PROTISTS
The Kingdom Protista contains nearly all
of the single-celled eukaryotes as well as
multi-cellular algae.
Protists Have Complex Cells
Protists have a nucleus which
contains chromosomes.
Membrane-bound organelles,
such as chloroplasts and
mitochondria, are found in the
cell’s cytoplasm.
Chloroplasts occur in
autotrophic protists.
Most protists are either
autotrophic or heterotrophic,
though Euglena is both.
Many Protists Are Capable of Movement
•Cilia and Flagella are hair-like projections
that produce movement and consist of similar
internal microtubule structures.
•Euglena swim about powered by a flagellum,
that lashes back and forth like a whip.
Cilia video clip (.39)
Flagellates video clip (.50)
Paramecium are
covered with
thousands of tiny
hair-like projections
called cilia, that beat
back and forth like
miniature boat oars
to propel it forward
or backward.
Amoeba move and
feed using fingerlike, flowing
extensions of the
cell body called
pseudopods or
“false feet.”
Classification of Protists
• The members of the
Kingdom Protista
exhibit a greater variety
of sizes and structures
than do the members of
any other kingdom.
• Because of the diversity
in the Kingdom
Protista, biologists
disagree on how many
phyla it should contain.
Algae
•Most species of algae live in
fresh water or salt water,
although they can also be found
in moist soil, on damp rocks,
and on the shady sides of trees.
•Algae produce about 1/3 of the
oxygen in the atmosphere.
•They form the base of the
aquatic food web (fishes,
whales, and humans depend on
algae for the food they eat and
the air they breathe).
Heterotrophic Protists
•Most heterotrophic protists play the role
of either carnivore or herbivore.
•In the plankton, some heterotrophic
protists “graze” on phytoplankton, and
others prey on these grazers.
•Other heterotrophic
protists are
parasites or decomposers.
Diseases Caused By Protists
In central Africa, a protist transmitted by the bite
of a large fly, the tsetse fly, causes the disease
sleeping sickness. This disease is often fatal to
humans and domestic animals such as cattle,
sheep, and pigs. Livestock cannot be
raised in much of central
Africa because of the
presence of sleeping
sickness.
Protists and Disease
Many protists do not affect the health of
human beings.
However, millions of people are infected by
and die from various protist-caused diseases
each year.
Disease-causing protists are
transmitted mainly by insects
and contaminated water.
Malaria
•Currently, 300 million to 500
million people are infected with
malaria.
•This disease kills more than 2
million people each year, making
it one of the most serious human
diseases.
•Malaria is the leading cause of
death among young children in
tropical countries.
•Malaria is caused by protozoa of
the genus Plasmodium, which is
carried between human hosts and
mosquitoes.
•Symptoms of malaria are
high fever, delirium, and
sweating. Severe chills
follow the fever and can last
until the next outbreak.
•Malaria sometimes weakens
its victims so much that they
die from other infections.
•The drastic loss of blood
cells (up to 40%) causes
anemia and can result in fatal
brain or kidney damage.
•Quinine was used in the
1600s to reduce the
symptoms. Derivatives such
as chloroquine and
primaquine are used today to
treat and prevent malaria.
p. 367
Malaria Vaccine
Dr. Manuel Patarroyo, a Colombian
biochemist and physician, has developed an
unorthodox, synthetic malaria vaccine called
SPf66. This vaccine is made from malaria
proteins chemically linked together. The antibodies that it
includes recognize the real malaria parasites rather than
just the vaccine’s synthetic proteins. Trials have shown
that the vaccine offers some amount of prevention
against malaria infections, including those carried by the
drug-resistant parasites. At first, scientists were skeptical
about the vaccine because it originated from research in a
small country and its preparation was unusual. However,
the World Health Organization is calling for further
research.
Malaria Strikes Back
Malaria has not been eliminated.
•The number of cases has been increasing since the
mid-1970s.
•Human efforts have been thwarted by advances in the
parasite and the mosquito.
•The parasite frequently changes configurations
(mutation), making them invisible to the body’s
immune system.
•Parasites have also developed resistance to
some of the drugs.
•Mosquitoes have evolved resistance to
insecticides.
Human
Diseases
Caused By
Protists
Disease
Host
Organism
Amoebic
dysentery
Humans
Entamoeba
Malaria
Humans
Plasmodium
Toxoplasmosis
Humans, cats
Toxoplasma
Giardiasis
Humans
Giardia
Sleeping
Sickness
Humans, tsetse Trypanosoma
flies
Chagas’
disease
Humans,
kissing bugs
Trypanosoma
Leishmaniasis
Humans, sand
flies
Leishmania