বিখ্যাত ব্রিটিশ প্রকৃতিবিদ আলফ্রেড রাসেল ওয়ালেস প্রকৃতি নিয়ে কবে থেকে গবেষণা শুরু করেন ?
In 1872, at the urging of many of his friends, including Darwin, Philip Sclater, and Alfred Newton, Wallace began research for a general review of the geographic distribution of animals. He was unable to make much progress initially, in part because classification systems for many types of animals were in flux at the time. He resumed the work in earnest in 1874 after the publication of a number of new works on classification. Extending the system developed by Sclater for birds—which divided the earth into six separate geographic regions for describing species distribution—to cover mammals, reptiles and insects as well, Wallace created the basis for the zoogeographic regions still in use today. He discussed all of the factors then known to influence the current and past geographic distribution of animals within each geographical region. These included the effects of the appearance and disappearance of land bridges (such as the one currently connecting North America and South America) and the effects of periods of increased glaciation. He provided maps that displayed factors, such as elevation of mountains, depths of oceans, and the character of regional vegetation, that affected the distribution of animals. He also summarised all the known families and genera of the higher animals and listed their known geographic distributions. The text was organised so that it would be easy for a traveller to learn what animals could be found in a particular location. The resulting two-volume work, "The Geographical Distribution of Animals", was published in 1876 and would serve as the definitive text on zoogeography for the next 80 years.
1872