Convergent, divergent, parallel and co-evolution

Divergent EvolutionWhen closely related species become less like each other over time due to different environmental conditions or selective pressuresWhen several species diverge from one common ancestor this is called adaptive radiation

Divergent EvolutionFruit Bat - VictoriaBlossom bat - QueenslandEastern Horseshoe Bat - NSWRight, large-eared variety

Adaptive Radiation

Convergent EvolutionWhen species that are not closely related have adapted similar features due to similar selective pressures

Also known as adaptive convergence

Left: A and B, a marsupial flying phalanger and a placental flying squirrel; C and D, marsupial and placental jerboas; E and F, marsupial and placental moles. Below: The marsupial Tasmanian wolf (left) and the familiar placental wolf (right), with the corresponding skulls.

Parallel EvolutionWhen closely related species develop similarities due to similar selective pressures that they are exposed to

Co-evolutionWhen two different species have a close relationship evolve in a way that enhances their relationship

What type of evolution do these diagrams show?

SpeciationEvolution by natural selection leads to gradual changesOver time, the species may change so much that a new species formsThis is called speciationTwo types:Phyletic evolutionBranching evolutionWhen speciation occurs due to geographical separation, this is called allopatric speciation

SpeciationPhyletic Evolution:When one population of a species changes so much that it is no longer able to breed with other members of the species and produce viable offspringBranching evolution:When a population of a species splits into two or more groups with one of the groups evolving separately from the others and forming a new species

Phyletic vs. Branching

Punctuated EquilibriumDarwin proposed that evolution was a very slow and gradual processIn 1974 a punctuated equilibrium model was proposedSpecies can remain unchanged for long periods of time and the evolution of a species can occur rapidly due to sudden changesEvidence in fossil record

ExtinctionIf a species is unable to change or evolve through natural selection it may be unable to survive some selective pressuresIf all of the reproductive individuals of a species die, the species is lost and said to be extinct

Comparative Genomics Can be used to compare the entire genome of organisms to determine how closely related they are

Helps to determine whether similar species share an evolutionary history