The History of Life Chapter 14

Early Earth Was inhospitable! Very hot due to: Meteoric impact Volcanic eruptions Radioactive decay Early atmosphere contained: Mostly water vapor, nitrogen, and carbon dioxide Almost no oxygen.

Early Earth Timeline ~4.6 bya: Formation of the Earth ~4.6 bya: Formation of the Earth ~4.5 bya: Formation of the moon ~4.5 bya: Formation of the moon ~4.0 bya: Earth begins to cool ~4.0 bya: Earth begins to cool ~3.9 bya: ~3.9 bya: Oldest rocks Oldest rocks Primordial oceans begin to form Primordial oceans begin to form ~3.8 bya: First prokaryotic organisms ~3.8 bya: First prokaryotic organisms ~2.5 bya: First stable continents ~2.5 bya: First stable continents ~2.1 bya: First eukaryotic organisms ~2.1 bya: First eukaryotic organisms

Fossils Over 99% of the organisms that have ever lived on this Earth are now extinct!! Over 99% of the organisms that have ever lived on this Earth are now extinct!! We know about these organisms by impressions left in rocks, amber and ice. We know about these organisms by impressions left in rocks, amber and ice.

Dating Techniques Relative Dating Relative Dating Places items in sequence Places items in sequence No exact date is assigned No exact date is assigned Numeric Dating Numeric Dating Provides an actual date Provides an actual date Radioactive Dating: utilizes radioactive isotopes of elements. Radioactive Dating: utilizes radioactive isotopes of elements.

Geologic Time Scale

Early Theories on the Origin of Life Spontaneous Generation Spontaneous Generation Idea that nonliving material can produce life Idea that nonliving material can produce life Example: Rotting meat produces flies Example: Rotting meat produces flies Biogenesis Biogenesis Idea that living organisms must come from other living organisms. Idea that living organisms must come from other living organisms.

Spontaneous Generation Italian scientist, Francisco Redi, disproved the myth, but only for larger organisms. Italian scientist, Francisco Redi, disproved the myth, but only for larger organisms.

Biogenesis But scientists still believed that maybe microorganisms arose spontaneously from the air. But scientists still believed that maybe microorganisms arose spontaneously from the air. French scientist, Louis Pasteur, finally disproved spontaneous generation by designing an experiment where air but no organisms were allowed to contact a nutrient broth…nothing grew! French scientist, Louis Pasteur, finally disproved spontaneous generation by designing an experiment where air but no organisms were allowed to contact a nutrient broth…nothing grew!

Pasteur’s Experiment

Modern Theories Two developments must have preceded life on Earth Two developments must have preceded life on Earth Formation of organic (carbon-containing) molecules Formation of organic (carbon-containing) molecules Formation of protocells (early cells) Formation of protocells (early cells)

Formation of Organic Molecules Simple organic molecules (carbon containing) must have formed Simple organic molecules (carbon containing) must have formed These molecules must have organized into more complex molecules like proteins, carbohydrates, lipids and nucleic acids. These molecules must have organized into more complex molecules like proteins, carbohydrates, lipids and nucleic acids. In 1930, Russian scientist, Alexander Oparin, hypothesized life began in oceans by chemical reactions with the atmosphere, lightning, and Earth’s heat to produce organic molecules. In 1930, Russian scientist, Alexander Oparin, hypothesized life began in oceans by chemical reactions with the atmosphere, lightning, and Earth’s heat to produce organic molecules.

Primordial Soup Theory Developed by Alexander Oparin. Developed by Alexander Oparin. Earth’s ancient atmosphere probably contained nitrogen, methane, and ammonia gases, but little to no oxygen. Earth’s ancient atmosphere probably contained nitrogen, methane, and ammonia gases, but little to no oxygen. Energy from sun fueled chemical reactions in the atmosphere forming organic molecules (Carbon based molecules) like amino acids Energy from sun fueled chemical reactions in the atmosphere forming organic molecules (Carbon based molecules) like amino acids These molecules were then washed into the oceans making a primordial soup of organic molecules These molecules were then washed into the oceans making a primordial soup of organic molecules Eventually these proteins, lipids, and other organic molecules formed the first cells. Eventually these proteins, lipids, and other organic molecules formed the first cells.

Miller and Urey’s Experiment In 1953, American scientists, Stanley Miller and Harold Urey tested Oparin’s hypothesis. In 1953, American scientists, Stanley Miller and Harold Urey tested Oparin’s hypothesis. Their result was the formation of amino acids, sugars and other simple organic molecules. Their result was the formation of amino acids, sugars and other simple organic molecules. This supported Oparin’s hypothesis. This supported Oparin’s hypothesis.

Formation of Protocells Various experiments during the 1950’s showed how complex organic molecules might have formed from small organic molecules in pools of heated water. Various experiments during the 1950’s showed how complex organic molecules might have formed from small organic molecules in pools of heated water. American scientist, Sidney Fox, provided a mechanism to explain the formation of protocells. American scientist, Sidney Fox, provided a mechanism to explain the formation of protocells. A protocell is a large, ordered structure, enclosed by a membrane, that carries out some life activities such as growth and division. A protocell is a large, ordered structure, enclosed by a membrane, that carries out some life activities such as growth and division.

Evolution of the Cell First cells were prokaryotes that may have evolved from protocells. First cells were prokaryotes that may have evolved from protocells. They were anaerobic organisms, meaning they lived in the absence of oxygen. They were anaerobic organisms, meaning they lived in the absence of oxygen. They were also heterotrophs, meaning they obtained food rather than making it themselves. They were also heterotrophs, meaning they obtained food rather than making it themselves.

First Autotrophs Auto means self ; troph means energy Auto means self ; troph means energy Were probably similar to today’s archaebacteria: prokaryotic chemosynthetic organisms found in harsh conditions such as deep sea vents. Were probably similar to today’s archaebacteria: prokaryotic chemosynthetic organisms found in harsh conditions such as deep sea vents. Chemosynthesis is the process of releasing energy from inorganic compounds such as H 2 S. Chemosynthesis is the process of releasing energy from inorganic compounds such as H 2 S.

First Photosynthetic Organisms Are responsible for the first atmospheric oxygen. Are responsible for the first atmospheric oxygen. Were also prokaryotes. Were also prokaryotes. Also responsible for the ozone layer. Also responsible for the ozone layer. The ozone layer provided protection against high energy radiation such as UV and gamma rays. The ozone layer provided protection against high energy radiation such as UV and gamma rays. This allowed organisms to move on to land. This allowed organisms to move on to land. This allowed for more aerobic organisms. This allowed for more aerobic organisms.

Endosymbiont Theory Proposed in the 1960’s by American biologist, Lynn Margulis. Proposed in the 1960’s by American biologist, Lynn Margulis. Explains how eukaryotic cells may have arisen. Explains how eukaryotic cells may have arisen. States that: States that: Mitochondria and chloroplasts were actually once prokaryotic cells. (They both have their own DNA similar to prokaryotic DNA.) Mitochondria and chloroplasts were actually once prokaryotic cells. (They both have their own DNA similar to prokaryotic DNA.) A cell ingested these bacteria and the bacteria were protected while providing energy for the cell. Eventually the bacteria could no longer live on their own, and the eukaryotic cell evolved. A cell ingested these bacteria and the bacteria were protected while providing energy for the cell. Eventually the bacteria could no longer live on their own, and the eukaryotic cell evolved.