Chapter 6: Bacteria
and Viruses
6-1: Classifying Organisms
• Today, Scientists have identified at least 1.7 million
organisms on earth.
• This includes:
Bacteria
Simple
Protists
Fungi
Plants
Animals
Complex
• It is important for Biologists to organize all living
things so they are easier to study.
• Classification is the process of grouping things
based on similarities.
• The scientific study of classification is called
taxonomy.
•
1)
2)
3)
Early Classification Systems
The first classification system was developed by
Aristotle in 4th Century B.C. and it had three groups:
Those that fly
Those that swim
Those that crawl, walk, or run
What was this first system based on?
Movement
• The next classification system was developed by
Carlos Linnaeus in the 1750’s
• It was based on observable features of organisms.
• Linnaeus also devised a naming system called
binomial nomenclature- each organism had a 2-part
name.
Kingdom
Phylum
Class
Order
Family
Genus
Species
Levels of Classification
Largest/Broadest Category
Smallest/Most Specific Category
• In Linneaus’ System, the 2-part name is made up of:
First word: Genus- grouping of similar, closely
related organisms.
Second Word: Species- grouping of similar
organisms that can mate and produce fertile
offspring; Often describes a distinctive feature.
Q: Why is Linneaus’ System important?
What is this?
______________
Cougar?
Mountain Lion?
Panther?
Puma?
Scientific Name: Felis concolor
A: For many species, there are regional
differences in their common name.
5
It is kind of like the way you are named:
Example: Malik would be like the “genus”….but there
are other Maliks.
Stephanie would be the species that
distinguishes me from other Maliks.
How to write an organism’s name in binomial
nomenclature:
1) The Genus is ALWAYS capitalized
2) The Species is ALWAYS lower case
3) It is ALWAYS in latin
4) It is ALWAYS written in italics.
Example: Felis domesticus is a house cat
Classification Today:
• The theory of evolution changed the way biologists
think about classification.
• Certain organisms share a common ancestor.
• When organisms share a common ancestor, they
share evolutionary history.
• Today’s system considers evolutionary history.
• Species with similar evolutionary histories are
classified more closely together.
Comparing Classification Levels to Everyday Concept:
Kingdom: Earth
Phylum: United States (Country)
Class: Michigan (State)
Order: Temperance (City)
Family: Silo Meadows (Neighborhood or Street)
Genus: 627 Briar Lane (Address)
Species: Individual Living There
Classifying an Owl (pg. 187):
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
Q: How do you learn the identity of an organism?
A: Using a Taxonomic Key (Dichotomous Key)- A series
of paired opposite statements that describe physical
characteristics of different organisms.
Practice with Non-living things:
Step 1:Brainstorm Characteristics Present:
Long and tubular
For writing Not Plastic Plastic
Short non-tubular Not for writing has a cap no cap
Green and gray Blue and clear Black and silver Silver
9
Step 2: Make a spider key
2 Main groups (as close to 50-50 as you can get)
Further breakdown
10
Step 3: Using your spider key as a guide,
construct your dichotomous key. When
something can no longer be divided, name it!
***You cannot fill in
1b until later….leave it
blank at first.
11
6-2: The Six Kingdoms
Archaebacteria
Prokaryote
No Nucleus
Might resemble
some of earth’s
early life forms
Unicellular
Autotroph or
Heterotroph
Live on ocean floor, in salty water, or
hot springs.
Live in Harsh
Conditions
Archaebacteria means : “Ancient
Bacteria”
DNA is free
floating.
Eubacteria
Prokaryote
Bacteria that
causes strep
throat is
classified here
No Nucleus
Help make
yogurt
Unicellular
“Common” Bacteria
Autotroph or
Heterotroph
Different chemical make-up than
archaebacteria
Live in common places
DNA is free
floating.
Protists
Eukaryote
Nucleus
Present
Other cell
structures: cilia,
flagella,
pseudopods
Unicellular, some
multicellular
Seaweed and
other algae are
examples
Sometimes called the “junk drawer”
kingdom.
Autotroph or
Heterotroph
Other examples: ameba,
euglena, paramecium
DNA is in the
nucleus
Fungi
Nucleus
Present
Eukaryote
Cell walls
contain chitin
Multicellular, one
unicellular: yeast
Mushrooms,
mildew, and
molds are
examples
Found almost all over the world on
land, very few in water.
Heterotrophs
Most feed on dead or
decaying organisms
Absorb their
food through
their cell
walls.
DNA is in the
nucleus
Plants
Nucleus
Present
Eukaryote
Cell walls
contain
cellulose
Multicellular
Dandelions,
mosses, and
vegetables are
examples
Plants feed almost all the
heterotrophs on earth.
Autotrophs
Some produce
flowers, some do not
Make their
own food
using sunlight
DNA is in the
nucleus
Animals
Eukaryote
No cell wall,
just a cell
membrane
Nucleus
Present
Multicellular
Jellyfish, fleas,
fish, birds,
frogs, snakes,
birds, and dogs
are all examples
Different adaptations allow them to
locate, capture, and digest food.
Heterotrophs
Found in diverse
environments on
Earth
DNA is in the
nucleus
6-2 Classification of Life Table
Kingdom
Archaebacteria
Cell Type
Eubacteria
Protists
Fungi
Plants
Prokaryote Prokaryote
Eukaryote
Eukaryote
Eukaryote Eukaryote
Cell
Structures
No
Nucleus
Cilia
Flagella
Pseudopods
Cell Wall
with Chitin
Cell Wall
with
Cellulose
No Cell wall
Number of
Cells
Unicellular Unicellular
Unicellular
or Multicellular
Mostly
Multicellular
Multicellular
Multicellular
Nutrition
Autotroph, Autotroph, Autotroph,
HeteroHeteroHeterotroph
troph
troph
Heterotroph
Autotroph Heterotroph
Other Info.
Live in
harsh
conditions
Absorb
food
Many
varieties
No
Nucleus
“common”
bacteria
“Junk
Drawer”
Kingdom
Animals
19
Adaptations to get
food
6-3: Bacteria
• Bacteria are found in nearly every place on earth.
• There are more bacteria in your mouth than there
are people on earth.
• Bacteria- single celled prokaryotic organisms
• Since bacteria are the only prokaryotes (all other
living things are eukaryotes) you can use either
word: BACTERIA = PROKARYOTES
• Since bacteria are prokaryotes, they do not have a
nucleus.
Q: Where then is the DNA of a prokaryote located?
A: Throughout the cytoplasm
• Bacteria also lack many other organelles, but are still
able to carry out all life functions: use energy, grows,
responds, reproduces.
Bacteria Shapes
1) Spherical (Round)- Coccus
2) Rodlike (Pill Shaped)- Bacilli
3) Spiral- Spirilla
Bacteria Arrangements
1) Chains- Strepto
2) Clusters- Staphylo
3) Pairs- Diplo
Example: The bacteria that causes strep throat is chains of
round bacteria, therefore would be called:
Streptococcus
Q: What would a cluster of pill shaped bacteria be called?
A: Staphylobacilli
Diplococcus
Streptococcus
Staphylococcus
1)
2)
3)
4)
5)
6)
Bacteria Structures
Cell Wall- Protects the cell
Cell Membrane- Controls what passes in and out
Cytoplasm- Jelly-like substance that holds other
structures.
Ribosomes- Make proteins
Chromosome (DNA)- Circular strand that contains the
instructions for building proteins
Flagellum- Whip-like structure that helps the cell move
Q: If a bacteria cell does not have flagellum, how does it
move from place to place?
A: Air, water, human activity
Q: What are the two Kingdoms of Bacteria?
A: Archaebacteria, Eubacteria
Archaebacteria
• Live in extreme environments like hot springs, acidic
waters, mud swamps, and sewage.
Eubacteria
• Live EVERYWHERE!!! Like in your bodies and all over
surfaces.
• Help maintain the earth’s physical conditions and help
other organisms survive by being at the beginning of a
food chain:
sunlight----autrophic bacteria----small hertotrophs----larger heterotrophs
• May have been responsible for adding oxygen to the
earth’s early atmosphere.
• Help keep the level of oxygen in the atmosphere at 20%
•
•
•
•
Reproduction in Bacteria
When bacteria are in favorable conditions, they can
reproduce rapidly. Sometimes as often as doubling
their population every 20 minutes.
Fortunately conditions are rarely ideal…because if they
were, the earth would be covered in bacteria!
Asexual Reproduction
Asexual Reproduction- is the type of reproduction that
involves only one parent and produces offspring that
are identical to the parent.
Bacteria reproduce asexually using a process called
binary fission- the process by which
one cell divides to make two identical
cells.
•
1)
2)
3)
4)
In binary fission, these steps occur:
DNA is copied (replication)- one copy for each new cell.
Cytoplasm is divided evenly into 2 new cells.
Ribosomes divided evenly into 2 new cells.
Two new cells “pinch” off to live independently.
Sexual Reproduction
• Sometimes, bacteria undergo a simple form of sexual
reproduction called conjugation- a process where one
bacterial cell transfers genetic information to another
cell using a thin, hollow bridge called a pili.
• Conjugation does not increase the number
of bacteria, but it does increase the new
combinations of genetic material in
bacteria (makes more variety)
• After conjugation, binary fission takes place.
Describe the two
types of
reproduction in
bacteria
.
Bacteria Survival Needs
• Both kingdoms of bacteria need certain things to
survive:
1) A way of obtaining food
2) A way of using that food for energy (respiration)
3) Survival techniques when conditions become
unfavorable (endospore formation)
Obtaining Food
• Autotrophic bacteria can use the sun to make food.
• Some bacterial autotrophs don’t live in places where
the sun shines like deep in oceans and in mud.
Therefore they are called chemoautotrophs- use
chemical substances to make food.
• Some bacteria are heterotrophs that consume other
organisms.
Respiration
• Most bacteria use the same kind of respiration you
learned about in chapter 2.
• Some bacteria need oxygen for this process to take
place.
• However there are some bacteria that do not use
oxygen, in fact it is poison to them!
Endospore Formation
• When conditions become unfavorable for reproduction,
bacteria have a way to protect themselves.
• Bacteria can form an endospore- a small, round, thick
walled cell that forms inside of the bacterial cell that
contains the DNA.
• The endospore protects the DNA from being destroyed
by freezing, heating, drying, and can survive for many
years.
Describe the
three basic
survival needs of
bacteria.
Bacteria and the Living World
Bacteria are involved in fuel and food production as well as
in environmental recycling and clean-up. However some
bacteria cause diseases and other harmful effects.
Fuel
• Archaebacteria that live deep in muddy places produce
a gas called methane.
• Methane is in about 20% of the earth’s deposits of
natural gas.
• Natural gas is used to heat homes and cook foods.
Food
• Bacteria help make foods like cheese, yogurt, and apple
cider.
• Bacteria can also be harmful to food and spoil it.
Environmental Recycling
• Bacteria that live in soil are “recyclers” or in other
words decomposers- organisms that break down large
chemicals in dead organisms into small chemicals.
• Decomposers are “natures recyclers” because they
return basic chemicals to the environment for other
living things to use.
• Example: a tree dies and fall in the forest- bacteria
break down the dead leaves and return nutrients to the
soil so something new can grow there.
• There is bacteria that lives in symbiosis with a plants
roots that helps the plant survive.
Environmental Clean-up
• There is a type of bacteria that feasts on oil.
• These bacteria help clean up oil spills.
Describe the four
ways bacteria are
useful in the
world.
Illness and Health
• Some bacteria can cause infectious disease- illnesses
that pass from one organism to another.
• Ways infectious disease spreads:
1) Direct contact- touching, kissing
2) Indirect contact- coughing, sneezing
3) Environmental contact- in the soil, enters through a
wound. These types of bacteria produce a toxinpoison that causes harm.
• Fortunately bacterial diseases can be cured with
medicines known as antibiotics- a chemical that can kill
a bacteria without harming the persons’ own cells.
• Example of antibiotic- penicillin
• There are bacteria that help keep you healthy- like in
your intestines
Define: infectious
disease, toxin,
and antibiotics
6-4: Viruses
• Virus- a small, non-living particle that invades and
then reproduces inside a living cell.
Q: Why are viruses considered non-living?
To answer this, look back in chapter 1 and list the
characteristics of living things below:
 Cellular Organization
 Contain Similar Chemicals
 Use Energy
 Grow and Develop
 Respond to Their Surroundings
 Reproduce
Now, let’s check off the characteristics that viruses have
A: Since viruses do not have all of these characteristics,
they are considered non-living.
• Viruses are similar to other organisms in one main
way: The way they can multiply (reproduce).
• Viruses can only reproduce when they are living inside
of a living cell.
• The organism that the virus enters and reproduces
inside of is called the host. The host provides a source
of energy.
• An organism that lives inside another organism and
causes harm is called a parasite.
• Viruses act a lot like parasites because they destroy
cells when they multiply.
• All organisms can be infected by a virus, but viruses
are specific to what type of species they infect.
Examples: Cold virus- nose and throat cells of humans
Tobacco Mosaic Virus- leaf cells of tobacco
plants
Naming Viruses
• Remember most organisms are named using binomial
nomenclature….but viruses are not living. So they are
not named using this system.
• Viruses are named in one of these ways:
How it is named
Example
By the disease it causes
Polio Virus
By the organism it infects
Tomato Mosaic Virus
By where it was first found
Ebola Virus
By the scientists who discovered it
Epstein-Barr Virus
The Shapes and Sizes of Viruses
There are a wide variety of virus shapes and sizes.
Shapes:
Shape
Example
Round
Influenza (Flu)
German
Measles
Spaceship/Insect
Bacteriophagevirus that only
infects
bacteria
Rod/Tube
Tobacco
Mosaic
Bullet
Rabies
Picture
The Shapes and Sizes of Viruses
Sizes:
• Viruses are smaller than cells and smaller than bacteria.
• It takes a powerful microscope to view viruses.
• They are measured in nanometers (nm). Nanometers
are one-billionth of a meter (m).
• Most viruses measure between 50 and 60 nm in
diameter.
•
•
1)
2)
Virus Structure
Although viruses look much different from one another,
they all have a similar overall structure.
All viruses have two basic parts:
An outer coat of made of protein- protection and ID
An inner core of genetic material- code for
reproduction
Label the two parts below:
•
•
•
The protein coat plays an important role in the virus invasion
process:
The protein coat is unique to each virus. Depending on the shape
of the proteins in the coat, that determines what type of host
cell it will attach to and invade.
It is kind of like a lock and key: only one fits:
= The proteins on the host cell surface
= The proteins in the virus coat
1) Why are viruses considered non-living? 3
2) What is one way viruses are LIKE other living things? 6
3) Describe the relationship between a host and a
parasite. 9
4) How are viruses like parasites that harm? 12
5) List the four ways viruses are named. 3
6) List the four shapes of viruses. 6
7) What are viruses measured in? 9
8) Which is the largest? 12
a) a eukaryotic cell
b) a prokaryotic cell (bacterial cell)
c) a virus
9) Give the two basic structures of a virus and the
functions of each. 3
10) List three examples of viruses. 6
•
•
•
•
•
1)
2)
How Viruses Multiply
After a virus attaches to its host, it enters inside.
Once inside the virus takes over the cell’s functions.
The genetic material directs the cell to produce the
virus’s genetic material and protein instead of the cell’s
genetic material and protein.
After the instructions are switched to the virus’s, new
viruses are assembled.
There are two types of ways in which this process takes
place:
Active Viruses (Lytic Infection)
- Active viruses act immediately and destroy the
host cell quickly.
Hidden Viruses (Lysogenic Infection)
- Hidden viruses are inactive for long periods of time
before they destroy the host cell.
Active Viruses: Lytic Cycle
1
5
2
4
3
1)
2)
3)
4)
5)
Steps of Active Viruses: Lytic Cycle
The virus attaches to the surface of the
host cell.
The virus injects its genetic material into
the host cell.
The virus’s genetic material takes over the
host cell and the starts to produce virus
parts.
The virus parts assemble into new viruses
and fill the host cell.
The host cell bursts open and releases new
viruses that can go and infect new cells.
Hidden Viruses: Lysogenic Cycle
1
6
2
5
3
4
1)
2)
3)
4)
5)
6)
Steps of Hidden Viruses: Lysogenic Cycle
The virus attaches to the surface of the
host cell.
The virus injects its genetic material into
the host cell.
The virus’s genetic material becomes part
of the genetic material of the host.
After time, the virus’s genetic material
removes itself and becomes active.
The cell produces virus parts that assemble
into new viruses.
The new viruses fill the host and burst out.
Viral Diseases
• Some viral diseases are mild and don’t last long- like
the flu.
• Some viral diseases can cause death- like HIV/AIDS
• Viral diseases are spread in the same ways bacterial
diseases are spread.
Examples of Viral Diseases:
- AIDS
- Chicken Pox
- Measles
- Polio
- Rabies
• There are no medications that cure viral diseases, just
some that help control symptoms.
• The best treatment is rest, eating healthy, and drinking
water.
Preventing Infectious Diseases
• One important way to prevent the spread of infectious
disease is a vaccine- a substance that stimulates the
body to produce chemicals that destroy viruses and
bacteria.
Q: How are vaccines made and given?
A: Vaccines are made from dead or weakened bacteria or
viruses. Then they are usually injected into the body to
“activate” the body’s immune system.
• So when you are given a vaccine, your body goes “on
alert.” If a strong virus or bacteria happens to enter
your body, your immune system will hopefully destroy
it before it causes symptoms.
Common Vaccines: tetanus, pertussis, measles, mumps,
polio.