9.1 Geologic Time, The Fossil Record, and the Origin of Life KEY CONCEPTS VOCABULARY How old is the earth? What is the difference between spontaneous generation and biogenesis? What are the first living things on the earth? What does the fossil record tell us? Spontaneous generation Abiogenesis Fossils Carbon dating Law of superposition

Spontaneous Generation Spontaneous generation – the idea that living things arise from non-living things. Francisco Redi – performed experiments with maggots meat that disproved spontaneous generation.

Spontaneous Generation Louis Pasteur & later Lazzaro Spallazani performed similar experiments and found the same results. How does their experiment relate to science? Trials (accuracy), repeatable experiments to support results.

Biogenesis Biogenesis – law that living things only come from other living things. LIFE FROM LIFE!

Early Earth The earth formed about 4.6 BILLION years ago. The earth formed from a cloud of condensing dust and gases. The atmosphere was made of carbon dioxide, nitrogen, ammonia, methane, and water vapor. What was missing? (There was no Oxygen!) As the earth cooled, water vapor condensed into water and formed the oceans.

Origins of Life Scientists believe that living cells evolved from simple organic molecules. Alexander Oparin – developed a theory that organic molecules were created by chemical reactions stimulated by lightening and UV light on early earth. Stanley Miller and Harold Urey tested Oparin’s hypothesis in a lab and created amino acids, ATP, DNA and RNA. - these are the ingredients needed for life!

Origins of Life Simple organic molecules reacted to produce large polymers, membranes, RNA, and eventually living cells.

Origins of Life - first living cells The first living cells were heterotrophic – they obtained food by absorbing it from their environment. Hetero = “Other” Trophic = “Feeder” Ex. Microbial mats (mostly bacteria) Microbial mats are the earliest form of life on Earth for which there is good fossil evidence, from 3500 million years ago

Geologic Time Scale

Fossil Record Fossils – the remains or imprints of the remains of once-living organisms. Fossils are formed in layers of SEDIMENTARY ROCK or in VOLCANIC ASH. They can help show how life has changed over time and provide evidence for evolution.

Dating Fossils The Principal of Superposition – age is determined from a fossil’s position in rock layers. Older fossils are below younger fossils. This is a RELATIVE DATING method. Youngest Oldest

Dating Fossils Actual/Absolute AGE of fossils can be determined using radioactive dating. Carbon-14 Dating: Radioactive element carbon-14 decays into stable carbon-12. The half-life of carbon-14 is 5600 years. (time for half the carbon-14 in a sample to decay into carbon-12) By comparing the amount of carbon-14 to carbon-12 you can determine age. WHAT DOES THIS ACTUALLY MEAN? Using math & ratios Scientists can determine the actual age of a fossil!