Overview of the Origin of Life Chapter 14

Biogenesis vs Spontaneous Generation Spontaneous generation- the thought before the 17th century, living things could come from non-living things Biogenesis=all living things come from other living things

Redi’s Experiment Italian Scientist Flies Meat Eggs No Maggots Maggots

John Needham

Spallanzani Experiment Italian Scientist #2

Pasteur’s Experiment

History of Earth

Formation of Earth 5 billion years ago the solar system was a swirling mass of gas and dust The planets are thought to have formed from violent collisions of space debris. The age of earth is approx. 4 billion years old It is based on studying the layers of sediment in the earth’s crust

Radioactive Dating Establishes the age of material All atoms of the same element have the same atomic number However, they can differ in the number of neutrons? (What is that called?)

Radioactive Dating Cont. Answer: Isotope Mass # = proton and neutrons in the nucleus Ex: Mass of carbon is 12, 6 protons and 6 neutrons Most elements have isotopes Isotopes are designated by their mass #- eg. Carbon-12 = mass of 12 How about Carbon -14?

Isotopes Isotopes have unstable nuclei They undergo radioactive decay This are called radioactive isotopes The length of time it takes for half of an isotope to decay is referred to as: Half Life The age of the material can be determined by measuring the particular radioactive isotope it contains

Example of Carbon Dating

Alexander Oparin Thought the earth was once very different and contained ammonia NH3, hydrogen gas, and water vapor. Thought these elements formed organic compounds of amino acids. Complex chemical reactions might have occurred to bring about macromolecules essential for life. (Name some?)

Harold Urey and Stanley Miller Ideas from Oparin Experiment: contained a chamber of gas, as gas circulated electric sparks, (acting as lightening) supplied the energy to drive the chemical reaction Other experiments branched off from this one including how ATP and DNA were formed. 

Molecules to Cell-like Structures Microspheres: organic molecules that spontaneously form, spherical in shape and contain protein-organized in a membrane

Coacervates COACERVATES, polymer-rich colloidal droplets, have been studied in the Moscow laboratory of A. I. Oparin because of their conjectural resemblance to prebiological entities. These coacervates are droplets formed in an aqueous solution of protamine and polyadenylic acid. Oparin has found that droplets survive longer if they can carry out polymerization reactions.

Making Coacervates Our Lab Experiment

First Life Forms 3.5 billion year old fossils found near the north pole (unicellular organisms) Why is RNA necessary and DNA must have RNA to carry out life functions? What does RNA have that DNA doesn’t (besides Uracil)?

What was the Role of RNA? Thomas Cech- unicellular eukaryotes had RNA that was able to act as an enzyme- ribozymes Life is thought to have started with self replicating RNA Competition between RNA molecules may have occurred- What does that remind you of today that contains RNA?

The 1st Prokaryotes Very little oxygen Must have been anaerobic Very small in size Most likely heterotrophic-taking organic molecules from the environment As the resources for the heterotrophs became limited autotrophs are thought to have evolved.

Archeabacteria Kingdom of Unicellular organism that thrive in harsh environments Most are autotrophic Obtain energy by chemosynthesis and not photosynthesis Chemosynthesis- Carbon dioxide is the carbon source, producing carbohydrates from inorganic sources instead of from light. Energy is obtained from inorganic molecules (sulfur)

Cyanobacteria One of the 1st photosynthetic microorganisms Able to withstand the change from carbon dioxide to oxygen The ozone formed and even though toxic to plants and humans helps to prevent UV radiation on earth. CYANOBACTERIA OZONE

FIRST EUKARYOTES Began 2-1.5 billion years ago Small eukaryotes are thought to have developed inside larger prokaryotes that were anaerobic Lynn Margulis-proposed they lived in an endosymbiotic relationship- mutually beneficial relationship Aerobic prokaryotes are thought to have produced the 1st mitochondria Later invaders thought to have given rise to chloroplasts Both chloroplasts and mitochondria contain some genetic material (single stranded circular DNA) so they are able to reproduce independently.

http://cosmology.com/Cosmology2.html

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