Chapter 2: Viruses and Bacteria
Section 3: Viruses,
Bacteria, and Your Health
Chapter Test Review Material
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Lesson Objectives ·
Give reasons why viruses are considered to be nonliving. ·
Describe the basic structure of a virus. ·
Explain how viruses multiply. |
New Standards S2a: Structure and function in living
systems. S2b: Reproduction and heredity. S2c: Regulation and behavior. S2d: Populations and ecosystems. S2e: Evolution, diversity, and
adaptation of organisms. |
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What Is a Virus? Virus: A small, nonliving particle that invades and then
reproduces inside a living cell. Viruses are not cells.
They do not use energy to grow or to respond to their surroundings. Host: a living thing that provides a source of energy
for a virus or an organism. Parasites: Organisms that live on or in a host and cause
harm to the host. Viruses are named after
the disease it causes, organisms they infect, a place, or people first
infected. |
Rabies Virus
German Measles Virus
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The Shapes and Sizes of Viruses Bacteriophage: A virus that infects bacteria. Viruses are smaller
than cells and cannot be viewed with school microscopes. |
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Structure of Viruses All viruses have two
basic parts: an outer coat that protects the virus and an inner core made of
genetic material. The shape of the
proteins allows the virus’s coat to attach to, or lock onto, certain cells in
the host. |
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How Viruses Multiply Once inside, a virus’s
genetic material takes over the cell’s functions. The genetic material
directs the cell to produce the virus’s proteins and genetic material. These
proteins and genetic material are then assembled into new viruses. Active Viruses: These viruses genetic material
take over the cell’s functions and the cell quickly begins to produce the
virus’s proteins and genetic material. Several copies of the virus are made
and the host cell bursts open and releases the new viruses. Hidden Viruses: The virus’s genetic material
becomes part of the cell’s genetic material. The virus may stay in this “hidden
state” for a long time. At some point, the virus becomes active and functions
as an active virus. |
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Viruses and the Living World Viruses can cause
disease in organisms including humans, plants, and animals. Gene Therapy: Using viruses as a “messenger”
to deliver genetic material to cells with incorrect genetic information. |
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Quiz Topics
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Homework
Section 1 Review page 54. |
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Lesson Objectives ·
Describe ways in which bacteria cells are different from all other
organism’s cells. ·
List positive roles that bacteria play in people’s lives. ·
Name the two kingdoms of bacteria and tell how bacteria reproduce and
survive. |
New Standards S2a: Structure and function in living
systems. S2b: Reproduction and heredity. S2c: Regulation and behavior. S2d: Populations and ecosystems. S2e: Evolution, diversity, and
adaptation of organisms. |
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The Bacterial Cell Anton van Leeuwenhoek
discovered bacteria by accident as he was examining scrapings from his teeth
with his microscope in the late 1600’s. Bacteria are
Prokaryotes. The genetic material in their cells is not contained in a
nucleus. Bacteria are alive
because they use energy, grow and develop, respond to the environment, and
reproduce. Bacteria have three
basic shapes: spherical, rod-like, and spiral. |
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Cell Structure Cell Membrane: Controls what goes in and out
of the cell. Cytoplasm: a gel-like substance inside the cell membrane. Ribosomes: Chemical factories where proteins are produced. Genetic Material: A thick, tangles string
located in the cytoplasm. Flagellum: A long, whip-like structure that extends from the
cell membrane and passes out through the cell wall. That helps a cell to
move. |
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Archaebacteria These bacteria have
existed on Earth for billions of years and resemble Earth’s first life forms. Archaebacteria live in extreme environments
such as hot or salty water, at the bottom of swamps, or in raw sewage. |
Eubacteria Eubacteria help maintain some of Earth’s
physical conditions and thus help other organisms to survive. Some eubacteria float in water and do photosynthesis and keep the
oxygen level stable on the planet. |
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Reproduction in Bacteria In ideal conditions,
some bacteria can reproduce every twenty minutes. Asexual Reproduction: Reproduction involving only
one parent. Binary Fission: Process in which one cell
divides to form two identical cells. (Mitosis)
Sexual Reproduction: Involves two parents who
combine their genetic information to produce a new organism. Conjugation: One bacterium transfers some
of its genetic material to another bacterial cell through a thin, threadlike
bridge that joins the two cells. This results in offspring with new
combinations of genetic material.
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Survival Needs Autotrophic bacteria
make food by capturing and using the sun’s energy or using energy from
chemical substances in their environment to make their food. Heterotrophic bacteria
consume a variety of foods such as milk, meat, and decaying leaves. Respiration: The process of breaking down
food to release its energy. Endospore: A small, rounded, thick-walled, resting cell that forms inside a
bacterial cell containing the bacteria’s genetic information and some
cytoplasm. |
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Bacteria and The Living World About 20% of natural
gas deposits can be attributed to archaebacteria
respiration. Bacteria that grow in
milk produce dairy products such as buttermilk, sour cream, yogurt, and
cheeses. Decomposers: Organism that break down large
chemical in dead organisms into smaller chemicals. Some bacteria are used
to clean the environment such as devouring oil spills. Many bacteria exist in
your digestive tract to help you digest food.. By manipulating
bacteria genetic material, certain bacteria can be put to work producing
medicine such as insulin. |
Quiz Topics
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Homework
Section 2 Review page 65. |
Check out these sites for further information: