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Table of Contents – pages iii. Unit 1: What is Biology? Unit 2: Ecology Unit 3: The Life of a Cell Unit 4: Genetics Unit 5: Change Through Time Unit 6: Viruses, Bacteria, Protists, and Fungi Unit 7: Plants Unit 8: Invertebrates Unit 9: Vertebrates Unit 10: The Human Body.

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Table of Contents – pages iii

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Table of contents pages iii

Table of Contents – pages iii

Unit 1:What is Biology?

Unit 2:Ecology

Unit 3:The Life of a Cell

Unit 4:Genetics

Unit 5:Change Through Time

Unit 6:Viruses, Bacteria, Protists, and Fungi

Unit 7:Plants

Unit 8:Invertebrates

Unit 9:Vertebrates

Unit 10:The Human Body


Table of contents pages vii xiii

Table of Contents – pages vii-xiii

Unit 1: What is Biology?

Chapter 1:Biology: The Study of Life

Unit 2: Ecology

Chapter 2:Principles of Ecology

Chapter 3:Communities and Biomes

Chapter 4:Population Biology

Chapter 5:Biological Diversity and Conservation

Unit 3:The Life of a Cell

Chapter 6:The Chemistry of Life

Chapter 7:A View of the Cell

Chapter 8:Cellular Transport and the Cell Cycle

Chapter 9:Energy in a Cell


Table of contents pages vii xiii1

Unit 4: Genetics

Chapter 10:Mendel and Meiosis

Chapter 11:DNA and Genes

Chapter 12:Patterns of Heredity and Human Genetics

Chapter 13:Genetic Technology

Unit 5: Change Through Time

Chapter 14:The History of Life

Chapter 15:The Theory of Evolution

Chapter 16:Primate Evolution

Chapter 17:Organizing Life’s Diversity

Table of Contents – pages vii-xiii


Table of contents pages vii xiii2

Unit 6: Viruses, Bacteria, Protists, and Fungi

Chapter 18:Viruses and Bacteria

Chapter 19:Protists

Chapter 20:Fungi

Unit 7: Plants

Chapter 21:What Is a Plant?

Chapter 22:The Diversity of Plants

Chapter 23:Plant Structure and Function

Chapter 24:Reproduction in Plants

Table of Contents – pages vii-xiii


Table of contents pages vii xiii3

Table of Contents – pages vii-xiii

Unit 8: Invertebrates

Chapter 25:What Is an Animal?

Chapter 26:Sponges, Cnidarians, Flatworms, and

Roundworms

Chapter 27:Mollusks and Segmented Worms

Chapter 28:Arthropods

Chapter 29:Echinoderms and Invertebrate

Chordates


Table of contents pages vii xiii4

Table of Contents – pages vii-xiii

Unit 9: Vertebrates

Chapter 30:Fishes and Amphibians

Chapter 31:Reptiles and Birds

Chapter 32:Mammals

Chapter 33:Animal Behavior

Unit 10: The Human Body

Chapter 34:Protection, Support, and Locomotion

Chapter 35:The Digestive and Endocrine Systems

Chapter 36:The Nervous System

Chapter 37:Respiration, Circulation, and Excretion

Chapter 38:Reproduction and Development

Chapter 39:Immunity from Disease


Unit overview pages 472 473

Unit Overview – pages 472-473

Viruses, Bacteria, Protists, and Fungi

Viruses and Bacteria

Protists

Fungi


Chapter contents page ix

Chapter Contents – page ix

Chapter 18Viruses and Bacteria

18.1:Viruses

18.1:Section Check

18.2:Archaebacteria and Eubacteria

18.2:Section Check

Chapter 18Summary

Chapter 18Assessment


Chapter intro page 474

Chapter Intro-page 474

What You’ll Learn

You will identify the structures and characteristics of viruses and bacteria.

You will explain how viruses and bacteria reproduce.

You will recognize the medical and economic importance of viruses and bacteria.


18 1 section objectives page 475

18.1 Section Objectives – page 475

Section Objectives:

  • Identify the different kinds of viruses and their structures.

  • Compare and contrast the replication cycles of viruses.


Section 18 1 summary pages 475 483

Section 18.1 Summary – pages 475-483

What is a virus?

  • You’ve probably had the flu—influenza—at some time during your life.

  • Nonliving particles called viruses cause influenza.

  • Viruses are nonliving particles composed of nucleic acids enclosed in a protein coat and are smaller than the smallest bacterium.


Section 18 1 summary pages 475 4831

Section 18.1 Summary – pages 475-483

What is a virus?

  • Most biologists consider viruses to be nonliving because they don’t exhibit all the criteria for life.

  • They don’t carry out respiration, grow, or develop. All viruses can do is replicate—make copies of themselves—and they can’t even do that without the help of living cells.

  • A cell in which a virus replicates is called the host cell.


Section 18 1 summary pages 475 4832

Section 18.1 Summary – pages 475-483

What is a virus?

  • Viruses, such as rabies viruses and polioviruses, were named after the diseases they cause.

  • Other viruses were named for the organ or tissue they infect.

  • They do not get Latin names because they

  • are nonliving.


Section 18 1 summary pages 475 4833

Section 18.1 Summary – pages 475-483

What is a virus?

  • Today, most viruses are given a genus name ending in the word “virus” and a species name.

  • However, sometimes scientists use code numbers to distinguish among similar viruses that infect the same host.

  • A virus that infects a bacterium is called a bacteriophage (bak TIHR ee uh fayj), or phage for short.


Section 18 1 summary pages 475 4834

Section 18.1 Summary – pages 475-483

Viral Structure

  • A virus has an inner core of nucleic acid, either RNA or DNA, and an outer protein coat called a capsid.

Capsid

Nucleic

acid

Envelope


Section 18 1 summary pages 475 4835

Section 18.1 Summary – pages 475-483

Viral Structure

  • Some relatively large viruses, such as human flu viruses, may have an additional layer, called an envelope, surrounding their capsids.

Capsid

Nucleic

acid

Envelope


Section 18 1 summary pages 475 4836

Section 18.1 Summary – pages 475-483

Viral Structure

  • Envelopes are composed primarily of the same materials found in the plasma membranes of all cells.

Capsid

Nucleic

acid

Envelope


Section 18 1 summary pages 475 4837

Section 18.1 Summary – pages 475-483

Viral Structure

Nucleic acid

  • Viral nucleic acid is either DNA or RNA and contains instructions ONLY for making copies of the virus.

Capsid

  • Some viruses have only four genes, while others have hundreds.


Section 18 1 summary pages 475 4838

Section 18.1 Summary – pages 475-483

Viral Structure

Nucleic acid

  • The tobacco mosaic virus has a long, narrow helical shape.

Capsid


Section 18 1 summary pages 475 4839

Section 18.1 Summary – pages 475-483

Viral Structure

  • The arrangement of proteins in the capsid of a virus determines the virus’s shape.

Capsid

Nucleic acid

  • Polyhedral viruses resemble small crystals.


Section 18 1 summary pages 475 48310

Section 18.1 Summary – pages 475-483

Viral Structure

  • The protein arrangement also plays a role in determining what cell can be infected and how the virus infects the cell.

Capsid

Nucleic acid


Section 18 1 summary pages 475 48311

Section 18.1 Summary – pages 475-483

Attachment to a host cell

  • Before a virus can replicate, it must enter a host cell.

  • A virus recognizes and attaches to a host cell when one of its proteins interlocks with a molecular shape that is the receptor site on the host cell’s plasma membrane.


Section 18 1 summary pages 475 48312

Section 18.1 Summary – pages 475-483

Attachment to a host cell

  • A protein in the tail fibers of the bacteriophage T4 recognizes and attaches the T4 to its bacterial host cell.

Capsid

Nucleic

acid

Tail

Tail fiber


Section 18 1 summary pages 475 48313

Section 18.1 Summary – pages 475-483

Attachment to a host cell

Capsid

  • In other viruses, the attachment protein is in the capsid or in the envelope.

Nucleic

acid

Tail

Tail fiber


Section 18 1 summary pages 475 48314

Section 18.1 Summary – pages 475-483

Attachment is a specific process

  • Each virus has a specifically shaped attachment protein. Therefore, each virus can usually attach to only a few kinds of cells.

  • In general, viruses are species specific, and some also are cell-type specific. For example, polio viruses normally infect only intestinal and nerve cells.


Section 18 1 summary pages 475 48315

Section 18.1 Summary – pages 475-483

Attachment is a specific process

  • The species specific characteristic of viruses is significant for controlling the spread of viral diseases.


Section 18 1 summary pages 475 48316

Section 18.1 Summary – pages 475-483

Viral Replication Cycles

  • Once attached to the plasma membrane of the host cell, the virus enters the cell and takes over its metabolism.

  • Only then can the virus replicate.

  • Viruses have two ways of getting into host cells.


Section 18 1 summary pages 475 48317

Section 18.1 Summary – pages 475-483

Viral Replication Cycles

  • The virus may inject its nucleic acid into the host cell like a syringe injects a vaccine into your arm.

  • The capsid of the virus stays attached to the outside of the host cell.

  • An enveloped virus enters a host cell in a different way.


Section 18 1 summary pages 475 48318

Section 18.1 Summary – pages 475-483

Viral Replication Cycles

  • After attachment by these enveloped viruses, the plasma membrane of the host cell surrounds the virus and produces a virus-filled vacuole inside the host cell’s cytoplasm.

  • Then, the virus bursts out of the vacuole and releases its nucleic acid into the cell.


Section 18 1 summary pages 475 48319

Section 18.1 Summary – pages 475-483

Lytic cycle

  • Once inside the host cell, a virus’s genes are expressed and the substances that are produced take over the host cell’s genetic material.

  • The viral genes alter the host cell to make new viruses.


Section 18 1 summary pages 475 48320

Section 18.1 Summary – pages 475-483

Lytic cycle

Bacteriophage

Bacterial DNA

Nucleic

acid

Bacterial

host cell

B. Entry

A. Attachment

The bacteriophage

injects its nucleic acid

into the bacterial cell.

E. Lysis and Release

The host cell breaks open and

releases new virus particles.

C. Replication

D. Assembly

The host’s metabolic

machinery makes viral

nucleic acid and proteins.

New virus particles

are assembled.


Section 18 1 summary pages 475 48321

Section 18.1 Summary – pages 475-483

Lytic cycle

  • The host cell uses its own enzymes, raw materials, and energy to make copies of viral genes that along with viral proteins are assembled into new viruses, which burst from the host cell, killing it.


Section 18 1 summary pages 475 48322

Section 18.1 Summary – pages 475-483

Lytic cycle

  • The new viruses can then infect and kill other host cells. This process is called a lytic (LIH tik) cycle.

Click image to play movie


Section 18 1 summary pages 475 48323

Section 18.1 Summary – pages 475-483

Lysogenic cycle

  • Not all viruses kill the cells they infect.

  • Some viruses go through a lysogenic cycle, a replication cycle in which the virus’s nucleic acid is integrated into the host cell’s chromosome.

Click image to play movie


Section 18 1 summary pages 475 48324

Section 18.1 Summary – pages 475-483

Lysogenic cycle

  • A lysogenic cycle begins in the same way as a lytic cycle.

  • However, in a lysogenic cycle, instead of immediately taking over the host’s genetic material, the viral DNA is integrated into the host cell’s chromosome.


Section 18 1 summary pages 475 48325

Section 18.1 Summary – pages 475-483

Lysogenic cycle


Section 18 1 summary pages 475 48326

Section 18.1 Summary – pages 475-483

Disease symptoms of proviruses

  • Many disease-causing viruses have lysogenic cycles. However, when in the lysogenic cycle, there are no symptoms of the disease. It’s like a dormant stage.

  • Three examples of these viruses are herpes simplex I (causes cold sores), herpes simplex II that causes genital herpes, and the hepatitis B virus that causes hepatitis B.


Section 18 1 summary pages 475 48327

Section 18.1 Summary – pages 475-483

Disease symptoms of proviruses

  • When a cold sore is present, the virus is in the lytic cycle. When the cold sore disappears, the virus is in the lysogenic cycle.

  • Another lysogenic virus is the one that causes chicken pox.


Section 18 1 summary pages 475 48328

Section 18.1 Summary – pages 475-483

Disease symptoms of proviruses

  • Having chicken pox, which usually occurs before age ten, gives lifelong protection from another infection by the virus. However, some chicken pox viruses may remain as proviruses in some of your body’s nerve cells.


Section 18 1 summary pages 475 48329

Section 18.1 Summary – pages 475-483

Disease symptoms of proviruses

  • Later in your life, these proviruses may enter a lytic cycle and cause a disease called shingles—a painful infection of some nerve cells.


Section 18 1 summary pages 475 48330

Section 18.1 Summary – pages 475-483

Release of viruses

  • Either lysis, the bursting of a cell, or exocytosis, the active transport process by which materials are expelled from a cell, release new viruses from the host cell.


Section 18 1 summary pages 475 48331

Section 18.1 Summary – pages 475-483

Release of viruses

  • In exocytosis, a newly produced virus approaches the inner surface of the host cell’s plasma membrane.

  • The plasma membrane surrounds the virus, enclosing it in a vacuole that then fuses with the host cell’s plasma membrane.

  • Then, the viruses are released to the outside.


Section 18 1 summary pages 475 48332

Section 18.1 Summary – pages 475-483

HIV: An infection of white blood cells

  • Once inside a human host, HIV infects white blood cells.

Normal white blood cells

  • Newly made viruses are released into the blood stream by exocytosis and infect other white blood cells.


Section 18 1 summary pages 475 48333

Section 18.1 Summary – pages 475-483

HIV: An infection of white blood cells

  • Infected host cells still function normally because the viral genetic material is a provirus that produces only a small number of new viruses at a time.

  • Because the infected cells are still able to function normally, an infected person may not appear sick, but they can still transmit the virus in their body fluids.


Section 18 1 summary pages 475 48334

Section 18.1 Summary – pages 475-483

HIV: An infection of white blood cells

  • Most people with an HIV infection eventually get AIDS because, over time, more white blood cells are infected and produce new viruses.

  • Because white blood cells are part of a body’s disease-fighting system, their destruction interferes with the body’s ability to protect itself from organisms that cause disease, a symptom of AIDS.


Section 18 1 summary pages 475 48335

Section 18.1 Summary – pages 475-483

Retroviruses

  • Many viruses, such as the human immunodeficiency virus (HIV) that causes the disease AIDS, are RNA viruses—RNA being their only nucleic acid.

HIV virus


Section 18 1 summary pages 475 48336

Section 18.1 Summary – pages 475-483

Retroviruses


Section 18 1 summary pages 475 48337

Section 18.1 Summary – pages 475-483

Cancer and Viruses

  • Some viruses have been linked to certain cancers in humans and animals (Human papilloma virus – HPV- cervical cancer).

  • These viruses disrupt the normal growth and division of cells in a host, causing abnormal growth and creating tumors.


Section 18 1 summary pages 475 48338

Section 18.1 Summary – pages 475-483

Plant viruses

  • The first virus to be identified was a plant virus, called tobacco mosaic virus, that causes disease in tobacco plants.

Tobacco mosaic virus causes yellow spots on tobacco leaves, making them unmarketable.


Section 18 1 summary pages 475 48339

Section 18.1 Summary – pages 475-483

Plant viruses

  • Viruses cause as many as 1000 plant diseases and are named according to their host plant.

  • Viruses can cause stunted growth and yield losses in their host plants.


Section 18 1 summary pages 475 48340

Section 18.1 Summary – pages 475-483

Plant viruses

  • Plant viruses require wounds or insect bites to enter and infect a host, and do not use surface recognition.

  • They do not undergo lytic or lysogenic phases.


Section 18 1 summary pages 475 48341

Section 18.1 Summary – pages 475-483

Plant viruses

  • Not all viral plant diseases are fatal or even harmful.

  • Some mosaic viruses cause striking patterns of color in the flowers of plants.

Rembrandt tulips


Section 18 1 summary pages 475 48342

Section 18.1 Summary – pages 475-483

Prions and viroids

  • Researchers have recently discovered some particles that behave somewhat like viruses and cause infectious diseases.

  • Prions are composed of proteins but have no nucleic acid to carry genetic information.


Section 18 1 summary pages 475 48343

Section 18.1 Summary – pages 475-483

Prions and viroids

  • Prions are thought to act by causing other proteins to fold themselves incorrectly, resulting in improper functioning.

  • Prions are responsible for many animal diseases, such as mad cow disease and its human equivalent, Creutzfeldt-Jakob disease, which causes nerve cells in the brain to burst.


Section 18 1 summary pages 475 48344

Section 18.1 Summary – pages 475-483

Prions and viroids

  • Viroids are composed of a single circular strand of RNA with no protein coat.

  • Viroids have been shown to cause infectious diseases in several plants.

  • The amount of viroid RNA is much less than the amount found in viruses.


Section 18 1 summary pages 475 48345

Section 18.1 Summary – pages 475-483

Origin of Viruses

  • For replication, viruses need host cells; therefore, scientists suggest that viruses might have originated from their host cells.

  • Some scientists suggest that viruses are nucleic acids that break free from their host cells while maintaining an ability to replicate parasitically within the host cells.


Section 1 check

Section 1 Check

Question 1

Which of the following is NOT a reason that viruses are considered to be nonliving?

A. Viruses don’t replicate.

B. Viruses don’t respire.

C. Viruses don’t grow.

D. Viruses don’t develop.

The answer is A.


Section 1 check1

Section 1 Check

Question 2

Which is NOT a component of a virus?

A. RNA

B. capsid

C. DNA

D. phage

The answer is D.


Section 1 check2

Section 1 Check

Question 3

Which of the following is NOT determined by the arrangement of proteins in the capsid of a virus?

A. shape

B. what cell can be infected by the virus

C. whether or not the virus will have an envelope around it

D. how the virus infects a cell


Section 1 check3

Section 1 Check

The answer is C.


Section 1 check4

Section 1 Check

Question 4

What two ways do viruses have of getting into host cells?

Answer

The virus can inject its nucleic acid into the host cell, or attach to the host cell’s membrane and become surrounded by the membrane and placed in a vacuole. The virus then bursts out of the vacuole and releases its nucleic acid into the cell.


Section 1 check5

Section 1 Check

Question 5

In the lytic cycle, after the host’s metabolic machinery makes viral nucleic acid and proteins the next phase is _______.

A. lysis and release

B. replication

C. assembly

D. attachment


Section 1 check6

Section 1 Check

The answer is C. In the assembly phase, the new virus particles are assembled.


Section 2 objectives page 484

Section 2 Objectives – page 484

Section Objectives

  • Compare the types of prokaryotes.

  • Explain the characteristics and adaptations of bacteria.

  • Evaluate the economic importance of bacteria.


Section 18 2 summary pages 484 495

Section 18.2 Summary – pages 484-495

Diversity of Prokaryotes

  • Recall that prokaryotes are unicellular organisms that do not have a nucleus or membrane-bound organelles.

  • They are classified in two kingdoms—archaebacteria and eubacteria.

  • Many biochemical differences exist between these two types of prokaryotes.


Section 18 2 summary pages 484 4951

Section 18.2 Summary – pages 484-495

Diversity of Prokaryotes

  • Because they are so different, many scientists propose that archaebacteria and eubacteria arose from a common ancestor several billion years ago.


Section 18 2 summary pages 484 4952

Section 18.2 Summary – pages 484-495

Archaebacteria: The extremists

  • There are three types of archaebacteria that live mainly in extreme habitats where there is usually no free oxygen available.

  • One type of archaebacterium lives in oxygen-free environments and produces methane gas.


Section 18 2 summary pages 484 4953

Section 18.2 Summary – pages 484-495

Archaebacteria: The extremists

  • These methane-producing archaebacteria live in marshes, lake sediments, and the digestive tracts of some mammals, such as cows.


Section 18 2 summary pages 484 4954

Section 18.2 Summary – pages 484-495

Archaebacteria: The extremists

  • They also are found at sewage disposal plants, where they play a role in the breakdown of sewage.


Section 18 2 summary pages 484 4955

Section 18.2 Summary – pages 484-495

Archaebacteria: The extremists

  • A second type of archaebacterium lives only in water with high concentrations of salt.

Dead Sea


Section 18 2 summary pages 484 4956

Section 18.2 Summary – pages 484-495

Archaebacteria: The extremists

  • A third type lives in the hot, acidic waters of sulfur springs.


Section 18 2 summary pages 484 4957

Section 18.2 Summary – pages 484-495

Archaebacteria: The extremists

  • This type of anaerobic archaebacterium also thrives near cracks deep in the ocean floor, where it is the autotrophic producer for a unique animal community’s food chain.


Section 18 2 summary pages 484 4958

Section 18.2 Summary – pages 484-495

Eubacteria: The heterotrophs

  • Eubacteria, the other kingdom of prokaryotes, includes those prokaryotes that live in places more hospitable than archaebacteria inhabit and that vary in nutritional needs.

  • The heterotrophic eubacteria live almost everywhere and use organic molecules as their food source.


Section 18 2 summary pages 484 4959

Section 18.2 Summary – pages 484-495

Eubacteria: The heterotrophs

  • Some bacterial heterotrophs are parasites, obtaining their nutrients from living organisms.

  • Others are saprophytes—organisms that feed on dead organisms or organic wastes.


Section 18 2 summary pages 484 49510

Section 18.2 Summary – pages 484-495

Eubacteria: Photosynthetic autotrophs

  • A second type of eubacterium is the photosynthetic autotroph.

  • These eubacteria live in places with sunlight because they need light to make the organic molecules that are their food.


Section 18 2 summary pages 484 49511

Section 18.2 Summary – pages 484-495

Eubacteria: Photosynthetic autotrophs

  • Cyanobacteria are photosynthetic autotrophs.

  • Most cyanobacteria are blue-green and some are red or yellow in color.

Cyanobacteria


Section 18 2 summary pages 484 49512

Section 18.2 Summary – pages 484-495

Eubacteria: Photosynthetic autotrophs

  • Cyanobacteria commonly live in ponds, streams, and moist areas of land.

  • They are composed of chains of independent cells.

Cyanobacteria


Section 18 2 summary pages 484 49513

Section 18.2 Summary – pages 484-495

Eubacteria: Chemosynthetic autotrophs

  • A third type of eubacterium is the chemosynthetic autotroph.

  • Unlike the photosynthetic bacteria, the chemosynthetic bacteria do not obtain the energy they need to make food from sunlight.


Section 18 2 summary pages 484 49514

Section 18.2 Summary – pages 484-495

Eubacteria: Chemosynthetic autotrophs

  • Instead, they break down and release the energy of inorganic compounds containing sulfur and nitrogen in the process called chemosynthesis.


Section 18 2 summary pages 484 49515

Section 18.2 Summary – pages 484-495

What is bacterium?

  • A bacterium consists of a very small cell.

  • Although tiny, a bacterial cell has all the structures necessary to carry out its life functions.


Section 18 2 summary pages 484 49516

Section 18.2 Summary – pages 484-495

The structure of bacteria

  • Prokaryotic cells have ribosomes, but their ribosomes are smaller than those of eukaryotes.

  • They also have genes that are located for the most part in a single circular chromosome, rather than in paired chromosomes.


Section 18 2 summary pages 484 49517

Section 18.2 Summary – pages 484-495

The structure of bacteria

Ribosome

Cytoplasm

Chromosome

Flagellum

Cell Membrane

Gelatinlike

capsule

Cell Wall


Section 18 2 summary pages 484 49518

Section 18.2 Summary – pages 484-495

A Typical Bacterial Cell

  • A typical bacterium, such as Escherichia coli would have some or all of the structures shown in this diagram of a bacterial cell.

Cell Wall

Capsule

Chromosome

Plasma membrane

Flagellum

Plasmid

Pilus


Section 18 2 summary pages 484 49519

Section 18.2 Summary – pages 484-495

The structure of bacteria

  • A bacterial cell remains intact as long as its cell wall is intact.

  • If the cell wall is damaged, water will enter the cell by osmosis, causing the cell to burst.

  • Scientists used a bacterium’s need for an intact cell wall to develop a weapon against bacteria that cause disease.


Section 18 2 summary pages 484 49520

Section 18.2 Summary – pages 484-495

The structure of bacteria

  • In 1928, Sir Alexander Fleming accidentally discovered penicillin, the first antibiotic—a substance that destroys bacteria—used in humans.


Section 18 2 summary pages 484 49521

Section 18.2 Summary – pages 484-495

The structure of bacteria

  • Later, biologists discovered that penicillin can interfere with the ability of some bacteria to make cell walls.

  • When such bacteria grow in penicillin, holes develop in their cell walls, water enters their cells, and they rupture and die.


Section 18 2 summary pages 484 49522

Section 18.2 Summary – pages 484-495

Identifying bacteria

  • One trait that helps categorize bacteria is how they react to Gram stain.

  • Gram staining is a technique that distinguishes two groups of bacteria because the stain reflects a basic difference in the composition of bacterial cell walls.


Section 18 2 summary pages 484 49523

Section 18.2 Summary – pages 484-495

Identifying bacteria

  • After staining, Gram-positive bacteria are purple and Gram-negative bacteria are pink.

Gram-positive bacteria

Gram-negative bacteria


Section 18 2 summary pages 484 49524

Section 18.2 Summary – pages 484-495

Identifying bacteria

  • Gram-positive bacteria are affected by different antibiotics than those that affect Gram-negative bacteria.

Gram-positive bacteria

Gram-negative bacteria


Section 18 2 summary pages 484 49525

Section 18.2 Summary – pages 484-495

Identifying bacteria

  • Bacterial cell walls also give bacteria different shapes.

  • Shape is another way to categorize bacteria.


Section 18 2 summary pages 484 49526

Section 18.2 Summary – pages 484-495

Identifying bacteria

  • The three most common shapes are spheres, called coccus; rods, called bacillus; and spirals, called spirillum.


Section 18 2 summary pages 484 49527

Section 18.2 Summary – pages 484-495

Identifying bacteria

  • In addition to having one of these shapes, bacterial cells often grow in characteristic patterns that provide another way of categorizing them.


Section 18 2 summary pages 484 49528

Section 18.2 Summary – pages 484-495

Identifying bacteria

  • Diplo–is a prefix that refers to a paired arrangement of cell growth.

  • The prefix staphylo–describes an arrangement of cells that resemble grapes.

  • Strepto–is a prefix that refers to an arrangement of chains of cells.


Section 18 2 summary pages 484 49529

Section 18.2 Summary – pages 484-495

Reproduction by binary fission

  • Bacteria reproduce asexually by a process known as binary fission.

  • To reproduce in this way, a bacterium first copies its chromosome. Then the original chromosome and the copy become attached to the cell’s plasma membrane for a while.


Section 18 2 summary pages 484 49530

Section 18.2 Summary – pages 484-495

Reproduction by binary fission

  • The cell grows larger, and eventually the two chromosomes separate and move to opposite ends of the cell.


Section 18 2 summary pages 484 49531

Section 18.2 Summary – pages 484-495

Reproduction by binary fission

  • Then, a partition forms between the chromosomes. This partition separates the cell into two similar cells.


Section 18 2 summary pages 484 49532

Section 18.2 Summary – pages 484-495

Reproduction by binary fission

  • Because each new cell has either the original or the copy of the chromosome, the resulting cells are genetically identical.


Section 18 2 summary pages 484 49533

Section 18.2 Summary – pages 484-495

Reproduction by binary fission

  • Under ideal conditions, some bacteria can reproduce every 20 minutes, producing enormous numbers of bacteria quickly.

  • But bacteria don’t always have ideal growing conditions. They run out of nutrients and water, they poison themselves with their own wastes, and predators eat them.


Section 18 2 summary pages 484 49534

Section 18.2 Summary – pages 484-495

Sexual reproduction

  • In addition to binary fission, some bacteria have a form of sexual reproduction called conjugation.

  • During conjugation (kahn juh GAY shun), one bacterium transfers all or part of its chromosome to another cell through or on a bridgelike structure called a pilus that connects the two cells.


Section 18 2 summary pages 484 49535

Section 18.2 Summary – pages 484-495

Sexual reproduction

  • Conjugation results in a bacterium with a new genetic composition.

  • This bacterium can then undergo binary fission, producing more cells with the same genetic makeup.


Section 18 2 summary pages 484 49536

Section 18.2 Summary – pages 484-495

Adaptations in Bacteria

  • Based on fossil evidence, some scientists propose that anaerobic bacteria were probably among the first photosynthetic organisms, producing not only their own food but also oxygen.

  • As the concentration of oxygen increased in Earth’s atmosphere, some bacteria probably adapted over time to use oxygen for respiration.


Section 18 2 summary pages 484 49537

Section 18.2 Summary – pages 484-495

Diversity of metabolism

  • Modern bacteria have diverse types of respiration.

  • Many bacteria require oxygen for respiration. These bacteria are called obligate aerobes.

  • There are other bacteria, called obligate anaerobes, that are killed by oxygen.


Section 18 2 summary pages 484 49538

Section 18.2 Summary – pages 484-495

Diversity of metabolism

  • There are still other bacteria that can live either with or without oxygen, releasing the energy in food aerobically by cellular respiration or anaerobically by fermentation.


Section 18 2 summary pages 484 49539

Section 18.2 Summary – pages 484-495

A survival mechanism

  • Some bacteria, when faced with unfavorable environmental conditions, produce endospores.

  • An endospore is a tiny structure that contains a bacterium’s DNA and a small amount of its cytoplasm, encased by a tough outer covering that resists drying out, temperature extremes, and harsh chemicals.


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Section 18.2 Summary – pages 484-495

A survival mechanism

  • As an endospore, the bacterium rests and does not reproduce.

  • When environmental conditions improve, the endospore germinates, or produces a cell that begins to grow and reproduce.

  • Some endospores have germinated after thousands of years in the resting state.


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Section 18.2 Summary – pages 484-495

A survival mechanism

  • Endospores can survive a temperature of 100˚C, which is the boiling point of water.


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Section 18.2 Summary – pages 484-495

A survival mechanism

  • To kill endospores, items must be sterilized—heated under high pressure in either a pressure cooker or an autoclave.


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Section 18.2 Summary – pages 484-495

A survival mechanism

  • Canned food must be sterilized and acidified.

  • This is because the endospores of the bacterium called Clostridium botulinum easily get into foods being canned.


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Section 18.2 Summary – pages 484-495

A survival mechanism

  • If the endospores of C. botulinum get into improperly sterilized canned food, they germinate.

  • Bacteria grow in the anaerobic environment of the can and produce a powerful deadly poison, called a toxin, as they grow.

  • This deadly toxin saturates the food and, if eaten, causes the disease called botulism.


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Section 18.2 Summary – pages 484-495

A survival mechanism

  • A different bacterium, Bacillus anthracis, lives in the soil.

  • B. anthracis causes anthrax, a disease that commonly infects cattle and sheep, but can also infect humans.

  • Most human anthrax infections are fairly harmless and occur on the skin as a result of handling animals.


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Section 18.2 Summary – pages 484-495

A survival mechanism

  • The bacterial spores can become airborne, however, and if inhaled in large amounts, can germinate in a person’s lungs, causing an infection.

  • This infection is more serious than a skin infection and often fatal.


Section 18 2 summary pages 484 49547

Section 18.2 Summary – pages 484-495

The Importance of Bacteria

  • Disease-causing bacteria are few compared with the number of harmless and beneficial bacteria on Earth.

  • Bacteria help to fertilize fields, to recycle nutrients on Earth, and to produce foods and medicines.


Section 18 2 summary pages 484 49548

Section 18.2 Summary – pages 484-495

Nitrogen fixation

  • All organisms need nitrogen because the element is a component of their proteins, DNA, RNA, and ATP.

  • Yet few organisms, including most plants, can directly use nitrogen from the air.


Section 18 2 summary pages 484 49549

Section 18.2 Summary – pages 484-495

Nitrogen fixation

  • Several species of bacteria have enzymes that convert N2 into ammonia (NH3) in a process known as nitrogen fixation.

  • Other bacteria then convert the ammonia into nitrite (NO2–) and nitrate (NO3–),which plants can use.

  • Bacteria are the only organisms that can perform these chemical changes.


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Section 18.2 Summary – pages 484-495

Nitrogen fixation

  • Some nitrogen-fixing bacteria live symbiotically within the roots of some trees and legumes.

  • Farmers grow legume crops after the harvesting of crops such as corn, which depletes the soil of nitrogen.


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Section 18.2 Summary – pages 484-495

Recycling of nutrients

  • Autotrophic bacteria and also plants and algae, which are at the bottom of the food chains, use the nutrients in the food they make.

  • This food is passed from one heterotroph to the next in food chains and webs.

  • In the process of making food, many autotrophs replenish the supply of oxygen in the atmosphere.


Section 18 2 summary pages 484 49552

Section 18.2 Summary – pages 484-495

Food and medicines

  • Some foods that you eat—mellow Swiss cheese, crispy pickles, tangy yogurt—would not exist without bacteria.


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Section 18.2 Summary – pages 484-495

Food and medicines

  • Specific bacteria are used to make different foods, such as vinegar, cheeses, and sauerkraut.

  • Bacteria also inhabit your intestines and produce vitamins and enzymes that help digest food.


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Section 18.2 Summary – pages 484-495

Food and medicines

  • In addition to food, some bacteria produce important antibiotics that destroy other types of bacteria.

  • Streptomycin, erythromycin, bacitracin, and neomycin are some of these antibiotics.


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Section 18.2 Summary – pages 484-495

Bacteria cause disease

  • Bacteria cause diseases in plants and animals, causing crops and livestock losses that impact humans indirectly.

  • Bacteria also cause many human diseases.

  • Disease-causing bacteria can enter human bodies through openings, such as the mouth.


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Section 18.2 Summary – pages 484-495

Bacteria cause disease

  • Bacterial diseases harm people in two ways.

  • The growth of the bacteria can interfere with the normal function of body tissue, or it can release a toxin that directly attacks the host.


Section 18 2 summary pages 484 49557

Section 18.2 Summary – pages 484-495

Bacteria cause disease

Diseases Caused by Bacteria

Treatment

Transmission

Symptoms

Disease

Fever, sore throat,

swollen neck glands

Antibiotic

Inhale or

ingest through

mouth

Strep throat

(Streptococcus)

Antibiotic

Inhale

Fatigue, fever, night

sweats, cough, weight

loss, chest pain

Tuberculosis

Puncture

wound

Stiff jaw, muscle

spasms, paralysis

Tetanus

Open and clean wound,

antibiotic; give antitoxin

Rash at site of bite,

chills, body aches,

joint swelling

Antibiotic

Lyme disease

Bite of

infected tick

Remove and fill the

destroyed area of tooth

Bacteria

in mouth

Destruction of tooth

enamel, toothache

Dental

cavities (caries)

Vaccination to prevent, antibiotics

Sore throat, fever,

heart or breathing

failure

Inhale or

close contact

Diptheria


Section 18 2 summary pages 484 49558

Section 18.2 Summary – pages 484-495

Bacteria cause disease

  • In the past, bacterial illnesses had a greater effect on human populations than they do now.

  • In the last 100 years, human life expectancy has increased to about 75 years.


Section 18 2 summary pages 484 49559

Section 18.2 Summary – pages 484-495

Bacteria cause disease

  • This increase is due to many factors, including better public health systems, improved water and sewage treatment, better nutrition, and better medical care.

  • These improvements, along with antibiotics, have reduced the death rates from bacterial diseases to low levels.


Section 2 check

Section 2 Check

Question 1

Which of the following best describes archaebacteria?

A. anaerobic autotrophs

B. photosynthetic autotrophs

C. chemosynthetic autotrophs

D. parasitic heterotrophs

The answer is A.


Section 2 check1

Section 2 Check

Question 2

What part of a bacterial cell is most affected by penicillin?

A. pilus

B. plasmid

C. flagellum

D. cell wall


Section 2 check2

Section 2 Check

The answer is D, cell wall.

Cell Wall


Section 2 check3

Section 2 Check

Question 3

Which of the following is not a way to identify bacteria?

A. the way in which their cell walls

reflect Gram stain

B. shape

C. characteristic growth patterns

D. lack of a plasma membrane

The answer is D.


Section 2 check4

Section 2 Check

Question 4

Given their rapid reproductive rates, why aren’t there more bacteria than there actually are?

Answer

Bacteria don’t always have ideal growing conditions. They run out of nutrients and water, they poison themselves with their own wastes, and predators eat them.


Section 2 check5

Section 2 Check

Question 5

What is a pilus used for in a bacterium?


Section 2 check6

Section 2 Check

A pilus helps a bacterium stick to a surface. It is also a bridge through or on which two bacteria can exchange DNA.

Cell Wall

Capsule

Chromosome

Flagellum

Plasma membrane

Pilus

Plasmid


Chapter summary 18 1

Chapter Summary – 18.1

Viruses

  • Viruses are nonliving particles that have a nucleic acid core and a protein-containing capsid.

  • To replicate, a virus must first recognize a host cell, then attach to it, and finally enter the host cell and take over its metabolism.


Chapter summary 18 11

Chapter Summary – 18.1

Viruses

  • During a lytic cycle, a virus replicates and kills the host cell. In a lysogenic cycle, a virus’s DNA is integrated into a chromosome of the host cell, but the host cell does not die.

  • Retroviruses contain RNA. Reverse transcriptase is an enzyme that helps convert viral RNA to DNA, which is then integrated into the host cell’s chromosome.


Chapter summary 18 12

Chapter Summary – 18.1

Viruses

  • Prions and viroids are virus-like particles. Prions are composed of only a protein, while a viroid is a singular strand of RNA.

  • Viruses probably originated from their host cells.


Chapter summary 18 2

Chapter Summary – 18.2

Archaebacteria and Eubacteria

  • There are two kingdoms of prokaryotes: archaebacteria and eubacteria. Archaebacteria inhabit extreme environments. Eubacteria live almost everywhere else. They probably arose separately from a common ancestor billions of years ago.


Chapter summary 18 21

Chapter Summary – 18.2

Archaebacteria and Eubacteria

  • Bacteria are varied. Some are heterotrophs, some are photosynthetic autotrophs, and others are chemosynthetic autotrophs. Bacteria can be obligate aerobes, obligate anaerobes, or both aerobic and anaerobic.


Chapter summary 18 22

Chapter Summary – 18.2

Archaebacteria and Eubacteria

  • Bacteria usually reproduce by binary fission. Some have a type of sexual reproduction called conjugation. Some bacteria form endospores that enable them to survive when conditions are unfavorable.


Chapter assessment

Chapter Assessment

Question 1

With lysogenic viruses, what two phases of the lytic cycle are replaced by the lysogenic cycle?

A. entry and replication

B. replication and assemble

C. assembly and lysis and release

D. attachment and entry


Chapter assessment1

Chapter Assessment

The answer is D.

A. Attachment and Entry

LYSOGENIC CYCLE

LYTIC CYCLE


Chapter assessment2

Chapter Assessment

Question 2

Explain why you can be infected with a virus but may have no symptoms of disease for years after the initial infection.

Answer

The virus enters a lysogenic phase remaining inactive but replicating along with the host cell’s chromosomes. Eventually, the virus enters a lytic phase where it destroys its host cells and causes symptoms of disease.


Chapter assessment3

Chapter Assessment

Question 3

What is the difference between lysis and exocytosis with respect to host cells that contain viruses?

Answer

Lysis, the bursting of the host cell, is caused when viruses break out of it. In exocytosis, the virus is enclosed in a vacuole that then fuses with the host cell’s plasma membrane. The virus is then released to the outside.


Chapter assessment4

Chapter Assessment

Question 4

What is the importance of reverse transcriptase to a retrovirus?

Answer

The enzyme reverse transcriptase allows the retrovirus to make DNA from its RNA so the DNA may attach to the chromosomes of the host cell and divide with the host cell.


Chapter assessment5

Chapter Assessment

Question 5

Particles that are composed of proteins but have no nucleic acid to carry genetic information are _______.

A. proviruses

B. prions

C. viroids

D. retroviruses

The answer is B.


Chapter assessment6

Chapter Assessment

Question 6

During ______, a bacterium transfers all or part of its chromosome to another bacterium.

A. binary fission

B. attachment

C. conjugation

D. chemosynthesis

The answer is C.


Chapter assessment7

Chapter Assessment

Question 7

What causes botulism?

Answer

Endospores of C. botulinum bacteria get into an anaerobic environment like improperly canned food, germinate, and produce a toxin as they grow. This toxin is then ingested by humans and causes poisoning called botulism.


Chapter assessment8

Chapter Assessment

Question 8

What causes anthrax?


Chapter assessment9

Chapter Assessment

Endospores of B. anthracis bacteria produce endospores that can become airborne, and if inhaled in large amounts, can germinate in a person’s lungs causing a deadly infection that damages lung tissue and the circulatory system.


Chapter assessment10

Chapter Assessment

Question 9

Describe the process in which bacteria make nitrogen in the air accessible for use by plants.


Chapter assessment11

Chapter Assessment

Answer

Several species of bacteria have enzymes that convert nitrogen gas into ammonia. Other bacteria then convert the ammonia into nitrite and nitrate that plants can use.


Chapter assessment12

Chapter Assessment

Question 10

What are the two ways in which bacterial diseases harm people?

Answer

The growth of the bacteria can interfere with the normal function of body tissue, or the bacteria can release a toxin that directly attacks the host.


Photo credits

Photo Credits

Photo Credits

  • Scott Ransom

  • Centers for Disease Control, Atlanta, GA.  

  • Carolina Biological Supply Company

  • USDA  

  • Lappa/Marquart  


Photo credits1

Photo Credits

Photo Credits

  • Diamar  

  • NOAA  

  • Wards Natural Science Est.

  • Platinum  

  • PhotoDisc

  • Alton Biggs  


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