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Unformatted text preview: Lecture 27-28: A Brief History of Life on Earth History Outline of Lectures 27-28
I. How do we learn about Ancient Events? I. II. How Have Earth’s Continents and Climates Changed over Time?
A. Continental Drift: Earth’s continents have moved B. Atmospheric Change: Oxygen has steadily increased in Earth’s atmosphere C. Climate Change: Earth’s climate has changed over time D. Meteors: Extraterrestrial events have triggered changes on Earth III. What Are the Major Events in Life’s History?
Three major faunas have dominated life on Earth A. Precambrian life was small and aquatic A. Precambrian B. Life expanded rapidly during the Cambrian period B. Cambrian C. Geographic differentiation increased during the Mesozoic era C. Mesozoic D. The modern biota evolved during the Cenozoic era D. Cenozoic I. Learning about Ancient Events I.
Ideally, we would have a book of “The History of Life on Earth” Ideally, beginning 3.5 bya beginning Instead, we have _fossils_, the preserved remains of ancient organisms, _fossils_ the and the rock strata in which they are found rock We can date strata using _radioisotopes (e.g. C, K, P, U, etc.)_ We _radioisotopes These are the only direct evidence about the history of life, but this These direct version of the Book of Life has some problems: version
• Many pages lack numbers, so order of events is hard to reconstruct Many • Many pages are missing Many • The ink has run on pages, especially at the beginning of the book The • The book is written in many languages, over a long period of time The • etc. etc. For example, there are only ~250 million fossil species, of 50 billion For or more__ that have lived on earth! So we must understand both what or __ we know, and the limits of our knowledge... we II. How Have Earth’s Continents and Climates II. Changed over Time? Changed
The history of life is divided into _geological eras__, which are _geological which subdivided into _ periods _, which are periods which further subdivided into _epochs (all subdivided into epochs)_________ subdivided • The boundaries are based on The changes in _types of fossils_ _types • The eras were established before The actual ages of rocks were known actual
PREgnant CAMels ORDinarily PREgnant SIt Down CARefully. PERhaps Their Joints CREak, Though QUietly. II. How Have Earth’s Continents and Climates II. Changed over Time? Changed
Major Changes in the Earth’s Continents and Climate have had enormous effects on the evolution and diversification of life on earth: earth: A. B. C. D. Continents have moved by _plate tectonics__ Continents _plate Earth’s atmosphere has changed, with O2 levels increasing Earth’s Earth’s _climate___has changed over time Earth’s _climate___ Collisions with large meteorites are probably the cause of several Collisions meteorites mass extinctions mass II. Changes in the Earth Over Time II. A. Continental Drift
The idea that land masses have moved over time was first suggested by The Alfred Wegener in 1912; By the 1960s, evidence of _plate tectonics_ convinced geologists that he was right convinced Earth’s crust is divided into Earth’s solid plates about 40 km thick solid The plates float on a fluid The layer of liquid rock (_magma) layer Heat from radioactive decay in Heat Earth’s core causes convection currents convection The movement of plates is The called _continental drift___ called _continental Animation1002.swf II. Changes in the Earth Over Time II. A. Continental Drift Green=Laurasia brown=Gondwana Pangea http://life8eiml.sinauer.com/ II. Changes in the Earth Over Time B. Atmospheric Change
Earth’s atmosphere has also changed Earth’s Early atmosphere probably contained little or no free oxygen (O2). O2 began to increase when some bacteria evolved the ability to use H2O as a source of H+ ions in _photosynthesis__. O2 was a waste _photosynthesis__ product. product. _cyanobacteria___formed formed rock-like structures called _stromatolites___which are _stromatolites___which abundant in the fossil record abundant Enough O2 was liberated to allow evolution of oxidation reactions to synthesize ATP reactions II. Changes in the Earth Over Time B. Atmospheric Change
The evolution of life changed the physical nature of Earth, which in turn changed the evolution of life... in When O2 first appeared in the atmosphere it was poisonous to the anaerobic prokaryotes, but then some evolved the ability to metabolize the O2 metabolize Advantages: aerobic metabolism is faster and more energy is aerobic harvested; so aerobes replaced anaerobes in most environments harvested; Atmospheric O2 also made possible _larger and more complex cells _larger About _1.5___ billion years ago, eukaryote cells appeared About _1.5___ II. Changes in the Earth Over Time II. B. Atmospheric Change
_permian _permian extinction__ extinction__ II. Changes in the Earth Over Time II. C. Climate Change
Earth’s climate has changed over time Sometimes Earth was considerably hotter than today; sometimes colder, Sometimes with extensive glaciation with Some climate changes have been _very rapid__; extinctions caused by Some _very extinctions them appear to be “instantaneous” in the fossil record them II. Changes in the Earth Over Time D. Meteorites!
Collisions with large meteorites are probably the cause of several _mass extinctions_ _mass Evidence of impacts include large craters; molecules with helium and Evidence argon isotope ratios characteristic of meteorites, and iridium deposits argon • A meteorite is thought to have caused or meteorite contributed to the mass extinction at the end of the __cretaceous period__, 65 __cretaceous 65 mya mya • A llarge crater has been found off the arge Yucatán Peninsula in Mexico Yucatán • A massive plume of debris from the massive impact heated the atmosphere, ignited fires, and blocked the sunlight fires, • Dinosaurs went extinct and mammals Dinosaurs took over took II. Changes in the Earth Over Time E. Summary of Geological History E.
6!! 5 4 3 2 1 II. Changes in the Earth Over Time II. E. Summary of Geological History E. III. What Are the Major Events in Life’s History? III.
There was a slow start... There Earth was formed ~___________years ago (bya) Life first evolved about ~___________ Eukaryotic organisms had evolved by about ~__________ The number of individuals and species started to increase The dramatically in the late Precambrian dramatically Then things really took off... Three great evolutionary radiations occurred that resulted in Three three major faunas: three • The Cambrian explosion lead to the _______________ The _______________ • 60 million years later, the radiation that resulted in the 60 ________________________ ________________________ • After the Permian extinction, in the Triassic, the After evolution of the _____________________ evolution _____________________ III. What Are the Major Events in Life’s History? III.
Three great evolutionary radiations that resulted __________ _______________________: _______________________: III. What Are the Major Events in Life’s History? A. Precambrian Era A.
The Precambrian Era (4.5 bya - 542 mya) The For most of this era, life was microscopic, _____________lliving in For _____________ iving oceans. oceans. Eukaryotes evolved about 2/3 through the Precambrian. By the late Precambrian, soft-bodied _____________animals had By evolved. An annelid An or early arthropod? arthropod? Type of Type animal is unknown unknown III. What Are the Major Events in Life’s History? B. Paleozoic Era Paleozoic
The Cambrian Period (542-488 mya) at the beginning of the The (542-488 Paleozoic Era (542-241 mya) (542-241 O2 concentration was approaching modern levels concentration Continents formed large land masses, the largest called ____________ Continents ____________ Rapid diversification of life took Rapid place—called the ___________ ____________________ ____________________ Most of the major groups of Most animals living today appeared in the Cambrian, including: arthropods, mollusks, echinoderms, mosses, vertebrates, cnidarians, etc. vertebrates, III. What Are the Major Events in Life’s History? III. B. Paleozoic Era B.
Three different Cambrian fossil beds have preserved the ___________of Three ___________of many animals—the Burgess Shale, Sirius Passet, and Chengjiang site many
Fossil from the Fossil Chengjiang site, in China China Arthropod Mollusk Arthropod
Fossils from the Burgess Shale in British Columbia, Canada Canada III. What Are the Major Events in Life’s History? III. B. Paleozoic Era B.
___________________ (416-359 mya) (416-359 Club mosses, horsetails, and tree ferns common in terrestrial habitats; roots accelerated soil formation accelerated ____________________began to occupy began land land III. What Are the Major Events in Life’s History? B. Paleozoic Era B. __________________ __________________ (359-297 mya) (359-297 Swamps of giant Swamps horsetails and treehorsetails ferns (made the fossil ferns fuels we use today) fuels III. What Are the Major Events in Life’s History? B. Paleozoic Era B. Carboniferous period Carboniferous (359-297 mya) (359-297 Gigantic insects! Like Gigantic the 3-foot long dragonfly, __________ __________
(some argue that the O2 content of the atmosphere must have been 30% to support them, but this is controversial) controversial) BBC Walking with Monsters: Life Before Dinosaurs http://www.youtube.com/watch?v=AsQV2wDb2k0 BBC http://www.youtube.com/watch?v=AsQV2wDb2k0 III. What Are the Major Events in Life’s History? B. Paleozoic Era B.
The lineage leading to mammals diverged from __________________ Near the end of the ________________(297-251mya) of the Paleozoic Near ________________(297-251mya) era, massive volcanic eruptions poured lava over large areas of Earth era, Volcanic ash blocked sunlight and caused climate cooling, resulting in Volcanic the largest glaciers in Earth’s history the III. What Are the Major Events in Life’s History? III. C. Mesozoic Era Mesozoic
At the start of the Mesozoic era (542-251 mya), the surviving organisms (542-251 the inhabited a relatively empty world inhabited The continents began to drift apart, so the biota became increasingly The __________________, with distinct biota’s evolving on each continent __________________ ________(251-200 mya): A great radiation of reptiles began, which gave (251-200 rise to dinosaurs, birds and crocodilians rise Jurassic (200-145 mya): Bad-ass predatory dinos on 2 legs ______ _____________, flowering plants _____________, ______________(145-65 mya): Another mass extinction at the end of the (145-65 Cretaceous was caused by a meteorite (in the Yucatán); all land animals larger than about 25 kg (including non-avian dinos) became extinct, and many insects extinct, III. What Are the Major Events in Life’s History? C. Mesozoic Era C. III. What Are the Major Events in Life’s History? D. Cenozoic Era Cenozoic
Cenozoic Era (65mya-present) is characterized by an extensive radiation of _______________ _______________ III. What Are the Major Events in Life’s History? D. Cenozoic Era D.
Tertiary Period (65-1.8 mya): Snakes, lizards, birds, and mammals underwent extensive radiations; Snakes, grasslands spread. _________________came to dominate forests except in cool regions. _________________ Evolution of symbiotic associations with N-fixing bacteria. This Evolution __________________________________________________ __________________________________________________ Mammals dispersed from Mammals Asia to North America North across the Bering land bridge (Rodents, marsupials, primates, and hoofed mammals) hoofed III. What Are the Major Events in Life’s History? III. D. Cenozoic Era D.
Quaternary Period (1.8 mya - present): Quaternary Divided into _____________and ____________________epochs Divided _____________ ____________________ The Pleistocene epoch (1.8 mya-0.01mya) was a time of drastic The cooling and climate fluctuation cooling Included four major and 20 minor “ice ages”; The last glaciers Included retreated from temperate latitudes about 15,000 years ago retreated The Pleistocene was also the The time of __________________ ______________(Homo sapiens ______________(Homo evolved 0.5-0.25 mya) evolved Many large mammal species Many became extinct in Australia and the Americas when H. sapiens H. arrived—possibly due to hunting pressure pressure III. What Are the Major Events in Life’s History? III. D. Cenozoic Era D.
We live in ________________, beginning 10,000 years ago and including all of human civilization and We are now experiencing the 6th major extinction, ________________. Animals are going extinct at 1,000 ________________. times the “regular” rate—at the same pace observed times at during the extinction of the dinosaurs! during Somewhere between 2.7 and 270 species are erased from Somewhere existence _________________. Including today. _________________ Including III. What Are the Major Events in Life’s History? D. Cenozoic Era D.
25-35% mammals, one in eight birds, one third of all amphibians and 25-35% 70% of the world’s assessed plants are in jeopardy according to the IUCN Red List; link to article in Science: http://www.sciencemag.org Science http://www.sciencemag.org ___________________: __________________: _______________: Western gorilla: population has declined by more than 60% over the last 20-25 years due to bushmeat hunting and Ebola virus Ebola Sumatran Orangutan: Sumatran threatened by habitat loss due to illegal and legal logging and forest clearance for palm oil plantations plantations Chimpanzee: recent Chimpanzee: surge in logging and bushmeat may cause extinction in wild within 15 years! within III. What Are the Major Events in Life’s History? D. Cenozoic Era D.
It’s not just the rare animals that can go extinct...
___________________ From Ohio to Gulf of From Mexico; only N. American parrot American Last bird died in 1918 Killed as agricultural Killed pests and for ladies’ hats; once populations were small, extinction likely by poultry disease likely Fed on cockleburs, Fed which have ironically become a major agricultural pest agricultural Link to story ___________________ during migration, flocks a mile during wide and 300 miles long, taking several days to pass and containing _____________birds _____________ Last bird (“Martha”) died in 1914 Link to story Link III. What Are the Major Events in Life’s History? D. Cenozoic Era D.
Some experts have estimated that up to half of presently existing Some up species may become extinct by 2100; Your kids may see this happen... happen... Why should you care? A few reasons: Why few • • _________________and an irreplaceable intellectual resource! __________________may come from nature, like penicillin, aspirin may & Taxol; only 5% of plants have been screened; we’re losing ~one valuable drug every other year. valuable ______________________ • Link to article: The Greatest Dying, about the current extinction Link The III. What Are the Major Events in Life’s History? D. Cenozoic Era D.
What are Ecosystem Services? What Ecosystem • Healthy ecosystems provide Ecosystem Services like waste Healthy Ecosystem disposal, nutrient cycling, soil formation, water purification, pollination and oxygen production. _____________________ ______________________________! Such services are best rendered by diverse ecosystems.
Example: Low water quality in NY due to destruction of Catskill Watershed . Restoration cost ~$700 million and filters the water; filtration plant would have cost __________________________ Example: Over 100,000 different animal species provide free pollination services for 1/3 of human food supply. Value from wild pollinators in the U.S. alone is _________________________ _________________________ Example: Carbon sequestration by rainforests. UN-REDD program to pay developing countries for C sequestration as an ecosystem service developing • • • • We can spent trillions of taxes and private dollars on technology to We do these things, or just protect the world’s ecosystems! or ...
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