History of Life

1. History of Life Chapter 14

2. Biogenesis • Biogenesis is the principle that all living things come from other living things • Spontaneous generation is the belief that living things arise from non-living things • Back in seventeenth century this was the explanation why maggots arise from rotten meat and fish appear in ponds

3. Francesco Redi • Italian scientist (1626-1697) that noticed and described the different forms of flies • Observed maggots turned into oval cases and flies emerge • Also observed maggots appear where adult flies landed • Created an experiment to prove his hypothesis that flies emerge from maggots

4. Francesco Redi’s Experiment • Jars were set up with meat inside and allowed to rot • Control group • The jars were exposed to the environment and notcovered at • Experimental group • Jars were covered with cloth so air can flow through, but organisms cannot enter or leave

5. Francesco Redi’s Experiment • Results • The uncovered jars that were exposed to flies had maggots growing that eventually turned into flies • The covered jars did not have any maggots or flies inside

6. LazzaroSpallanzani • Italian scientist (1729-1799) that used microscopes to observe microorganisms that could explain biogenesis • At this time, it was believed that “vitalforce” was how microorganisms arise from the air • Hypothesized that microorganisms formed from pre-existing microorganisms • Created an experiment to test his hypothesis

7. LazzaroSpallanzani’s Experiment • Boiled clear, fresh broth until the flasks filled with steam • Control group • Flask was remained open during experiment time • Experimental group • Flask was immediately covered before cooling so not to allow air or bacteria to enter

8. LazzaroSpallanzani’s Experiment • Results • The uncovered flask (control group) became contaminated with microorganisms when air entered • The experimental group flask did not have any growth • Scientists believed that boiling the broth killed the “vital force” and still continued to believe spontaneous generation

9. Louis Pasteur • French scientist (1822-1895) created an experiment to answer objections of Spallanzani’s experiment • Made a curved neck flask that allowed air into the flask, but prevented microorganisms to enter

10. Louis Pasteur’s Experiment • Started the experiment by boiling broth in the curved neck flask to kill any microorganisms inside • Left the flask to sit for one year – the broth was still clear • After a year, the neck of the flask was broken • Results • After one day being exposed to the air, the broth became contaminated with microorganisms • These results provided evidence for biogenesis and that spontaneous generation was not possible

11. Formation of Earth • Earth’s Age • The estimated age of the Earth is 4.5 billion years old • Scientists are able to explore the surface and its layers to study its geology and determine age

12. Formation of Earth • Radiometric Dating • A method of establishing the age of materials • Using isotopes (elements with more or less neutrons) of specific elements, scientists can date the age of rocks and fossils more accurately • Mass number = protons + neutrons • Isotopes have a different mass number due to change in neutrons • Radioactive decay – when isotopes have an unstable nuclei they release energy that we can calculate

13. Formation of Earth • Half-life • The length of time it takes for one-half of the same size of the isotope to decay to a stable form • Carbon-14 • All living things contain the isotope Carbon-14 in their cells • As they die, Carbon-14 decays into Carbon-12 at a known rate that scientists can calculate and determine the age of the organism • Organisms that are much older, scientists use different isotopes

14. Alexander Oparin & John Haldane • Soviet and American scientists that were able to determine the inorganic compounds found in the early atmosphere • They believed it contained • Ammonia (NH3) • Hydrogengas (H2) • Watervapor (H2O) • Methane (CH4)

15. Stanley Miller & Harold Urey • American scientists that created an experiment to explain how inorganic compounds that existed on Earth created our known atmosphere • Set up a chamber containing gases and allowed them to circulate with electric shock • Results • After going through experiment the end results were organic compounds that make up the modern day atmosphere

16. Origin of Heredity • First cells • The oldest known fossils that are thought to be cells are the size and shape of some living bacteria • Scientists believe that RNA was the first nucleic acid on Earth • Chemosynthesis • Archaea – related group of organisms that can survive under harsh conditions • Chemosynthesis – when CO2 serves as the source of energy as well as inorganic molecules like sulfur

17. Origin of Heredity • Photosynthesis & Aerobic Respiration • The ability for organisms to use inorganic matter and create oxygen gas • Cyanobacteria – most likely the earliest bacteria that created oxygen gas as a byproduct and release it into the atmosphere • After billions of years of oxygen gas forming and filling the atmosphere, O atoms reacted with O2 to form O3 which is our ozone • Without our ozone the UV light from the sun would damage our DNA and life could not have come to exist

18. The First Eukaryotes • Eukaryotes • Larger than prokaryotes • DNA is organized into chromosomes • Contain cytoskeleton and nucleus • Endosymbiosis • Theory that modern day organelles were engulfed by ancient eukaryotes and later became part of the cell’s function • Ex: chloroplast and mitochondria (contain their own DNA)