BIO 230: Exam 3 study guide: Fishes, Mammals, and Geologic Patterns of Diversity
MAMMALS:
1. What are the two characteristics of mammals and why did they evolve?
Lactation evolved to keep eggs moist; jaw developed from teeth à mandible
2. What are the three extant clades of mammals, how do they reproduce, and what are the advantages
of the marsupium (compared to eggs) and the placenta (compared to a marsupium?)
Monotremes: reproduce with leathery egg
Placentals: placenta for direct nutrient transfer; benefit of independence upon birth & efficient energy
transfer
Marsupials: live birth to embryo; benefit that mother protects young
3. List the four major clades of placental mammals. How does plate tectonics correlate with these
clades? Discuss in terms of dispersal vs. vicariance, and different types of evidence (fossils and molecular
clocks). VICARIANCE is a pattern of distribution caused by the range being split in two by a geological
event… like plate tectonics. So, the distribution of marsupials on Australia and South America today is
NOT due to dispersal from one continent to another; rather, it is because they were distributed across
Gondwanaland when the continents split apart.
Afrotheria, Xenartha, Euarchontaglires, Laurasiatheria
Island breakup = vicariance; dispersal from rafting (rodens Africa à SA)
4. What are the two most species-rich orders of mammals, and what fraction of mammalian diversity do
they each represent?
Rodents 50%, bats 20%
5. What mammal species in SC are here because of the great American biotic Interchange?
Marsupials and Xenarthans
6. There are lots of marsupials in SA, but they aren’t as ecologically diverse as the marsupials in
Australia. How come?
Australia had longer isolations from placentals
7. What Afrotherian species is represented in SC?
Manatee
8. Bats and shrews face an important difficulty as very small endotherms; especially bats that have extra
energetic demands of flight. How does each solve this problem?
Torpor in winter, lose 30% of body weight in organs
9. What is white-nose syndrome and how does it kill bats?
MAMMALS:
1. What are the two characteristics of mammals and why did they evolve?
Lactation evolved to keep eggs moist; jaw developed from teeth à mandible
2. What are the three extant clades of mammals, how do they reproduce, and what are the advantages
of the marsupium (compared to eggs) and the placenta (compared to a marsupium?)
Monotremes: reproduce with leathery egg
Placentals: placenta for direct nutrient transfer; benefit of independence upon birth & efficient energy
transfer
Marsupials: live birth to embryo; benefit that mother protects young
3. List the four major clades of placental mammals. How does plate tectonics correlate with these
clades? Discuss in terms of dispersal vs. vicariance, and different types of evidence (fossils and molecular
clocks). VICARIANCE is a pattern of distribution caused by the range being split in two by a geological
event… like plate tectonics. So, the distribution of marsupials on Australia and South America today is
NOT due to dispersal from one continent to another; rather, it is because they were distributed across
Gondwanaland when the continents split apart.
Afrotheria, Xenartha, Euarchontaglires, Laurasiatheria
Island breakup = vicariance; dispersal from rafting (rodens Africa à SA)
4. What are the two most species-rich orders of mammals, and what fraction of mammalian diversity do
they each represent?
Rodents 50%, bats 20%
5. What mammal species in SC are here because of the great American biotic Interchange?
Marsupials and Xenarthans
6. There are lots of marsupials in SA, but they aren’t as ecologically diverse as the marsupials in
Australia. How come?
Australia had longer isolations from placentals
7. What Afrotherian species is represented in SC?
Manatee
8. Bats and shrews face an important difficulty as very small endotherms; especially bats that have extra
energetic demands of flight. How does each solve this problem?
Torpor in winter, lose 30% of body weight in organs
9. What is white-nose syndrome and how does it kill bats?
