https://www.youtube.com/watch?v=Gyn754vw8ZQ

Warm up Draw a picture or describe what you think earth looked like 4 billion years ago

Change through Time: The History of Life

Earth’s Early Conditions Inhospitable living Conditions Volcanic Activity Lots of molten lava Earth was VERY hot (How hot was it?) No atmosphere initially No water Lots of ultraviolet radiation (no ozone layer)

Earth’s Early Conditions Volcanic gasses given off: H2 -- hydrogen N2 -- nitrogen H2 O vapor CO and C02 NH 4 -- ammonia CH4 -- methane

Changes in Earth’s History Weather began after the atmosphere built up from volcanic gasses. Torrential rains from water vapor built up Filled up Earths basins to become bodies of water Caused erosion

Changes in Earths History Plate tectonics (Pangaea – all continents) Supercontinent began to break apart and move around Earth Mountain formation Earth cooled down Several Ice ages occurred

Earths Present Conditions Atmosphere N2 ≈ 70% O2 ≈ 21% Misc. ≈ 9% Water 70% of surface Land 30% of surface

Earths Present Conditions Weather and climate varies around the world according to latitude. Earthquakes and volcanoes occur occasionally Lots of Life (great biodiversity)

Important Dates 15 Billion years ago (BYA) – Universe formed 4.6 BYA – Earth formed 3.9 BYA Earth cooled and oceans formed 3.5 BYA – first life appeared

Eras of Earths History Precambrian ( 3.4 BYA) - 87% of Earths history - oldest evidence of life found in Precambrian rock Prokaryotic → no nucleus Eukaryotic → have a nucleus By the end of this era, the oceans were filled with multicellular organisms like algae, sponges and jellyfish.

Paleozoic - Lasted until 248 million years ago (MYA) During the Cambrian Period there was a great increase in biodiversity (E.g. - worms, echinoderms, arthropods, fish, ferns, reptiles, amphibians) Mass extinction at the end of the Paleozoic. 90% of marine spp. And 70% of land spp. gone forever.

Mesozoic Era Divided into 3 periods: Triassic – 1st mammals (they were tiny then) and 1st dinosaurs Jurassic – the “age of dinosaurs” Cretaceous – more mammals and flowering plants (E.g. – oak, fig, and elm trees)

Cenozoic Era Began 66 MYA This is the era in which we live Primates evolved → we belong to this group of mammals Modern human spp. Evolved about 200,000 YA

Over 90% of the species that have lived on Earth are now extinct → consider how biodiverse the Earth would be had they not died off…

Answer the following questions Describe what Earth was like before life arose. Make a table listing the four major divisions of the geologic time scale, their time spans, and the major life forms that appearing during each interval.