Summary:
[[Image:Ernst Haeckel's Artforms of Nature of 1904.jpg|thumb|right|200px|''[[Artforms of Nature]]'' ([[1904]]) by [[Ernst Haeckel]]]]
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The '''species problem''' is a mixture of difficult, related questions that often come up when [[biologist]]s define the word "[[species]]". Definitions are usually based on how individual organisms reproduce, but biological reality means that a definition that works well for some organisms (e.g., birds) will be useless for others (e.g., bacteria).
One common but sometimes difficult question is how best to decide which species an [[organism]] belongs to, because reproductively isolated groups may not be readily recognizable. Thus, new data may indicate that one previously described species actually includes two or more separately [[evolution|evolving]] groups, each of which could justifiably be recognized as a separate species.
Another common problem is how to define reproductive isolation, because some separately evolving groups may continue to interbreed to some extent, and it can be a difficult matter to discover whether this [[hybrid (biology)|hybridization]] affects the long-term genetic make-up of the groups.
Many of the debates on species touch on philosophical issues, such as [[nominalism]] and [[Philosophical realism|realism]], as well as on issues of [[language]] and [[cognitive|cognition]].
The current meaning of the phrase "species problem" is quite different from what was meant by "species problem" during the 19th and early 20th centuries, as used by [[Charles Darwin]] and others.
== See also ==
*[[Evolutionarily Significant Unit]] (ESU)
*[[Ring species]]
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The '''species problem''' is a mixture of difficult, related questions that often come up when [[biologist]]s define the word "[[species]]". Definitions are usually based on how individual organisms reproduce, but biological reality means that a definition that works well for some organisms (e.g., birds) will be useless for others (e.g., bacteria).
One common but sometimes difficult question is how best to decide which species an [[organism]] belongs to, because reproductively isolated groups may not be readily recognizable. Thus, new data may indicate that one previously described species actually includes two or more separately [[evolution|evolving]] groups, each of which could justifiably be recognized as a separate species.
Another common problem is how to define reproductive isolation, because some separately evolving groups may continue to interbreed to some extent, and it can be a difficult matter to discover whether this [[hybrid (biology)|hybridization]] affects the long-term genetic make-up of the groups.
Many of the debates on species touch on philosophical issues, such as [[nominalism]] and [[Philosophical realism|realism]], as well as on issues of [[language]] and [[cognitive|cognition]].
The current meaning of the phrase "species problem" is quite different from what was meant by "species problem" during the 19th and early 20th centuries, as used by [[Charles Darwin]] and others.
== See also ==
*[[Evolutionarily Significant Unit]] (ESU)
*[[Ring species]]
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