Origin of Life and Evolution CP Biology 2013-2014
Origin of Life • Spontaneous Generation • ___________________________ • Proposed the theory of ____________________________ • Also called ____________________________ • Idea that living things can arise from nonliving matter • Idea lasted almost 2000 years
Example #1 • Observation:Every year in the spring, the Nile River flooded areas of Egypt along the river, leaving behind nutrient-rich mud that enabled the people to grow that year’s crop of food. However, along with the muddy soil, large numbers of frogs appeared that weren’t around in drier times
Example #1 • Conclusion: It was perfectly obvious to people back then that muddy soil gave rise to the frogs
Example #2 • Observation:In many parts of Europe, medieval farmers stored grain in barns with thatched roofs (like Shakespeare’s house). As a roof aged, it was not uncommon for it to start leaking. This could lead to spoiled or moldy grain, and of course there were lots of mice around.
Example #2 • Conclusion:It was obvious to them that the mice came from the moldy grain.
Example #3 • Observation:In the cities centuries ago, there were no sewers, no garbage trucks, no electricity, and no refrigeration. Sewage flowed down the streets, and chamber pots and left over food were thrown out into the streets each morning. Many cities also had major rat problems and a disease called Bubonic plague.
Example #3 • Conclusion:Obviously, all the sewage and garbage turned into the rats.
Example #4 • Observation:Since there were no refrigerators, the mandatory, daily trip to the butcher shop, especially in summer, meant battling the flies around the carcasses. Typically, carcasses were “hung by their heels,” and customers selected which chunk the butcher would carve off for them.
Example #4 • Conclusion:Obviously, the rotting meat that had been hanging in the sun all day was the source of the flies.
Abiogenesis Recipes • Recipe for bees: • Kill a young bull, and bury it in an upright position so that its horns protrude from the ground. After a month, a swarm of bees will fly out of the corpse.
Abiogenesis Recipes • Recipe for mice: Place a dirty shirt or some rags in an open pot or barrel containing a few grains of wheat or some wheat bran, and in 21 days, mice will appear. There will be adult males and females present, and they will be capable of mating and reproducing more mice.
Origin of Life • In 1668, Francesco Redi, an Italian physician, did an experiment with flies and wide-mouth jars containing meat Evidence against spontaneous generation: 1.Unsealed –_____________________________ 2.Sealed –_____________________________ 3. Gauze –_____________________________ The results of this experiment disproved the idea of spontaneous generation for larger organisms, but people still thought microscopic organisms like algae or bacteria could arise that way.
The Scientific Method • Observation • Hypothesis • Experiment • Accept, Reject, or Modify hypothesis
Origin of Life • Disproving Spontaneous Generation • Pasteur • Hypothesis:Microbes come from cells of organisms on dust particles in the air; not the air itself. • Pasteur put broth into several special ________________________ • Each flask was boiled and placed at various locations
How Do Microbes Arise? • By 1860, the debate had become so heated that the Paris Academy of Sciencesoffered a prize for any experiments that would help resolve this conflict • The prize was claimed in 1864 by Louis Pasteur, as he published the results of an experiment he did to disproved spontaneous generation in microscopic organisms
Pasteur's Problem • Hypothesis:Microbes come from cells of organisms on dust particles in the air; not the air itself. • Pasteur put broth into several special S-shaped flasks • Each flask was boiled and placed at various locations
Pasteur's Experiment - Step 1 • S-shaped Flask • Filled withbroth • The special shaped was intended to trap any dust particles containing bacteria
Pasteur's Experiment - Step 2 • Flasksboiled • Microbes Killed
Pasteur's Experiment - Step 3 • Flask left at various locations • Did not turn cloudy • Microbes not found • Notice the dust that collected in the neck of the flask
The Theory of Biogenesis • Pasteur’s S-shaped flask kept microbes out but let air in. • Proved microbes only come from other microbes (life from life) - biogenesis Figure 1.3
Modern Ideas of Origin of Life • Testable vs. Non-testable • Page 388 • Special Creation • Was life created by a supernatural or divine force? • not testable • Extraterrestrial Origin • Was the original source of organic (carbon) materials comets & meteorites striking early Earth? • testable • Spontaneous Generation • Did the original organisms on Earth spontaneously appear? • testable • Spontaneous Abiotic Origin • Did life evolve spontaneously from inorganic molecules? • testable
Biogenesis • Scientists have accepted the concept of biogenesis for more than 100 years. • It does not however, answer the question; How did life begin on Earth? • No one has yet scientifically proven how life on Earth developed, however, scientists have developed theories by testing scientific hypothesis about early Earth.
Formation of simple organic molecules. • Scientists hypothesize that two major developments must have preceded life on earth • ________________________containing carbon must have formed. • ________________________________________________into complex organic molecules like proteins, carbohydrates, and nucleic acids that are essential to life.
Modern Ideas on Origin of Life • Oparin • Miller and Urey
Early Earth’s Atmosphere • Contained __________________________ • Instead, composed of • _________________________ • _________________________ • _________________________ • _________________________ • _________________________ • But how could life have possibly formed from this?!
1930 Alexander Oparin • Hypothesized that life began in the oceans. • He said that energy from the sun, lightning, and Earth’s heat triggered chemical reactions to produce organic molecules. • These got washed into oceans to form a ___________________________
1953 Miller and Urey • Tested Oparin’s hypothesis by simulating the conditions of early Earth. They then sent an electric current that simulated lightning through the mixture. • Then they cooled it to produce rain and left it for a week. • They found several kinds of amino acids and sugars and used this to support Oparin’s hypothesis.
Water vapor Mixture of gases ("primitive atmosphere") Condenser Water Condensed liquid with complex, organic molecules Heated water ("ocean") Origin of Organic Molecules CH4 H2 NH3
It’s ALIVE! Stanley Miller University of Chicago produced -amino acids -hydrocarbons -nitrogen bases -other organics
What is the second thing that needed to happen? • __________________________________________________________________________ • 1950’s experiments showed that if amino acids are heated without oxygen they link and form proteins. • This convinced many scientists that complex organic molecules might have originated in pools of water.
So What Do We Know? • __________________________________________________________________________ • Protocells before that • Prokaryotes Eukaryotes
First Eukaryotes ~2 bya • Development of internal membranes • create internal micro-environments • advantage: specialization = increase efficiency • natural selection! nuclear envelope endoplasmicreticulum (ER) plasma membrane infolding of theplasma membrane nucleus DNA cell wall plasma membrane Prokaryotic cell Prokaryotic ancestor of eukaryotic cells Eukaryotic cell
Endosymbiosis • Evolution of eukaryotes • origin of mitochondria • engulfed aerobic bacteria, but did not digest them • mutually beneficial relationship • natural selection! internal membrane system aerobic bacterium mitochondrion Endosymbiosis Eukaryotic cell with mitochondrion Ancestral eukaryotic cell
Endosymbiosis Eukaryotic cell with mitochondrion • Evolution of eukaryotes • origin of chloroplasts • engulfed photosynthetic bacteria, but did not digest them • mutually beneficial relationship • natural selection! photosyntheticbacterium chloroplast mitochondrion Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion
People To Know • __________________ – spontaneous generation • __________________ – flies and maggots and jars of meat • __________________ – disproved spontaneous generation by S shaped flask. (bacteria) • __________________ – life began in the oceans – primordial soup theory • _____________________________________– simulated early Earth’s atmosphere to prove amino acids could be created.
What Changes Took Place Then? • Fossil Record made people wonder in 18th century
The Record of Life • How do we know what early Earth was like? • _________________________ • _________________________
18th Century Scientists began studying fossils and they wondered: 1. How did fossils form? 2. Why are some species extinct? 3. What is the relationship between extinct and modern species? Some scientists started coming to the conclusion that species have evolved.
How Are Fossils Formed • Page 373 Fossilization Process • Problem solving lab 14.1 page 372 ________________________________________________________________________________________________________________________________________________________________________________________________________________
Ridding ourselves of misconceptions. • Monkeys to humans. • Acquired Evolution (Lamarck)
Defining Evolution • ____________________________________________________________________________________________________________________________________________________
Ideas that species may have evolved ___________________ Evolution______________________________________
Evolution is a change over time. If 2 people out of 100 had green eyes. 100 years later, 2 people out of 100 have green eyes. Has evolution occurred? _______________ How could you change the scenario to show that evolution has occurred?
Darwin on the HMS Beagle Darwin’s Early Struggles