Domains

Archaea

Bacteria

Eukarya

Prokaryotes

Eukaryotes

Prokaryotes

Endosymbiotic Theory

4

Eukaryotes

Any organism with one or more

cells that contain a membrane-

bound nucleus (that holds the

genetic material) and

organelles.

Domains

Archaea

Bacteria

Eukarya

Prokaryotes

Eukaryotes

Viruses

small infectious

agents comprised

of genes (DNA or

RNA) inside a

protein coat

Viruses

• In isolation, viruses show none of

the expected signs of life. They do

not respond to stimuli, they do not

grow, they do not do any of the

things we normally associate with

life.

Viruses and Disease

Viruses and Disease

• common cold

• influenza

• chickenpox

• Ebola

• AIDS

• avian influenza

• SARS

• Zika

• Rabies

• And many others..

Domains

Archaea

Bacteria

Eukarya

Prokaryotes

Eukaryotes

Domain Archaea

Cell type: Prokaryotic

Cell membrane: Strong bonds

enable it to withstand

extreme environments

Cell wall: Present in almost all

(pseudopeptidoglycan)

Domain Archaea

Mode of Nutrition:

autotrophs

(lithoautotrophs or

photoautotrophs)

Reproduction: asexual

Habitat: mostly extreme

environments but also

living in swamps, soils,

and seas.

Halophiles

These are archaea that

can thrive above 20-

25% salinity.

Note: Seawater has

3.5% salinity.

Extreme halophiles

These salt-loving archaea

sometimes turn the waters

pink or magenta. Pink

halophiles have

bacteriorhodopsin and

use this for a type of

photosynthesis that does

not produce oxygen.

Thermophiles

These are organisms that

live in extremely hot

environments. Some

archaea are thermophiles

and can withstand

temperatures up to 121° C.

Extreme thermophiles

These are Archaea from

hot springs and other high

temperature environments.

Some can grow above the

boiling temperature of

water.

Alkaliphiles /

Acidophiles

These are archaea that

can thrive at extreme pH

conditions.

Acidophile = pH 0 – 4

Alkaliphile = pH 8 - 14

Acidophiles / Alkalophiles

Other archaea exist in very

acidic or alkaline conditions.

One of the most extreme

archaean acidophiles is

Picrophilus torridus, which

grows at pH 0.

Methanogens

They make methane

(natural gas) as a waste

product. They are

found in swamp

sediments, sewage,

and in buried landfills.

Methanogens

In the future, they could

be used to produce

methane as a byproduct

of sewage treatment or

landfill operation.