ORIGIN OF LIFE Theories Past and Present Nature of Early Cells Evolution of Cells RiverDell High School Biology Ms. C. Militano

I. Abiogenesis or Biogenesis ? Scientists Debate I. Abiogenesis or Biogenesis ? Scientists Debate A. Abiogenesis - life can arise from nonliving things B. Biogenesis – life can arise only from living things

C. Redi’s Experiment ( ) 1. control – uncovered jars with meat 2. experimental group – jars with meat covered with netting 3. results – maggots only in control 4. conclusion – flies come from eggs laid by other flies

Redi’s Experiments

D. Spallanzani’s Experiment ( ) 1. control – flask with boiled broth is left open 2. experimental group – flask with boiled broth is sealed immediately 3. results – open flask became cloudy closed flask remained clear 4. microrganisms came from the air

Spallanzani’s Experiment

E. Pasteur’s Experiment ( ) 1. broth boiled in a flask with a curved neck 2. after one year the broth stayed clear 3. when the necks were broken the broth became cloudy 4. conclusion – the air is the source of microorganisms

Pasteur

II. Earth’s History A. Solar System begins to form 5 billion years ago B. Sun begins to form a few million years later C. Earth forms billion years ago D. Volcanoes form earth’s atmosphere E. 2.2 billion years ago earth like today

Formation of the Solar System Began 5 billion Years Ago

Planet Earth formed 4.6 billion years ago conditions were very different 2.2 billion years ago Earth was similar to the planet we live on today

III. Evolution of Life A. Origin of Organic Compounds 1. Early atmosphere – ammonia (NH 3 ) hydrogen gas (H 2 ), water vapor (H 2 O) and methane gas (CH 4 ) 2. High temperatures, frequent volcanoes, electrical storms, and comets 3. Maybe some organic compounds came to to earth from space

Early Earth

III. Evolution of Life A. Origin of Organic Compounds 4. Oparin and Haldane a. early gases and high temperatures formed simple organic compounds that collected in water and reacted to form macromolecules necessary for life

Conditions – Early Earth

III. Evolution of Life A. Origin of Organic Compounds 5. Urey and Miller (1953) a. experiment to test Oparin’s hypotheses b. chamber with early gases and electric sparks form several organic compounds c. similar experiments formed amino acids, ATP and nucleotides

Urey-Miller Experimental Apparatus

Urey-Miller Experiment

III. Evolution of Life A. Origin of Organic Compounds 6. Other Hypotheses a. early atmosphere composed of carbon dioxide, nitrogen, hydrogen water vapor b. early life may have formed in chemicals found in thermal vents found at the bottom of the ocean

Origin of Life - Thermal Vent Hypothesis

III. Evolution of Life B. Cell Like Structures Form 1. Solutions of organic compounds can form coacervates (collection of droplets of amino acids, sugars and lipids) 2. Microspheres – spherical forms surrounded by a protein membrane 3. Both do not have all properties of life

Sidney Fox and others researched structures which may have formed early cells Sidney Fox and others researched structures which may have formed early cells

Evolution of Life C. The First Cells 1. First cells were probably anaerobic heterotrophs 2. Similar to some prokaryotes 3. Eventually competition for organic molecules gave autotrophs an adaptive advantage

Evolution of Life C. The First Cells 4. Chemosynthetic organisms evolve a. get energy from oxidation of inorganic substances b. carbon dioxide used to make organic molecules that store energy

Evolution of Life C. The First Cells - The RNA World 5. Self-replicating RNA molecules may have evolved first 6. Ribozyme – RNA that can act as a catalyst – even for self-replication 7. Maybe first case of heredity and competition

Thomas Cech The Ribozyme

Evolution of the First Cells

D. Photosynthesis Evolves 1.About 3 billion years ago 2. Organisms similar to cyanobacteria 3. Oxygen is a product that might damage some types of cells 4. Ozone layer forms from the oxygen a. reduces ultraviolet light

Present Day Ancient Cyanobacteria Cyanobacteria

Stromatolites Formed Carbon Deposits from by Cyanobacteria Ancient Cyanobacteria

Formation of the Ozone Layer Cyanobacteria release oxygen in the atmosphere O 2 is converted to O 3 (ozone) in the upper atmosphere Ozone layer blocks much of the UV light Allows life to move from the sea to land

Changes of O 3 Concentrations Between 1980 and 1991

Changes in Ozone Concentrations Between 1970 and 1998

E. Aerobic Respiration Evolves 1. More than one billion years before oxygen to reached current levels 2. Early function of aerobic respiration may have been to prevent oxygen from destroying essential organic compounds

F. Endosymbiosis Evolution of Eukaryote – 2.0 billion years ago 2. Aerobic prokaryote took residence inside a larger anaerobic prokaryote a. became the mitochondria 3. photosynthetic cyanobacteria may have evolved into chloroplasts

F. Endosymbiosis Evolution of Eukaryotes 4. Evidence of endosymbiosis a. both mitochondria and chloroplast 1) replicate independently from cell cycle 2) have their own genetic material 3) circular DNA like prokaryotes

Lynn Margulis – Theory of Endosymbiosis

Endosymbosis and Cell Evolution

Endosymbiosis and the Nucleus

Three Cell Organelles Formed by Endosymbiosis

Comparing Prokaryote and Eukaryote

Evolution From Prokaryotes to Eukaryotes The first cells were probably like Eubacteria or Archaebacteria (formely known as Monera) Unicellular eukaryotes came next Then multicellular eukaryotes evolved

Evolution of The Kingdoms

Cladogram of Evolutionary Relationships

IV. Radioactive Decay and Dating A. Isotope – atoms of the same element that differ in the number of neutrons B. Radioactive decay – process in which unstable nuclei release particles and/or energy until they are stable C. Half-life – the length of time it takes for ½ any amount of a radioactive isotope to decay

Half-lives C atoms at time 0

Half-lives C and N atoms after 5,600 years or 1 half-life

Half-lives C and N atoms after 11,200 years or 2 half-lives

Half-lives C and N atoms after 16,800 years or 3 half-lives

Half-lives C and N atoms after 22,400 years or 4 half-lives

Half-lives 8 14 C and N atoms after 28,000 years or 5 half-lives

Half-lives 4 14 C and N atoms after 33,600 years or 6 half-lives

Half-lives 2 14 C and N atoms after 39,200 years or 7 half-lives

The half-life of C-14 is 5,600 years and a sample today has 1,000 C-14 atoms, after 5,600 years  500 C-14 atoms will remain (1/2 original amount) After two half lives (11,200 years)  250 C-14 atoms will remain (1/4 original amount) Proportion of isotope left 1/4 1/8 1/16 1 1/ Half-lives 1

IV. Radioactive Decay and Dating D. Hyphen notation of radioisotopes (element symbol and mass number) - examples (C-12, C-14, O-16, O-18) E. Carbon-14 dating – compare ratio of C-14 and C-12 and use the ratio to determine age

IV.Radioactive Decay and Dating ISOTOPE Carbon-14 Uranium-235 Potassium-40 Uranium-238 HALF LIFE (years) 5, ,000,000 1,250,000,000 4,500,000,000

A. Problem Solving 1. The half-life of thorium-230 is 75,000 years. If a scientist has 40.0g of thorium, how much will remain after 225,000 years?

B. Half Life Problem Solving 2. The half life of carbon-14 is 5,370 years. How long will it take for ½ of the sample to decay? 3. If a biologist has 64.0g of C-14, how long will it take until 8.0g remain un- decayed?