Chapter 5

4.5 billion years ago, the Earth was born. Consider that the Earth formed, life arose: - the first tectonic plates arose and began to move - eukaryotic cells evolved - the atmosphere became enriched in oxygen – and - just before the end of the Precambrian, complex multicellular organisms, including the first animals, evolved

1700 – James Hutton began to question about changes of Earth; he came up the hypothesis about changing Earth over time. UNIFORMITARIANISM – Hutton’s theory Earth is an always-changing place The same forces of change at work today were at work in the past.

German scientist that proposed a hypothesis about continental drift in He called the landmass Pangaea His ideas led to the theory of Plate Tectonics Plate tectonics – states that Earth’s lithosphere is made up of huge plates that move over the surface of Earth

It divides Earth’s history into intervals of time defined by major events or changes on Earth Divisions of Geologic Time Eon – the largest time, Earth has 4 eons Era – Eons are divided into eras: Paleozoic, Mesozoic and Cenozoic Period - Each era is subdivided into a number of periods Epoch – The periods of the Cenozoic, are further divided into epochs

Make up almost 90 percent of Earth’s history Division of Precambrian Time Hadean Eon Archean Eon Proterozoic Eon

4.5 to 3.8 billion years ago the Solar System was forming

3.8 to 2.5 billion years ago With a reducing atmosphere of methane, ammonia, and other gases The Earth's crust cooled enough that rocks and continental plates began to form.

2.5 billion to 543 million years ago Stable continents first appeared and began to accrete, a long process taking about a billion years In the Middle Proterozoic comes the first evidence of oxygen build-up in the atmosphere

The majority of microscopic organisms, algal, fungal, plant and animal lived. approximately 544 million years ago Division Paleozoic Era Mesozoic Era Cenozoic Era

544 to 248 Million Years Ago Also known as the Ancient Life multicellular animals underwent a dramatic explosion in diversity At the other end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species During the Paleozoic there were six major continental land masses; each of these consisted of different parts of the modern continents.

Cambrian Period Ordovician Period Silurian Period Devonian Period Carboniferous Period Permian Period

248 to 65 Million Years Ago Whose name means middle life The Mesozoic is divided into three time periods: - the Triassic ( mya) - the Jurassic ( mya); - and the Cretaceous ( mya).

65 Million Years to the Present The name means recent life The Cenozoic is the most recent of the three major subdivisions of animal history Sometimes called the Age of Mammals

Tertiary Period Quaternary Period – stretches from 2 mya to the present Most of this period has been a series of ice ages, with much of the planet covered in thick sheet of ice Fossils of the modern humans are also from this period. They are about 100,000 years old.