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Geoclimatic changes that occurred throughout Earth history have affected the distribution of biotas through time.

Climate has changed under cosmic influences, such as the Milankovitch cycles. Kutzbach (1991) proposed that the 3-km uplift of the high plateaus in Tibet and in western North America in the Pliocene-Pleistocene were instrumental in provoking the late Tertiary trend of climatic cooling.

To begin the conversation about animals and pland word of North America is better to start with explanation of climate conditions and gografical situation of the region, in order to clear understanding of such a wide diversity of spices.

The composition of a fossil flora, based on the combined inventories provided by macro- and microfossil remains, leaf physiognomy, and dendrochronology, are all valuable methods for studying vegetational history and reconstructing the environments that influenced the development of North American vegetation through time.

The modern history of systematic botany and floristics in North America began when the first Europeans landed on these shores and began to collect objects of curiosity.

To a great degree, it was not until the twentieth century that Native Americans were recognized as knowledgeable about their plants.

By then, European thought dominated botany, and the Native American's botanical understanding was passed on only in an occasional native name retained in a Latinized form.

Climate determines the erosional and soil-forming processes that occur, and the life forms that are able to survive at a given locale, all of which may be affected secondarily by the types of bedrock and surficial deposits encountered in the area.

In turn, relief influences climatic patterns through elevation above sea level and its effects on wind patterns and rainfall.Climate, physiography, and geology play major roles in determining the distributions of present-day soil classes, vegetation types, floras, and faunas.Biogeographers agree that climate is the primary factor in the control of these distributions.Experience has shown that most elements comprising a fossil assemblage are broadly consistent in terms of habitat preference, or they can be sorted into subsets reflecting habitat diversity (viz., elevational gradients).This organization gives rise to the concept of paleocommunities from which it is possible to deduce past climates, paleophysiography, and biogeographic patterns.It was not until Columbus's second voyage, in 1493, that New World plants and animals were taken across the Atlantic.For the European scientific community, the unfamiliar specimens were a source both of great intellectual curiosity and of philosophical concern.It is surrounded by three oceans---the Arctic, Pacific, and Atlantic, respectively to the north, west, and east---and by the Gulf of Mexico to the south.It is separated from northeast Asia by the Pacific Ocean, and by the epicontinental Bering Sea, the Chukchi Sea, and the connecting Bering Strait.Such reconstructions are based on a direct comparison and presumed general equivalency of most members of a fossil flora with modern analogs (composition of the flora), on the observation that present-day plants with certain morphological attributes (e.g., leaf physiognomy) are found in certain habitats, and on the assumption that most fossil plants with similar morphological attributes occurred in comparable habitats.For example, modern plant assemblages containing many large-leaved, entire-margined species with drip-tips typically occur in humid tropical habitats; therefore, a fossil flora with many similar leaf types is taken to indicate a humid tropical paleoenvironment.

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