Biology Reference
In-Depth Information
Fig. 4.21
within groups is consistent among many different traits, from the anatomical to the
molecular, with each group defined by a unique set of characters. As we move up
the hierarchy, the organisms within the groups become less and less similar. This
hierarchical classification is explained by Darwin's idea of “descent with modi-
fication” because this idea predicts that groups of organisms are similar because
they have a common ancestry. The application of this hierarchical scheme to the
human species is illustrated in Fig. 4.21, which contains short definitions of each
group.
Biogeography
Biogeography is the study of biodiversity across all regions of the Earth. It aims
to determine not only the patterns of distribution and abundance of each species
but also what factors determine these patterns. These factors include such historical
events as continental drift, glaciation, and extinction, but of especial importance
is where each species originated. You might think that a given species should be
found wherever a suitable climate and food source are available, but it turns out that
geographical location is a better predictor of where similar species live than either of
these factors. Thus similar climatic regions contain very different animals. The two
major scientists who first came to this realisation were Wallace and Darwin, and they
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