|Species: groups of individuals based on common characteristics. See also biological species, natural kinds._____________Annotation: The above characterizations of concepts are neither definitions nor exhausting presentations of problems related to them. Instead, they are intended to give a short introduction to the contributions below. – Lexicon of Arguments. |
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|Gould I 216
Species/Darwin/Lamarck: Species are no natural units but "purely artificial combinations"... conceptual definitions.
Species/Ernst MayrVsDarwin/MayrVsLamarck: "Species are a product of evolution and not of the human mind."
Definition Species/Mayr: device for protecting balanced, harmonic genotypes. "Biological concept of species" seeks biological reasons for the existence of species. Maybe there are other properties by chance.
Biological species concept:
1. Problem: Asexual organisms do not form populations.
2. Problem: Spatial expansion with subspecies. They can become independent species in isolation over time (by acquiring new isolation mechanisms). (polytypical species).
Nominalist concept of species: in nature exclusively individuals, species artificially created by humans (MayrVs: that would be arbitrariness, and nature shows that there is no arbitrariness.).
Evolutionary species concept: temporal dimension, generational series of populations. MayrVs: the concept does not take into account that there are two possible ways of species development:
a) Gradual transformation of a stem line into another species without altering the number of species; and
b) The reproduction of species through geographical isolation.
Species/Mayr: is applied to three very different objects or phenomena:
1. The species concept
2. The category species
3. The species taxa
Some authors could not differentiate between them, leading to hopeless confusion in literature.
Species concept: biological meaning or definition of the word "species".
Category Species: certain rank in the Linnéian system. (Other categories: Order, Kingdom, Genus...)
Definition Species Taxa: special populations or population groups corresponding to the species definition. They are entities ("individuals") and cannot be defined as such. Individuals cannot be defined, but can only be described and delimited.
Evolution/Mayr: Species is the decisive entity of evolution.
Species: a species, regardless of the individuals belonging to it, interacts as a unit with other species in the common environment.
Macrotaxonomy: the classification of species (in higher-level groups)
Group: mostly easily recognizable: birds, butterflies, beetles.
Downward classification (actual identification). Division (aristotelian), heyday of medicinal botany.
E. g. warm-blooded or non-warm-blooded - having or not having feathers.
Organism types: most new types of organisms do not originate from the gradual transformation of a stem line, i. e. an existing type. Rather, a founder species penetrates into a new adaptive zone and is successful there thanks to rapid adaptive changes. For example, the more than 5000 species of songbirds are no more than the variation of a single theme.
Species: the two evolutionary ways to produce a new species: a) gradual change of the phenotype and b) increasing diversity (speciation) are only loosely related.
Selection pressure: may not apply if a founder species enters its very favourable adaptive zone.
Species/Mayr: very conservative estimate of 10 million animal species, of which are ca. 1.5 million described. So about 15% known. Legitimate estimate: 30 million species. Only 5% are known. On the other hand, 99% of all bird species are discovered and described. In many insects, arachnids, low vertebrates probably less than 10%. The same applies to mushrooms, protists and prokaryotes._____________Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution.
Das ist Biologie Heidelberg 1998