Comparing Biodiversity in Marine Ecosystems
Simpson’s Diversity Index is a measure of diversity. In ecology, it is often used to quantify the biodiversity of a habitat. It takes into account the number of species present, as well as the abundance of each species. Biological diversity can be quantified in many different ways. The two main factors taken into account when measuring diversity are richness and evenness. Richness is a measure of the number of different kinds of organisms present in a particular area. Evenness compares the similarity of the population size of each of the species present.
The equation for Simpson’s Index will calculate an index value, between 0 and 1
- a high D value (closer to 1) → high biodiversity
- a low D value (closer to 0) → low biodiversity
1 – D (Simpson’s Index of Diversity):
Measures the probability of picking two individuals of different species (ranges from 0 to 1, 1 = infinite diversity).
Calculation Steps (for 1 – D)
- Count Individuals: Determine ‘n’ (number of individuals for each species) and ‘N’ (total number of all individuals).
- Calculate Proportions: For each species, find the proportion (n/N).
- Square Proportions: Square each (n/N) value.
- Sum Squares: Add all the squared proportions together (Σ(n/N)²).
- Subtract from 1: Calculate D = 1 – Σ(n/N)² to get the final diversity index.
Here is a random data generator to create some practice problems for you to try:
Simpson’s Index of Diversity (1 − D)
Practice worksheet · randomised data every time · AICE Marine Science (9693)
Work through every step yourself: find N, then for each species compute (n/N)², total them, and finally subtract from 1. “Check my work” marks each box without giving the answers; the worked solution unlocks after your first check. Round to 4 d.p.
Data and working
Interpretation
In a sentence: does this value suggest high or low diversity for this shore, and what does that tell you about the number of species and how evenly they are spread?
Teacher tools
The answer key PDF is for teacher use. It is kept here, separate from the student controls above.
Simpson’s Diversity Index quantifies biodiversity by measuring the probability that two individuals randomly chosen from a sample belong to the same species, considering both species richness (number of species) and evenness (abundance distribution), with higher numbers (or 1-D) indicating greater diversity, and it’s used in marine science to assess ecosystem health, monitor pollution impacts, compare habitats, and guide conservation efforts by revealing shifts in balance due to stressors like climate change or pollution
How Simpson’s Diversity Index is used in marine environments:
- Habitat Health: Compares diversity in areas like coral reefs or seagrass beds, showing if a healthy, varied ecosystem is shifting towards dominance by fewer, tougher species.
- Pollution Monitoring: Detects ecological distress; a drop in diversity might signal pollution, leading to remedial action.
- Climate Change Impact: Tracks changes in species composition and abundance, helping develop strategies against biodiversity loss.
- Conservation: Identifies areas needing protection or sustainable management, informing policy by providing objective metrics.
- Ecosystem Resilience: Assesses stability; diverse systems are often more resilient to disturbances.
Example: A pristine coral reef might have a high Simpson’s Index (low D), showing many fish species in balanced numbers, while a polluted area might show low diversity (high D), dominated by only a few resilient species.
What does is mean if the Simpson’s Index = 0?
AICE Marine Practice Test
When you feel that you’re ready and you’d like to test your level of knowledge, take our online AICE Marine Practice Test to see where you’re at and the areas that still need some focus. Good luck!
If you need more help, here is the textbook from Cambridge Press:
