Biodiversity lab
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
- totally random distribution, calculate H (Shannon's index)
- uneven distribution: major species takes over, calculate H
- limited diversity example: few species, calculate H
- species richness, many species, even distribution, calculate H
- 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.
- wash your hands
- pour out a random number of different colored goldfish on your plate (your "pond")
- determine the number of distinct populations by color, using chopsticks, if available
- determine the proportion for each population (e.g. 5 red ones out of 20 total would be 5/20 or 0.25)
- calculate Shannon's index (H) for this "pond"
- repeat the experiment with a very low biodiversity, calculate H
- repeat with a very high biodiversity, calculate H
- record all of your data on your notes (not shared notes) for next class
- eat the contents of your "pond", representing a catastrophic event where the poor goldfish have poor resistance...
- what is the value of biodiversity in any community?
- what are the benefits and drawbacks of a low biodiversity?
- how does this play into competition?
- what is the difference between species richness and species evenness?
- what is the impact of this on a human population, e.g. the census?
- if you have 10 each of the six colors of M&M candies, what is the H value for this?
- You then eat some, leaving 10 brown, and 2 of each of the rest, what is H now?
- which of these colors would likely be an invasive species in a simulation?
- How does agriculture affect biodiversity? Discuss the impacts of monoculture farming compared to polyculture practices.
- Describe the primary threats to marine biodiversity, including overfishing and coral reef degradation.
Shannon Diversity: It might sound complex, but at its core, it quantifies ecological complexity, using an index for measuring the variety and abundance of life in a given area.
Here’s the key link to biodiversity: Shannon Index reflects how much we can predict about each species within a community based on observing others:
- Diversity Indices: The index assigns scores to communities, reflecting their diversity levels. A higher score means greater diversity!
- Species Abundance & evenness: The formula considers both the number of different species (species richness) and how equally abundant they are in terms of relative population sizes (evenness).
Why does this matter? Understanding biodiversity is crucial for these reasons: :
- Ecosystem Stability: High diversity often leads to more resilient ecosystems that can better withstand environmental changes.
- Conservation Efforts: Identifying areas with high biodiversity allows targeted conservation efforts, ensuring we protect the most valuable species and habitats.
- Predictive Models: 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.
How it works (simplified): 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.
Example:
- 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.
Keep in mind: 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
In summary: 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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