Kingdom Protista
Algae and Protozoans
Protista
Protista are categorized into
two taxons:
1. Protozoans- animal-like
single-celled organisms
2. Algae- plant-like single or
multi-celled organisms
Protozoans
Protozoans are protists that have animal-like
characteristics. They resemble animals in two
ways:
1. They are heterotrophs
2. They have the ability to move
They differ from animals because they are
unicellular while animals are multicellular.
Protozoans are classified by the way they
move. The 4 categories of Protozoans are:
Sarcodinians (move using a pseudopod)
Zooflagellates (move using flagella)
Ciliaphorans (move using cilia)
Sporozoans (form spores)
Sarcodinians
Sarcodinians move by extending lobes of cytoplasm, known as pseudopods.
The pseudopod is used for moving and eating. Cytoplasm streams into the
lobe and causes the lobe to grow and “ooze”. Because of these
pseudopods, sarcodinians have a “blob” like appearance.
Examples of sarcodinians are amoebas and foraminiferans.
pseudopod
Amoeba
Foraminiferan
Sarcodinians- Naegleria fowleri
There are a number of diseases caused by
sarcodinians. They include:
Naegleria fowleri: live in freshwater
lakes, natural warm water springs, or
streams, and can produce meningitis
(brain inflammation of the membranes
that covers the brain & spinal cord) in
swimmers. Although rare, the disease is
often fatal. The amoeba is inhaled and
burrows inside the nose, traveling to the
brain. Once there, the amoeba eats the
neurons (brain cells) and causes
meningitis.
Top Picture: image of amoeba
Bottom Picture: Brain tissue infected
by Naegleria fowleri. The dark dots
are the amoebas. Notice the empty
space around the dots; this space
used to be tissue before the
amoebas digested it.
Sarcodinians- Entamoeba histolytica
Entamoeba histolytica: transmitted thru
fecally (from feces) contaminated food and
water and causes amoebic dysentery.
Symptoms of amoebic dysentery are:
abdominal pain and cramps and diarrhea,
containing blood, pus, and mucous. Once
the amoeba is ingested and inside the
small intestine, it releases an enzyme that
dissolves tissue. This dissolving allows
them to penetrate into the intestinal lining,
where lesions develop and can turn into
extensive ulcers that cause dysentery with
watery stools containing blood. If left
untreated, the amoebas can contaminate
other parts of the body causing infection in
the liver and possibly the brain, lungs,
heart, or other tissues, and death can
result.
Entamoeba histolytica infecting cells
Liver “eaten” away by the amoebas
Zooflagellates
Zooflagellates move by moving a tail, known as a flagella. Some
zooflagellates are free-living freshwater organisms while others live inside
organisms- either in a symbiotic relationship or a parasitic relationship.
Examples of zooflagellates are trypasnosoma, leishmania, giardia,
trichonympha and chlamydomonas.
flagella
trypanosoma
giardia
Zooflagellates- Trichonympha
Trichonympha are a type of zooflagellates that live inside
the gut of termites. They have a symbiotic relationship
with termites- they give the termite the ability to break
down wood particles and the termite provides a home
and food for the zooflagellate. Trichonympha breaks
down the cellulose (a type of carbohydrate) in wood
and releases the nutrients from the wood that the
termite absorbs. If termites did not have
Trichonympha, they would not be able to eat wood.
Trichonympha
under the light
microscope
Left Picture: Termite
Right Picture:
Scanning electron
micrograph of a
Trichonympha
Zooflagellates-Trypanosoma
Trypanosoma is a parasitic zooflagellate that causes
African sleeping sickness. Trypanosoma produces a
toxin that destroys the host’s red blood cells, causing
the host to become weak. The initial bite leaves a
distinctive sore spot. Symptoms may include swollen
lymph nodes, irritability, fever, severe headache,
fatigue, muscle and joint pain, and a skin rash. During
the second stage of the disease, the parasite crosses
the blood-brain barrier and attacks the central nervous
system. Neurological complications include slurred
speech, confusion, and difficulty with walking. The
zooflagellate is transmitted from host to host through
the bite of a tsetse fly.
Trypanosoma infecting red blood cells
Tsetse Fly
Child with African sleeping sickness
Zooflagellates-Giardia
Giardia is found in the feces of infected
animals or humans. To become infected, a
person must consume contaminated food
or water including drinking from streams or
rivers. Once ingested, the Giardia adhere
to the lining of the small intestine and feed.
Symptoms of Giardia include: diarrhea,
stomach cramps, bloating, gas, fatigue
and weight loss. To avoid Giardia, hikers
will boil their water before they drink it to
kill the parasite.
Giardia infecting
intestinal cells
Scanning electron
micrograph of Giardia
Giardia
Ciliaphorans
Ciliaphorans, or ciliates, are protozoans that have bodies covered with short
hair like projections called cilia. The cilia beat like oars to propel these
protists through the water. Most ciliates live in freshwater habitats but some
live in salt water. Most ciliates are not parasitic to humans.
Examples of ciliates are paramecium, tetrahymena and balantidium.
cilia
Ciliates-Paramecium
Paramecium is one of the most abundant
ciliates found in freshwater. It is covered
with cilia that are used to move the
paramecium and help it to sweep food
into its oral groove. A oral groove is an
opening in the cell that allows the
organism to consume algae and prey.
Once food is in the oral groove, the cell
mouth pinches off around the food
forming a food vacuole.
Since paramecium live in an aquatic
environment, water is constantly diffusing
into the cell. To ensure that the cell does
not burst in this hypotonic environment,
the cell has a contractile vacuole. The
vacuole fills with water and when full, it
squeezes out the excess water. All
protozoans have a contractile vacuole.
Oral groove
Contractile vacuole
Ciliates- Balantidium
Balantidium is the only known parasitic ciliate
of humans. It is contracted through the
ingestion of water or food that has been
contaminated by feces. Balantidium
resides in the host’s intestine and feeds
on fecal material and cell fragments. The
ciliates often invade the lining of the
intestines and produce severe ulcers.
Symptoms of an infections include:
diarrhea, weight loss, nausea, vomiting,
abdominal pain, weakness and blood and
mucus in feces.
Balantidium in
the intestines
Balantidium
Sporozoans
Sporozoans are parasitic protozoans that form spores. When these protozoans
are immature, they form spores with thick, protective walls.
Examples of sporozoans are Plasmodium and Toxoplasma.
Spores inside host cells
Sporozoans-Plasmodium
Plasmodium is a sporozoan that causes malaria in
humans. Mosquitoes are the carriers of the
sporozoan. When the mosquito bites a human, the
sporozoan infects the liver and multiplies. It then
infects the red blood cells, causing them to burst
every 48 hours. Symptoms of malaria include high
swinging fever, shivering, chills and intense
perspiration.
Plasmodium spores bursting
from red blood cells
Life cycle of
Plasmodium
Sporozoans-Toxoplasma
Toxoplasma is a sporozoan that
infects human muscle and
nerve tissue. Cats are carriers
of the disease and toxoplasma
is found in cat feces.
Symptoms of the disease are:
headache, fever, confusion,
seizures, abnormal behavior,
and coma.
Toxoplasma Sporozoan
Life Cycle of Toxoplasma
Algae
Algae are protists that have plant-like characteristics
that can perform photosynthesis. They are similar
to plants because they contain chlorophyll and
produce oxygen as a by-product of
photosynthesis. Algae has been broken down
into 2 categories- each with sub categories. They
are:
1.
Uni-cellular algae
- Dinoflagellates
- Diatoms
- Euglenoids
2.
Multi-cellular algae
- Green Algae
- Red Algae
- Brown Algae
Uni-Cellular Algae
1. Dinoflagellates: algae with 2 flagella that spin
the cells through the water. Most
dinoflagellates are saltwater algae. Some
have symbiotic relationships with jellyfish,
sea anemones and coral by supplying
nutrients to these animals.
2. Diatoms: algae that have glasslike cell walls
containing silica and contain oil. Because of
this oil, the diatoms float in the water. When
they die, the silica cell wall sinks to the
bottom of the ocean and accumulates.
These accumulations can be used in
Diatoms
cleaners, abrasives and toothpaste.
3. Euglenoids (Euglena): algae that do NOT have
a cell wall, contain flagella and chloroplasts.
If euglena is grown in the dark, they loose
their chloroplasts and become heterotrophs.
Euglena
Multi-Cellular Algae
1. Green Algae (Chlorophyta):Most green
algae live in freshwater, but some are
found in shallow places in the ocean.
Examples of green algae include:
Chlamydomonas, Volvox and Ulva.
2. Red Algae (Rhodophyta): Red algae
grows mainly in warm saltwater. Not all
red algae is red- it is categorized as red
algae because of the other light
collecting pigments the algae has other
than chlorophyll. Many red algae are
found in the tropics around coral reefs.
3. Brown Algae (Phaeophyta): Brown
algae grows mainly in cool saltwater.
The body of brown algae is known as
the thallus and contain air bladders
that fill with air to allow the algae to float.
Kelp is an example of brown algae.
Chlamydomonas ulva
Red algae
Brown algae
with air
bladders
volvox