Lichen anatomy and physiology the Ascomycota, with about 40% of species forming such an association. Some of these lichenized fungi occur in orders with nonlichenized fungi that live as saprotrophs or plant parasites (for example, the Leotiales, Dothideales, and Pezizales). Other lichen fungi occur in only five orders in which all members are engaged in this habit (Orders Graphidales, Gyalectales, Peltigerales, Pertusariales, and Teloschistales). Lichenized and nonlichenized fungi can even be found in the same genus or species. Overall, about 98% of lichens have an ascomycetous mycobiont. Next to the Ascomycota, the largest number of lichenized fungi occur in the unassigned fungi imperfecti. Comparatively
Chlorophyll a each type of chlorophyll molecule, and alters the absorption spectrum of light. Chlorophyll "a" has a long hydrophobic tail, which anchors the molecule to other hydrophobic proteins in the thylakoid membrane of the chloroplast. Once detached from the porphyrin ring, this long hydrocarbon tail becomes the precursor of two biomarkers, pristane and phytane, which are important in the study of geochemistry and the determination of petroleum sources. Chlorophyll "a" biosynthetic pathway utilizes a variety of enzymes. Genes code for the enzymes on the Mg-tetrapyrroles of both bacteriochlorophyll "a" and chlorophyll "a". It begins with glutamic acid, which is transformed into