vertebrates; mammals; monotremes and marsupials Flashcards

1
Q

aus is only country with all

A

3 subclasses of mammals

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2
Q

3 subclasses of mammals

A

eutheria (eutherians)
metatheria (marsupials)
prototheria (monotremes)

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3
Q

monotreme, 5 species but name 2

A

platypus and short-beaked echidna (both native to aus)

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4
Q

where did monotremes originate

A

gondwana

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5
Q

monotremes retain several reptilian characteristics such as

A
  • oviparity (eggs)
  • meroblastic cleavage of embryo
  • produce venom
  • electroreception
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6
Q

defining characteristics of monotremes (7)

A
  • absence of calcified teeth
  • electroreception
  • reptile like stance
  • cloaca
  • oviparity
  • no teats
  • venom
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7
Q

crural glands

A
  • venom
  • more developed in playtpus than echidna
  • sharp keratinous spurs
  • medial aspect of tarsal joint
  • move independently
  • venom evolved independently of reptile venom
  • intense pain
  • non fatal to humans
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8
Q

electroreception of monotremes

A
  • located within skin of bill/beak
    more in platypus
  • scan for electrical disturbances
  • swing head from side to side while swimming
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9
Q

monotreme skull

A

pre-maxilla forms the bill/beak

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10
Q

monotreme pectoral girdle

A
  • coracoids, epicoracoids and inter-clavicle
  • reptilian features

(in eutherians, coracoid fused w scapula to become coracoid process)

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11
Q

monotreme pelvic girdle

A

epipubic bones

have ilium, ischium and pubis

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12
Q

monotreme limbs

A

right angle to body
reptilian features but rotate in socked to give mammalian gait

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13
Q

monotremes have multiple

A

X and Y chromosomes

in the male at meiosis form alternating XY chains, segregate into multiple X and multiple Y bearing sperm

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14
Q

sex determination in monotremes

A

lack SRY gene on Y chromosomes, unlikes marsupials and eutherians

monotreme system uis link between bird and therian mechanisms

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15
Q

in platypus only ____ ovary is functional

in echidna:

A

left
in echidna both ovaries functional

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16
Q

describe monotreme eggs

A

large, yolky, porous leathery shell

platypus; 1-3 eggs incubated in nest
echidna; 1 egg incubated in transient pouch and kicked out when spines start to develop

17
Q

do monotremes have mammary glands

A

yes but no teats so young lap milk from specialized hairs

18
Q

marsupials are named for their

A

marsupium or pouch (not all marsupial possess a pouch)

19
Q

marsupials are NOT

A

primitive mammals
marsupials and eutherians diverged from common ancestor, evolving independently since this time

20
Q

marsupials are unique in their mode of reproduction:

A

young born in altricial state
dependence on lactation rather than gestations

21
Q

marsupial chromosomes compared to eutherians

A

fewer and larger

22
Q

what chromosomes necessary for pouch rather than scrotum development

A

XX

can be
XX: female and pouch
X: female and scrotum
XY: male and scrotum
XXY: male and pouch

23
Q

explain why genital ducts and ureters are unique in marsupials

A
  • in all mammals embryo has ureters and mallerian ducts
  • in eutherians ureters pass laterally to mullarian ducts and distal end of mullerian ducts fuse to form vagina
  • in marsupials; ureters pass MEDIALLY to mullerian ducts, and distal ends of mullerian ducts cannot fuse so 2 lateral vaginae from mullerian ducts
24
Q

the unique way their ureters and ducts are means marsupials have

A

2 lateral vagina and a median vagina which becomes patent just before parturition, then may regress of remain patent after giving birth

sperm in lateral vagina only

25
marsupial pouch
encloses teats and young young constantly attached to teat
26
in marsupial species without a pouch, what do the young do
hang on!!!, when too big they are put in a nest
27
marsupial neonate
- born altricial - majority of development during lactation - hind limbs fetal paddles - no hair - kidneys and gonads yet to differentiate - periderm covers eyes and ear - at birth climbs from urogenital sinus to pouch; well developed forelimbs and claws, attaches to teath