Bio test 2 Lecture 9: Species, Speciation and Hybridization

sources of microevolution

• natural selection

• genetic drift

• gene flow

(quicker to accept microevolutionary processes)

Different definitions of a species

• Biological

• morphological (taxonomic)

• Phylogenetic

• Evolutionary

• Ecological

Biological Species Definition

Phylogenetic species concept

Morphological species concept

ecological species concept

evolutionary species concept

Darwins take on species

how/ where does speciation occur

• allopatric speciation

• sympatric speciation

allopatric speciation

sympatric speciation

what causes reproductive isolation

• pre-zygotic barriers

• post-zygotic barriers

Pre-zygotic barriers

prevent mating or fertilization so no zygote is formed

• geographical, ecological

• temporal, behavioural (mate recognition)

• Mechanical (genital structure compatibility): unable to conceive

• Cellular (sperm-egg compatibility)

What is an example of pre-zygotic isolation (habitat and temporal isolation)

• apple maggot flies

What is an example of pre-zygotic isolation (mechanical)

• abalone

Post-zygotic barriers

prevent proper functioning zygotes or individual once they are formed

Extrinsic post-zygotic barriers

Intrinsic post-zygotic barriers

• combination of genes with low fitness in the offspring

• offspring has a viability problem

• individual is unable to reproduce

• byproduct of evolutionary change where evolution acts separately in different populations

• species that evolved apart from each other for long periods of time

Is adaptive evolution required for speciation?

ecological speciation

hybridization

polyploid

allopolyploidy

autopolyploidy