Download Ch 16 Prokaryotes

Ch 16 Prokaryotes
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Thrive in moderate & extreme environments
Found everywhere (ubiquitous)
Some are beneficial (good)
Some are harmful
Earliest forms of life on Earth
Steps to Life
• Earth’s atmosphere contained
CO, CO2, N2, and H2O, but little
or no O2
• Energy sources like volcanoes,
lightning, and UV radiation from
the sun were all very intense
• “Early Earth” experiments
produce SIMPLE organic
compounds including all 20
amino acids, several sugars,
lipids, the nitrogenous bases
found in DNA and RNA, and
even ATP.
Steps to Life
• To imitate early Earth, organic molecules in lab
were placed in extreme places (volcanic rock,
sand, dirt, heat vents)
• They polypeptides and polysaccharides –
formed without living cells or enzymes being
present.
• Other experiments have shown that
polypeptides can come together and form
microscopic, fluid-filled spheres called pre-cells.
All of these experiments together support a
hypothetical four-stage sequence for how
life could have first developed on Earth.
• First, small organic molecules, such as amino acids
and nucleotides, formed from simpler molecules
present in the environment.
• Second, these small molecules joined together into
larger ones such as proteins and nucleic acids.
• Third, molecules that could copy themselves
provided a basis for the inheritance of molecular
information.
• In the last stage, these various organic molecules
became packaged within membranes and separated
from their surroundings forming pre-cells.
2 domains of prokaryotes
(Archaea and Bacteria)
Archaea
– Greek = meaning "ancient."
– prokaryotes, many live in extreme environments on Earth.
– extremophiles, meaning "lovers of the extreme."
• thermophiles (heat lovers) live in hot water such as the
hot springs of Yellowstone National Park or deep-sea
vents
• Halophiles (salt lovers) thrive in such environments as
Utah's Great Salt Lake, or in seawater evaporating
ponds.
• Some archaea live in oxygen-free environments such as
the mud at the bottom of lakes and swamps where they
produce bubbles of "swamp gas" (methane).
2 domains of prokaryotes
(Archaea and Bacteria)
• Bacteria
– Prokaryotic organisms classified as bacteria
differ from archaea in cell structure and
chemical makeup
– Scientists place the two groups of prokaryotes
in separate domains partly because of key
differences in the information contained in
their nucleic acids (DNA and RNA).
Structure of Bacteria
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Characteristics of Bacteria
1. Unicellular- only one cell
2. Prokaryotic- lacks a nucleus and membrane
bound organelles.
Form
A)Bacillus- rod
shaped
B)Spirilla- spiral
shaped
C)Coccispherical
Bacteria
Bacilli
Cocci
Spirilla
Bacteria is identified based partly
on three characteristics:
• Cell Shape
– Bacteria come in three basic
shapes:
– Spherical – cocci (berries)
– rod-shaped -- bacilli
– spiral-shaped -- spirochetes
• Cell Wall Structure
• Motility
– About half of all prokaryotes are motile, meaning
that they can move.
– flagellum (plural, flagella) or slime threads
Movement
A)gliding on slime
B)twisting in a
corkscrew fashion
C) Flagella
D) some don't
move
Reproduction
• Most prokaryotes reproduce at
a very fast rate under the right
conditions.
• Prokaryotic cells copy their
DNA almost continuously and
divide repeatedly.
• called binary fission
Modes of Nutrition
• "mode of nutrition" describes how
organisms obtain energy and
carbon atoms.
– energy by photosynthesis = photo– Energy from chemical sources =
chemo– Autotrophs obtain carbon atoms
from CO2
– Heterotrophs obtain carbon from
existing organic molecules (such
as those in food).
• Adding a prefix, photo- or chemoto either autotroph or heterotroph
fully describes the mode of
nutrition
Chemical Recycling
• Life depends on the cycling of chemical
elements between the biological and
nonliving parts of ecosystems.
Prokaryotes play a vital role in chemical
recycling.
• Many prokaryotes perform an essential
function by breaking down, or
decomposing, organic waste products
and dead organisms in the environment.
Human Uses of Prokaryotes
• bioremediation -- the use of organisms to
remove pollutants from water, air, and soil
• Pseudomonas is used to clean up oil spills on
beaches
• Other prokaryotes are used to clean up old
mining sites where the water is acidic and laced
with chemicals such as arsenic, copper, zinc,
lead, and mercury.
• In another example of the usefulness of
prokaryotes, pharmaceutical companies raise
bacteria that make vitamins and antibiotics.
Helpful Bacteria
A) Bacteria in the intestine help digest food
B) Bacteria help in production of cheese,
yogurt, sour cream, pickles, and
sauerkraut.
C) Bacteria decompose dead organisms
D) Some bacteria help plants by Nitrogen
Fixation
How Bacteria Cause Illness
• You are constantly exposed to bacteria -- they are in
the air you breathe, in the water and food you ingest,
and on the surfaces you touch.
• most bacteria are neither harmless or helpful to you,
BUT some bacteria can make you ill.
• Bacteria and other microorganisms that cause
disease are called pathogens.
• Some bacteria cause disease by invading tissues
and destroying cells.
• Most pathogenic bacteria cause disease by
producing bacterial poisons.
Harmful Bacteria
A) 1 - 5% of bacteria are Pathogens disease causing organisms
B) Disease is caused by attacking cells
directly or the production of toxinspoisons
Defense Against Bacterial
Diseases
• Since the discovery that bacteria cause
many diseases, cases of such diseases
have declined dramatically.
• the major reasons for this decline are
better hygiene and public health
measures.
– washing hands
– careful preparation of food
– attention to water quality help minimize the
risk of pathogen infection.
Defense Against Bacterial
Diseases
• The human body protects itself against
infection
– Your skin and the mucous lining of your mouth,
nose, and digestive system provide a physical
barrier to bacteria.
– Those bacteria that do manage to enter (through
a cut, for example) meet chemical and cellular
defenses that make up the immune system.
• Doctors and medicines also play a role in
fighting bacterial diseases.
– Antibiotics = chemicals that slow or prevent the
growth of microorganisms.
– Many antibiotics act by damaging or preventing
the formation of the bacterial cell wall.
Protection against bacteria
A) Antibiotics- chemicals produced by
fungus that inhibit bacterial growth or kill
the bacteria.
B) Penicillin- first antibiotic discovered by
Alexander Flemming in 1929.
Lab Conclusion:
1. Where did you expose your petri dish?
2. Why did you think there would be
bacteria present there?
3. Was bacteria present?
4. What are the conditions most favorable
for bacteria growth.
5. Where can we conclude bacteria lives?