How do we know how old things are?
Radiometric Dating: The use of radioactive isotopes as a
measure for determining the age of a rock or fossil
Radioactive isotope: an unstable form of an element that decays
into another element by radiation, that is, by
emitting energetic particles
Half-Life: the amount of time it takes for one half of a substance to decay
Uranium-238: has a half life of 4.5 billion years
Potassium-40: has a half life of 1.3 billion years
Stromatolites: are about 3.5 billion years old, calcareous mound built up
of layers of lime-secreting cyanobacteria and trapped
sediment, found in Precambrian rocks as the earliest known
fossils, and still being formed in lagoons in Australasia.
Prokaryotes: about 3.5 billion years ago, a microscopic single-celled
organism that has neither a distinct nucleus with a
membrane nor other specialized organelles.
Prokaryotes include the bacteria and cyanobacteria.
Bacteria and Archaea are prokaryotes, the two domains of prokaryotic life.
Types of Bacteria
Cyanobacteria in Fossils
Some but not all bacteria are pathogens: a disease causing agent
Some bacteria are purely beneficial and help with symbiosis: the relationship in which two different organisms live together, often interdependently.
Cell Division in Bacteria is Called Binary Fission
The other domain of prokaryotic life, tend to live in extreme environments
Grouped according to where they live (pg 371):
Archaea in hydrothermal vents:
The sea floor is an anaerobic environment, no oxygen
The beginnings of life in hydrothermal vent
The heated fluids rise back to the surface through openings in the seafloor. Hydrothermal fluid temperatures can reach 400°C (750°F) or more, but they do not boil under the extreme pressure of the deep ocean.
As they pour out of a vent, the fluids encounter cold, oxygenated seawater, causing another, more rapid series of chemical reactions to occur. Sulfur and other materials precipitate, or come out of solution, to form metal-rich towers and deposits of minerals on the seafloor.
Deep Sea Research Affects Engineering today:
Life in Hydrothermal Vents
Evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms.
That prokaryotes ate a mitochondria and kept it around, some ate a chloroplast and became plants (pg. 391)
Endosymbiotic theory deals with the origins of mitochondria and chloroplasts, two eukaryotic organelles that have bacteria characteristics. Mitochondria and chloroplasts are believed to have developed from symbiotic bacteria, specifically alpha-proteobacteria and cyanobacteria, respectively.
Mitochondria: an organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur. It has a double membrane, the inner layer being folded inward to form layers (cristae).
Mitochondria origin: The endosymbiotic hypothesis for the origin of mitochondria (and chloroplasts) suggests that mitochondria are descended from specialized bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm.
SO Mitochondria and Chloroplasts were bacteria billions of years ago.
They have their own DNA
Mitochondria and chloroplasts have striking similarities to bacteria cells.
Mitochondrial DNA (mtDNA or mDNA): is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP).
Mitochondrial DNA is double-stranded like cellular DNA in prokaryotes. However it is circular and similar in size and structure to the single DNA loops found in prokaryotes like bacteria.
Mitochondria and Chloroplasts can no longer live outside the eukaryotic cell, and cells cannot live without mitochondria or chloroplasts because that is how they get ATP.
Over millions of years of evolution, mitochondria and chloroplasts have become more specialized and today they cannot live outside the cell.
They are now interdependent/codependent
Cells would only be able to obtain energy from anaerobic respiration (in the absence of oxygen)
So mitochondria helped get archaea out of the hydrothermal vents
Evidence obtained so far indicates that the Bacteria and Archaea diverged from a common ancestor about 3.7 billion years ago, and somewhat later the Archaea diverged from the lineage that would become the Eukarya.
Around 2 billion years ago, archaea and bacteria found a way to share genes or merge some of their material and a third kingdom of life, eukaryotes, was born.
Mitochondria know both aerobic and anaerobic respiration: When oxygen is present, the mitochondria will undergo aerobic respiration which leads to the Krebs cycle.
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Learning about Exremeophiles can help us get clues about life on other planets