Most lineages (species, genera, and broader clades) in North and South America have very different evolutionary histories since North America (Nearctic region) was once part of the supercontinent Laurasia. Laurasia was separated from Gondowana (the supercontinent that contained South America (Neotropic region) for more than 100 million years. Choose is the best explanation for this pattern. a) Most species in North and South America have very similar evolutionary histories, but North America has experienced a higher extinction rate due to habitat fragmentation and thus has fewer species than South America. b) North and South America were separated until 6 million years ago, limiting dispersal. Different lineages evolved on each continent. c) The long separation limited dispersal until 60 million years ago. Different lineages evolved on each continent. d) North and South America have different abiotic conditions (different biomes), so different lineages have evolved on each continent. 2. Terrestrial (on land) biodiversity is higher in tropical (near the equator) than in temperate (mid-latitude) regions. Which of the following best explains the reason for this pattern? ( Check all statements that you think apply. ) a) Tropical regions are more pristine, with less human development and thus less species extinction. b) The annual average temperature in tropical regions is more variable than in the northern and the southern hemispheres. Higher temperature variability is likely to generate a wider variety of species. c) Tropical regions have had a longer evolutionary history than the northern and the southern hemispheres since the tropics worked as a refuge during several ice ages. A longer evolutionary history means that species have been able to diversify over a longer time. d) The tropics are more productive, leading to increased speciation and thus higher biodiversity. e) Tropical regions have larger landmass than the northern and southern hemispheres. A larger landmass allows for larger populations as well as geographical range of species, which both decreases extinction rates. .

1. Most lineages (species, genera, and broader clades) in North and South America have very
different evolutionary histories since North America (Nearctic region) was once part of the
supercontinent Laurasia. Laurasia was separated from Gondowana (the supercontinent that
contained South America (Neotropic region) for more than 100 million years.
Choose is the best explanation for this pattern.
a) Most species in North and South America have very similar evolutionary histories, but North
America has experienced a higher extinction rate due to habitat fragmentation and thus has fewer
species than South America.
b) North and South America were separated until 6 million years ago, limiting dispersal.
Different lineages evolved on each continent.
c) The long separation limited dispersal until 60 million years ago. Different lineages evolved on
each continent.
d) North and South America have different abiotic conditions (different biomes), so different
lineages have evolved on each continent.
2. Terrestrial (on land) biodiversity is higher in tropical (near the equator) than in temperate
(mid-latitude) regions. Which of the following best explains the reason for this pattern? ( Check
all statements that you think apply. )
a) Tropical regions are more pristine, with less human development and thus less species
extinction.
b) The annual average temperature in tropical regions is more variable than in the northern and
the southern hemispheres. Higher temperature variability is likely to generate a wider variety of
species.
c) Tropical regions have had a longer evolutionary history than the northern and the southern
hemispheres since the tropics worked as a refuge during several ice ages. A longer evolutionary
history means that species have been able to diversify over a longer time.
d) The tropics are more productive, leading to increased speciation and thus higher biodiversity.
e) Tropical regions have larger landmass than the northern and southern hemispheres. A larger
landmass allows for larger populations as well as geographical range of species, which both
decreases extinction rates.