Flashcards in Marsupials Deck (30)
Where are marsupials found ?
In Australia and the southern hemisphere (New Guinea)
Where are the oldest marsupial fossils found ?
In present day china and north America.
How have we documented the ancestral spread of marsupials ?
Through molecular analysis, Studying the fossil record and use of tectonic models
Describe the relationship between the Australian and south American marsupial groups.
A Single South American marsupial became the ancestor of the Australian marsupials
(Australian marsupials, within wider group of SA marsupials)
When did marsupials evolve ?
168 ya, In the early cretaceous period.
Describe the adaptive radiation of marsupials.
Evolved in Laurasia (Europe, asia, N America)
crossed from S America to Antartica and then Australia
Continents then began to split leading to considerable adaption of marsupials in isolated habitats.
How were marsupials able to cross from South America to Australia ?
Gondwana, giant land mass linking South America, Antarctica and Australia
How many species exist in the modern day ?
300 species of marsupial
How many orders of marsupial ?
Give the causes of marsupial extinction 3 million years ago
Placental mammals are thought to have hunted some marsupials to extinction
Give an example of the extreme diversity found within the marsupials.
Planigale and Adult red kangaroo
(20,000 times heavier)
Huge weight difference!
Give an ecological equivalent of the marsupial Sugar glider, from Australia
Northern flying squirrel,
Give an ecological equivalent of the Eutherian Spotted hyena
Both have sloped hindquarters, Big jaws
Give the ecological equivalent of the marsupial Kangaroo
Give the ecologically equivalent mole species
Southern Marsupial Mole
European Eutherian Mole
Why are marsupial and eutherian equivalents, analogous not homologous ?
They are not ancestral features
Instead characteristics due to CONVERGENT evolution
Are comparable due to similar morphological features
Shared ancestry between species
When did the Eutherians evolve from the Marsupials ?
In the late Jurassic, 140 million years ago
Describe the difference in uterus horns between Eutherians and marsupials.
Eutherians have a 1 horned uterus
Marsupials have 2, 3 horned uterus
To fully fertilise the 2 horned uterus, what have some marsupial males evolved ?
Doubled lobed penis
Describe a marsupials placenta.
Nutrients are exchanged via the egg sac
What are the Bandicoots ?
A marsupial group consisting of 20 species who have developed placentas
However they are much smaller and lack villi
Describe the gestation period of marsupials in comparison to that of the eutherian
Much shorter (13-35 days)
Eutherians much longer
Give the longest eutherian gestation period
650 days, 2 years
Describe the life cycle of the new-born marsupial
Crawls up female to pouch
Attaches to nipple (by smell?)
The nipples swell, new born able to move until jaw muscles developed
Released when comparatively same size as placental offspring
After giving birth to offspring when are marsupials again able to reproduce ?
Immediately- Postpartum estrus
However if fertilised the zygote will be arrested at the blastocyst stage until current offspring die or develop further
Give the advantage of this rapid reproduction
(arrested blastocyst stage)
Enables rapid generation of offspring in breeding season
If nipple feeding offspring die, new offspring to take place.
What was the first marsupial to have its genome coded ?