Evolution “The History of Life” Edwin P. Davis, M.Ed. 2/22/2019 Biology

History of the Earth Formed 4.6 billion year ago Started as hot ball of rock Earth cooled 4.4 billion years ago First life began between 3.9 and 3.4 bya 2/22/2019 Biology

Fossils Evidence of an organism that lived long ago Paleontologists Study ancient life Uses fossils to: understand events that happened long ago Determine the kinds of organisms that lived during the past and their behaviors Study ancient climate and geography 2/22/2019 Biology

How fossils form Organisms are buried in mud, sand, or clay Sediments cover the organism, slows decomposition Minerals from sediments seep into body Over time, sedimentary layers compressed into rock Mineral replace the body’s bone material Earth’s movement or erosion expose the body Rocks form at relatively low temperatures and pressure Prevent damage of organism 2/22/2019 Biology

Types of Fossils Trace fossils An indirect evidence left by an animal Include a footprint, a trail, or a burrow 2/22/2019 Biology

Casts A replica or cast Minerals in rocks fill a space left by a decayed organism 2/22/2019 Biology

Molds An empty space left by an organisms after it decays 2/22/2019 Biology

Minerals penetrate and replace the hard parts of an organism Petrified Minerals penetrate and replace the hard parts of an organism Permineralized Void spaces in original organism is filled by minerals Petrified Permineralized 2/22/2019 Biology

Amber-preserved or frozen An entire organism quickly trapped in ice or tree sap and hardens Amber preserved 2/22/2019 Biology Frozen

Dating fossils Relative dating uses the position of fossils in sediment layers oldest fossil at the bottom layer, youngest on top Can only determine whether one fossil is older than another Cannot determine the actual age 2/22/2019 Biology

Radiometric dating use radioactive isotopes (atoms with unstable nuclei that break down or decay) decay of each radioactive element is known and continues at a steady rate 2/22/2019 Biology

Half-life the time it takes a radioactive element to get to half its original amount Potassium 40 - 1.3 billion yrs Carbon 14 - 5730 years 2/22/2019 Biology

Geologic Time Scale a type of calendar based on the different types of living organisms that have appeared on Earth 2/22/2019 Biology

Precambrian Era Starts 4.7 bya Accounts for 87% of Earth’s history Oldest rock dates 3.4 bya Unicellular prokaryotes appeared Eukaryotes appeared 2.1 bya Ended 345 mya 2/22/2019 Biology Oldest rock from Yukon, 4 byo

Paleozoic Era 345 to 248 mya Appearance of plants and animals including fishes, reptiles, amphibians and ferns 90% of Earth’s marine species and 70% of land species disappeared 2/22/2019 Biology

Mesozoic Era 248 to 65 mya Triassic Jurassic Cretaceous Oldest Mammals appeared Dinosaurs first appeared Jurassic Age of dinosaurs Cretaceous Mammals and flowering plants Dinosaurs and 2/3 of living species became extinct 2/22/2019 Biology

Theory of Continental Drift Continents were joined in a landmass known as Pangaea Pangaea broke apart resulting in two large masses At the end of the Mesozoic, most of the continents had taken on their modern shapes Explained by plate tectonics Movement of the continents 2/22/2019 Biology

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The Origin of Life 2/22/2019 Biology

The Early Ideas Spontaneous generation Nonliving material can produce life Experiments to disprove this theory Francesco Redi Used maggots in covered and uncovered jars Louis Pasteur Used curved flasks with heated broth 2/22/2019 Biology

Francesco Redi 1668 Showed that rotting meat kept away from flies would not produce new flies Maggots appeared only on meat that had been exposed to flies Eggs laid on meat 2/22/2019 Biology

Louis Pasteur Mid- 1800s Used curve-necked flasks Microorganisms were prevented from entering the flask When curved necks were broken, broth became cloudy with microorganims 2/22/2019 Biology

Biogenesis All living things come from other living things Became cornerstone of biology after Pasteur’s experiment 2/22/2019 Biology

The Modern Ideas Alexander Oparin Life began in the oceans that formed on early Earth Energy from sun + lightning+ Earth’s heat = simple compounds (eg. amino acids) Earth cooled, water vapor condensed to form lakes and seas, compounds collected in the water 2/22/2019 Biology

Stanley Miller and Harold Urey Used Oparin’s hypothesis to setup experiment Produced amino acids and other organic compounds 2/22/2019 Biology

Formation of Protocells Sidney Fox Produced protocells Large, ordered structure, enclosed by a membrane Carries out some life activities (growth and division) Heated amino acids 2/22/2019 Biology

The First True Cells Prokaryotes evolved from a protocell Heterotrophs Anaerobic Archaebacteria Prokaryotic Autotrophs Made glucose by chemosynthesis Lived in harsh environments Deep-sea vents and hot springs 2/22/2019 Biology

Photosynthesizing prokaryotes Eukaryotes evolved from prokaryotes Increased oxygen in atmosphere Eukaryotes evolved from prokaryotes 2/22/2019 Biology

Endosymbiont Theory Eukaryote provided beneficial environment Prokaryote provided method of energy synthesis Endosymbiotic, aerobic prokaryotes evolved into modern mitochondria Photosynthetic cyanobacteria evolved into chloroplasts 2/22/2019 Biology