1

Mammals

2

All Mammals belong to the Class Mammalia

Approx. 4000 living species

that are classified in 17 different orders

Rodentia

Carnivora

Perissodactyla Lagomorpha

Primates

3

Mammals were present but not very widespread during the Mesozoic era (Recall that This was the age of the dinosaurs)

The Cenozoic Era (This“time” started 65 million years ago and goes up to the

present day)

The Cenozoic Era is known as….“the age of the mammals”

4

Characteristics•Mammals are Endothermic

(Endothermic means that they can maintain a constant body temperature and a relatively high body temp – relative to the environment)

•Mammals have hair (even whales have a few!)

•Well-developed brains (enlarged cerebrum –

the thinking part of the brain)

5

River otter (Endotherm)

Largemouth bass (Ectotherm)

Ambient (environmental) temperature (°C)

Bod

y te

mpe

ratu

re (

°C)

40

30

20

10

10 20 30 400

The mammal (otter) has a constant, high body temp

Endotherms (warm blooded) animals need to consume a lot more food to produce heat energy than ectotherms (cold blooded animals)

6

•Mammals have a single lower jaw, the upper jaw is “fused” or directly attached to the skull

•Most species have 4 different types of teeth (incisors, canines, premolars, molars)

Smilodon

The saber-toothed “tiger”

8http://static.howstuffworks.com/flash/saber-tooth-skull.swf

Animation

9http://static.howstuffworks.com/flash/saber-tooth-scale.swf

Animation

11

Characteristics•Almost all mammals are

viviparous- this is the biological term for females carrying their young internally inside a uterus until they are born fully formed.

• All mammalian females secrete milk from mammary glands to feed newborn young.

Classification:

Class: Mammalia:

Note: That you are only expected to know the red names below. These are the technical classifications for the “3 main types” of mammals:

Subclass: Prototheria Subclass: Theria Subclass: Theria

Order: Monotremata Infraclass: Metatheria Infraclass: Eutheria

Order: Marsupialia 12

13

Order Monotremata and

Order MarsupialiaOnly 5 percent of all living mammal

species’ are placed in these two orders

14

Monotremata

• Egg laying mammals

the term for this is oviparous• Only 3 living species.• Duck-billed platypus (one species) and

two species of “spiny anteaters” these are called Echidna.

• Their body temperature is lower and it fluctuates more than other mammals

15

Marsupialia– opossums, kangaroos, and koalas are examples

of this order that you should know

16

Marsupials give birth to tiny immature young that crawl from out of the vagina then move up to a “pouch” (called the marsupium) immediately after they are born.

Note that this is a very risky journey!! – many young do not survive the trip

This is why true placental mammals became the dominant type of mammal on earth – they simply had a higher reproductive survival rate!

Once inside the pouch they attach themselves to milk secreting nipples, nursing until they are mature enough to survive outside the pouch.

17

There are about 250 living species of marsupial - mainly found in Australia

and New Guinea.

18

There are some in other parts of the world- The American opossum

19

SO WHY are these two groups of “primitive mammals” so numerous in Australia?

ANSWER: The Australian continent separated from the other land masses before placental mammals had evolved!

Watch this gif animation in slideshow mode

20

Australia became a “biological ark” for the monotremes and marsupials. Why do we use this term?

Because they were geographically isolated, placental mammals had not yet evolved when Australia broke away from

the other continents

21

Eutherians or Placental Mammals

22

• Placental mammals carry unborn young in the uterus until young can survive in the wild. (The gestation period is the time from fertilization until birth )

• Oxygen and nutrients are transferred from mother’s blood to baby’s blood just by diffusion - the blood does not mix.

The umbilical cord attaches placenta to the fetus

23

The Placenta is name the special organ that allows the diffusion and exchange of essential materials between mother and baby

placenta

Umbilical cord

Final Review activity - Watch the animation summary of vertebrate evolution below. Note that It has AUDIO

Mammalian Adaptive Radiation: With the demise of the dinosaurs many different

Ecological Niches became available to the placental mammals

The huge variety in form and function on the basic placental mammal design – is known as

Adaptive Radiation.Mammals have evolved that fly (bats) swim (whales

and dolphins) and live on land (lions)

http://uccpbank.k12hsn.org/courses/CPBiology/bio_6_1_1_4.swf