Flashcards in lecture 7 - mammals of fraser island Deck (26)
what animals came to australia in the Early jurassic?
> monotreme ancestors diverged early in 'gondwana' and spread throughout the southern globe, probably
what animals came to australia in the early cretaceous?
> placentals probably split form metatherian ancestors in asia
> placentals also dispersed but few reached australia at this time
> because of land ridges
what happened in late cretaceous?
> passage to australia was getting more difficult because it was separated from gondwana by water
what happened in the K/T event
> wiped out the dinosaurs and many other things.
> opened to way for remaining mammals to diversify
> in gondwana, the S.American mixture evolved in isolation
> in Australia, the marsupials radiated
> new cicumpolar currents started to freeze antartica
how did the mass extinction event allow for the radiation of marsupials?
> wiped out a lot of animals - thus creating empty niches
> these niches were then filled by the marsupials
what happened by the oligocene?
> australia was on its way to warmer and drier climates, shaping the organisms that live here
what are prototherians/monotremes?
>neonates hatch from an egg laid in pouch
what are metatherians/marsupials?
> neonates born early and develop in pouch attached to teat
what are eutherians/placentals?
> neonates born after development supported through a chorioallentoic placenta
what sub-class and order is the short-beaked echidna in?
> subclass Prototheria
> order Monotremata
what subclass and order is the yellow footed antechinus in?
- rat/mice sized
what subclass and order is the common dunnart in?
- teeth are pointy for piercing prey
what subclass and order are long-nosed bandicoots in?
- pointy front teeth, then molars for grinding
what order and subclass are northern brown bandicoots in?
what is the subclass and order of the short-eared brushail?
what subclass and order are swamp wallabies in?
what happened in the pleistocene?
> the australian plate collided with the asian plate forming an opportunity for new mammals to add to the fauna
> HOWEVER, there is trace evidence of placentals already being here as early as the Eocene (50mya), before the final split from gondwana
> there are a few teeth and jaw fragments from murgon controversially assigned to a placental, plus a fossil bat
> presumably these managed to disperse here from the south, but they didn't persist
during which era did multiple waves of invasions ocur
what different organisms are in the sub-class Eutheria ad Order - Rodentia
> a mosaic tailed rat whose ancestor arrived after the first 'old endemics' and before the 'new endemics'
> bush rat
> have typical rodent dentition
what is in the subclass -eutheria and order Chiroptera
> gould's wattled bat
> a micro-chiropteran' that uses echolocation
when were all the new endemics present before?
what sub class and order are black rats in?
how do you make abundance estimates?
> mark and recapture
> if you know what proportion of the population you catch, then you know the size of the population, sort of.
> trap initially and mark all the animals you catch.
> trap again and see what proportion are marked
> assume all your marked animals mix into the population in the meantime
> all animals, marked and unmarked are equally likely to be caught
> and the population size has not changed
> of your recaptured animals, the proportion of marked animals in the second event gives an estimate of the proportion you catch in any event
> apply this to the first event to get the original population size
what is an example of the mark and recapture technique?
> suppose you trap 30 animals the first time round. you mark and release them.
> suppose you then trap 25 animals, 5 of which are marked
> based on a single estimate so far, your traps successfully retraped 5 in 25, or 1 in 5 animals
> so you assume that your first trapping event successfully trapped 1 in 5 animals, i.e., there were 150 (5x30) animals out there
what are some assumptions of the mark and recapture technique?
> animals are equally likely to be trapped each time
- not always the case
- trap happy or trap shy animals