vertebrates; mammals; monotremes and marsupials

Question 1

aus is only country with all

Answer 1

3 subclasses of mammals

Question 2

3 subclasses of mammals

Answer 2

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

Question 3

monotreme, 5 species but name 2

Answer 3

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

Question 4

where did monotremes originate

Answer 4

gondwana

Question 5

monotremes retain several reptilian characteristics such as

Answer 5

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

Question 6

defining characteristics of monotremes (7)

Answer 6

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

Question 7

crural glands

Answer 7

• 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

Question 8

electroreception of monotremes

Answer 8

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

Question 9

monotreme skull

Answer 9

pre-maxilla forms the bill/beak

Question 10

monotreme pectoral girdle

Answer 10

• coracoids, epicoracoids and inter-clavicle
• reptilian features

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

Question 11

monotreme pelvic girdle

Answer 11

epipubic bones

have ilium, ischium and pubis

Question 12

monotreme limbs

Answer 12

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

Question 13

monotremes have multiple

Answer 13

X and Y chromosomes

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

Question 14

sex determination in monotremes

Answer 14

lack SRY gene on Y chromosomes, unlikes marsupials and eutherians

monotreme system uis link between bird and therian mechanisms

Question 15

in platypus only ____ ovary is functional

in echidna:

Answer 15

left
in echidna both ovaries functional

Question 16

describe monotreme eggs

Answer 16

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

Question 17

do monotremes have mammary glands

Answer 17

yes but no teats so young lap milk from specialized hairs

Question 18

marsupials are named for their

Answer 18

marsupium or pouch (not all marsupial possess a pouch)

Question 19

marsupials are NOT

Answer 19

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

Question 20

marsupials are unique in their mode of reproduction:

Answer 20

young born in altricial state
dependence on lactation rather than gestations

Question 21

marsupial chromosomes compared to eutherians

Answer 21

fewer and larger

Question 22

what chromosomes necessary for pouch rather than scrotum development

Answer 22

XX

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

Question 23

explain why genital ducts and ureters are unique in marsupials

Answer 23

• 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

Question 24

the unique way their ureters and ducts are means marsupials have

Answer 24

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

Question 25

marsupial pouch

Answer 25

encloses teats and young
young constantly attached to teat

Question 26

in marsupial species without a pouch, what do the young do

Answer 26

hang on!!!, when too big they are put in a nest

Question 27

marsupial neonate

Answer 27

• 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