Many plant species lived during the Quaternary Period, including bushes, shrubs, prairie grasses, birch, pine, spruce, oak, maple and flowering plants of all types. Due to ice ages, plant populations and their ecosystems increased and decreased during the past 2.6 million years of the Quaternary Period.
The Quaternary Period includes the present day, so plants that are alive now should be included in a list of fauna alive during this geologic time of the Earth. Scientists determined that climate changes shifted plant life depending on expanding and retreating ice sheets. Around 12,500 years ago, Pennsylvania resembled a tundra biome with plentiful coniferous trees and prairie grasses.
Scientists track plant dispersion by studying fossilized pollen patterns. During cold spells in Earth's climate cycle, flora were more abundant near the equator. After glaciers retreated to the north, plants gradually returned. This cyclical ice pattern changed weather patterns, acidity of oceans and precipitation amounts. Temperature and weather changes altered where plants grew.
Plants spreading across the planet determined human evolution during the Quaternary Period. As plant species died off, very large animals such as woolly mammoths and bison became extinct. Humans adapted, migrated and then formed permanent settlements. People invented agriculture and horticulture as they built cities and towns.