Chapter 9:
Single-celled
Organisms & Viruses
Characteristics of living things
All living things…
Have cells
(organized)
2. Grow &
develop
3. Adapt
1.
4. Respond to the
environment
5. Reproduce
6. Use energy
Levels of Organization
Cells
Tissue
Organ
Organ system
Organism
• Needs of Life
– All living things need :
• Energy – comes from the food
and eventually the sun
• Materials – such as carbon
dioxide, oxygen, & water
• Living Space – ex) plants die if
weeds invade their living space
• Unicellular – living thing
made up of a single cell
– Usually to small to see with
the human eye
– 1 cell carries out all life
functions
– Ex. bacteria and most
protists
Chapter 9:
Single-celled Organisms
& Viruses
Section 2
Bacteria
• the simplest kind of life known on
Earth
• composed of just one cell without a
nucleus
• genetic material is in loops within the
cell
• reproduces using binary fission
Anatomy of Bacteria
Capsid
Arrangement
• Paired: diplo• Grape-like clusters: staphylo• Chains: strepto-
Rod shaped Bacteria
• Bacilli
(Bacillus)
• may occur
singly or in
chains
Spiral Shaped
•Spirillia
•Occur in
single
strands
Round Shaped Bacteria
•Coccus
•singly or
in pairs,
•chains, or
clusters
Examples of bacterial
names
• Streptococcus: chains of
spheres
• Staphylospirillum: Grapelike
clusters of spirals
• Streptobacillus: Chains of
rods
Bacteria are grouped
by their
environmental jobs
Producers
• transform energy from
sunlight into energy that
can be used by cells & are
a food source for
organisms that cannot
make their own food.
Decomposers
• get energy by breaking
down materials in
decaying organisms &
help other organisms
reuse materials in
decaying matter.
Parasites
• live in a very close
relationship either inside
or on the surface of a
host & cause harm to
their hosts.
Archaea are grouped
by where they live…
Archaea
• single-celled organisms that can
survive in the largest range of
environments.
• environments may be in hot, very
cold, or contain poisonous materials
Methanogens
–Produce the natural gas
methane & die if exposed
to oxygen
–Live in muddy swamps and
marshes, and guts of
animals such as cows and
termites.
Halophiles
–live in very salty bodies
of water (ex. Dead Sea)
& can die if there is too
little salt in water
–can survive drying and
begin dividing again
when water returns to a
pond
Thermophiles
–thrive in extreme heat
or cold
–may live in hot springs,
near hot vents deep
under the sea, or buried
deep in the ice
Bacteria…
Is it GOOD or BAD?!?
Viruses
Section 3
Dead or alive?
Viral structure
• Viruses are not cells.
• Basic structure:
– Protein coat
– Nucleic acid core (RNA or
DNA)
– Lipoprotein coat
• (second coat – only in enveloped
viruses)
Virus Categories
• DNA viruses – stable, do not
mutate rapidly
– Single-stranded or double-stranded
– Smallpox, Hepatitis B
• RNA viruses – mutate rapidly,
unstable
– Single-stranded or double-stranded
– HIV, Rhinovirus
Are viruses alive?
• Only 1 characteristic of
life: reproduction
• Can only reproduce inside
a host cell!
• Process of reproduction =
lytic cycle
Lytic Cycle
• Attachment
– The virus attaches to the
surface of a bacterium.
Lytic Cycle
• Injection
– The virus injects its DNA into
the bacterium.
Lytic Cycle
• Production
– Using the same machinery used by the
host cell for copying its own DNA, the
host cell makes copies of the viral DNA.
Lytic Cycle
• Assembly
– New viruses assemble from
the parts that have been
created.
Lytic Cycle
• Release
–The cell bursts open,
releasing 100 or more new
viruses.
9.4 Notes
Protists
Protists
• Have a nucleus
• Do not fit into:
– Plant
– Animal
– Fungus
• They are the “left overs”
• Mostly
– single celled
– Live in water
Protists obtain energy in
3 ways
• Eating other organisms (animallike)
• Making their own food (plantlike)
Absorbing their food (funguslike)
Types of protists
•Algae
–Both multi- &
unicellular
–Are plant-like protists
–Are producers
Types of movement in
protists
• Pseudopods (false feet) –
tiny extensions of the body
–move out and drag the
protist along.
•Found in Amoeba
Types of movement in
protists
• Flagella – Whip-like tail
(or tails)
–Act as a rutter and moves
back and forth pushing
the protist forward and
directing it
•Ex) Euglena
Types of movement in
protists
• Cilia – tiny hairs
–Act as many tiny boat oars
and sweep back and forth to
move the protist
•Ex) Paramecium