Question

Ancient plant ____________________ found in lake bottoms provides scientists with evidence about ancient climates.

Answer 1

The answer is pollen!

Answer 2

I believe it's "pollen".

When the pollen grains are washed down into lakes/rivers, scientists can take a sample of the sediment layers and see what plants were growing at that time. They can then make inferences about the climate and how that affected the plants growing there.

Hope this helps!