BIOSCI101 Evolution - Lecture 6

Upon studying whether the classification of species is arbitrary or real, the general finding confirms that species are real and represent discrete groups that can reflect morphological, genetic and behavioural differences. However at present there is no one general agreed species definition.

The biological species concept is at present the most commonly used concept. A species is a group of [blank_start]populations[blank_end] whose members can [blank_start]interbreed[blank_end] and produce viable offspring but [blank_start]do not[blank_end] interbreed with members of other species.

One limit of the biological species concept is that it doesn’t apply to asexual organisms e.g. prokaryotes.

Other species concepts The biological species concept focuses on reproductive barriers keeping species apart, other concepts emphasise unity within species. 1. [blank_start]Morphological[blank_end] species concept, distinguishes a species based on body shape and size. 2. [blank_start]Ecological[blank_end] species concept, defines a species in terms of its ecological niche. 3. [blank_start]Phylogenetic[blank_end] species concept, defines a species as the smallest group of individuals that share a common ancestor. 4. [blank_start]Specific mate recognition[blank_end] species concept, defines a species as a group of organisms that share a common mate recognition system.

ALLOPATRIC SPECIATION Allopatric speciation occurs when [blank_start]gene flow[blank_end] is interrupted as a result of a population being divided into geographically isolated subpopulations.

Label the images as either vicariance or dispersal allopatric speciation.

SYMPATRIC SPECIATION Sympatric speciation can occur via [blank_start]polyploidy[blank_end], [blank_start]sexual selection[blank_end] and [blank_start]habitat differentiation[blank_end]. Two forms of polyploidy have been observed in plants – autopolyploidy ([blank_start]self[blank_end]) and allopolyploidy ([blank_start]other[blank_end]).

What type of sympatric speciation is this diagram representing?

Select all that are CORRECT with regards to Allopolyploidy.

PATTERNS OF SPECIATION [blank_start]Anagenesis[blank_end] is gradual change within a single lineage over time. [blank_start]Cladogenesis[blank_end] is evolutionary change produced by the branching of populations to form new species. [blank_start]Adaptive radiation[blank_end] is the rapid formation of many new species from a single ancestral group, characteristically to fill a new ecological area / zone. [blank_start]Extinction[blank_end] is the disappearance of a species from the earth, the fossil record reveals a low steady rate of extinction interrupted periodically by mass extinction.

Both anagenesis and cladogenesis occur but cladogenesis is generally considered to be responsible for the diversity of species over evolutionary time.