Q.How does molecular markers work to unlock the evolutionary history of organisms?

Molecular taxonomy (molecular systematics / molecular phylogenetics) is the branch of phylogeny that analyses hereditary molecular differences - mainly DNA sequences - to establish genetic relationships between taxonomic groups, with results expressed as a phylogenetic tree; the advent of DNA cloning and sequencing methods drove the field forward enormously. It uses a range of molecular markers: allozyme electrophoresis (enzyme-level variation); mitochondrial DNA markers (non-recombining, homologous organellar markers); microsatellites (short, highly variable tandem-repeat sequences); RFLP (Restriction Fragment Length Polymorphism - differences in DNA fragment lengths after cutting with restriction enzymes); RAPD (Random Amplified Polymorphic DNA - a randomly synthesised primer amplifies unknown regions, useful within/between close species though hard to replicate); AFLP (Amplified Fragment Length Polymorphism - similar to RFLP, used in population genetics and higher-level cladistics); SNPs (Single Nucleotide Polymorphisms - the most abundant genome polymorphism, detected by PCR/microchip arrays/fluorescence); and DNA microarrays/chips (immobilised DNA fragments matching a known probe against an unknown sample). Its significance: identifying large numbers of species via conserved sequences; investigating evolutionary patterns of biodiversity; supporting phytogeography, genome mapping and biodiversity conservation; and designing DNA-ba …