How Did Life Originate Remember The Origin Of

How Did Life Originate?

Remember: The Origin Of The Earth Ø ~4. 6 Billion years the earth was formed Ø ~3. 4 Billion years ago the first organisms appear l These blue-green algae made oxygen, which began to accumulate in the atmosphere.

Theories on the Origin of Life Ø Spontaneous Generation Ø Biogenesis Ø Divine Origins Ø Meteorites Ø “Primordial Soup”

Spontaneous Generation l The idea that organisms simply “appear” from non – living matter • Example: Maggots arose from rotting meat

Do not write the examples!!!!!! Examples of Spontaneous Generation copyright cmassengale 5

Example #1 Ø 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 copyright cmassengale 6

Example #1 Conclusion: It was perfectly obvious to people back then that muddy soil gave rise to the frogs copyright cmassengale 7

Example #2 Ø 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. copyright cmassengale 8

Example #2 Conclusion: It was obvious to them that the mice came from the moldy grain. copyright cmassengale 9

Example #3 Ø 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. copyright cmassengale 10

Example #3 Conclusion: Obviously, all the sewage and garbage turned into the rats. copyright cmassengale 11

Example #4 Ø 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. copyright cmassengale 12

Example #4 Conclusion: Obviously, the rotting meat that had been hanging in the sun all day was the source of the flies. copyright cmassengale 13

Spontaneous Generation was disproved in 1668 by Francesco Redi, an Italian physician: • Used 3 samples of rotting flesh placed in flasks • open to air • sealed • covered with gauze • Maggots were generated in the open container, where flies had access to meat and were able to lay their eggs

Redi’s Experiment Evidence against spontaneous generation: 1. Unsealed – maggots on meat 2. Sealed – no maggots on meat 3. Gauze – few maggots on gauze, none on meat

Redi’s experiments led to a new theory ØBiogenesis: l Life can only come from preexisting life.

More conclusive evidence for biogenesis Ø Louis Pasteur -1864 l Experiment showed that life did not spontaneously appear

Pasteur’s experiment: 1. Meat broth was boiled in a flask to kill microorganisms 2. The neck of the flask was heated and bent into the shape of an S 3. Microorganisms could not get into broth because they would settle in S shaped neck before contact with broth 4. No growth was in discovered in the broth 5. Broth was tilted into the S component and microorganisms contaminated broth and grew

Diagram of Pasteur’s experiment

Divine Origins Ø Christianity Ø Judaism Ø Islam Ø Etc. Ø Each has their own belief of where life came from.

Or… Meteorite theory Life came from space on comets l There is some evidence! l • September 28, 1969 Murchison, Australia l Meteorite shower fell • Analysis determined it was carbon rich • Many organic compounds • Many of the protein amino acids found in biological systems http: //meteorites. asu. edu/images/education/allende-big. jpg Image provided by NASA JPL

Primordial Soup Theory l l Says that there was just the right mixture of chemicals on Earth, and life just appeared. Right time, right place! Believe it or not, there is some experimental evidence for this, too. http: //en. wikipedia. org/wiki/Image: Miller-Urey_experiment_en. png#file

Dr. Stanley Miller and Dr. Harold Urey-1953 • Put the following ingredients into an elaborate flask apparatus: • ammonia (NH 3) • methane (CH 4) • water (H 2 O) • hydrogen (H 2) • Electricity was passed through the apparatus • Amino Acids, sugars, and other small organic molecules were synthesized – the basis of life!

Which Theory Do You Think Is Correct? Ø The pros and cons to each theory l What evidence is there to support or disclaim a theory • For example: Fossil records Ø Could there be another theory?