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Early Origins. Chapter 19.1 & 19.3. How Did Life Begin?. The ideas presented here are hypotheses. The evidence for life’s origin’s are speculative and difficult to find (since these events occurred much further back in Earth’s history). Early Earth.

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Early origins

Early Origins

Chapter 19.1 & 19.3


How did life begin
How Did Life Begin?

  • The ideas presented here are hypotheses.

  • The evidence for life’s origin’s are speculative and difficult to find (since these events occurred much further back in Earth’s history)


Early earth
Early Earth

  • Early Scientists hypothesized that the Earth’s early atmosphere was rich in ammonia, methane, water vapor, and hydrogen.

  • Earth’s atmosphere lacked oxygen


How did life begin1
How Did Life Begin?

  • Step 1: Formation of the building blocks of life

  • Step 2: Formation of cells

  • Step 3: Formation of a reliable CODE for building proteins


Step 1 formation of the building blocks of life
Step 1: Formation of the Building Blocks of Life

  • Can the components of living organisms form all by themselves from simple chemicals? YES

  • The Miller-Urey experiment demonstrated how cellsformed all by themselves.


Step 1 formation of the building blocks of life1
Step 1: Formation of the building blocks of life

  • Miller-Urey Experiment:

  • Miller and Urey placed Ammonia, Water, Methane, and Hydrogen gases into a device.

  • To simulate lightening they used electrical sparks. Heat could also be used

  • They found organic molecules in the device after 3 days. (fats/lipids & amino acids).



Step 2 formation of cells
Step 2: Formation of cells

  • The Miller-Urey experiment did NOT yield living organisms … so how did the first cells form?

  • Experiments show that membranes can form by themselves when lipids (fats) are added to water.


Step 3 formation of a reliable code for building proteins
Step 3: Formation of a reliable CODE for building proteins

  • Cells may have formed on their own, but eventually cells would need to replicate and pass on their ability to make proteins to offspring cells.

  • Some evidence exists that the

    earliest code for building proteins

    may have been an RNA code.


Step 3 formation of a reliable code for building proteins1
Step 3: Formation of a reliable CODE for building proteins

  • RNA can code for building proteins as well as serving as enzymes to speed up other reactions.

  • Later, a DNA code developed which

    was more stable and held the protein

    code longer.


History of life on earth 19 3
History of Life On Earth 19.3

  • Earth is 4.6 billion years old

  • Fossil evidence indicates that the earliest life on Earth might have existed 3.5 billion years ago…………

  • Suggesting that it took approximately 1.1 billion years for life to evolve


Oldest fossils
Oldest Fossils

  • Stramatolites or mats of Cyanobacteria


History of life on earth
History of Life On Earth

  • The earliest life forms on Earth were prokaryotic.(before the nucleus)

  • They were also almost certainly heterotrophsearly on.  


Early history of life can be characterized by 3 developments
Early History of Life Can Be Characterized By 3 Developments

  • Development #1: Autotrophy

  • Development #2: Evolution of Eukaryotic cells

  • Development #3: Evolution of Multicellular Organisms


Development 1 autotrophy
Development #1: Autotrophy

  • Autotrophs make their own food by the process of photosynthesis.

  • The byproduct that autotrophs release into the atmosphere is oxygen.


Development 1 autotrophy1
Development #1: Autotrophy

  • Cyanobacteria were photosynthetic organisms that began adding oxygen to the atmosphere.


Development 1 autotrophy2
Development #1: Autotrophy

  • Over time oxygen built up in the atmosphere, eventually forming the Ozone Layer O3

  • The Ozone Layer blocked UV rays to allow for land life


Development 2 evolution of eukaryotic cells
Development #2: Evolution of Eukaryotic Cells

  • The evolution of some eukaryotic organelles such as chloroplasts and mitochondria can be explained by the endosymbiotic theory.


Development 2 evolution of eukaryotic cells1
Development #2: Evolution of Eukaryotic Cells

  • Endosymbiotic Theory:

  • Large Prokaryotic Cells engulfed Smaller aerobic bacteria and cyanobacteria, which then began to live inside the larger cells.

  • Aerobic bacteria are thought to give rise to the mitochondria.

  • Cyanobacteria (contain chlorophyll) are thought to give rise to chloroplasts.


Development 2 evolution of eukaryotic cells2
Development #2: Evolution of Eukaryotic Cells

  • Evidence that supports the Endosymbiotic Theory:

  • Size & Structure: Mitochondria & Chloroplasts are the same size as most bacteria

  • Genetic Material: Mitochondria & Chloroplasts contain DNA different from the nucleus

  • Reproduction: Mitochondria and Chloroplasts reproduce similarly to bacteria (binary fission)


Development 3 evolution of multicellular organisms
Development #3: Evolution of Multicellular Organisms

  • Only organisms made of eukaryotic cells can be multicellular

  • Multicellularity first developed in protists in Precambrian Time



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