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The Simpson's Diversity Index allows us to use math and numbers to compare the biodiversity in two locations. The goal of this equation is to solve for a variable 'D' using variables 'n' and 'N'. The closer D is to 1, the more diversity a population has🦌🐦🐺🐍. Yet, the closer the D value is to zero, the less diverse the population is🐍. The Simpson's Diversity Equation is as follows: 

Variables You Need to Know

  • D - This variable helps us determine how much biodiversity an area has.
  • n - Lil' n represents the number of a species🦌🦌🦌🦌 in a population.
  • N - Big N represents the total number of organisms🦌🦌🐦🐦🐦🐺🐺 in a population.

An Example

The best way to understand an equation is to do an example. This equation looks really difficult😲, but it isn't that hard once you go through it one time😌.
Our Sample Population:

  • Rattlesnake🐍: 18
  • Whitetail Deer🦌: 25
  • Bald Eagle🦅: 15
  • Lizard🦎: 22
  • Bears🐻: 11
  • Bobcat🐈: 19
  • Total: 110
  1. The first step is to solve for n(n-1) for each species, and add all those values together. This takes care of the numerator of that big fraction that makes up 50% of the equation.

2. Next, we are going to calculate N(N-1)
This can easily be done. Our N value is 110, because that is how many organisms are in our population. This takes care of the denominator of our fraction.

N(N-1) = 110(110-1) = 110(109) = 11990

3. Finally, we take all that we've calculated, and solve for D.

Comparison and Conclusion

Using this number that we calculated, we evaluate the biodiversity of our sample population. Our sample population had a Simpson's Diversity Index of 0.83. This value is very close to one. That tells us that our sample population has a great amount of biodiversity🏅.
We can also use this number to compare the biodiversity in two different populations. For example, if we calculated the Simpson's Diversity Index for another population and got .43, we would know our first population has greater biodiversity. This is because our first population had a Simpson's Index value of 0.83 which is closer to one than 0.43.
This equation can be used to compare to locations at the same time, or it can be used to see whether the biodiversity in a population has increased or decreased over time. This is why these equations can be very useful for biologists and environmental scientists🌲.

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