26 The concept of a species is fundamental to understanding biology, yet there m

Question

26 The concept of a species is fundamental to understanding biology, yet there may not be one definition that fits all “types” of organisms (e.g. animals, plants, fungi, bacteria, slime mold, lichens, etc.). Discuss several of the definitions of a species as presented in class and present your own definition for a species. Compare the strengths and weaknesses of each definition. Ernst Mayr is strong proponent of the biological species concept. How does he justify his position? Do you agree or disagree? If we employ the biological species concept, when did species first exist? What were organisms before then, if not species? What might the consequences of the emergence of species be for processes of adaptation and diversification? Be sure to explain your reasoning thoroughly.

Explanation / Answer

The concept of species is a controversy because there is no universal definition of the species has existed. there are different theories defining the species so far. These concepts have limitations describing some specific organisms.

1) Ecological species concept: The group of organisms that share a common ecological niche were considered as species. Strength: it may also include the interspecific hybrids. Limitation: but this theory violates the possibility of the organisms that change their respectable niches over time. For example, aqueous animals that came out to the terrestrial habitat for breeding.

2) Phenotypic species: Includes all animals having specified phenotypic similarities. This is a simplistic method could classify species without much scientific effort. This concept has limitation while considering the morphotype of a single species, but possess different morphological patterns due to ecological regions.

3) Biological species concept: The group of individuals that successfully produce viable offspring, and these must be reproductively separated from other groups. Strength: It is basic and simple definition easily discriminates the different group of individuals. Limitation: This concept not explains asexual species and the possibility of interspecific hybrids.

4) Evolutionary species: It includes a group of individuals evolved in a single lineage from a common ancestor and which maintains such identity from such other lineages. Strength: It includes both asexual and extinct organisms. Limitation: This concept excludes the species with lack of fossil record and species which continuously evolves.

5) Phylogenetic species concept; the group of individuals share common evolution, and which have a high degree of resemblance in many unique traits which give them monophyletic clusters based on discriminative phenotypes. Strength: it applies to both sexual and allopatric populations, Limitation: there are some problems with this concepts it is highly difficult to reconstruct the recently past evolutionary lineage.

If we consider all concepts there is no single concept that includes all factors of a species, because species may otherwise be defined as a group of individuals that mostly interbreed, most of the times reproductively isolated, share common ecological niche with exception, have common ancestor and possibly the similar evolutionary history, and the maximum number of resemblances in their sequences.

Biological species concept is most popular one, because of its simplicity, in nature two biological species, for example, plants cannot interbreed even those are grown in the same area. Biological species concept is also most relevant to the most of the already classified animal and plant species. But this concept is hard to consider as a universal theory because it is neglecting the asexual reproduction, which is common or major reproduction in some of the species of plants.

If we employ the biological species concept the first species existed in nature only after the sexual reproduction evolved in organisms, the organisms before then maybe clasified under different groups of individuals that share some similarities which are needed to be classified further into basic units. The major consequences of species adoptation and emergence, one species is either evolved into the other or diveded from its related spiece into a new species. The evolutionary force always drives the existing species either evolving into new species or extinct it.

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