Alexander von Humboldt noted that within a region, species richness __________ as the explored area increases. Which word best completes the sentence?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → increases
Alexander von Humboldt explored the jungles of South America. He found that within a region, the number of species rises as the explored area grows, but only up to a limit. Plotted on a graph, this gives a rectangular hyperbola, as in the figure.
Option (1) increases — Correct. Species richness increases with the explored area. The rise slows down and levels off at large areas, but the trend is upward.
Option (2) decreases — Incorrect. Species richness does not fall as the area grows. A larger area holds more kinds of habitat and so more species.
Option (3) decreases up to a limit — Incorrect. The limit applies to the increase, not to a decrease. Richness goes up until it levels off; it does not go down.
NCERT Extract:
Patterns of Biodiversity – “… (ii) Species-Area relationships : During his pioneering and extensive explorations in the wilderness of South American jungles, the great German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with increasing explored area, but only up to a limit. In fact, the relation between species richness and area for a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) turns out to be a rectangular hyperbola (Figure 13.2).”
Figure 13.2 Showing species area relationship. Note that on log scale the relationship becomes linear