Tom: - By the way, let me ask you a simple question: how do you explain the wide variety of organisms on Earth? Philip: - I don't think it is a simple question with a simple answer. A lot can be said in answer to this question. Tom: - ---- Philip: - Alright. One major explanation is that, since Earth has many different climates, ranging from cold, snow-covered polar climates to hot tropical climates where it rains almost every day, each climate has its own organisms which have adapted to it and differ widely from the organisms of other climates.