Overview of natural history

Breakdown of time Different periods of Earth’s history are broken into sets of time just like a year is broken into months, weeks, days and hours Earth history is broken into eons, eras, periods, epochs

Eons – Millions and Billions of years Haden: Earth before life evolved 4.6 to 3.5 Billion years ago (13% of Earth’s history) Achaean: Earth with only bacteria like cells 3.5 to 2.5 Billion years ago (28% of Earth’s history) Proterozoic: Multicellular life forms 2.5 BYA to 540 MYA (48% of Earth’s history) Phanerozoic: Dinosaurs to now 540 MYA – present day (11% of Earth’s history)

How time periods are distinguished Major geological events: The movement of tectonic plates to form continents & super-continents Changes in climate: a change from an ice ace to a warming period Mass extinctions or explosions: Changes in the types of life forms on earth

Haden Eon 4.6-3.5 BYA So hot that the rock was molten & Water was vapor Lifeless, little O2 in the atmosphere Relative to a calendar year: Jan 1st – Feb. 25th It’s difficult to comprehend time in billions of years, we have no point of reference. In order to make it easier to understand the relative amount of time that has passed during each of the Earth’s phases think of the entire 4.6 billion years of Earth’s history as one calendar year starting January first with today as midnight Dec 31st. For the first 2 months of Earth’s existences its only seas were molten lava, the water steam in the atmosphere. It took that long for the radioactive core to cool enough for solid land to form. It’s difficult to comprehend time in billions of years, we have no point of reference. In order to make it easier to understand the relative amount of time that has passed during each of the Earth’s phases think of the entire 4.6 billion years of Earth’s history as one calendar year starting January first with today as midnight Dec 31st. For the first 2 months of Earth’s existences its only seas were molten lava, the water steam in the atmosphere. It took that long for the radioactive core to cool enough for solid land to form.

Achaean Eon 3.5-2.5 BYA Earth cooled enough to have a crust & ocean Life forms in the sea Bacteria & photosynthetic blue-green algae Feb. 25th - April 17th The earth’s core is still extremely hot and that energy drives the tectonic forces that move the continents and oceans of the planet. It is the reason there are still earthquakes and volcanoes. What defined the next phase of earth's history, the Achaean was the formation of solid land and oceans of water. With water life could evolve from a primordial soup of amino acids and nucleic acids. Exactly how the first cell form is still a mystery, but experiments have shown how the 1st organics molecules could have formed on that ancient earth. It took a long time before the 1st photosynthesis organisms to evolve, but when they did they changed the planet. The earth’s core is still extremely hot and that energy drives the tectonic forces that move the continents and oceans of the planet. It is the reason there are still earthquakes and volcanoes. What defined the next phase of earth's history, the Achaean was the formation of solid land and oceans of water. With water life could evolve from a primordial soup of amino acids and nucleic acids. Exactly how the first cell form is still a mystery, but experiments have shown how the 1st organics molecules could have formed on that ancient earth. It took a long time before the 1st photosynthesis organisms to evolve, but when they did they changed the planet.

Proterozoic Eon: Precambrian Era 2.5 BYA – 540 MYA Super continent Rodinia 21% O2 in Atmosphere First complex cell -July 13th First multicellular organism (seaweed/algae) Aug 31st It’s spring and those 1st photosynthetic prokaryotes slowly began to infuse the oceans and atmosphere with oxygen gas. By the middle of summer the atmosphere had gone from having 1 to 21% oxygen. All this oxygen allowed for a new form of respiration to evolve, aerobic respiration. Which as you know is far more efficient. Bacteria that used this new form of respiration became incorporated into the cells of larger bacterium forming the 1st eukaryotic cells. It took a relatively short period of time for multicellular life to evolve from there. The fist plants being seaweed and the 1st animals being sponges. Very simple life forms with a few tissue types but no organs. It’s spring and those 1st photosynthetic prokaryotes slowly began to infuse the oceans and atmosphere with oxygen gas. By the middle of summer the atmosphere had gone from having 1 to 21% oxygen. All this oxygen allowed for a new form of respiration to evolve, aerobic respiration. Which as you know is far more efficient. Bacteria that used this new form of respiration became incorporated into the cells of larger bacterium forming the 1st eukaryotic cells. It took a relatively short period of time for multicellular life to evolve from there. The fist plants being seaweed and the 1st animals being sponges. Very simple life forms with a few tissue types but no organs.

Review of Earth’s first 3.9 Billion years Haden lifeless Earth Proterozoic Eukaryotic life, multicellular plants, First plants & soft bodied animals in oceans later vascular plants fish, arthropods in ocean Insects, amphibians & reptiles on land Achaean Prokaryotic life Little O2 This graphic shows the earth’s history condensed into one day, its 10:30 at night and dinosaurs have not yet arrived at the scene.

From the Cambrian explosion to the dawn of the dinosaurs Paleozoic Era From the Cambrian explosion to the dawn of the dinosaurs

Cambrian - Permian period:540 MYA – 248 MYA Cambrian: Starts with a burst of new life forms & all life in ocean Plants & animals evolved from simple seaweed & sponges to fish in the oceans & insects, amphibians, and early reptiles on land 1 Mass extinction in the ocean Nov. 17 – Dec 6 Once multicellularity evolved there was an explosion of new life forms, creatures we would think of as bizarre today. All these new life forms with a variety of body plans and survival strategies competed for the same resources until only the best remained. After the Cambrian was the Ordovician Period which was marked by the first fish and land plants. Next came the Silurian Period with vascular plants on land and jawed fish in the sea. The Devonian is often called the age of fish, with many of the fish we see today, the first vertebrates stepped on to land and insects evolved. In Carboniferous Period the earth was swampy there reptiles on land as well as large insects. There was a mass extinction in the Permian where 99% of all species went extinct. The life forms that exist today all descend from that 1%.

Triassic period to Holocene Epoch 248 MYA – present From the early dinosaurs to extinction 65 MYA 1st mammals, birds, and flowering plants The ice age to modern civilization Dec 7th - Midnight Dec 31st It is now the last month of the year the first dinosaurs come and go in 25 days. the 1st mammal, birds – which are the direct descendants of dinosaurs begin to spread across the earth. The first flowering plants evolve toward the end of the age of dinosaurs. Beas and other pollinators coevolve with this new type of plant. The extinction of the dinosaurs and 99% of all life forms 65 million years ago opened up niches for more insects, mammals, birds and flowering plants another explosion of diversity. Humans have only existed for a minute of the year.

Review of last 248 Million years First human First monkey Last Dinosaurs First bird Flowering Plants First Mammals First Dinosaurs Review of last 248 Million years

Review What was the surface of the earth like during the Haden Era? During which era did multicellular life evolve? Which is a shorter period of time and eon or an era? Which came first birds or mammals?