Previous Year Question
Which of the following statements is NOT true?
Species diversity increases from equator towards poles.
Tropics harbour more species than temperate areas.
Greatest biodiversity occurs in Amazonian rain forest.
Species diversity decreases from temperate areas towards poles.
Correct Answer: A
Detailed Solution
Species Diversity refers to the number of different species present in a particular region and their relative abundance. Species are not distributed uniformly across the Earth. Generally, Species Diversity decreases from the Equator towards the Poles, a pattern known as the Latitudinal Diversity Gradient. Tropical Regions support the greatest species diversity, whereas Temperate and Polar Regions generally have comparatively lower diversity. However, exceptions to this general pattern occur in certain groups of organisms and geographical regions.
The major reasons for high biodiversity in Tropical Regions include greater year-round availability of solar energy, relatively stable climatic conditions, and high Primary Productivity. Additionally, their long Evolutionary History and diverse Ecological Habitats have provided opportunities for species diversification and coexistence. Temperate and Polar Regions have experienced greater seasonal temperature variations, lower solar energy availability, and stronger influences from historical Glaciations. These factors help explain differences in Species Richness between geographical regions.
The Amazon Rainforest, located in South America, is among the most biodiverse terrestrial ecosystems in the world. According to NCERT, it contains more than 40,000 plant species, approximately 3,000 fish species, 1,300 bird species, 427 mammal species, and 378 reptile species. Its dense vegetation, multiple Forest Layers, extensive river systems, and numerous Microhabitats provide food, shelter, and breeding grounds for different organisms.
According to NCERT examples of latitudinal diversity, Colombia, located near the Equator, has approximately 1,400 bird species, compared with about 105 species in New York (41° N latitude) and 56 species in Greenland (71° N latitude). These textbook figures illustrate the general decline in biodiversity with increasing latitude. Consequently, Tropical Regions support more species than Temperate Regions, while Species Diversity generally decreases further from temperate latitudes towards the Poles.