Marsupials

Question 1

Where are marsupials found ?

Answer 1

In Australia and the southern hemisphere (New Guinea)

Question 2

Where are the oldest marsupial fossils found ?

Answer 2

In present day china and north America.

Question 3

How have we documented the ancestral spread of marsupials ?

Answer 3

Through molecular analysis, Studying the fossil record and use of tectonic models

Question 4

Describe the relationship between the Australian and south American marsupial groups.

Answer 4

A Single South American marsupial became the ancestor of the Australian marsupials
(Australian marsupials, within wider group of SA marsupials)

Question 5

When did marsupials evolve ?

Answer 5

168 ya, In the early cretaceous period.

Question 6

Describe the adaptive radiation of marsupials.

Answer 6

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.

Question 7

How were marsupials able to cross from South America to Australia ?

Answer 7

Gondwana, giant land mass linking South America, Antarctica and Australia

Question 8

How many species exist in the modern day ?

Answer 8

300 species of marsupial

Question 9

How many orders of marsupial ?

Answer 9

7

Question 10

Give the causes of marsupial extinction 3 million years ago

Answer 10

Placental mammals are thought to have hunted some marsupials to extinction

Question 11

Give an example of the extreme diversity found within the marsupials.

Answer 11

Planigale and Adult red kangaroo
(20,000 times heavier)
Huge weight difference!

Question 12

Give an ecological equivalent of the marsupial Sugar glider, from Australia

Answer 12

Eutherian
Northern flying squirrel,
North America

Question 13

Give an ecological equivalent of the Eutherian Spotted hyena

Answer 13

Marsupial
Tasmanian Devil

Both have sloped hindquarters, Big jaws

Question 14

Give the ecological equivalent of the marsupial Kangaroo

Answer 14

Eutherian

Patagonian Mara

Question 15

Give the ecologically equivalent mole species

Answer 15

Southern Marsupial Mole

European Eutherian Mole

Question 16

Why are marsupial and eutherian equivalents, analogous not homologous ?

Answer 16

They are not ancestral features

Instead characteristics due to CONVERGENT evolution

Question 17

Define analogous

Answer 17

Are comparable due to similar morphological features

Question 18

Define Homologous

Answer 18

Shared ancestry between species

Question 19

When did the Eutherians evolve from the Marsupials ?

Answer 19

In the late Jurassic, 140 million years ago

Question 20

Describe the difference in uterus horns between Eutherians and marsupials.

Answer 20

Eutherians have a 1 horned uterus

Marsupials have 2, 3 horned uterus

Question 21

To fully fertilise the 2 horned uterus, what have some marsupial males evolved ?

Answer 21

Doubled lobed penis

e.g. Kangaroos

Question 22

Describe a marsupials placenta.

Answer 22

Short lived
Not intricate
Nutrients are exchanged via the egg sac

Question 23

What are the Bandicoots ?

Answer 23

A marsupial group consisting of 20 species who have developed placentas
However they are much smaller and lack villi

Question 24

Describe the gestation period of marsupials in comparison to that of the eutherian

Answer 24

Much shorter (13-35 days)
Eutherians much longer 
(45-650d)

Question 25

Give the longest eutherian gestation period

Answer 25

650 days, 2 years

Question 26

Describe the life cycle of the new-born marsupial

Answer 26

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

Question 27

After giving birth to offspring when are marsupials again able to reproduce ?

Answer 27

Immediately- Postpartum estrus

However if fertilised the zygote will be arrested at the blastocyst stage until current offspring die or develop further

Question 28

Give the advantage of this rapid reproduction

arrested blastocyst stage

Answer 28

Enables rapid generation of offspring in breeding season

If nipple feeding offspring die, new offspring to take place.

Question 29

What was the first marsupial to have its genome coded ?

Answer 29

Opossum

Question 30

What were the immune findings of the first marsupial genome sequence ?

Answer 30

The common ancestor of E & M; M had the basic building blocks for the human immune system

Modern day eutherian genetic invention is mostly due to changes in regulatory DNA and non-coding sections rather than new genes