I. History of Life on Earth

Transcription

1 Evolution

2 I. History of Life on Earth

3 I. History of Life A. Early History of Earth I. Early earth was inhospitable hot, with many volcanoes little free oxygen and lots of carbon dioxide other gases present: nitrogen, methane, ammonia, hydrogen and water vapor

4 I. History of Life B. History in Rocks Fossils are clues to the past Any trace of a species that once lived can infer the structure of the organisms, what they ate, what ate them, and the environment that they lived in Paleontologists- detectives to the past scientists who collect, study and classify fossils

5 I. History of Life Fossils occur in sedimentary rock sedimentary rock is formed when exposure to rain, heat, wind and cold breaks down existing rock into small particles of sand, silt and clay. The particles are carried by streams and rivers into lakes or seas where they eventually settle to the bottom. As layers of sediment build up over time, dead organism may also sink to the bottom and become buried. The weight of layers of sediment gradually compresses the lower layers and along with chemical activity, turns into rock

6 Non-rock fossils I. History of Life Fossils can be found in ice Ex. Woolly Mammoth preserved in ice Fossils can be found in amber Organisms preserved in amber Amber is a form of tree resin exuded as a protective mechanism against disease and insect infestation that has hardened and been preserved in the earth s crust for millions of years

7 I. History of Life C. Age of a fossil Relative Dating oldest fossils are in deepest layers paleontologists can compare fossils with that of older fossils

8 C. Age of a Fossil Radiometric Dating I. History of Life Use of radioactive isotopes in rocks to date fossils The technology of radiometric dating provides evidence that the earth is at least 4.5 billion years old Certain elements convert to other elements at known rates, which can be measured, thus revealing the age of the specimen One half Potassium40 decays to Argon40 in about 1.3 billion years Carbon 14 decays to half of its original amount in 5730 years

9 Bacteria were the earliest life Formed colonies called stromatolites (age 3.5 billion years old) Best colonies in Australia

10 Era Period Million Years Ago Major Events Major Life Forms Precambrian 3500 Life evolves Photosynthetic bacteria 3000 Prokaryotes 2000 Eukaryotes Paleozoic Cambrian 540 Invertebrates Ordovician 510 First Invertebrates Silurian 439 First land plants Devonian 408 First Amphibians Carbonifero us 362 First reptile Permian 290 Conifers dominant Mesozoic Triassic 245 First dinosaurs First mammals Jurassic 208 First birds First flowering plants Cretaceous 146 Dominant flowering plants Cenozoic Tertiary 66 Quaternary 1.8 Humans

11 II. Origins of Life

12 II. Origins of Life A. Origins: The Early Ideas Spontaneous generation - non-living material can produce life Disproved by Redi experiment meat and maggots

13 II. Origins of Life Disproved by Pasteur - S flask experiment boils broth in S flask broth is free of microorganisms for a year removes curved neck broth is teeming with microorganisms Biogenesis - living comes from living things.

14 II. Origins of Life B. Modern Ideas Oparin - suggested sun, lightning, and molecules such as water vapor, carbon dioxide, nitrogen, methane and ammonia formed a primordial soup that was the beginning of simple organic molecules

15 II. Origins of Life Miller and Urey Tried to answer the question by simulating conditions on the early Earth Filled flask with hydrogen, ammonia, methane, and water = atmosphere They passed electric sparks through the mixture to simulate lightning Within a few days amino acids were present - the building blocks of protein

16 II. Origins of Life

17 II. Origins of Life Sidney Fox - showed how sort chains of amino acids could cluster to form protocells Experiments like Miller and Urey s are currently studied at major universities Georgia Tech University of Michigan

18 II. Origins of Life C. Evolution of Cells (based on fossil record) First true cells - were probably prokaryotic, autotrophic and anaerobic single celled no nucleus consumed food for energy did not need oxygen to survive Then came chemosynthetic organisms Then autotrophs - were probably archaebacteria that live in harsh environments Next came photosynthetic prokaryotes - releases oxygen into atmosphere

19 II. Origins of Life Endosymbiotic theory Proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms - Lynn Margulis of Boston University

20 II. Origins of Life Endosymbiotic Theory Explained: Mitochondria and chloroplasts contain DNA similar to bacterial DNA. Mitochondria and chloroplasts have ribosomes whose size and structure resemble those of bacteria Like bacteria, mitochondria and chloroplasts reproduce through binary fission Eukaryotic cells evolved from prokaryotic cells

21 Endosymbiotic Theory Endo = Into Symbiosis = relationship of two organisms living close together According to the theory of endosymbiosis eukaryotic cells evolved when aerobic eubacteria either infected or were engulfed by a larger host cell and later established a symbiotic relationship

22 III. Natural Selection and Evidence for Evolution

23 History of the Theory of Evolution Darwin s Role u/evosite/history/index.sht ml