in the Pelycosaur

A

this feature developed on the lower jaw bone. It eventually becomes the support for what is now our ear drum

60
Q

Describe the Pelycosaur skull morphology (3)

A

the jaw articulation is primitive being quadrate / articular
the lower jaw consists of several bones
teeth are homodont ie non differentiated

61
Q

what is special about the 3 bones in the back of the jaw in Pelycosaurs?

A

they eventually become the three bones of the middle ear

62
Q

Stem tetrapods appear when?

A

devonian

63
Q

the stem tetrapods are largely replaced by what and when?

A

synapsid amniotes in the permian

firstly Pelycosaurs and then early Therapsids

64
Q

Pelycosaurs give way to more derived ____ some of which made it through which extinction?

A

therapsids

end permian

65
Q

Amemiya et al 2013 still say the Coelacanth is crucial to our understanding of the aquatic land transition why?

A

because the lungfish have intractable genome sizes and so the coelacanth can be used to understand genome changes that were vital for the transition

Mammals and evolution (6 decks)

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