# 24.11.15: biodiversity lab

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Biodiversity has two elements:

- Species richness: the number of different species in an ecosystem
- Species evenness: the relative proportion of individuals within the different species in a given area

<div id="bkmrk-we%27ll-be-using-color">We'll be using colored goldfish (species) to demonstrate this, in several cases:</div><div id="bkmrk-totally-random-distr">

1. totally random distribution, calculate H (Shannon's index)
2. uneven distribution: major species takes over, calculate H
3. limited diversity example: few species, calculate H
4. species richness, many species, even distribution, calculate H

<div>We'll be using a formula that looks scary, but is not really, called Shannon's index:</div></div><div class="sandbox" id="bkmrk--3"><div id="bkmrk--4"><div id="bkmrk--5"><div><div class="container"><div class="frontside"><div class="iframe">![](https://bookstack.kamuela.org/uploads/images/gallery/2026-09/bvTZvC1Iy3igULqn-screen-shot-2022-10-16-at-12-09-43-pm-gpvcehqf.png)</div></div></div></div></div></div></div><div id="bkmrk--7">  
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- In each case, record the number of each species (color of goldfish), H for each, and take a photo of each bowl (ecosystem).
- Low numbers are like 1.5, high numbers are 4.5
- Make sure to bring YOUR notes on YOUR data to class next for a quiz.

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</div><div id="bkmrk-lab%3A-calculating-sha"><span style="font-weight: bold; font-size: 13px;">Lab</span>: Calculating Shannon's index, using baked goldfish (the cheddar kind, not the ones that stink)

1. wash your hands
2. pour out a random number of different colored goldfish on your plate (your "pond")
3. determine the number of distinct populations by color, using chopsticks, if available
4. determine the proportion for each population (e.g. 5 red ones out of 20 total would be 5/20 or 0.25)
5. calculate Shannon's index (H) for this "pond"
6. repeat the experiment with a very low biodiversity, calculate H
7. repeat with a very high biodiversity, calculate H
8. record all of your data on your notes (not shared notes) for next class
9. eat the contents of your "pond", representing a catastrophic event where the poor goldfish have poor resistance...

<span style="font-weight: bold; font-size: 13px;">Questions</span>: email your answers before next class

1. what is the value of biodiversity in any community?
2. what are the benefits and drawbacks of a low biodiversity?
3. how does this play into competition?
4. what is the difference between species richness and species evenness?
5. what is the impact of this on a human population, e.g. the census?
6. if you have 10 each of the six colors of M&amp;M candies, what is the H value for this?
7. You then eat some, leaving 10 brown, and 2 of each of the rest, what is H now?
8. which of these colors would likely be an invasive species in a simulation?
9. How does agriculture affect biodiversity? Discuss the impacts of monoculture farming compared to polyculture practices.
10. Describe the primary threats to marine biodiversity, including overfishing and coral reef degradation.

<div>Notes on Shannon's index:</div><div><span style="font-weight: bold; font-size: 13px;">Shannon Diversity:</span> It might sound complex, but at its core, it quantifies <span style="font-weight: bold; font-size: 13px;">ecological complexity</span>, using an index for measuring the variety and abundance of life in a given area.

<span style="font-weight: bold; font-size: 13px;">Here’s the key link to biodiversity:</span> Shannon Index reflects how much we can <span style="font-style: italic; font-size: 13px;">predict</span> about each species within a community based on observing others:

1. <span style="font-weight: bold; font-size: 13px;">Diversity Indices:</span> The index assigns scores to communities, reflecting their diversity levels. A higher score means greater diversity!
2. <span style="font-weight: bold; font-size: 13px;">Species Abundance &amp; evenness:</span> The formula considers both the number of different species (species richness) and how equally abundant they are in terms of relative population sizes (evenness).

<span style="font-weight: bold; font-size: 13px;">Why does this matter? Understanding biodiversity is crucial for these reasons: :</span>

- <span style="font-weight: bold; font-size: 13px;">Ecosystem Stability:</span> High diversity often leads to more resilient ecosystems that can better withstand environmental changes.
- <span style="font-weight: bold; font-size: 13px;">Conservation Efforts:</span> Identifying areas with high biodiversity allows targeted conservation efforts, ensuring we protect the most valuable species and habitats.
- <span style="font-weight: bold; font-size: 13px;">Predictive Models:</span> The index helps researchers predict how a change in one species might impact another (e.g., top-down or bottom-up effects) within a community.

<span style="font-weight: bold; font-size: 13px;">How it works (simplified):</span> Imagine an area with:

- Lots of different plant and animal species, like rainforests.
- Some plants are very common, some rare, making for uneven distribution in the ecosystem

The Shannon Index would consider these factors to calculate its diversity score based on how much we can predict about each unique life form within that community given what's already known.

<span style="font-weight: bold; font-size: 13px;">Example:</span>

- A diverse forest with numerous tree species (high richness) and a relatively even population of those trees across the area (evenness) will likely have a higher Shannon Index value compared to an area dominated by just one or two dominant species, indicating less diversity.

<span style="font-weight: bold; font-size: 13px;">Keep in mind:</span> The Shannon index is not perfect. It doesn't capture everything about biodiversity; it focuses on predicting the overall 'information content' of the system based on observed species variation within a specific community

<span style="font-weight: bold; font-size: 13px;">In summary</span>: The Shannon Index offers a valuable tool for biologists and ecologists to quantify ecological diversity, which helps in understanding how nature functions as a whole.

  
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