| Classification | Plant
Evolution | Animal Evolution
| Homology |
Before scientists started to base evolutionary studies more on
genetics botanists and zoologists classified organisms into different
categories based on their physical characteristics. This ordering
of organisms into groups based on similarities and differences is
called classification. In the 18th and 19th centuries leading naturalists
identified and named newly discovered plants and animals. These
European biologists believed that plants and animals including humans
had been created in their present form so they did not seek explanations
for the patterns of similarities and differences between organisms.
However one important 18th Century naturalist was Karl von Linne
(1707-1778), a Swedish botanist and medical doctor. In 1735 Carolus
Linnaeus (the latinised form of his name) published a book called
systema naturae in which he outlined his scheme for classifying
all known and unknown organisms according to the greater or lesser
extent of their similarities. This book was very influential and
the Linnaean system of classification was widely accepted by the
early 19th century and is still the basic framework for taxonomy
today.
Taxonomy is a term coined by Augustin Pyramus de Candolle in 1813 and is the study of the principles and methods of classification.
The
Linnaean System
depends upon the hierarchical structure in which organisms
are grouped. According to this system the animals belonging
to the higher level, need not necessarily be similar to its
other members, but the members of the lower levels are very
similar and can reproduce. The typical hierarchical system
of classification is:
- Kingdom
- Phylum (Division is used here for plants)
- Class
- Order
- Family
- Genus
- Species
- Variety (for plants)
Note: You will see this system in use in the fossil images descriptions. Although this system is somewhat arbitrary given that many of the descriptions are based on the physical characteristics of the organism, modern use of genetics is allowing more accurate links between organisms to be developed.
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