I want to know the answer to the following question:
What can scientists learn from the fossil record?
All the background I'm provided with is that "The new photosynthetic plants (along with their algal relatives) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen-free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years.". Is that enough to answer the question?