Last week you collected data that allowed you to examine the effects of nutrient levels on population growth rates in the Spotted False Duckweed Landoltia punctata. This week you will use the same experimental
setup to look for evidence that the populations in these same canisters
are approaching their carrying capacity. What might this evidence be?
Well, if the populations are continuing to grow at an exponential rate,
then the per capita growth rate the first week of the experiment should
not be significantly different from the per capita growth rate for the
second week. Thus, we need to do little more than record population sizes,
calculate per capita growth rates for each week, and look for significant
differences over time. Because there were more than likely significant
differences in growth rates among the different nutrient levels, you will
need to analyze the weekly growth rates of each nutrient level separately.
## ProceduresRepeat last week's procedures. That is, record the number ofLandoltia thalli in each canister, and enter the data in
one of the laptops at your bench. To test your hypotheses, you will need
to convert raw population sizes to per capita growth rates. This is simple
to do in Excel. To calculate per capita growth rates during the first
week, create a new column with an Excel formula that is equivalent to:
(C, where _{1} / C_{0}) - 1C =
the starting population size (which should be 10!), and
_{0}C = the population size at the first census. Likewise,
to calculate per capita growth rates during the second week, create a new
column with an Excel formula that is equivalent to: _{1}(C, where _{2} /
C_{1}) - 1C = the population size
at the second census. _{2} |

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