Unit D: Microbiology
1. Describe the characteristics of the two kingdoms of prokaryotes.
Archaebacteria lack peptidoglycan, and their membrane lipids are quite different. Also,
the DNA of key archaebacterial genes are like those of eukaryotes.
2. What factors can be used to identify prokaryotes?
They are identified by their shapes, the chemical natures of their cell walls, the ways they
move, and the ways they obtain energy.
3. Give one example of how bacteria maintain equilibrium in the environment.
Bacteria are vital to maintaining the living world. Some are producers, others are
decomposers, and others have human uses.
4. Identify the parts of a prokaryote.
Cell wall, cell membrane, cytoplasm, DNA, ribosomes, pili and flagella.
5. What are some ways that prokaryotes obtain energy?
Some consume organic molecules made by other organisms, whereas others make their
own food from inorganic molecules.
6. Why might an infection by Gram-negative bacteria be more difficult to treat than a
Gram-positive bacterial infection?
Gram-positive bacteria have only one cell membrane, whereas gram-negative bacteria
have a second, outer, layer of lipid and carbohydrates. Therefore, gram-negative bacteria
might be more difficult to kill.
Making a Venn Diagram
Create a Venn diagram that illustrates the similarities and differences between eubacteria and
archaebacteria. Hint: Before you start, you may want to list the similarities and differences.
1. What are the parts of a virus?
A typical virus is composed of a core of either DNA or RNA surrounded by a protein
coat, which is called a capsid.
2. Describe the two ways that viruses cause infection.
In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to
burst. In a lysogenic infection, a virus embeds its DNA into the DNA of the host cell and
3. What is the difference between a bacteriophage and a prophage?
A bacteriophage is a virus that infects bacteria. A prophage is the lysogenic viral DNA
that is embedded in the host’s DNA.
4. What is a retrovirus?
A retrovirus is a virus that contains RNA.
5. Do you think viruses should be considered a form of life? Describe the reasons for
Most students will assert that viruses should not be considered a form of life because they
do not exhibit all the characteristics of life.
Structure and Function
Viruses and cells are similar yet different. Compare the structure of a virus to the structure of a
eukaryotic cell. Organize your information in a table. You may wish to refer to Chapter 7,
which discusses the structures of cells in detail.
Diseases Caused by Bacteria
1. What are the two ways that bacteria cause disease?
Some damage cells and tissues directly by breaking down the host’s cells for food.
Others release toxins that interfere with the host’s normal activity.
2. Describe the three methods of preventing bacterial growth in food.
Students should describe sterilization, disinfectants and food storage and processing.
3. Describe how viruses cause disease.
Viruses cause disease by disrupting the body’s normal equilibrium.
4. What are viroids?
Single-stranded RNA molecules that have no surrounding capsids.
5. You think you might have a bacterial infection. Would you ask for a vaccination
against the bacteria? Why or why not?
It would probably not be a good idea because vaccinations prevent infection rather than
attacking and destroying bacteria.
6. How might epidemiologists collaborate with scientists who study viruses as they
investigate viral diseases?
Epidemiologists are primarily concerned with tracking and preventing the spread of
diseases. They might collaborate with virologists to find out the characteristics of
specific viruses, including how they spread and how they infect a host.
In War of the Worlds Earth is invaded by aliens. No weapons can kill the invaders. Earth is
saved when the invaders die from diseases they contract. Write a summary of a story about
people from Earth voyaging to another planet. Include information on how the people from
Earth might protect themselves from possible new diseases.
The Kingdom Protista
1. What is a protist?
A protist is a eukaryote that is not a member of the kingdoms Plantae, Animalia, or
2. Describe Margulis’s theory about the evolution of protists.
The first eukaryotic cells may have evolved from a symbiosis of several prokaryotes with
3. Are most protists unicellular or multicellular?
Most are unicellular.
4. What are the three methods that protists use to obtain food?
Animal-like protists ingest or absorb food; plantlike protists produce food by
photosynthesis; and funguslike protists obtain their food by external digestion either as
decomposers or as parasites.
5. Identify the characteristics of organisms belonging to the kingdom Protista.
Protists are eukaryotic organisms and most are unicellular.
6. In what way is the kingdom Protista similar to a group of people who do not belong
to a political party.
Like people who do not belong to a political party, protists are defined less by what they
are and more by what they are not.
Write and illustrate a brief newspaper story explaining the hypothesis that eukaryotic cells
evolved from a symbiosis of several prokaryotes with larger cells. Hint: Begin with a draft and
then revise that draft, looking at organization and word choice.
1. What are the four major phyla of animal-like protists? How do members of each of
these groups move?
Zooflagellates swim with flagella; sarcodines move by extensions of their cytoplasm;
ciliates move by means of cilia; and sporozoans do not move at all.
2. What animal-like protists cause disease?
Plasmodium causes malaria; Trypanosoma causes African sleeping sickness; Entamoeba
causes amebic dysentery; and Giardia can cause diarrhea and digestive problems.
3. How does a macronucleus differ in function from a micronucleus?
A macronucleus contains multiple copies of most of the genes that the cell needs; a
micronucleus contains a copy of all the genes.
4. Describe the role of animal-like protists in the environment.
Some live symbiotically. Others recycle nutrients by breaking down dead matter. Many
live in seas and lakes, where they are eaten.
5. Compare animal-like protists that have flagella to those that have cilia.
Zooflagellates have flagella; some live within other organisms. Ciliates have cilia; most
are free living.
6. Summarize how Plasmodium can cause a major disruption in the equilibrium of a
Students should describe the effects of the disease malaria, caused by Plasmodium.
Information and Heredity
Compare asexual and sexual processes in paramecia. Include the terms mitosis and meiosis in
your answer. You may wish to refer back to Chapters 10 and 11 to review mitosis and meiosis.
Plant-like Protists – Unicellular
1. What do chlorophyll and accessory pigments do in algae.
They allow algae to harvest and use the energy from sunlight.
2. What are the four phyla of unicellular plantlike protests?
Euglenophyta, Pyrrophyta, Chrysophyta, Bacillariophyta
3. How do most unicellular algae get food? How does this differ from the way most
animal-like protists get food?
Most unicellular algae use the energy of sunlight to product food. Animal-like protists get
food by absorbing, capturing or trapping it.
4. What is the role of unicellular algae in the environment?
They are at the base of aquatic food chains, and they make up a considerable part of the
phytoplankton. Unicellular algae also form symbiotic relationships with other organisms.
5. Identify two ways to reduce the problem of algal blooms in fresh water.
Sample answer: Eliminate sewage discharge and reduce the amount of plant fertilizers.
6. Summarize the role of a red tide in disrupting an ecosystem.
The dinoflagellates that cause a red tide produce a potentially dangerous toxin. Filter-
feeding shellfish become filled with the toxin, and fish that eat those shellfish can
become seriously ill.
Write a News Broadcast
Use the library or the Internet to investigate the number of algal blooms off the California coast
in the last five years. Be sure to note the causes, the types of protists identified, and the effects on
wildlife and people. Present your findings to the class as an unbiased investigative report.
Plantlike Protists – Coloured Algae
1. Describe the main features of the major phyla of multicellular algae.
Students should describe the main features of algae in the phyla Rhodophyta, Phaeophyta
2. What is alternation of generations?
A process in which algae switch back and forth beween haploid and diploid during their
3. How are multicellular algae important at a global level?
Multicellular algae provide food and generate oxygen and are an important part of the
food chain along coastal waters and in the Sargasso Sea.
4. Why can red algae live in deeper water than green algae?
Red algae contain the reddish accessory pigments known as phycobilins, which are
especially good at absorbing blue light, which penetrates deeper, enabling red algae to
live deeper in the ocean than other algae.
5. Choose a green alga and illustrate its life cycle. Identify which parts are haploid
and which are diploid. Show where meiosis and mitosis occur. Illustrate which part
of the life cycle involves sexual reproduction and which involves asexual
Students may choose any of the examples of green algae discussed in the section. A
typical response will illustrate either Chlamydomonas or Ulva and use Figure 20-17 or
20-18 for reference.
Make a poster illustrating three types of multicellular algae. Your poster should have detailed
drawings or photographs of each group. Each illustration should show the correct classification
and list two written characteristics of each group.
1. How are funguslike protists and fungi similar? How are they different?
Like fungi, funguslike protists are heterotrophs that absorb nutrients from dead or
decaying organic matter. Unlike most true fungi, funguslike protists have centrioles and
lack and chitin cell walls of true fungi.
2. Compare acellular slime molds, cellular slime molds, and water molds.
The individual cells of cellular slime molds remain distinct throughout the life cycle.
Acellular slime molds pass through a stage in which their cells fuse to form large cells
with many nuclei. Water molds have a diploid life cycle. The only haploid stage is the
3. What is the role of slime molds in the environment?
They recycle organic material.
4. How can water molds affect other living things?
Water molds can cause plant diseases, such as potato blight.
5. How is the sluglike mass of cellular slime molds similar to the plasmodium of
acellular slime molds? How do they differ?
Both the cellular slime mold mass and the plasmodium function like a single organism,
and both produce a fruiting body. They differ in that the cells of a plasmodium fuse,
while cells in a slime mold mass preserve their separate cellular identities.
Constructing a Flowchart
Draw two flowcharts – one showing the steps from unicellular existence through multicellular
existence and reproduction in cellular slime molds and one showing those steps in acellular slime
The Kingdom Fungi
1. Identify the characteristics all fungi have in common.
Fungi are eukaryotic heterotrophs that have cell walls. Fungi do not ingest food; they
digest food outside their cells and absorb it.
2. Describe the structure of the body of a typical fungus.
The bodies of multicellular fungi are composed of many hyphae tangled together into a
thick mass called a mycelium. The visible portion of the mycelium is the reproductive
structure, or fruiting body.
3. Briefly describe asexual and sexual reproduction in fungi.
Asexual reproduction takes place when cells or hyphae break off from a fungus and begin
to grow on their own. Some fungi also produce asexual spores. Sexual reproduction in
fungi usually involves two different mating types, which mate to form zygote nuclei.
4. By what means are fungal spores spread to new locations?
Some spores are scattered by the wind and some, by animals.
5. Tissue from several mushrooms gathered near the base of a tree were tested and
found to be genetically identical. How might you explain this?
The genetically identical mushrooms were part of the same mycelium, which means they
were part of the same organism.
Writing a Proposal
A house may become uninhabitable because of the presence of mold spores. Research how to
detect and identify mold allergens in the home. Assume you are a contractor. Write a proposal
for how you will assess this problem in preparation for a cleanup. Hint: Write a draft of your
Classification of Fungi
1. List the four phyla of fungi, and identify the main characteristics of the members of
Zygomycota have life cycles that include a zygospore. Ascomycota have asci that
contain spores. Basidiomycota have a reproductive structure that resembles a club.
Deuteromycota do not have an observed sexual phase.
2. How do conidia form? What is their function?
In asexual reproduction of some ascomycetes, tiny spores called conidia are formed at the
tip of specialized hyphae.
3. Which fungal phylum contains the largest number of species?
4. Compare the structure and function of an ascus and a basidium.
The ascus, a sac that contains spores, forms within the fruiting body of an ascomycete.
Within the ascus, two nuclei fuse to form a diploid zygote. The spore-bearing structure
of a basidiomycete, called the basidium, is found on the gills of mushrooms. A
basidiospore germinates to produce a haploid primary mycelium.
5. Compare asexual and sexual reproduction in bread mold. At what stage does
Students should describe both sexual and asexual reproduction, as discussed on page 530
and in Figure 21-5. Meiosis occurs when conditions become favorable and the zygospore
Exploring Your Community
Visit a local supermarket to find out how fungi are used in the cuisines of different cultures.
Select a particular fungus, research recipes in which it is used, and try one of the recipes. You
may also want to find the scientific name of the fungus you have selected.
Ecology of Fungi
1. What is the major role of fungi in an ecosystem?
To recycle nutrient material by breaking down organic matter.
2. Explain the roles of fungi in causing disease in humans and in other living things.
Parasitic fungi cause serious plant and animal diseases, including those in humans.
3. Describe two mutualistic relationships that fungi form with other organisms.
A lichen is a symbiotic association between a fungus and an alga or a cyanobacterium.
Mycorrhizae are mutualistic relationships between plant roots and fungi.
4. Describe the life cycle of wheat rust.
Spores produced by the rust in barberry plants are carried by wind into wheat fields
where they infect wheat plants and produce a second type of spore that infects other
wheat plants. Another type of spore survives through the winter and produces yet
another spore that infects barberry plants.
5. What might happen to a garden if it were sprayed with a long-acting fungicide?
The garden plants would not flourish, because the mycorrhizae between plants and fungi
benefit both plants and fungi.
6. Summarize the role of fungi in disrupting the equilibrium in an ecosystem. Give
one specific example.
Answers will vary. Most students will focus on plant or animal diseases caused by fungi.
Structure and Function
Both bacteria and fungi are decomposers. What characteristics do these two groups share that
allow them to function in this ecological role? Use the information in Chapter 19 to help answer