Mammals

Question 1

Definitive characteristics of a mammal

Answer 1

Fur
Feeds young on milk
Single lower jaw bone
Warm blooded/Endotherms (the cause of their survival of the meteor that hit earth after the Cretaceous ~66 mya)
Diaphragm

Question 2

Three subclasses of mammals

Answer 2

1. Prototheria / Monotremes (egg laying mammal, 3 species)
2. Metatheria / Marsupialia (pouched mammals, 275 species)
3. Eutheria / Placentals (well developed placenta, 3982 species)

Question 3

Where did Marsupialia originate?

Answer 3

North America (early Cretaceous, 141-97 Mya) some fossils from Asia as well, but most from NA.

Earliest known Australian marsupial is 55 Mya.

Question 4

Where did Monotremes originate?

Answer 4

Australia (141-65 Mya)

Question 5

Why did Marsupialia do well in Australia but not in South America?

Answer 5

Marsupialia have slower reproduction and lower nutrient requirements than placental mammals.

Placental mammals outcompeted marsupials in SA because they have higher reproduction.

MAYBE marsupials outcompeted placental mammals in Australia, because of low nutrient availability.

Question 6

Rodents in Australia

Answer 6

Of Asian origin, entered early Pliocene (5 Mya)
Found throughout Australia from about 2 mya.

Different groups arrived at different times.
- old endemics ( most species, 3 subgroups) Conilurines (~50), mosaic-tailed rats (6) and water rats (2).

• new endemics (genus Rattus, 8 species) arrived ~ 1-2 mya
• recent introductions (house mouse and 2 rats?

Now: very high level of species endemicity, mostly endemic genera.

Rodents are placental mammals.

Question 7

Megafauna in the Pleistocene

Answer 7

Examples

Diprotodon optatum, biggest fossil ever found in Australia.
Browser, ate shrubs. 25.000 years ago.

Thylacoleo carnifex, marsupial lion. Ecological nice similar to lions in Africa, apex predator.

Thylacines, ecologically similar to dingoes today, medium sized carnivores

Question 8

What is the difference between a browser and a grazer?

Answer 8

Important ecological distinction

A grazer is like a cow, eating grasses, somewhat picky but not really.

Browsers eat leaves and other plant material from trees, that can eat grass but don’t as much as grazers do. Shrubs (diprotodon)

Question 9

Only venomous mammal in the world

Answer 9

Platypus

Question 10

What is Bergman’s rule?

Answer 10

Bergmann’s ruleis anecogeographical rulethat states that within a broadly distributed taxonomicclade, populations and species of larger size are found in colder environments, and species of smaller size are found in warmer regions. Although originally formulated in terms of species within a genus, it has often been recast in terms of populations within a species.

Question 11

Subclass: Metatheria / Marsupials

Answer 11

~200 species in Oz

Found in many different ecological niches in Oz

Reproductive organs are weird; female has doubled reproductive tract but gives birth through a third canal (pseudo vagina), male has bifid penis.

It is thought that Marsupialia give birth to their young as early in the development as they do, to protect the baby from the mother’s immune system. In placental mammals, the placenta protects the baby.( This is controversial)

Question 12

Order: Dasyuromorphia

Answer 12

Marsupial carnivores

Three families:
1. Dasyuridae (small insectivores and carnivores)
E.g. Tasmanian devil, quoll, antechinus, planigale
2. Myrmecobidae (numbats)
3. Thylacindae (thylacines - extinct)

Characteristics
Nocturnal, long range movement, live in burrows or nests.
Can’t sweat, bad eyesight - smell and hearing reliant.

Many species under threat. Virus causing facial tumors in Tasmanian devils.

Question 13

Semelparous Vs iteroparous

Answer 13

Semelparous: only breeding once in your life

Iteroparous: breeding multiple times throughout a lifetime