What are the homologous organs in plants

Order in diversity

Caution trap: analogy and homology

A whale "fish" actually looks like a fish. But as a mammal it is of course much more closely related to us humans. The reason for the similarity between whale and fish is simple: adaptation to equal living conditions. These are called analogies (or convergences) in biology. The best example are cactus forms: You can find them in the deserts of America with the real cacti (they are related to the carnations), but also in the arid regions of Africa, e.g. with milkweed plants (euphorbias, which are related to the poinsettia). Since the classical system was strongly determined by morphological features, such environmental similarities of unrelated species have led to errors in the system.


Analogy: spherical succulents in milkweed plants (left) and oleander relatives (right)

The biologist and systematist is on the lookout for characteristics that are given on the basis of a common ancestry: the so-called homologies. A detailed analysis of the blueprint of a whale fish quickly shows that many of its structures (e.g. limbs converted into fins) correspond to the rest of the mammals, i.e. are homologous. These homologies indicate a relationship.


Homology: reshaping of leaves

More information about the system

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