Species-area relationship: what Z means
"Species-area relationship: what Z means" is a free, interactive Class 12 Biology simulation for NEET, built on the lesson "Species-area relationship" in Biodiversity and Conservation. The green square is a forest; the 40 tiles are its species. By log S = log C + Z log A, a patch with a smaller area holds fewer species. Move the area and the slope Z, and watch the tiles and the straight log-log line. Log S = log C + Z log A is a straight line on log scales. Z is 0.1-0.2 within regions and much steeper, 0.6-1.2, for whole continents; a steep slope means area matters a great deal.
From the lesson Species-area relationship in Biodiversity and Conservation. Change the values and watch what happens.
The idea behind it
NCERT §13.1.2
- Exploring South American jungles, Alexander von Humboldt saw that within a region, species richness rose as the explored area grew, but only up to a limit.
- For many taxa (angiosperm plants, birds, bats, freshwater fishes) species richness against area is a rectangular hyperbola.
- On logarithmic scales the relationship becomes a straight line: log S = log C + Z log A, where S is species richness, A is area, Z is the slope (regression coefficient) and C is the Y-intercept.
- Z lies between 0.1 and 0.2 whatever the taxonomic group or region: plants in Britain, birds in California and molluscs in New York state give remarkably similar slopes.
- For very large areas such as whole continents the line is much steeper, with Z between 0.6 and 1.2.
- For frugivorous (fruit-eating) birds and mammals in tropical forests of different continents, Z is 1.15.
- A steeper slope means species richness climbs much faster with area, so losing area costs more species.
Questions
2 answers
- What does the "Species-area relationship: what Z means" simulation show?
- The green square is a forest; the 40 tiles are its species. By log S = log C + Z log A, a patch with a smaller area holds fewer species. Move the area and the slope Z, and watch the tiles and the straight log-log line.
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Species-area relationship" in Biodiversity and Conservation (Class 12 Biology).
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