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DO NOW 1. Grab Weekly 2. Grab Chapter 12 Packet Ch. 12 History of Life on Earth Age of Earth 1. 4.5 billion years ago Earth was a fiery ball of rock 2. Surface of Earth cooled 3. Water vapor in air condensed to form ocean water where life first evolved How did Life Begin? Measurin g the Age of Earth Scientist have measured the age of the rocks found on Earth using radiometric dating The age of the rock is measured based on how much it has broken down throughout the years called radioactive decay How did Life Begin? Measuring the Age of Earth Radioactive Decay of a rock’s content of certain “isotopes” is measured in Half-Lives Half Life Time it takes for one half of a certain amount of radioisotope to decay By measuring this, scientists can calculate how many half lives have passed since a rock was formed How did Life Begin? Measuring the Age of Earth The Theories – How Life Began 1. Formation of Life’s Chemicals Nonliving matter was energized by sun and volcanic heat Caused chemical reaction to produce simple organic molecules Organics became more complex First cells developed The Theories – How Life Began Primordial Soup Model Hypothesized that Earth’s oceans were once filled with organic molecules (“soup”) But, there was no oxygen in the air: only nitrogen, hydrogen, water, ammonia, methane The Theories – How Life Began Primordial Soup Model Solar radiation, volcanic eruptions, lightning excited electrons in gases Electrons reacted with Hydrogen in the air to form organic molecules This hypothesis was actually tested and SUPPORTED! Results – found a complex collection of organic molecules! Compounds included life’s building blocks – amino acids, fatty acids – Hypothesis Supported! The Theories – How Life Began Bubble Model Scientists Louis Lerman hypothesized that the key processes that formed the chemicals needed for life took place within bubbles on the oceans surface The bubbles contained the gases needed to make organic molecules Chemical reactions took place inside the bubbles and UV radiation made this process occur quickly Lerman suggested this theory occurred much more quickly than the Primordial Soup Model Whiteboard – Quick Questions According to scientists how old is the Earth? After three half-lives of a radioisotope have passed, how much of the original isotope is undecayed? (1)1/8 (2) ¾ (3) ½ What is “Primordial Soup”? (4) 7/8 When did the 1st Organisms Form? Evolution of Prokaryotes The best evidence we have to study early life are fossils Fossil- preserved remains (bone, tooth, shell) or imprint of an organism from long ago How did Life Begin? Evolution of Prokaryotes Oldest fossils photosynthetic prokaryotes (cyanobacteria) 2.5 billion years old Released oxygen into oceans Oxygen eventually escaped into air as more and more was produced Quick Check - Prokaryotes Evolution of Prokaryotes Hold up 1 finger if prokaryotes do have a nucleus Hold up 2 fingers if they do not Hold up 1 finger if they are unicellular Hold up 2 fingers if they are multicellular Two Groups of Prokaryotes Evolution of Prokaryotes Eubacteria Cell walls contain peptidoglycan Cause disease and decay Ex: E.Coli Archaebacteria Cell walls lack peptidoglycan Unique lipid cell membranes The 1st eukaryotic cells evolved from archaebacteria The Evolution of Eukaryotes Evolution of Eukaryotes About 1.5 million years ago the first eukaryotes appeared With your shoulder partner try to come up with 3 characteristics of Eukaryotes Eukaryotes Larger More Complex Internal Membranes DNA in a nucleus Mitochondria Chloroplasts The Kingdoms Evolution of Eukaryotes Biologist group all living things into six kingdoms. The first two kingdoms are Eubacteria and Archaebacteria TRY THIS Name the other four kingdoms Circle the kingdom you believe came first before all the rest Protists – Fungi – Plants - Animals The 1st Eukaryotes The first Eukaryotic Kingdom were Protists Includes both multi and unicellular organisms Single celled organisms STILL carry out all of activities for life’s processes (ex: metabolism, homeostasis) Multicellular protists include Algae Extinction Mass Extinctions Extinction- Death of all members of a species Mass Extinction- Episode during which large numbers of species become extinct The fossil records show large percentages of the Earth’s organisms were becoming extinct A total of 5 have occurred Extinction Mass Extinctions Most devastating- end of Permian period 245 million years ago 96% of all species became extinct Cause may have been worldwide geological and weather changes How did Life Begin? Mass Extinctions Fifth mass extinction 2/3 of all land species (including dinosaurs) become extinct Extinction Mass Extinctions A sixth mass extinction event? May be currently occurring due to destruction of tropical rain forests by human activity Can you name the most recent extinction or a species? The Ozone Layer Ozone Layer Life began in the oceans, why did life suddenly form on land? UV radiation from the sun is harmful As cyanobacteria began supplying the air with oxygen, chemical reactions in the atmosphere created the ozone The Ozone layer blocked the UV radiation and made the Earth’s land a safe place to live Whiteboard – Quick Questions Name the kingdom that includes single and multicellular organisms Yes or No would today’s organisms exist if the mass extinctions did not occur? Think – Why or why not How did cyanobacteria contribute to the beginning of more complex life on Earth? Do Now Grab a textbook Turn in Chapter 11 Take home Exam p. 8 Wednesday DoNow **Don’t forget – Weekly Due Friday Section 3 – Gallery Walk Each group will be assigned a section from Pages 265 – 268 Make a poster of your section in 15 minutes Make sure you can answer your questions We will walk around to each groups poster and have 5 minutes to review and discuss each Section 3 – Gallery Walk Each group will be assigned a section from Pages 265 – 268 Sections: Plants & Fungi on Land – p.265 Arthropods – p. 266 Fish – p.267 Amphibians – p.267 Reptiles – p.268 Mammals & Birds – p.268 Section 3 – Gallery Walk Each group will be assigned a section Make a poster of your section in 15 minutes Make sure you can answer your questions We will walk around to each groups poster and have 5 minutes to review and discuss each How did Life Begin? Plants and Fungi on Land Plants evolved from photo. bacteria Use sunlight to generate nutrients Cannot harvest materials from bare rock How did Life Begin? Plants and Fungi on Land Fungi Can harvest materials from bare rock Cannot use sunlight to generate nutrients How did Life Begin? Plants and Fungi on Land Together, they form a mutualistic relationship (both benefit) Mycorrhizae- fungus provides minerals to plant, and plant provides nutrients to fungi How did Life Begin? Arthropods First animals to successfully invade land (first most likely scorpion) Hard, outer skeleton Segmented body Paired, jointed limbs Lobsters, crabs, insects, spiders How did Life Begin? Arthropods Insects Most plentiful, diverse group on Earth First to have wings and fly Efficient at searching for food, mates and nesting sites How did Life Begin? Vertebrate s (animals with a backbone) A. Fishes First vertebrates- small jawless fishes Jawed fish evolved- allowed predation Most successful of living vertebrates Developed into land dwellers How did Life Begin? Vertebrate s (animals with a backbone) B. Amphibians First land vertebrates (to come out of sea) Smooth skinned, four legged Frogs, toads, salamanders Developed lungs for absorbing oxygen from air Limbs derived from bones in fish fins Strong, flexible internal skeleton for walking Lay eggs in moist areas How did Life Begin? Vertebrate s (animals with a backbone) C. Reptiles Evolved from amphibians Snakes, lizards, turtles, crocodiles Watertight skin locks moisture in while living on land Can lay eggs on dry land How did Life Begin? Vertebrate s (animals with a backbone) D. Mammals and Birds Evolved from reptiles 5th mass extinction: only dinosaurs that were ancestors to birds, small reptiles and small mammals survived How did Life Begin? Continental Drift Movement of land masses over Earth’s surface through geologic time Explains why there are Marsupials in both Australia and South America although they are extremely far apart ajkf Assessment Three Summarize how ozone was important in enabling organisms to live on land Name the first multicellular organisms that colonized land Identify the first kinds of animals to live on land Describe the first kinds of vertebrates that inhabited land Defend the argument that invasion of land could not have happened until well after the evolution of cyanobacteria