Environmental Science / Unit 3: Biomes and Biodiversity
3.3 Measuring Biodiversity
Notes
Biodiversity is the variety of life. It has three levels: genetic diversity (variation within a species), species diversity, and ecosystem diversity.
- Species richness is the number of different species in an area.
- Species evenness is how evenly individuals are spread among species.
- Higher biodiversity makes ecosystems more resilient to disturbance and disease.
- Biodiversity is usually highest near the equator and decreases toward the poles.
- Genetic diversity helps a species adapt; a population with little genetic variation is at risk from a single disease.
- Example: Forest A has 5 species with 20 individuals each. Forest B has 5 species with 96 of one species and 1 each of the others. Both have richness 5, but A has higher evenness.
Practice
What is species richness?
Richness counts species, not individuals.
A farm field has one crop species. A nearby prairie has dozens of plant species. Which is most likely to survive a single new disease?
Diverse systems are less likely to be wiped out by one threat.
Two ponds each contain 4 species. Pond X has 25 individuals of each species. Pond Y has 97 of one species and 1 of each of the others. Compared with Y, pond X has:
Richness is equal (4 each), but pond X's individuals are evenly spread.
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