The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. What major climatic and biological events happened during the Pleistocene? (E)

The Pleistocene Epoch is a geological time period that began about 2.6 million years ago and ended about 11,700 years ago. It is characterized by significant climate fluctuations, often referred to as ice ages. These ice ages led to major biological events and changes in biodiversity on Earth.

During the Pleistocene, Earth experienced alternating periods of glacial advances, where ice sheets expanded across the continents, and interglacial periods, where ice sheets retreated and climates warmed. There were at least 11 major glacial-interglacial cycles during the Pleistocene, with the most recent one marked by the Last Glacial Maximum (LGM) about 21,000 years ago. These climate fluctuations were primarily driven by changes in Earth's orbit and axial tilt, which affected the distribution of solar energy across the planet.

The glaciations of the Pleistocene had significant effects on the global distribution of species and ecosystems. As glaciers expanded and sea levels dropped, vast amounts of land were exposed, allowing for the migration of species and the formation of new habitats. In turn, the retreat of ice and the rise of sea levels led to changes in habitat availability, population isolation, and the formation of new species.

Some notable biotic events during the Pleistocene include: 1. Expansion of grasslands: Due to the cooler and drier climate conditions, grasslands expanded across much of the Earth, providing new habitats for grazing herbivores. 2. Evolution of megafauna: Large mammals, called megafauna, evolved during the Pleistocene, such as mammoths, mastodons, sabre-toothed cats, and giant ground sloths. These species were well-adapted to the harsh conditions of the ice age. 3. Extinctions of megafauna: As the climate warmed at the end of the Pleistocene, many of the megafauna went extinct, due to both climate-related habitat changes and human hunting pressures. Some examples of extinct Pleistocene megafauna are the woolly mammoth, the giant ground sloth, and the sabre-toothed cat. 4. Human expansion: Human populations also expanded during the Pleistocene, adapting to varied environments and developing new technologies that allowed them to survive and thrive in different habitats. In conclusion, the Pleistocene Epoch saw significant climatic events, such as the ice ages and glacial-interglacial cycles, which in turn led to major biological changes, including the expansion of grasslands, the evolution of megafauna, and the expansion of human populations.