This is an interesting addition to the above (I'm going through a bunch of material right now and trying to clean up my files!).
It has been argued on this form that 'species' has a definition. My question would be, then, in light of the below, which one?
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“There is probably no other concept in biology that has remained so consistently controversial as the species concept.” [ Mayr, Dr. Ernst; THE GROWTH OF BIOLOGICAL THOUGHT; Belknap Press, Harvard; 1982; Pg. 251]
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“SPECIES = group of physically and genetically similar individuals that interbreed under natural conditions. Over 30-0,000 plant species and more than 1,000,000 animal species have been identified and 15-20,000 new ones are identified every year. [Random House Encyclopedia, 1990]
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Following from: ACQUIRING GENOMES: A Theory of the Origins of Species
By Lynn Margulis and Dorion Sagan
Basic Books --- 2002
Pg. 7 – “However, the ‘phylogenetic’ or ‘evolutionary’ or ‘cladistic’ concept of species is entirely wrongheaded, and its adoption interferes with understanding how species arise. … No visible organism or group of organisms is descended ‘from a single common ancestor.’ The purpose of this book is to explain, with abundant evidence collected by scientists around the world, this new concept of how new species really come into being.”
Pg. 10 – “But what puzzled Darwin was, where does the inherited variation come from? Why, that is, aren’t organisms always just like their parents, or just like their single parent? What is the source of evolutionary variations? In the end, Darwin didn’t know.”
Pg. 58 -- “Many millions of words have been written on the definitions of species. Here we suggest a new testable idea about what species are.”
“An organism (A) belongs to the same species as another organism (B) if and only if A and B have precisely the same cellular ancestors, that is, they are descended from the same genomes, and the relations between these genomes are the same.”
“Zoologists have long recognized the validity of Ernst Mayr’s biological species concept: Two organisms belong to the same species if they recognize each other, can mate, and can produce fertile offspring.”
Pg. 60 –“Our definition, however, recognizes the heterogenomic composition of all nucleated organism and is the far broader. Our ‘species-component list’ approach acknowledges the existence of tens of thousands of species of protoctists, fungi, plants and animals that don’t mate to produce offspring.” [DAB adds: Two interesting examples of proposed symbiotic fusion of genomes cited on Pgs. 60 – 65 … read original for details necessary for full comprehension.).
Pg. 141 – “To understand the origin of species we need to agree on what they are, but we are very inconsistent. Zoologists and botanists are often satisfied with the rule of thumb that members of the same species produce fertile offspring, whereas members of disparate species do not”
Pg. 142 – “Botanists, zoologists, and all other biologists assign organisms to species based on morphology: the overall appearance and behavior of bodies. ….. Bacteriologists … employ a different rule of thumb: If two kinds of bacteria share 85 percent of their measurable traits in common, they are taken to be members of the same species.”
“Our new defination of species, that organisms with the same number and kind of integrated genomes in common belong to the same species, depends on the recognition that all nucleated organism are composite. All are products of integrated symbionts.
Pg. 207 – GLOSSARY
“SPECIES – A group of organisms, minerals, or other entities formally recognized as distinct from other groups. A taxon of the rank of species; in the hierarchy of biological classification, the category below genus; the basic unit of biological classification. In this book we suggest that organisms with the same kinds and numbers of integrated genomes in common are members of the same species.”
ACQUIRING GENOMES: A Theory of the Origins of Species
By Lynn Margulis and Dorion Sagan
Basic Books --- 2002