Menge and colleagues performed experiments in which they exposed some populations of mussels to sea stars and excluded sea stars from other mussel populations. Suppose that the sea star population consists of 20 individuals and the two populations of mussels are of the same size prior to the mussel treatment. In the treatment condition there are 500 individuals without sea stars and 100 individuals with sea stars. What is the per capita interaction strength of sea stars on mussels?
a. ln 0.5 ÷ 20
b. ln 20 ÷ 5
c. ln 100 ÷ 20
d. ln 0.2 ÷ 20
e. ln 500 ÷ 100
From the equation I used, I;m getting d as the correct answer, but the book says it is a. I don't understand how to get the a answer. Is it even correct, or could there be a mistake?
To calculate the per capita interaction strength of sea stars on mussels, we need to determine the change in mussel population size when exposed to sea stars and compare it to the sea star population size.
The per capita interaction strength measures the impact of one individual from one species on one individual from another species. In this case, we want to find the impact of each sea star on each mussel.
The formula to calculate per capita interaction strength is:
Interaction Strength = ln(Nf/Ni) / Ns
Where:
- Nf is the final population size of mussels after the treatment (exposed to sea stars).
- Ni is the initial population size of mussels before the treatment (without sea stars).
- Ns is the population size of sea stars.
Given information:
- Ni = 500 (population size of mussels without sea stars)
- Nf = 100 (population size of mussels with sea stars)
- Ns = 20 (population size of sea stars)
Now let's calculate the per capita interaction strength:
Interaction Strength = ln(100/500) / 20
= ln(0.2) / 20
≈ -1.609437912 / 20
≈ -0.080471896
Based on the given options, we can see that the correct answer is d. ln 0.2 ÷ 20, which is approximately equal to -0.080471896.
It seems there might be an error in the book. The correct answer should indeed be d, not a.