Three Domains of Life

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Three Domains of Life

• Arcahaea
• Eubacteria
• Eukarya

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• Each cell type has unique characteristics

Archaea
Eukaryotic cell
Eubacteria cell
Nucleus
Organelles
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ARCHAEA AND EUBACTERIA

• Prior to 1970s, were grouped together as
  prokaryotes - still see this used.

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Archaea Recognized

• Advances in molecular biology identified Archaea
  as unique type of cells (Carl Woese, late 70s, U
  of Illinois)
• DNA is very different from bacterial DNA

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Characteristics of Archaea

• Look like Eubacteria
• rod, spiral, and marble-like shapes.
• Circular DNA
• share certain genes with eubacteria
• so they function similarly in some ways.
• share genes with eukaryotes
• so they function similarly in some ways.
• Have many genes that are completely unique

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'archae' meaning 'ancient'

• Believed to be the least evolved life forms
• Called Extremophiles due to the extreme
  conditions they live in
• similar to the conditions of early Earth
• Planets with an environment where Archaea might
  survive include Venus, Jupiter, Saturn, and
  Jupiter's moon Io, the past environment of Mars.

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EXTREME CONDITIONS
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Extremeophiles

• Live at 100 C or greater
• hot springs, sea vents
• Are Methanagens, produce methane
• Extremely alkaline or acid conditions
• digestive tracts of cows, termites, and marine
  life
• Anoxic muds of marshes and sea floors
• Petroleum deposits deep underground

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• Archaea do not require sunlight
• Do not require oxygen
• Archaea absorbs CO2, N2, or H2S
• chemically transforms them
• Give off methane gas or sulfur as a waste
  product.

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Archaea Morphology

• Size lt one micron (1µ)
• Shapes vary
• spherical (coccus)
• rod-shaped (bacillus)
• hair-like
• triangular
• square

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Archaea Morphology CONTINUDED

• May have one or more flagella
• If multiple, they attach on one side

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• No internal membranes
• DNA is a single loop called a plasmid
• tRNAs are unique
• "transfer RNA are important in decoding the
  message of DNA and in building proteins.
• Ribosomes are similar to eukaryotes.

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ARCHAEA Cell Structure

• The cell membrane surrounds the cytoplasm
• Most have a cell wall surrounding cell membrane
• a semi-rigid layer that helps maintain its shape
  and chemical equilibrium
• All three structures (cell wall, cell membrane
  and cytoplasm) are biochemically unique to
  Arcahaea

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Basic Archaea Cell Structure
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EUBACTERIA

• True Bacteria
• Found in the air, water, soil and on most moist
  surfaces
• Includes the spirochetes, gram-positive
  bacteria and cyanobacteria.

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Eubacteria shapes

• Their cells are either spherical, rod-shaped or
  spiral
• Coccus are spherical, Bacillus are rod-shaped and
  Spirillum are spiral.

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Bacteria live singly or are found in clusters.

• Clusters are named based on the arrangement of
  the bacterial cells. Using cocci as an example
• Diplococcus are in sets of two
• Staphylococci  a number of cells clustered
  together (like grapes)
• Streptococci    a number of cells arranged in
  chains

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Eubacteria Nutrition

• Photoautotrophs use the sun to manufacture
  sugars.
• Chemoautotrophs need carbon dioxide to obtain
  energy from inorganic substances.
• Photoheterotrophs are unique and use light to
  generate energy but must obtain carbon in organic
  forms.
• Chemoheterotrophs use organic molecules such as
  sugar for energy.

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Eubacteria Morphology

• Vary in size from 1.25 µm to 10µm
• Largest know is 0.75mm Thiomargarita namibiensis

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Eubacteria Morphology

• Have rigid cell walls and a capsule
• May have flagella
• Have pili extensions of cell wall used to
  touch/exchange material with other cells
• No nucleus or membrane bound organelles
• Have a nucleotide region circular nucleotides
  plasmid

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Prokaryotic flagella
Nucleoid region (DNA)
Ribosomes
Plasma membrane
Cell wall
Capsule
Pili
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Eukaryotic cells

• Have a nucleus and membrane bound organelles
• Are larger than Archaea and Eubacteria
• Task Use your textbook to define the terms
  eukaryotic and prokaryotic.
• Classify the Archaea and Eubacteria as either
  eukaryotic or prokaryotic. Justify your answer.
• Cut and paste activity Make a poster of the
  three domains, matching pictures with appropriate
  descriptions.