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 Fossils are remains of plants, animals, fungi, bacteria, and single celled living things that have been replaced by rock material or impressions of organisms preserved in the rocks.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.  

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.