Q.Assertion : The Environmental conditions of the Tropics are favourable for speciation and diversity of organisms. Reason : The climate seasons, temperature, humidity and photo period are more or less stable and congenial.

Tropical regions show high species diversity largely because their stable climate (temperature, humidity, day-length) throughout the year favours greater rates of speciation and specialisation -- a true Assertion correctly explained by a true Reason.

Ecologists have long observed that species diversity is generally much higher in the tropics than in temperate or polar regions -- a pattern with several supporting explanations, one of which is climatic stability. Because seasonal fluctuations in temperature, humidity and day length (photoperiod) are comparatively mild and consistent in tropical regions across the year (unlike sharply seasonal temperate/polar climates), organisms there face fewer extreme environmental stresses and can specialise into narrower ecological niches, promoting higher rates of speciation and th …