. Biology; the story of living things. THE BIOLOGICAL CONQUEST OK TIIL :U barriers may be in vertical zones, extending from tlie ocean level to mountain tops, as well as horizontal, spreading out north and south from the equator in zones of Map showing ancient and modern ranges of the elephants and their ancestors. The shaded area shows the former habitat of the maniniolh and mastodon, ant^estor of the modern elephant. A land connection probal)Iy existed I)etween Asia and North America. Note the restricted range of the present-day elephants indicated by heavy shading. How can
. Biology; the story of living things. THE BIOLOGICAL CONQUEST OK TIIL :U barriers may be in vertical zones, extending from tlie ocean level to mountain tops, as well as horizontal, spreading out north and south from the equator in zones of Map showing ancient and modern ranges of the elephants and their ancestors. The shaded area shows the former habitat of the maniniolh and mastodon, ant^estor of the modern elephant. A land connection probal)Iy existed I)etween Asia and North America. Note the restricted range of the present-day elephants indicated by heavy shading. How can this be accounted for.^ Sometimes natural barriers occur, such as high mountain ranges with eternal snow, deserts with unfavorable conditions of moisture, or in the case of water-distributed animals such as fishes, high water- falls may prevent them from moving up a stream beyond a cciiain point. The barrier for one organism, however, might l)e a highway for another. A desert would be an impassable barrier- to a squirn^l but not to a camel. Geographical barriers have not always been fixed. Geological history reveals the fact that some land surfaces were once occujiied by water and what is now water may have been land. The presence of in the Panama Canal area indicates that the Isthmus was formerly submerged, and there is evidence that as late as Eocene times there was a land connection Bering Straits. As bar- riers have changed so has the resulting distribution of organisms. Distribution often indicates the geography of the i)ast. .Mnnbers of the same genus may differ widely in certain isolated localities, as, for example, the tapirs found in tropical America and the Malay. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hunter, George W. (George William), 1873-1948; Walter, Herbe
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Keywords: ., bookauthorwalterherberteugeneb1867, bookcentury1900, bookpublish
