Give three hypotheses for explaining why tropics show the greatest levels of species richness.
(i) Favourable Climate. In tropics: The climate is favourable for growth throughout the year.
(ii) No Glaciation: Tropics have not faced any glaciation which has caused the destruction of species in temperate and subarctic regions.
(iii) Sunlight: Abundant sunlight is available throughout the year in tropics only.