The key events in speciation are the isolation of a population's gene pool, which can occur through external barriers like geographic separation, or internal barriers that develop later. External barriers initially isolate populations, exposing them to different environments where natural selection can cause adaptations. Over time, internal barriers to reproduction may form as a byproduct and further maintain genetic isolation between the species. Sympatric speciation differs in that internal barriers form first without an initial external cause, often through chromosome changes making organisms unable to mate.
Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.There are few mechanisms through which this process can be well understood.
Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.There are few mechanisms through which this process can be well understood.
Organisms are classified into a hierarchical classification that groups closely related individuals.
The species is the basic biological unit around which classifications are based.
To determine the variation and the limitation between species, many concepts have been proposed.
When a taxonomist study a particular taxa, he/she must adopted a species concept and provide a species limitation to define this taxa.
Plant kingdom as other living kingdoms has a hierarchy structure ends mostly with species rank.
Species are one of the basic units to compare in almost all fields of biology.
A species is defined as the largest group of organisms in which two individuals are capable of reproducing fertile offspring, typically using sexual reproduction.
Definition of a species as a group of interbreeding individuals cannot be easily applied to organisms that reproduce only or mainly asexually.
If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species?
Idea of a species is something that we humans invented for our own convenience.
‘‘No matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as distinguish a species permanently; one species never springs from the seed of another nor vice versa” - JOHN RAY.
Used a sexual system ‘‘natural system” for defining species - LINNAEUS.
‘‘A species is a collection of all the individuals which resemble each other more than they resemble anything else, which can by natural fecundation produce fertile individuals, and which reproduce themselves by generation, in such a manner that we may from analogy suppose them all to have sprung from one single individual” - DE CANDOLLE.
Vocabulary review for Genetics and Evolutionary Biology unit.
Please note slide 15 is an animated gif which does not show correctly on SlideShare. You may view the gif here: http://thenextweb.com/2009/08/07/evolution-impressive-animated-gif/
The evolutionary development or history of a species or of a taxonomic group of organisms (The phylogeny of a group of taxa (singular: taxon) (species, etc.) is its evolutionary history)