Mammalia

• Kingdom: Animalia

• Phylum: Chordata

• Subphylum: Vertebrata

• Class Mammalia

Class Mammalia Major Characteristics

• Endothermy• Hair• Completely divided, 4-

chambered heart• Milk• Single jawbone• Specialized teeth• Amniotes• 3 inner ear bones

Key characteristics

• Endothermy-Mammals produce body heat internally through metabolism.

• Hair- All mammals have hair. The main function of hair is to insulate the body against heat loss.

• Completely Divided Heart- Mammals have a four chambered heart with two completely separate ventricles.

Key Characteristics Cont.

• Milk- Female mammals produce milk from their mammary glands. They do this to feed their offspring.

• Single Jawbone- This helps identify mammalian fossils. (Reptiles have several jawbones.)

• Specialized Teeth-Front teeth are used for biting, cutting, or seizing prey. Side teeth are for crushing, grinding, or slicing.

Amniotic• Eggs developed with a set of membranes

(placenta) to protect them in a terrestrial environment

• they prevent dessication, in other words, they ensure that the embryos do not dry-out

• they enable gas exchange between the embryo and its environment as its develops

• they allow waste materials to be disposed of while the embryo develops

• they enable the embryo to receives the nutrition it needs to develop

Mammal’s

• 5,000 species

• 26 orders

Groups

• Order Monatremata: duckbill platypuses, spiny anteaters

• Order Marsupialia: opossums, kangaroos, koalas, wallabies

• Placental mammals (18 orders)

Order Monetremata

• In this order the animal lays eggs

• They include many of the mammals that people consider as abstract or weird.

• Only three species exist in this order.

• The species only live in Australia and New Guinea.

Order Marsupialia

• 280 species exsist within this order.

• Australia, New Guinea, & The Americas is where these animals populate.

• The incubation period for these animals is very short so many babies are born underdeveloped in a shorter period of time, e g. kangaroo joeys are born after a 4-5 week gestation.

Placental Mammals

• 95 percent of mammals are placental mammals.

• There are 18 different orders within the group of placental mammals.

• The incubation period of these animals is longer than that of the marsupials

Placental mammals• Primates: Monkeys, Lemurs, Gibbons, Orangutans, Gorillas, Chimpanzees,

Humans• Insectivora: Moles and Shrew• Chiroptera: Bats• Enentata: Armadillos, Sloth, Anteaters• Pholidota: Pangolins• Rodentia: Squirrels, Woodchucks, Mice Rats, Muskrats, Beavers• Lagomorpha: Rabbits, Hares, Pikas• Carnivora: Whales, Porpoises, Dolphins• Sirenia: Sea Cows, Dugongs, Manatees• Proboscidea: Elephants• Pinnipedia: Seals, Sea Lion, Walruses• Perissodactyla: Rhino’s, Horses, Zebras• Artiodactyls: Hippos, Camels, Deer, Giraffes, Cattle, Sheep, Goats• Macroscelidea: Elephant Shrew• Scandentia: Tree shrew• Hyracoidea: Hyraxes• Dermoptera: Flying lemurs• Tubulidentata: Aardvark

Trophic categoriesScientists place placental mammals in 4 trophic categories based on what they eat:•Instectivore

– Eat insects and other small invertebrates– Moles, shrews, anteaters

•Herbivores– Eat vegetation (primary consumers)– Rabbits, deer, horses

•Carnivores– Feed on herbivores (secondary/tertiary consumers)– Wolves, lynx

•Omnivores– Feed on both plants and animals– Raccoons, primates

What is this?

Evolutionary history:Synapsids

• “mammal-like reptiles”

• Diverged from a common ancestor with reptiles

• Have a very distinct skull with a hole in the jaw for attachment of muscles of the jaw

Reproduction

• Monotreme mothers typically one or two eggs and incubates them with her body heat.

• Newborn marsupials emerge form their mothers uterus when they are ready. Its growth and development continues in its mothers pouch.

• Placental mammals: Once the egg is fertilized it attaches to its mothers uterus and is nourished by the placenta.

Remember, Synapsids gave rise to mammals and mammal-like

reptiles, the first of which were the THERASPIDS:

Pentadactyl limbs• Pentadactyl (pent

= 5, dactyl = finger)

• Type of adaptive radiation in mammals

• The pentadactyl limb has become adapted to different environmental conditions and modes of life

Convergent evolution• Structures of unrelated

species can evolve to look alike because the structures are adapted to a similar function. These are called analagous structures

• They differ from each other in their microscopic details and their embryonic development

• The process by which they evolve to resemble each other is called convergent evolution