Visualizing Life on Earth (Berkeley) Worksheet
Go to: http://evolution.berkeley.edu/evolibrary/article/ldg_01
0. Where is the most life concentrated on Earth? Why do you think that is the case?
Question 1: Imagine you are a scientist with a large database of information
about different species: where they are found, their habitat types, other
ecological information, classification information, population sizes, etc. You
want to find out if the LDG is real
a. What information in your database would you examine to find out if the LDG is
real?
b. If you wanted to communicate this to a colleague, how would you display it as a
graph or chart? Sketch an imaginary version of the graph or chart, being sure to
label the axes and types of data it displays
Question 2:
a. Based on the evidence presented above, do you think that the LDG is real – in
other words, are more species generally found at lower latitudes than at high ones?
Explain how the data above support your thinking
b. What sort of evidence would it take for you to change your mind about this?
Question 3:
a. List at least two explanations for this blip in the graph
b. Should blips like this one cause us to write off the LDG? Why or why not?
Question 4:
a. Based on the evidence presented above, do you think that species are crowded
into the tropics or spread out evenly over Earth’s surface? Explain how the data
above support your thinking
b. What sort of evidence would it take for you to change your mind about this?
Question 5:
a. Based on the evidence presented above, do you think that the LDG is a recent
phenomenon or an old one? Explain how the data above support your thinking
b. What sort of evidence would it take for you to change your mind about this?
Question 6:
Think about extinction and migration. Can these processes help explain why the
tropics are more diverse than other regions? Write down two or more other
hypotheses that might help explain the LDG – at least one having to do with
extinction, and at least one having to do with migration:
Extinction:
Migration:
Question 7:
a. Do you think one of the hypotheses for the LDG is a more likely explanation than
the others? If so, which one and why?
b. Do you think that the three explanations given are mutually exclusive – i.e., that
only one of them can be right? Why or why not?
Question 8:
a. Based on the evidence presented, do you think that the tropics are a cradle for
biodiversity – in other words, is our hypothesis about diversification rates being
higher in the tropics accurate? Explain how the data above support your thinking
b. What sort of evidence would it take for you to change your mind about this?
Question 9:
Does the graph above support the hypothesis that the tropics are a museum – in
other words, that extinction rates are lower in the tropics than in other regions of
the world? Or can you tell for these data? Explain your answer.
Question 10:
Does the graph and pie chart support the hypothesis that the tropic are a museum
– in other words, that extinction rates are lower in the tropics than in other regions
of the world? Or can you tell from these data? Explain your answer
Question 11: Does the graph above support the idea that genera that first evolve in
the tropics tend to spread into other climates? How does the graph above support
your thinking?
Question 12: Imagine a hypothetical planet on which organisms that first evolve in
one climate don’t spread to others. If you were to study the fossil record of that
planet, what would it look like? Sketch a hypothetical graph
Question 13: Pick one of the following evolutionary patterns:
 High tropical speciation rate
 Low tropical extinction rate
 High rate of species spreading out of the tropics and into other regions
a. Based on your knowledge of tropical and non-tropical regions and your
understanding of evolution, come up with a hypothesis that helps explain the
pattern. Feel free to look up information online, in the library, or in your
textbook to help
Hint: Try writing your hypothesis in this form: The tropics have a high speciation rate
(or low extinction rate or high rate of spreading) because…
b. How could you begin to test this hypothesis?
Hint: To figure our how to test your hypothesis, fill in the blank: If this hypothesis were
true, then I would expect to observe ____________. The expected observation might be the
result of an experiment, a pattern in fossil data, or a pattern in the distribution of
modern organisms on Earth. Ask yourself what a graph that supports this hypothesis
would look like. The important part is thinking carefully about yout hypothesis and
figuring out what sorts of observable outcomes are likely to result from that
mechanism.