Homologiska

Homologiska (homologous) describes features that arise from a common ancestor. In biology, homologous traits can be anatomical structures, developmental patterns, or genetic sequences that reflect shared evolutionary history rather than just similar function.

Homology is contrasted with analogy or homoplasy, where similarities are due to convergent evolution or parallel development rather than shared ancestry. A classic example is the pentadactyl limb: the forelimbs of humans, cats, whales, and bats are structurally similar because they evolved from a common ancestral limb, even though their functions differ.

Genetic or sequence homology refers to genes or regions that derive from a common ancestor. Relationships among such sequences are described as orthologs (between species) and paralogs (within a species). High sequence similarity between genes supports common origin; however, functional divergence may occur over time.

Researchers identify homologs using sequence alignments, phylogenetic analysis, and synteny (conserved genomic context). Homology underpins comparative genomics and phylogenetics and helps transfer functional knowledge from model organisms to less-studied species.

Origin of the term derives from Greek homo (same) and logos (relation, study). In Swedish scientific writing, the adjective is homologisk and the noun homolog, while the form homologiska is used for the plural or feminine form of the adjective.