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.
Jan Baptista van Helmont’s 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.
SPONTANEOUS GENERATION The hypothesis that some vital force contained in or given to organic matter can create living organisms from inanimate objects. Believed then as much as you believe the Earth is round !!!!!!
The first true experiment? Open Jars with Meat Francesco Redi-1600s Italian scientist Maggots appear on meat! Closed Jars with Meat Even with different types of meat closed jars=no maggots Did this show that life did not come from non-life?
Microscopes Invented REVEALED A WHOLE NEW WORLD OF LIVING THINGS THAT APPEARED TO ARISE SPONTANEOUSLY !!!! THEY WERE CALLED “ANIMALCULES”---WE NOW KNOWTHEM ASMICROORGANISMS----
Microorganisms grow—Broth spoils ! Broth left open To air or vital force !!!!! Seal flask with Cork stopper— Microorganisms Appear !! SPONTANEOUS GENERATION EXISTS !!!!! Boiling kills micro- organisms !!!! Needhams’s Experiment—Eng clergy--1745
Spallanzani’s Experiment—Italian Priest--1767 Microorganisms grow—Broth spoils ! Broth left open To air or vital force if it exists !!!!! Seal flask with melted glass--- NO MICROORGANISMS PEOPLE DID NOT BELIEVE HIM HE SEALED OUT THE VITAL FORCE !!!!!! Drew off air to create vacuum Boiled broth
The French Academy of Sciences sponsored a contest for the best experiment either proving or disproving spontaneous generation!!!
Pasteur’s Experiment 1859 French Chemist
Pasteur disproved spontaneous generation! The French Academy of Sciences sponsored a contest for the best experiment either proving or disproving spontaneous generation!!! HE WON!!!
HERE ARE PASTEUR’S ORIGINAL FLASKS STILL ON DISPLAY AT THE PASTEUR INSTITUTE IN PARIS STILL FREE OF MICROORGANISMS
Terms to Know Prefix for life? Bio Word for beginning? Genesis Biogenesis—Living things come from living things! Prefix for without? A- Abiogenesis—Living things can come from non-living things! This is the same thing as spontaneous generation—living things can spontaneously generate from non-living things—like the recipes !!!!
Molecules of the Atmosphere Carbon Dioxide Hydrogen Cyanide (HCN)
Oparin, Aleksandr Ivanovich (1894-1980) Oparin postulated that the infant Earth had possessed a strongly reducing atmosphere, containing methane, ammonia, hydrogen, and water vapor. In his opinion, these were the raw materials for the evolution of life.
The Miller-Urey Experiment Organic molecules appear here
These are the substances found in Miller and Urey’s apparatus !
The formation of protocells Section 14.2 Summary – pages 380-385 • The work of American biochemist Sidney Fox in 1992 showed how the first cells may have occurred. • Fox produced protocells by heating solutions of amino acids. • A protocell is a large, ordered structure, enclosed by a membrane, that carries out some life activities, such as growth and division.
The first true cells Section 14.2 Summary – pages 380-385 • For food, the first prokaryotes probably used some of the organic molecules that were abundant in Earth’s early oceans. These would be heterotrophs ! • Over time, these heterotrophs would have used up the food supply.
Section 14.2 Summary – pages 380-385 The first true cells • However, organisms that could make food had probably evolved by the time the food was gone. These would be autotrophs ! • These first autotrophs were probably similar to present-day archaebacteria.
The first true cells • Archaebacteria (ar kee bac TEER ee uh) are prokaryotic and live in harsh environments, such as deep-sea vents and hot springs. Note the similarity to early Earth!!!! Section 14.2 Summary – pages 380-385
Section 14.2 Summary – pages 380-385 The first true cells • The earliest autotrophs probably made food by chemosynthesis rather than by photosynthesis. • In chemosynthesis, autotrophs release the energy of inorganic compounds, such as sulfur compounds, in their environment to make their food.
Section 14.2 Summary – pages 380-385 Photosynthesizing prokaryotes • Photosynthesizing prokaryotes might have been the next type of organism to evolve. • As the first photosynthetic organisms increased in number, the concentration of oxygen in Earth’s atmosphere began to increase. • Organisms that could respire aerobically would have evolved and thrived.
The endosymbiont theory Section 14.2 Summary – pages 380-385 • Complex eukaryotic cells probably evolved from prokaryotic cells. • The endosymbiont theory,proposed by American biologist Lynn Margulis in the early 1960s, explains how eukaryotic cells may have arisen. • The endosymbiont theory proposes that eukaryotes evolved through a symbiotic relationship between ancient prokaryotes.
Section 14.2 Summary – pages 380-385 The endosymbiont theory A prokaryote ingested some aerobic bacteria. The aerobes were protected and produced energy for the prokaryote. Some primitive prokaryotes also ingested cyanobacteria, which contain photosynthetic pigments. Over a long time, the aerobes become mitochondria, no longer able to live on their own. The cyanobacteria become chloroplasts, no longer able to live on their own. Chloroplasts Cyanobacteria Mitochondria Aerobic bacteria Plant cell Prokaryote Animal Cell
The similarities of the mitochondrial and chloroplast organelles in the eucaryotic cell to an entire procaryotic cell are striking. They are membrane-bound structures that contain DNA, RNA, and the same kind of ribosomes. This has led many biologists to speculate on the evolutionary origin of the two organelles. Figure 2.31 summarizes some of the current thinking. The prevailing hypothesis is that certain bacteria came to be permanently associated (in symbiosis) with precursor procaryotic amoeboid cells, thus establishing the first true eucaryote.
Section 14.2 Summary – pages 380-385 The endosymbiont theory • New evidence from scientific research supports this theory and has shown that chloroplasts and mitochondria have their own DNA and ribosomes that are similar to the ribosomes in prokaryotes. • In addition, both chloroplasts and mitochondria reproduce independently of the cells that contain them.