Fossils of hippopotamus, critters that live in rivers of the tropical savanna, found near London, England. B. Pollen analysis 1. The male sex cell of plants. Since they can't move, they cannot select mates. Instead, they have sex by pollen dispersal.
Most pollen simply falls on the ground and gets washed into rivers and lakes.
Scientists recover cores of mud that accumulate at the bottom of lakes, and sift through to look at the kinds of pollen that have been dispersed in the region during the period of lake history. Shows evidence of historical changes in distribution of vegetation types and dominant species C. Tree-ring analysis 1. In climates with a pronounced winter or dry season, plants grow during only part of the year and go dormant. This leaves annuals rings in the wood. Scientists extract cores from trees and analyze the variation in ring-widths to make educated guesses about past climates.