Mammal Characterisitcs And Evolution

Question 1

What are monotremes?

Answer 1

Egg laying mammals
Extended maternal care: incubation followed by lactation from tufts of hair
3 extant species, platypus and 2 echidnas
Tribosphenic cheek teeth present

Question 2

In what way are echidnas I’m convergent evolution with marsupials?

Answer 2

Have a pouch to incubate young

Question 3

How many species of marsupials are there and where are they?

Answer 3

334 species

70% I’m Australia, rest in S America, with a few in central and N America

Question 4

What is there on a grand scale between marsupials and placentals around the world

Answer 4

Convergent evolution

Question 5

How are marsupials distinct from monotremes?

Answer 5

• seperate anus and urinogenital sinus (mono - one, monotremes shit pee and lay eggs out of 1 hole)
• tested in scrotum outside body
• paired lateral virginal and bifid penis (forked vaginas and penises)
• placenta, gestation (vs shelled egg incubated internally)
• discrete mammary glands with teats

Question 6

What is different about marsupial internal development compared to placentals

Answer 6

Marsupials don’t have much yolk in yolk sac, so are born at a low developmental stage

Question 7

How long is marsupial gestation?

Answer 7

10-20 days

Question 8

Where do marsupials give birth through?

Answer 8

Medial canal

Question 9

Marsupial young are precocious, what does this mean?

Answer 9

They migrate unaided to teat in search of milk

Question 10

Marsupial young are permanently attached to the tea initially, what development in mammals allows this?

Answer 10

Secondary palate, so they can breath