There is evidence that human industrial activity is responsible for the recent increase in carbon dioxide concentration in the atmosphere. The concentration of carbon dioxide in the atmosphere had fluctuated between 200-300 ppm prior to the year 1800. As a consequence of burning fossil fuels, the relative concentration of C-14 in the atmosphere is declining. The layer of the atmosphere most changed by human actions such as . Ozone reacts with and degrades chlorophyll, and thus lowers the plant's productivity.
Ozone reduces photosynthetic efficiency by competing with carbon dioxide.
Small increases in the UV radiation can cause mutations during the cell replication process. The ozone shield was a prerequisite to the colonization of the land. None of the above. The fossil record suggests that high temperatures and carbon dioxide concentrations have been correlated for more than 100 million year b. During the last 100 million years there has been a general upward trend in carbon dioxide concentrations.