Biodiversity and sampling
Biodiversity
- An ecosystem is all the living things in an area plus their non-living surroundings.
- A niche is a species' particular role and place within it.
- Biodiversity measures the variety of life — at three levels.
An ecosystem is:
An ecosystem includes the living community and the abiotic surroundings; a niche is a species' role within it.
Three levels of biodiversity
- the number and range of different ecosystems and habitats.
- the number of species and their abundance (how common each is).
- the genetic variation within each species.
Biodiversity is measured at three levels: ecosystems/habitats, species/abundance, and:
The three levels are ecosystem diversity, species diversity (and abundance), and genetic diversity.
Sampling an area
- You can't count everything, so you take samples. Random sampling avoids bias.
- quadrats — square frames to count species inside them.
- transects — counting along a line across the area.
- mark-release-recapture — for moving animals: mark and release some, then see what fraction of a later catch is marked.
Why is random sampling used?
Choosing positions by chance avoids bias, so the sample fairly represents the whole area.
Mark-release-recapture is best for estimating numbers of:
You mark and release some animals, then use the marked fraction of a later catch to estimate the population.
Measuring diversity
- Simpson's index of diversity turns biodiversity into a single number.
- A higher value means more diverse — and usually more stable.
A higher Simpson's index of diversity means the area is:
Simpson's index gives a single diversity number; higher means more diverse and generally more stable.
You've got it
- ecosystem = living + non-living; niche = a species' role
- biodiversity has three levels: ecosystems/habitats, species + abundance, genetic variation
- sample with quadrats & transects (fixed organisms) and mark-release-recapture (moving animals); use random sampling
- Simpson's index: higher = more diverse (and usually more stable)