Classification Essentials: Distinguishing between Bacteria,
Protists and Fungi
Chapter 19: Bacteria (19-1 and 19-2)
19-1 Prokaryotes
The smallest and most common microorganisms are prokaryotes - single-celled organisms that lack a
nucleus and other membrane-bound organelles.
Prokaryotes typically range in size from 1 to 5 micrometers. One micrometer is equal to 1/1000 of a
millimeter.
Classifying Prokaryotes
All bacteria used to be in one kingdom called Monera. They are now placed in two kingdoms Eubacteria and Archaebacteria.
Eubacteria are found almost everywhere and have cell walls containing peptidoglycans, a carbohydrate.
Archaebacteria are found primarily in harsh environments. Their cell walls do not contain
peptidoglycans.
Identifying Prokaryotes
Prokaryotes are identified by the shapes, the chemical natures of their cell walls, the ways they move, and
the ways they obtain energy.
Shapes- Bacteria come in three shapes. They may occur by themselves or in clumps or chains.
-The rod-shaped ones are called bacilli (bacillus).
-The spherical (round) ones are called cocci (coccus).
-The spiral and corkscrew-shaped ones are called spirilla (spirillus).
Movement
Some move with flagella which are whiplike “tails.” Some glide on a slime-like material. Some do not
move by themselves at all.
Obtaining Energy
Autotrophs are organisms that make their own food. Some make food from sunlight energy. These are
called photoautotrophs. Chemoautotrophs use chemical reactions to get energy from inorganic molecules
like ammonia or iron. These prokaryotes usually use sulfur and live in the deep ocean where there is no
light.
Heterotrophs, like animals and fungi, obtain their energy from taking in organic (food) molecules
Releasing Energy
Bacteria release energy through cellular respiration (more about this later in the year). Cells that need
oxygen to release energy are called obligate aerobes. Cells that do not need oxygen to release energy are
called obligate anaerobes.
Growth and Reproduction
The type of asexual reproduction that prokaryotes are capable of is called binary fission. The cells
simply divide into two separate cells.
Some are capable of sexual reproduction called conjugation. There are no male and female prokaryotes.
They merely combine the contents of their cells to form a new individual organism.
19-2 Bacteria in Nature
Some bacteria are decomposers. These break organic matter down into its basic molecules and return
them to the soil to be recycled.
Some are nitrogen fixers. They can take nitrogen gas from the air and “fix” it (or change it into solid
form) by combining it with other elements. Plants need nitrogen to make amino acids and can only use in
the solid form.
Some cause disease. One way they can cause disease is to damage the tissues of the infected organism.
Two examples of these are the bacteria that cause tuberculosis and the strain of streptococcus that is
called the “flesh-eating” bacteria. Others release toxins. Two examples of these are Salmonella (causes
food poisoning) and the strain of streptococcus that causes sore throats.
Antibiotics are compounds that block the growth and reproduction of bacteria.
Human Uses of Bacteria- 3 general ways that humans use bacteria: Food, synthesize drugs, & industry
Controlling Bacteria- 4 ways that bacteria can be controlled to prevent the spread of disease and
infection:
sterilization (heat), refrigeration , disinfectant, preservation of food (canning, freezing,salting)
Chapter 20: The Protista Kingdom
20-1 The Kingdom Protista
The members of the Protista kingdom, called protists, are eukaryotes and mostly are unicellular. They
have a variety of characteristics that do not fit in the Fungi, Plant, or Animal kingdoms.
Classification of Protists- Protists can be classified in several ways. One way is how they obtain their
nutrition.
20-2 Animal-like Protists: Protozoans
There are several phyla of animal-like protists.
Some have flagella (whiplike “tails” ) and absorb nutrients through their cell membranes.
Some use pseudopods (“false feet”) for movement and feeding. They surround food particles and take
them inside to digest. Amoeba are examples.
Some move by using cilia (hairlike) for movement and feeding. Paramecium are examples.
Some do not move and are parasites (live in or on other living things). The organism that causes malaria
is an example.
20-3 Plant-like Protists: Unicellular Algae
Some have flagella and chloroplasts so they can undergo photosynthesis and make their own food.
Euglena are examples.
Some are called diatoms. These have hard outer covering and can be used in scrubbing cleansers and
aquarium filters.
20-4 Plant-like Protists: Red, Brown, and Green Algae
Some of these kind of algae can be large and are called by another name, seaweed. They get their colors
because in addition to chlorophyll that is green, they also have other pigments. Some live in colonies.
Benefits and Human Uses of Algae
Algae is a major food source for organisms living in the oceans. Algae produces most of the oxygen
found in the air. Algae can be used in medicines, as wraps for sushi (a Japanese dish), and as
preservatives and in making plastics and other products.
20-5 Funguslike Protists
Examples of these are called slime molds, which live on rotting vegetation in the forest, and water mold.
Chapter 21: Fungi
21-1 The Kingdom Fungi
Fungi are eukaryotic heterotrophs that have cell walls. Their cell walls made of chitin.
Fungi digest food outside of their bodies and then absorb it. They absorb nutrients from decaying matter
in the soil. Some live like parasites absorbing nutrients from the bodies of their hosts.
Most fungi are multicellular. However, a common fungi, yeast is unicellular.
Structure and Function of Fungi
Multicellular fungi are composed of tiny filaments called hyphae. The bodies of multicellular fungi are
composed of many hyphae tangled together into a thick mass called a mycelium.
The reproductive structure is called a fruiting body . This is the part that grows above the ground (what
you see when you see a mushroom, for example.)
Reproduction in Fungi
Fungi reproduce both asexually and sexually. Asexually, the fruiting body produces a sporangia which
releases spores. That’s the “puff” or “smoke” that comes out of a puffball. Sexually, the nuclei of two
separate organisms join to form a new individual.
How Fungi Spread
Fungi spores are spread by the-wind, water, insects, and people.
21-2 Classification of Fungi
There are four main groups of fungi - common molds, the sac fungi, the club fungi, and the imperfect
fungi. An example of the common molds is bread mold. Yeast is an example of the sac fungi. Yeasts are
used in baking, brewing, and other types of fermentation.
An example of the club fungi is the mushroom, puffballs and shelf fungi. Not all mushrooms are edible.
If they are not edible, they are poisonous.
Penicillium is an example of a imperfect fungi. This is the organism from which the medicine, penicillin,
is made.
Ecology of Fungi
All Fungi Are Heterotrophs. A heterotroph does not make its own food. It must rely on other organisms
for its energy. Many fungi are saprobes. Saprobes (saprophytes) are organisms that obtain food from
decaying organic matter. Others are parasites and some are symbionts, these live in close and mutually
beneficial association with other species.
Fungi as Decomposers
As decomposers, fungi recycle nutrients by breaking down the bodies and wastes of other organisms.
Fungi as Parasites
Parasitic fungi cause serious plant and animal disease. Some of the fungal plant diseases include mildew
and wheat rust.
Human diseases include athlete’s foot, ringworm (not a worm, but a fungus), and yeast infections.
Symbiotic Relationships
One of the most common symbiotic relationships is between a fungus and an alga. This is called a lichen.
Spanish moss is a lichen that is seen in hanging in the trees in the south. Many lichens can be seen
growing on tree bark.