In fact, some flattened protoctists discovered in the Ediacaran biota had characteristics resembling lichens. The seed has a hard coat surrounded by a fleshy outer layer (aril).
[Lichens are organisms resulting from genetic mergers betweeen protists and fungi.] All the Ediacaran biota became extinct by about 530 million years ago and were replaced be shelled Cambrian animals. The drupelike seed often sits on a fleshy red or purple base or cone axis that is called an aril in some references.
These remarkable organisms are now placed in the domain Archaea. Left: Monterey cypress (Cupressus macrocarpa) in Point Lobos State Park on the coast of central California. nevadensis) in the Piute Mountains, with Lake Isabella and the snow-covered Sierra Nevada in the distance.
Other prokaryotes, including eubacteria and cyanobacteria, are placed in the domain Bacteria. The Piute cypress are more drought resistant, with gray (glaucous), glandular (resinous) foliage similar to the Arizona cypress. A grove of Sargent cypress (Cupressus sargentii) in the San Rafael Mountains of Santa Barbara County, California.
Known as the Ediacaran biota, these deposits date back 600 million years ago. Minute female cones are composed of 2-4 reduced scales, but usually only one scale bears an ovule that matures into a seed.
Some of these ancient protoctists may have been ancestral to certain animal and plant phyla. There is little resemblance to a cone in the mature seed.
They also place the macroscopic, multicellular brown algae (Division Phaeophyta) and red algae (Division Rhodophyta) in the Kingdom Plantae. In the latter species, the naked seed sits partially exposed in a red, cup-shaped aril.Lipids of archaebacterial cell membranes differ considerably from those of both prokaryotic and eukaryotic cells, as do the composition of their cell walls and the sequence of their ribosomal RNA subunits.In addition, recent studies have shown that archaebacterial RNA polymerases resemble the eukaryotic enzymes, not the eubacterial RNA polymerase.The archaebacteria could have flourished more than 3 billion years ago under conditions previously thought to be uninhabitable to all known life forms.Although many conservative references place the archaebacteria in a separate division within the kingdom Monera, most authorities now recognize them as a 6th kingdom--The kingdom Archaebacteria.Archaebacteria also have introns in some genes, an advanced eukaryotic characteristic that was previously unknown among prokaryotes.