Is there a single species definition that can define all species?

No but its a real thing, difficult to define because speciation is a process not an event

If not, does this mean that the concept of a species is a human idea and not a biological reality?

complex process rather than a single event

How can we reconcile this discrepancy

recognizing its a process

evolutionary species concept

lineage of populations which maintains identity from other such lineages and which has its own evolutionary tendencies and historical fate.

3 ways to define species

Morphological species concept

organisms look different from other species. dichotomous key

strengths: time efficient and no equipment needed

weakness: education on terms (technical expertise), not enough morphological diversity to -

Biological species concept

used by defining rates of gene flow. can they exchange genetic material and at what level? only related to sexually reproducing species. groups of potentially interbreeding populations which are reproductively isolated from other such groups.

strengths: more scientific and objective method

weaknesses what point do we draw the line? Takes time and effort, asexually reproducing species

Phylogenetic species concept

smallest clade in a monophyletic group and call it a species. objective methodology. smallest diagnosable cluster of individual organisms within which there is a parental pattern of ancestry and descent.

strenghts

weaknesses: difficulties in asexual species, takes time and effort

Others

Ecological species concept - based on the way a species makes a living, what is their niche?

Review Wheeler paper and his arguments for the Phylogenetic Species concept PSC being the single, unifying species concepts

There really is no single one.

What biological process does the PSC have a particular problem with?

HGT. creates networks and there's no clear way to define connections. asexual reproducers.

Geographic separation

force that causes speciation (allopatric speciation)

competition for resources is driving source

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