Pre Assessment What is a Fossil?

History of Life How did Life begin? What were the conditions when earth was formed? Well, nobody was there to witness and observe. I wasn’t there! you weren’t there! Your grandma was not there either! All we have are clues from really old rocks and the atmosphere.

Molten Body Scientists that studies Earth’s life history have concluded that Earth was a molten body when it formed about 4.6 billion years ago. From the oldest rocks remaining today, scientists assume that Earth at one time had many volcanic features. Back then, Earth was a very hot place, no life could’ve survived then.

Gases Released by Volcanoes Another clue comes from Earth’s atmosphere. Scientist believe that 4.6 billion years ago Earth’s atmosphere was compose of gases released by volcanoes. Minerals found in older rocks suggest that the early atmosphere had little or no oxygen, making impossible for life to take place. Water vapor (H2O) Carbon dioxide (CO2) Sulfur Dioxide (SO2) Carbon monoxide (CO) Hydrogen Sulfide (H2S) Hydrogen Cyanide (HCN) Nitrogen (N) Hydrogen (H2) No Oxygen

Earth Now and Then Eventually Earth cooled down, and liquid water appeared on the surface, forming oceans.

The Fossil Record A Fossil is any preserved evidence of an organism. Only organism that are buried rapidly in sediments are readily preserved. Plants, animals and bacteria can form fossils. Answer to pre-assessment

Fossil Formation Fossils do not form in igneous rocks. Most fossils are formed in sedimentary rocks. When an organism dies, it is buried by sediments. Sediments build up in layers, eventually encasing the remains in sedimentary rocks.

Law of Superposition The law of Superposition, states that younger layers of rocks are deposited on top of older layers. Newspaper demonstration Radiometric dating uses the decay of radioactive isotopes to measure the age of a rock. Relative dating is a method used to determine the age of the rocks by comparing them with those in other layers.

Geologic Time Scale Events to remember: Geologic time scale is a model that expresses the major geological and biological events in Earth’s history. (book p.397) Events to remember: Mass extinction after the Cenozoic era. Mass extinction after the Mesozoic era. Mass extinction after the Silurian period, during the Paleozoic era.

The Origin of Life Section 14.2 Spontaneous Generation Theory of biogenesis Miller and Urey Experiment Endosymbiont Theory

Spontaneous generation is the idea that life arises from nonlife. Chapter 14 The History of Life 14.2 The Origin of Life Origins: Early Ideas Spontaneous generation is the idea that life arises from nonlife. Francesco Redi, an Italian scientist, tested the idea that flies arose spontaneously from rotting meat.

In 1668 Francesco Redi, observed in his experiment that maggots appeared only in flasks that were open to flies. He proved that flies and maggots did not arise spontaneously from rotting meat. The idea of spontaneous generation was not completely rejected until the mid-1800s.

Chapter 14 The History of Life 14.2 The Origin of Life The theory of biogenesis states that only living organisms can produce other living organisms. Louis Pasteur designed an experiment to show that biogenesis was true even for microorganisms.

Chapter 14 The History of Life 14.2 The Origin of Life Stanley Miller and Harold Urey were the first to show that simple organic molecules could be made from inorganic compounds. Later, scientists found that hydrogen cyanide could be formed from even simpler molecules in simulated early Earth environments. Hydrogen cyanide can react with itself to eventually form adenine, a nucleotide base in the genetic code.

In 1953, Miller and Urey built a glass apparatus to simulate the early Earth conditions. They filled with water and gases that they thought had made up the early atmosphere. The water was boiled and electric discharges were used to simulate lightening as energy source. The resulting mixture contained a variety of organic compounds, including amino acids

The building block of which macromolecule? __________________ The Miller-Urey experiment showed that organic molecules important to life could be produced from gases that made up the atmosphere of early Earth. Further confirmation- in 1970 a meteorite was found to contain 7 amino acids, two of which are not found in living things on Earth. Review: What is an Amino Acid? The building block of which macromolecule? __________________

Chapter 14 The History of Life 14.2 The Origin of Life Cellular Evolution Scientists hypothesize that the first cells were autotrophic and prokaryotes. Many scientists think that modern prokaryotes called archaea are the closest relatives of Earth’s first cells.

Previous knowledge review: What is the difference between Eukaryotic and prokaryotic cells?

Photosynthesizing Prokaryotes Chapter 14 The History of Life 14.2 The Origin of Life Photosynthesizing Prokaryotes Archaea are autotrophic. Review: What are autothrophs? They do not obtain their energy from the Sun. Archaea also do not need or produce oxygen. They are also called extremophiles because they can live in ______________

Chapter 14 The History of Life 14.2 The Origin of Life Many scientists think that photosynthesizing prokaryotes evolved not long after the archaea. Prokaryotes, called cyanobacteria, have been found in rocks as old as 3.5 billion years. Cyanobacteria, which are photosynthetic, converted the Earth’s early atmosphere from anoxia to one which contained free oxygen

The Endosymbiont Theory Chapter 14 The History of Life 14.2 The Origin of Life The Endosymbiont Theory The ancestors of eukaryotic cells lived in association with prokaryotic cells. The relationship between the cells became mutually beneficial, and the prokaryotic symbionts became organelles in eukaryotic cells. This theory explains the origin of chloroplasts and mitochondria.

Chapter 14 The History of Life 14.2 The Origin of Life

Foldable Activity

Post Assessment true or false: The theory of biogenesis states that only living organisms can produce other living organisms

Let’s Review What We Cover so Far!!

Which is an example of the theory of spontaneous generation? Chapter 14 The History of Life Chapter Diagnostic Questions Which is an example of the theory of spontaneous generation? Tadpoles become frogs. A starfish can grow from a severed arm. Damp hay and corn create mice. From a tiny acorn, an oak can grow.

What gas do scientists think was absent from Earth’s early atmosphere? Chapter 14 The History of Life Chapter Diagnostic Questions What gas do scientists think was absent from Earth’s early atmosphere? sulfur nitrogen oxygen water vapor

In which type of rock do paleontologists search for fossils? Chapter 14 The History of Life 14.1 Formative Questions In which type of rock do paleontologists search for fossils? igneous metamorphic sedimentary volcanic

Which dating method determines the age of Chapter 14 The History of Life 14.1 Formative Questions Which dating method determines the age of rocks by comparing them to rocks in other layers? absolute dating geological dating relative dating sedimentary dating

At one time people believed that mold growing Chapter 14 The History of Life 14.2 Formative Questions At one time people believed that mold growing on a piece of cheese was created by the cheese. This is the idea of __________. biogenesis transgenesis primordial generation spontaneous generation

According to the endosymbiont theory, what may Chapter 14 The History of Life 14.2 Formative Questions According to the endosymbiont theory, what may have happened to a prokaryotic cell that entered a host cell? It was digested by the host cell. It became an organelle in the host cell. It became a harmful parasite in the host cell. It was removed from the host cell by exocytosis.

An ancient prokaryote containing photosynthetic Chapter 14 The History of Life 14.2 Formative Questions An ancient prokaryote containing photosynthetic pigments that was engulfed by a host cell may have become a _________. chloroplast lysosome centriole ribosome

Use the illustration to infer what Pasteur’s experiment showed? Chapter 14 The History of Life Chapter Assessment Questions Use the illustration to infer what Pasteur’s experiment showed?

Tilted bottles often spill. Microorganisms do not grow in flasks. Chapter 14 The History of Life Chapter Assessment Questions Tilted bottles often spill. Microorganisms do not grow in flasks. Sterile liquids cannot spoil. Microorganisms can enter the tilted flask.

Which factor made it unlikely that life existed on Chapter 14 The History of Life Standardized Test Practice Which factor made it unlikely that life existed on Earth 4 billion years ago? absence of oxygen absence of food intense heat intense sunlight

In this experiment using water and the gases to simulate Earth’s early Chapter 14 The History of Life Standardized Test Practice In this experiment using water and the gases to simulate Earth’s early atmosphere, which was not one of the final products?

amino acids nucleotides RNA molecules sugar molecules Chapter 14 The History of Life Standardized Test Practice amino acids nucleotides RNA molecules sugar molecules

Why do scientists believe that archea are Chapter 14 The History of Life Standardized Test Practice Why do scientists believe that archea are the closest relatives to Earth’s first cells? They are eukaryotes. They contain DNA. They carry out photosynthesis. They live in extreme environments.