Species-Area Relationship (Alexander von Humboldt)
Biology · Biodiversity and Conservation · NEET
The Species-Area Relationship says that within a region, the number of species (species richness) increases as the area you explore increases, but only up to a limit. The German naturalist Alexander von Humboldt first observed this while exploring South American jungles. Memory hook: "Humboldt = bigger area, more species, until it flattens" — the curve is a rectangular hyperbola.
Left: on a normal scale the species-area relationship is a rectangular hyperbola that rises then flattens (richness increases with area up to a limit). Right: on a logarithmic scale the same relationship becomes a straight line, log S = log C + Z log A.
Your doubts, answered
Who first described the species-area relationship?
Alexander von Humboldt, the German naturalist and geographer. NCERT says he observed it during his explorations in the wilderness of the South American jungles. In NEET this is a direct one-liner fact, so link the name Humboldt firmly to species-area relationship.
Does species richness keep rising forever as area increases?
No. Species richness increases with increasing explored area, but only up to a limit. After a point, adding more area adds very few new species, so the curve flattens (levels off). This 'up to a limit' phrase is the exact NCERT wording NEET likes to test.
What is the shape of the species-area curve?
On a normal (arithmetic) scale, the relation between species richness and area is a rectangular hyperbola — it rises fast, then flattens. When you plot it on a logarithmic scale, the same relationship becomes a straight line. Students often confuse the two: hyperbola on normal axes, straight line on log axes.
Is the species-area relationship the same as the latitudinal gradient?
No. The latitudinal gradient explains why tropics have more species (a location pattern). The species-area relationship explains how richness grows with the size of the area explored. Both are 'patterns of biodiversity' in NCERT, but they answer different questions — do not mix them up in MCQs.
For which groups is this relationship true?
NCERT states it holds for a wide variety of taxa: angiosperm plants, birds, bats, and freshwater fishes. So it is a general ecological pattern, not limited to one group.
⚠️ The NEET trap ✗ Attributing the species-area relationship to Robert May or Alexander von Humboldt giving the population growth equation. ✓ Alexander von Humboldt described the species-area relationship. Robert May estimated global species number (~7 million). Do not swap these scientists. 🧠 Humboldt = species-AREA. May = species-NUMBER. Two different H/M scientists, two different facts.
Real NEET questions
NEET 2017
Alexander Von Humbolt described for the first time:
A · Ecological Biodiversity
B · Laws of limiting factor
C · Species area relationships ✓
D · Population Growth equation
Solution: NCERT credits Alexander von Humboldt with first observing that within a region species richness increases with explored area, up to a limit — the species-area relationship. He is not linked to the laws of limiting factor or the population growth equation, and 'ecological biodiversity' is not the term he introduced.
Solved Biodiversity and Conservation NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
What is the species-area relationship in one line?
Within a region, species richness increases with the increasing explored area, but only up to a limit.
Who proposed the species-area relationship?
Alexander von Humboldt, the German naturalist and geographer, based on his explorations of the South American jungles.
What curve does the species-area relationship form?
A rectangular hyperbola on a normal scale, which becomes a straight line on a logarithmic scale.
Why is this important for NEET?
It is a high-yield one-liner from the Patterns of Biodiversity topic. NEET has directly asked who described it (Humboldt) and its curve shape, so a clean fact-name link earns easy marks.
