Evolution of photoreceptors.
D000818:Animals; D000845:Annelida; D001181:Arthropods; D005075:Biological Evolution; D002923:Cilia; D007448:Invertebrates; D007865:Leeches; D008027:Light; D008974:Mollusca; D010986:Platyhelminths; D011984:Sensory Receptor Cells