Question

Consider 1000 terrestrial species that have geographical ranges of different shapes and sizes. If the Earth were entirely covered by land (no oceans), and the ranges of these species were overlaid on the surface of the Earth at random, which one of the following patterns is expected?

• A. Highest species richness per unit area in the tropics
• B. Highest species richness per unit area at higher latitudes
• C. Roughly equal species richness per unit area at all latitudes
• D. Geographically restricted species found only near the poles

Hint:

Species richness patterns are affected by factors such as climate, geography, and ecological processes, leading to greater richness in the tropics.

Answer 1

The Correct Option is C

When considering species distributions over the Earth's landmass, if species' ranges are overlaid randomly, the distribution of species richness across different latitudes would be expected to be roughly equal. This is because without any bias or ecological restrictions (such as climatic gradients or geographical features like mountains and oceans), the species are randomly distributed across the landmasses.
In such a scenario, there would be no preferential clustering of species in the tropics or higher latitudes, as the placement of each species is random, and their geographical range does not follow natural patterns like the latitudinal gradient of species richness observed in real ecosystems.
Thus, roughly equal species richness would be expected across the entire surface of the Earth (answer C). This pattern contrasts with the observed natural world, where the tropics typically exhibit higher species richness due to environmental factors like temperature, humidity, and primary productivity.