Presentation on theme: "Ideas on the Origin of Life on Earth"— Presentation transcript:
1Ideas on the Origin of Life on Earth Name___________________Ideas on the Origin of Life on EarthGeneral BiologyANSWER KEY
2Early IdeasSpontaneous generation - the idea that nonliving material can produce life.Examples:mud producing fishgrain producing micedecaying meat producing maggots
3Redi’s Experiment Effort to disprove spontaneous generation Decaying meat in uncovered control jars vs. covered experimental jars.Results: maggots and flies filled the open jars but not covered jars. Showed only flies produce flies.
4People still didn’t believe it… Although Redi disproved spontaneous generation of large organisms, many scientists thought microorganisms must arise spontaneously, probably from a vital force in the air.
6Two things must have occurred before life arose: The formation of simple organic moleculesThe organization of those molecules into more complex organic molecules such as proteins, carbohydrates, and nucleic acids.
7Earth’s Early Atmosphere Contained:Little oxygenMostly water vapor, carbon dioxide gas, nitrogen gas, methane gas, ammonia gasEnergy sources - heat from Earth’s formation, lightning, UV radiation
9Oparin’s HypothesisEnergy from the sun, lightning, and earth’s heat triggered chemical reactions to produce small organic molecules from the substances in the atmosphere. Rain washed these into the oceans, forming a “primordial soup”.
10Miller and Urey (1953)Set up a simulation of conditions on early earth.After 1 week, found they had produced several kinds of amino acids, sugars and other small organic molecules.Supported Oparin’s hypothesis.
11How did simple organic molecules form complex organic molecules? Studies in 1950’s showed that if amino acids are heated without oxygen, they form proteins. A similar process produces ATP and nucleic acids from small molecules.Therefore, this may have occurred on early earth in the warm pools of water.
12How did these molecules become CELLS? Sidney Fox: Protocells could be formed by heating solutions of amino acids.Protocell is a large, ordered structure, enclosed by a membrane, that carries out some life activities, such as growth and division.
13~LIFE BEGAN!~We have found fossils of photosynthetic prokaryotic cells from 3.5 billion years ago. However, these were probably not the first cells.Reminder:prokaryotic:example:eukaryotic:examples:
14~LIFE BEGAN!~We have found fossils of photosynthetic prokaryotic cells from 3.5 billion years ago. However, these were probably not the first cells.Reminder:prokaryotic: simple cell structure, no nucleusexample: bacteriaeukaryotic:complex cell structure, has nucleusexamples: protists, fungi, plants, animals
15The First CellsFirst cells were probably prokaryotes that evolved from protocells; didn’t need oxygen, used molecules in oceans for food.At some point, some cells developed the ability to make their own foodCHEMOSYNTHESIS - making glucose from inorganic molecules, probably near deep sea vents or in hot springs. No light needed.
16And later...Some cells developed the ability use light to perform PHOTOSYNTHESIS. This started increasing the amount of oxygen in the atmosphere.Some cells developed the ability to use oxygen through respiration.Lightning caused some oxygen (O2) to form ozone (O3).Protective layer, prevents most UV radiation from sunstopped origin of cells; enabled evolution of more complex cells.
17Evolution of Eukaryotic Cells Lynn Margulis (1960s) - Endosymbiont TheoryAncient bacteria may have “taken in” other bacteria, which evolved to become cell structures such as mitochondria and chloroplasts.Supporting Evidence:M & C have their own DNA (similar to prokaryotes)M & C have ribosomes (similar to prokaryotes)M & C reproduce independently within cells
18And finally...Over millions of years, these early cells evolved to the diversity of living things we have on Earth today!!This likely involved many, many different mutations over time. Survival was likely determined through natural selection (“survival of the fittest”).
20Time From the Present First Records of: a4.5 billion years agoorigin of the Earthb* billion years agoprokaryotic heterotrophsc*2.5-3 billion years agoprokaryotic autotrophs, first evidence of photosynthesisd1.5 billion years agounicellular (single celled) eukaryotese650 million years agomulticellular eukaryotesf400 million years agoplants invade the landg300 million years agoanimals invade the landh200 million years agofirst mammalsi150 million years agofirst dinosaursj100 million years agolast dinosaursk*100,000 years agohuman development