Biology 11Phylum Chordata

Subphylum Vertebrata

Class Mammalia: US!

Class Mammalia

Mammalian Evolution:• Also evolved from the reptiles in late Mesozoic• Existed as small rodent-like animals that burrowed in the

ground• Were able to survive end of Mesozoic and were pre-

adapted to the new cool dry reality• Completed the vertebrate evolution to land

Mammalia Objectives

• General characteristics• 6 body systems: circulatory, respiratory,

integumentary, reproductive, nervous, skeletal• 3 subclasses and example animals

Mammalian Characteristics

• 4 chambered heart• Hair or fur• Diaphragm for breathing• Amniotic egg• Mammary glands for

nursing young• Extensive post natal care• Learning and reasoning

levels of behavior

Class Mammalia

Advances and Characteristics:1. Circulatory System• Complete four chamber heart and

circulatory pattern (same as Aves except for the whole air sac business )

2. Respiratory System• Highly efficient lungs with muscular

diaphragm

Class Mammalia

3. Body Covering• Covered with hair for insulation

(modified scales) and sensing• All mammals are endothermic• Have a layer of subcutaneous fat for

insulation and food storage

Class Mammalia

4. Reproduction• Internal fertilization & development• Amniotic egg: modified to include placenta• Nurse young with mammary glands• Young born very immature - require extensive

post natal care (18yrs worth! )

Class Mammalia

5. Nervous System• Most advanced nervous system in the

animal kingdom• Great increase in cerebrum (convoluted)• Very well developed senses• Behavior reaches learning and reasoning

levels – infant care, mating & societies

Brain Regions and Functions

Frontal Lobe thinking, planning, & central executive functions; motor execution.

Parietal Lobe somatosensory perception, integration of visual & somatospatial information.

Temporal Lobe language function and auditory perception involved in long term memory and emotion.

Occipital Lobe visual perception and processing.

Class Mammalia

6. Skeletal• Limbs are well adapted for land and water &

allow very rapid movement

Class Mammalia

1. Subclass Prototheria (the monotremes)

• Have fur & nurse young• Have a bird bill & lay eggs

which they incubate outside body

• Today represented only by Duck Billed Platypus and the two species of Anteater

• An evolutionary dead end

ClassificationThe mammals are placed into three Orders:

Class Mammalia

2. Subclass Metatheria (the marsupials)

• Do not have a uterus (but do have a short lived placenta!) complete development in the pouch fused to mammary gland

• First major group of mammals to evolve – spread all over Earth – adaptive radiation

• Became reduced globally due to competition from placental mammals

Class MammaliaExample Marsupials:• The North American

marsupial is the opossum – an omnivore

• The Australian marsupials are represented by kangaroos, wallabies, possums and koala bears among many others – all herbivores

Possum (Australian)

Opossum (American)

Class Mammalia

3. Subclass Eutheria

(the placental mammals) Complete internal development due to placenta – an organ of exchange between mother & fetus

• Most common order of mammals today - includes us!

• Dominant land vertebrate - adaptive radiation!