Biogeography. Types of evolutionary change

Biogeography studies the distribution of animals and plants on Earth. By the distribution of mammals, birds and plants, land is divided, following A. Wallace, into 6 biogeographic regions (some modern classifications also separate Antarctic and Oceanian regions): Palaearctic (northern Eurasia, North Africa), Nearctic (North America), Neotropical (Central and South America), the Ethiopian (Afrotropical) region of Africa, and the Indo-Malayan and Australian regions. In Australia the mammals include egg-laying (platypus, echidna) and marsupial (kangaroo, koala) animals, and placental mammals are few – because Australia separated from other land long before placental mammals spread widely and remained apart for a long time. South America has marsupial opossums, anteaters, sloths and armadillos. The Palaearctic and Nearctic faunas are similar (bear, wolf, deer, moose) with differences in species, because they were at times connected by a land bridge. The cause is the history of continents: according to A. Wegener’s theory of continental drift (1912), about 300–200 million years ago there was one landmass, Pangaea, which split into Laurasia and Gondwana and then into the modern continents; today this is supported by plate tectonics (continents move a few centimetres a year). After continents separated, populations became isolated and evolved independently. Islands and lakes have many endemic species; relict species (for example ginkgo) are remnants of ancient groups. The distribution of species reflects their origin and history.