Three Domains of Life Arcahaea Eubacteria Eukarya.

Three Domains of

Life

ArcahaeaEubacteria

Eukarya

• Each cell type has unique characteristics

Archaea

Eubacteria cell Nucleus Organelles

Eukaryotic cell

wwwsciencenews.org/view/generic/id/42241/tit.

ARCHAEA AND EUBACTERIA

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

Archaea Recognized

• Advances in molecular biology identified Archaea as unique type of cells (Carl Woese, late 70’s, U of Illinois)

• DNA is very different from bacterial DNA

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

'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.

EXTREME CONDITIONS

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

• 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.

Archaea: Morphology

• Size < one micron (1μ)

• Shapes vary • spherical (coccus)• rod-shaped (bacillus) • hair-like • triangular • square

Archaea: Morphology CONTINUDED

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

• 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.

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

Basic Archaea Cell Structure

EUBACTERIA

• True Bacteria

• Found in the air, water, soil and on most moist surfaces

•Includes the spirochetes, gram-positive bacteria and cyanobacteria.

Eubacteria shapes

• Their cells are either spherical, rod-shaped or spiral

• Coccus are spherical, Bacillus are rod-shaped and Spirillum are spiral.

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

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.

Eubacteria Morphology

• Vary in size from 1.25 μm to 10μm

• Largest know is 0.75mm Thiomargarita namibiensis

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

Prokaryoticflagella

Nucleoid region (DNA)

RibosomesPlasmamembrane

Cell wall

Capsule

Pili

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.