BIOL 112 Lecture 36

« previous | Friday, November 30, 2012 | next »

Ch. 22–34,42

Amniotes: Birds

• 4-chambered heart (unlike most reptiles
• endothermic
• unusual lung system

Lungs

Auxiliary air sacs surrounding lungs

More efficient compared to mammalian lungs:

• Air Moves in one direction
• is completely replaced with each breath

Reproduction

• Elaborate courtsihp behaviors
• internal fertilization
• Egg matures outside of female
• parental care

Mammals

Around during same time as dinosaurs

Cretaceous extinction (65 mya)

• no more dinosaurs
• allowed mammals to take over as dominant organisms
• adaptive radiation

Derived characteristics

• Mammary glands: nourishment of offspring
• Body hair made from keratin
• Endothermic
• Larger brains than other vertebrates of same size
• Modification of jaw bones to form inner ear structure

Three groups of Mammals

1. Monotremes
   • Lay eggs, but still nurse young
   • Platypus, Echidna
2. Marsupials
   • Name comes from marsupium (maternal pouch)
   • Simple placenta
   • "Immature" birth
   • Kangaroos
3. Eutherian (a.k.a. Placental mammals)
   • Complex placenta
   • Fetus completes development prior to birth

Geographic isolation:

• Monotremes and Marsupials are found mostly in the southern hemisphere (Australia, South America)
• Eutherians are mostly found in the northern hemisphere
• allowed all 3 types of mammals to survive