Researchers recently discovered an exquisite fossil of a fern (land plant) in sweden. the plant was preserved instantaneously when buried in a lava flow. under a microscope, scientists can see nuclei, some in different stages of cell division, along with some individual chromosomes. this fossil fern was found in a layer along with dinosaur fossils. how old could this fossil be, based upon this information and dates of events in the history of life

The fern may be 650 million years

Explanation:

Fossilization of organisms and plants took place many years ago. Fossils are remains of plants, animals, fungi, bacteria, and single celled living things that have been replaced by rock material or impressions of organisms preserved in the rocks. This happened when there was an anaerobic decomposition of burried dead organisms and plants that contained energy derived from photosynthesis. The organisms fossilized and became preserved in rocks.  

The cell organelle is a semi permeable membrane which allows some materials to pass through.