Although there are many different tropical rainforests, organisms playing equivalent roles in ecosystems, appear very similar, regardless of where they are found. Corresponding patterns of rainfall, temperature, humidity, and soil type result in similar – but not identical – ecosystems in tropical forests in Asia, Africa and the Americas. These forests all have trees which are sun-loving; those which prefer shade; plants which grow on trees (lianas and creepers); and many other types. Animals of all kinds are also to be found – those which eat seeds or fruits or vegetation or other animals; those which live on the ground, or in the forest canopy, or in dead trees; those which are active in daytime or at night. Plants or animals in different forests but fulfilling equivalent functions (occupying similar niches) will not be of the same species, but will have many similarities. This is so because the conditions of their particular habitats require similar adaptations. Trees exposed to bright sunlight need to be protected against drying (dessication), for example, and so will have adaptations which permit them to survive under these conditions; those living in shade must be able to photosynthesize under restricted light conditions. Over long periods of time, then, species in equivalent habitats on different continents will adapt to their circumstances and will appear very much alike, a phenomenon known as “evolutionary convergence.” Because of the evolutionary consequences of natural selection, tropical rainforests everywhere may appear very similar.

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