Download 1 Bacteria and Archaea

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CHAPTER 10
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Bacteria and Viruses
SECTION
1 Bacteria and Archaea
National Science
Education Standards
BEFORE YOU READ
After you read this section, you should be able to answer
these questions:
LS 1b, 1c, 2a, 3a, 3b, 4b
• What are bacteria and archaea?
• What are the characteristics of bacteria?
• How do archaea and bacteria differ?
What Are Bacteria and Archaea?
Organisms are grouped by traits they have in common. All living things can be grouped into one of three
domains: Bacteria, Archaea, or Eukarya.
All organisms in domain Eukarya are eukaryotes.
Each cell of a eukaryote has a nucleus and membranebound organelles. All organisms in domains Bacteria and
Archaea are prokaryotes. A prokaryote is an organism
that is single-celled and has no nucleus.
Although many prokaryotes live in groups, they are
single organisms that can move, get food, and make copies of themselves. Most prokaryotes are very small and
cannot be seen without a microscope. However, you can
see some very large bacteria with your naked eye.
Prokaryotes
Eukaryotes
• single-celled
• single-celled or multicellular
• no nucleus
• nucleus
• no membrane-bound organelles
• membrane-bound organelles
Domain Bacteria
Domain Archaea
STUDY TIP
Underline Use colored
pencils to underline the
characteristics of bacteria in
red, characteristics of archaea
in blue, and characteristics
shared by both in green.
READING CHECK
1. Identify What are two
characteristics of prokaryotes?
Domain Eukarya
What Characteristics Do Archaea and
Bacteria Share?
NO NUCLEUS
Prokaryotes do not store their DNA in a nucleus as
eukaryotes do. Their DNA is stored as a circular loop
inside the cell.
READING CHECK
2. Describe What does the
DNA of a prokaryote look like?
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REPRODUCTION
READING CHECK
Prokaryotes copy themselves, or reproduce, by a process called binary fission. Binary fission is reproduction
in which a single-celled organism splits into two singlecelled organisms. Before a prokaryote can reproduce, it
must make a copy of its loop of DNA. After the cell splits,
the two new cells are identical to the original cell.
3. Identify How do
prokaryotes reproduce?
Binary Fission
1 The cell grows.
2 The cell makes a copy of
its DNA. Both copies attach
to the cell membrane.
3 The DNA and its copy
separate as the cell
grows larger.
TAKE A LOOK
4 The cells separate.
Each new cell has a
copy of the DNA.
4. Describe After binary
fission, how do the two cells
compare to the original cell?
What Are Some Characteristics of Bacteria?
Most of the prokaryotes that scientists have found are
bacteria. Domain Bacteria has more individual members
than domains Archaea and Eukarya combined have.
Bacteria can be found almost everywhere.
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SHAPE
Most bacteria are one of three shapes: bacilli, cocci,
and spirilla. Bacilli are rod-shaped. Cocci are spherical.
Spirilla are long and spiral-shaped. Different shapes help
bacteria survive. Most bacteria have a stiff cell wall that
gives them their shape.
Some bacteria have hairlike parts called flagella
(singular, flagellum). A flagellum works like a tail to push
a bacterium through fluids.
READING CHECK
5. List What are three
common shapes of bacteria?
The Most Common Shapes of Bacteria
Bacilli are rod shaped. They have a
large surface area, which helps them
take in nutrients. However, a large
surface area causes them to dry out
quickly.
Cocci are spherical. They do not
dry out as quickly as rod-shaped
bacteria.
TAKE A LOOK
6. Compare What advantage
do cocci have over bacilli?
7. Compare What advantage
do bacilli have over cocci?
Spirilla are long and spiral-shaped.
They have flagella at both ends.
These tail-like structures help the
bacteria move through fluids.
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ENDOSPORES
STANDARDS CHECK
LS 4b Populations of organisms
can be categorized by the
functions they serve in an
ecosystem. Plants and some
microorganisms are producers—
they make their own food. All
animals, including humans, are
consumers, which obtain their
food by eating other organisms.
Decomposers, primarily bacteria
and fungi, are consumers that
use waste materials and dead
organisms for food. Food webs
identify the relationship among
producers, consumers, and
decomposers in an ecosystem.
Most bacteria do well in warm, moist places. Some
species of bacteria die in dry and cold surroundings.
However, some bacteria form endospores to survive
these kinds of conditions. An endospore is a thick,
protective covering that forms around the DNA of a
bacterium. The endospore protects the DNA from
changes in the environment. When conditions are good,
the endospores break open, and the bacteria begin to grow.
CLASSIFICATION
Scientists can classify bacteria by the way the bacteria
get food. There are three ways for bacteria to get food:
consume it, decompose it, or produce it.
• Consumers eat other organisms.
• Decomposers eat dead organisms or waste.
• Producers make their own food. Some bacteria can
make food using the energy from sunlight.
Word Help: categorized
to put into groups or
classes
8. List Name three roles
bacteria can play in an
ecosystem.
Decomposers, such as the ones helping to decay this leaf, return nutrients
to the soil. This allows other living
things to use those nutrients.
CYANOBACTERIA
Cyanobacteria are producers. These bacteria have a
green pigment called chlorophyll. Chlorophyll traps the
energy from the sun. The cell uses this energy to make food.
Some scientists think that billions of years ago, bacteria
similar to cyanobacteria began to live inside larger cells.
According to this hypothesis, the bacteria made food for
itself and the larger cells. In return, the larger cells
protected the bacteria. This relationship may have led to
the first plant cells on Earth.
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How Do Archaea Differ from Bacteria?
Like bacteria, archaea are prokaryotes. However,
archaea are different from bacteria. For example, not all
archaea have cell walls. When they do have them, the cell
walls are made of different materials than the cell walls
of bacteria.
There are three types of archaea: heat lovers, salt
lovers, and methane makers. Heat lovers live in hot ocean
vents and hot springs. They usually live in water that is
60°C to 80°C. However, they have been found in living in
water as hot as 250°C.
Salt lovers live where there are high levels of salt, such
as the Dead Sea. Methane makers give off methane gas.
Methane makers often live in swamps. They can also live
inside animal intestines.
READING CHECK
9. Identify What is one
difference between archaea
and bacteria?
TAKE A LOOK
10. Identify What type of
archaea do you think would
live in this swamp?
HARSH ENVIRONMENTS
Although bacteria can be found almost anywhere,
archaea can live in places where even bacteria cannot
survive. For example, many archaea live in places with
little or no oxygen. Many can also survive very high temperatures and pressures.
Scientists have found archaea in the hot springs at
Yellowstone National Park and beneath 430 m of ice in
Antarctica. Archaea have even been found 8 km below
the surface of the Earth! Even though they can be found
in harsh environments, many archaea also live in more
moderate environments, such as the ocean.
Critical Thinking
11. Infer What kind of
prokaryote would most likely
be found near vents at the
bottom of the ocean with
extremely high temperatures?
Explain your answer.
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Section 1 Review
Date
NSES
LS 1b, 1c, 2a, 3a, 3b, 4b
SECTION VOCABULARY
binary fission a form of asexual reproduction
in single-celled organisms by which one cell
divides into two cells of the same size
endospore a thick-walled protective spore that
forms inside a bacterial cell and resists harsh
conditions
prokaryote an organism that consists of a single
cell that does not have a nucleus
1. List What are the three domains that include all living things?
2. Compare Fill in the Venn Diagram to compare bacteria and archaea.
3. Describe How do some scientists think the first plants appeared on Earth?
4. List Name three kinds of archaea.
5. Infer Do you think it would be possible to find bacteria and archaea living in the
same environment? Explain your answer.
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Life Science Answer Key continued
6. They break down materials in the environ-
3. Some scientists think that bacteria similar to
ment and absorb them.
7. 23
8. ability to move
9. Answers may vary. Venus’ flytrap is in kingdom Plantae.
cyanobacteria started living in larger cells.
The bacteria made food for themselves and
the larger cells. The larger cells gave the
bacteria protection. This relationship may
have led to the first plant cells.
4. heat lovers, salt lovers, methane makers
5. Yes; although some archaea can live in harsh
environments where bacteria cannot survive, some archaea live in more moderate
places, such as the ocean. Bacteria live in
most places, other than the most extreme
environments, so they are likely to be found
in the same environments as some archaea.
Review
1. Domain Eukarya is made up of only
eukaryotes. Domains Bacteria and Archaea
are made up of only prokaryotes.
2. As scientists discover more organisms that
do not fit into existing groups, they add new
groups.
3. Linnaeus probably did not know that many
of these organisms existed. Because they are
so small, and because many archaea live in
extreme environments, Linnaeus would not
have been able to study the characteristics
of these organisms.
4. kingdom Protista
SECTION 2 BACTERIA’S ROLE IN THE
WORLD
1. by eating plants
2. 700 billion
3. It lets them make products that are hard to
find in nature.
4. The insulin can be taken out of the bacteria
and given to people with diabetes.
5. antibiotics
Chapter 10 Bacteria and
Viruses
Review
1. Nitrogen fixation is a process in which cer-
SECTION 1 BACTERIA AND ARCHAEA
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
They are single-celled and have no nucleus.
a single loop inside the cell
by binary fission
They are the same.
bacilli, cocci, spirilla
Cocci don’t dry out as quickly.
Bacilli have a large surface area to help
them take in nutrients.
as producers, consumers, or decomposers
Not all archaea have cell walls. When they
do, the walls are made of different materials
than those in bacterial cell walls.
methane makers
Archaea—they can survive in harsher environments than most bacteria.
2.
3.
4.
5.
Review
1. Bacteria, Archaea, Eukarya
2. Bacteria: Some can form endospores to
6.
tain bacteria take in nitrogen from the air
and change it to a form that plants can use.
Nitrogen from the air passes into the soil.
Bacteria in the soil and on plant roots change
nitrogen to another form. Plants use this form.
Animals eat the plants to get nitrogen.
Possible answers: Bacteria in soil turn nitrogen into a form that plants can use. Some
bacteria break down dead plant and animal
matter. This makes nutrients available to
other living things.
In genetic engineering, scientists change the
genes of bacteria or any living thing. Scientists
can put genes from one organism into another.
They get into a host organism and take
nutrients from the host’s cells.
nitrogen
SECTION 3 VIRUSES
survive harsh conditions; they are the most
plentiful organisms on Earth.
Archaea: Some can live in extreme environments; not all have cell walls.
Center: prokaryotes, no nucleus, singlecelled, reproduction by binary fission
1. Viruses change quickly.
2. They cannot reproduce without a host; they
cannot eat or grow.
3. DNA and RNA
4. spacecraft shape
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Life Science