EVERYDAY SCIENCE

Detailed explanation-1: -The eukaryotes developed at least 2.7 billion years ago, following some 1 to 1.5 billion years of prokaryotic evolution. Studies of their DNA sequences indicate that the archaebacteria and eubacteria are as different from each other as either is from present-day eukaryotes.

Detailed explanation-2: -From 2 to 1.5 billion years ago simple eukaryotic organisms (protists) evolved and diversified rapidly. Acritarchs are believed to be the fossils of early eukaryotic cells and are present in the fossil record as of 1.5 billion years ago.

Detailed explanation-3: -The first fossils of prokaryotic (bacterial) cells are known from 3.5 and 3.4 billion years ago.

Detailed explanation-4: -The oldest eukaryotic fossil is the multicellular alga, Grypania. Coiled Grypania is found as thin films of carbon in rocks as old as 2, 100 Ma in Michigan and young specimens have been recovered from 1, 100 Ma rocks in China.

Detailed explanation-5: -Our analyses support an ancient (late Paleoproterozoic) origin of photosynthetic eukaryotes with the primary endosymbiosis that gave rise to the first alga having occurred after the split of the Plantae (i.e., red, green, and glaucophyte algae plus land plants) from the opisthokonts sometime before 1, 558 MYA.