The History of Life EQ: When did life form on earth? Presenter notes: Life is what makes our planet different. As far as we know Earth is the only planet in the Solar System ever to have harbored life, although it is not impossible that it may have once existed on Mars in the distant past. Life is hugely important for the way our planet works and has altered almost every aspect of it’s atmosphere, ocean and land. This talk discusses the History of Life from the earliest times to the present day. Being a historical account of how life evolved, it does not deal with the process by which that change happened. This is examined in depth in a companion talk on Evolution. Background note: The companion talk on Evolution can be downloaded from the Your Earth website: http://www.earth4567.com/talks/evolution.html © NASA www.fossilmuseum.net/Fossil-Pictures/Ammonites/Ammonite-5/Ammonite-5-1024.jpg 1

Diversity (1): Simple organisms Bacteria http://www.earthlife.net/images/bacteria.gif en.wikipedia.org/wiki/Image:Halobacteria.jpg Two types of organism exist on our planet. One group has simple cells with DNA strands floating in a capsule. These prokaryotes, as they are called, include various types of bacteria

Diversity (2): Complex organisms en.wikipedia.org/wiki/Image:Chlamydomonas_(10000x).jpg en.wikipedia.org/wiki/Image:Laurencia.jpg Golden algae Fungi Protozoa A second group, eukaryotes, have complex cells that have compartments with special jobs and DNA in a nucleus www.earthlife.net/images/eury-cell.gif Plants Animals en.wikipedia.org/wiki/Image:Elephant_near_ndutu.jpg en.wikipedia.org/wiki/Image:Amanita_muscaria_(fly_agaric).JPG

The Fossil Record Fossils provide a record of life forms that once existed in the past www.discoveringfossils.co.uk/royalty_free_photos_fossil_hunting_collecting.jpg

Geological Time The whole geological timescale http://en.wikipedia.org/wiki/Geologic_time_scale The Phanerozoic in detail The study of fossils in the context of the 4500 million years of geological time allows us to piece together the History of Life

In the Sea (1): Bombardment Early Earth Cratered moon Mars ? © Julian Baum with permission NASA NASA During its early history, the Earth was bombarded by meteorites. Such inhospitable conditions probably prevented life from evolving. http://en.wikipedia.org/wiki/Geologic_time_scale 4500-3800 million years ago

In the Sea (2): First living things Life evolved shortly after the bombardment ended, early in Earth History. The first living things were simple bacteria Modern bacterial mounds Fossil bacteria? en.wikipedia.org/wiki/Image:Stromatolites_in_Sharkbay.jpg www.fas.org/irp/imint/docs/rst/Sect20/A12.html http://en.wikipedia.org/wiki/Geologic_time_scale 3800-3500 million years ago

In the Sea (3): Oxygen Early photosynthetic bacteria produced oxygen and released it as a waste product. This added oxygen to the atmosphere for the first time. Iron oxide rocks Photosynthetic bacteria Presenter notes: This talk has three parts. In the first part, we will discuss the early history of life and see how life began in the Sea about 3800 million years ago. In the first activity we will then examine the ecology of one of the most famous fossil sites anywhere in the world: the Burgess Shale of British Columbia, Canada. In the second part, we will learn about the invasion of land, which began about 500 million year ago, and in the following activity we will compare two early land ecosystems and think about the progressive development of food webs. Finally, in the third part, we will see how life continued to diversify to the present day, but was occasionally subject to waves of extinction. Five mass extinctions have occurred over the past 500 millions and have profoundly shaped Life on Earth. We will conclude by asking whether human activity is now triggering a sixth mass extinction. http://www.globalchange.umich.edu/globalchange1/current/lectures/first_billion_years/bif.gif en.wikipedia.org/wiki/Image:Anabaena_sperica.jpg http://en.wikipedia.org/wiki/Geologic_time_scale 3800-3500 million years ago 8

In the Sea (4): Complex cells Acritarch Two billion years later complex eukaryote cells appeared. These had compartments with special functions such as energy factories called mitochondria. Eukaryote cells need oxygen - this explains their late evolution Presenter notes: The second group of organisms, which we call eukaryotes, have complex cells that have compartments with special jobs and DNA located in a nucleus. This group includes the familiar kingdoms of organisms like animals, plants and fungi. Most of the organisms in these kingdoms are multicellular, made up of many cells working together. However, other eukaryotes include the single-celled kingdoms of the protozoa and the ‘golden brown algae’ or chromists. www.cushmanfoundation.org/resources/images/slide16.gif 1900 million years ago http://en.wikipedia.org/wiki/Geologic_time_scale 9

In the Sea (5): Multicellular life Grypania After another half billion years many-celled life appeared Grypania was a coiled tube, 2 mm wide and up to 5 cm long © Bruce Runnegar with permission http://en.wikipedia.org/wiki/Geologic_time_scale 1400 million years ago

In the Sea (6): Biology’s Big Bang! evolution.berkeley.edu/evolibrary/images/bangiomorpha1.jpg Red algae en.wikipedia.org/wiki/Image:Sexual_cycle.svg A short time later, 1200 mya, algae evolved sexual reproduction http://en.wikipedia.org/wiki/Geologic_time_scale 1200 million years ago

In the Sea (7): Ediacara Evidence www.peripatus.gen.nz/paleontology/Ediacara.html By 630 mya, the familiar kingdoms of animals, plant and fungi had evolved. The Ediacara fauna of this time interval were strange bizarre organisms from the dawn of animal life http://en.wikipedia.org/wiki/Geologic_time_scale 630-542 million years ago

Beginnings (8): Diversity explodes palaeo.gly.bris.ac.uk/palaeofiles/lagerstatten/Burgess/Anomalocarishunts.jpg www.newarkcampus.org/professional/osu/faculty/jstjohn/Cool Fossils/Anomalocaris-canadensis.jpg Burgess Shale fossils Claw of Anomalocaris Presenter notes: When organisms die they may leave behind a record in the form of their skeleton or shell or stem. These fossil remains can survive for millions and sometimes billions of years. Palaeontologists extract fossil remains from the rock and use them to piece together the History of Life. Organisms are only preserved in special conditions so only a tiny proportion of all living things ever become fossils. Consequently the fossil record is incomplete and many questions remain unanswered about the History of Life. Nevertheless in general terms the fossil record gives a surprising clear insight into the historical sequence of events that gave rise to the life we see around us today. Around 542 mya, several fossil sites show that the diversity of animal life on Earth dramatically exploded over a short time. http://en.wikipedia.org/wiki/Geologic_time_scale 542-515 million years ago 13

Left Side Activity Draw the entire geological timescale. Presenter notes: When organisms die they may leave behind a record in the form of their skeleton or shell or stem. These fossil remains can survive for millions and sometimes billions of years. Palaeontologists extract fossil remains from the rock and use them to piece together the History of Life. Organisms are only preserved in special conditions so only a tiny proportion of all living things ever become fossils. Consequently the fossil record is incomplete and many questions remain unanswered about the History of Life. Nevertheless in general terms the fossil record gives a surprising clear insight into the historical sequence of events that gave rise to the life we see around us today. http://en.wikipedia.org/wiki/Geologic_time_scale 542-515 million years ago 14