• Protist means “the very first”
• They are mostly unicellular, but
some are multicellular (algae).
• Protists can be heterotrophic or
autotrophic.
• Most protists live in water, although
there are some that live in moist
soil or even the human body.
• ALL protists are eukaryotic, meaning
they have a nucleus.
• Protists are extremely important to
human life, they help us recycle,
eliminate organic wastes and
bacteria, and they are also crucial
in the production of many
medicines, vaccines, and other
medical advancements.
Lots of pretty protists!
• The phylum Rhizopoda includes a
large group of protists that move
by means of pseudopods (fake
feet), extensions of the
cytoplasm.
• Most Rhizopodians use their
pseudopodia to capture prey and
also for locomotion. Rhizopods
are heterotrophic, feeding on a
wide range of bacteria, algae and
other protists.
• Rhizopods are found in
freshwater, marine habitats, and
in soil.
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Domain: Eukaryota
Kingdom: Rhizaria
Phylum: Foraminifera
Foraminifera (forams for short) are unicellular
protists with shells. Their shells are also referred to
as tests because in some forms the protoplasm covers
the exterior of the shell. The shells are commonly
divided into chambers which are added during growth,
though the simplest forms are open tubes or hollow
spheres. Depending on the species, the shell may be
made of organic compounds, sand grains and other
particles cemented together, or crystalline calcite.
Forams are highly porous in structure, having millions
of small holes in their shells.
They move and catch their food with a network of thin
extensions of cytoplasm called reticulopodia, similar to
the pseudopodia of an amoeba, although much more
numerous and thinner. The reticulopodia emerge from
the pores of the shell, and extend outwards.
Forams are the most common marine plankton species.
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Of the approximately 4000 living species of foraminifera
the life cycles of only 20 or so are known. There are a
great variety of reproductive, growth and feeding
strategies, however the alternation of sexual and
asexual generations is common throughout the group.
An asexually produced haploid generation commonly
form a large proloculus (initial chamber) and are
therefore termed megalospheric. Sexually produced
diploid generations tend to produce a smaller
proloculus and are therefore termed microspheric.
The largest living species have a symbiotic relationship
with algae, which they "farm" inside their shells.
The most unique aspect of forams is that their benthic
prehistoric fossils can be found by the millions on ocean
floors, they are particularly useful for dating sediments
and rocks with great accuracy.
The pink sands of some Bermuda beaches get much of
their color from the pink to red-colored shells of a
foraminiferan. In regions of the deep ocean far from
land the bottom is often made up almost entirely of the
shells of planktonic species.
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Domain: Eukaryota
Kingdom: Protista
Phylum: Tubulinea
Amoebas were originally named Proteus
animalcule, after the Greek god Proteus,
who could change his shape.
Amoebas are unicellular organisms ,
they use their pseudopodia to move and
engulf food particles (phagocytosis).
They will eat anything that is smaller
than themselves, usually bacteria or
protozoans.
Amoebas have one or more nuclei, a
simple contractile vacuole that helps
keep maintain osmotic equilibrium
(osmoregulation), a membrane to let
things in and out of the cell, and a food
vacuole for engulfed food particles.
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When amoebas move, they extend their
pseudopodium, anchor their tips, and then more
cytoplasm streams into the pseudopodium.
Amoebas inhabit both freshwater and marine
environments, and are also abundant in soils. The
majority of amoebas are free-living, but some are
important parasites including Entamoeba
histolytica, which causes amoebic dysentery, an
infection of the intestines marked by severe
diarrhea with blood in humans.
Amoebas usually reproducs asexually by a
process called binary fission (splitting in two), in
which the cytoplasm simply pinches in half and
pulls apart to form two identical organisms
Amoebas are helpful when they control algae in
ponds, lakes, and streams. They also provide
small animals with food. Amoebas are a problem
when they live in unhealthy areas, such as places
with raw sewage.
Amoebas can range in size from
.5 mm to 3 mm or more!
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While most amoebas are benign, there are a select few that cause
considerable damage to humans.
In the summer of 2011, there were 8 deaths caused by an amoeba
that was found in rivers.
The amoeba, called Naegleria fowleri, is the only type that infects
humans and is more than 95% lethal. The first death in 2011
occurred in June in Louisiana, according to the CDC.
The amoebas enter the human body through the nose after an
individual swims or dives into warm fresh water, like ponds, lakes,
rivers and even hot springs.
But when an amoeba gets lodged into a person's nose, it starts
looking for food. It ends up in the brain and starts eating neurons.
Early symptoms include headache, fever, nausea, vomiting and neck
stiffness. Later symptoms include confusion, lack of attention to
people and surroundings, loss of balance, seizures and
hallucinations.
The amoeba multiplies, and the body mounts a defense against the
infection. This, combined with the rapidly increasing amoebas,
cause the brain to swell, creating immense pressure. At some point,
the brain stops working.
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Radiolaria are protozoa distinguished 1) by segregation of their soft
anatomy into the central capsule, containing the endoplasm, and the
surrounding ectoplasm, and 2) by their siliceous (glassy) skeletons of
the large majority of species. Radiolarians have existed since the
beginning of the Paleozoic era, producing an astonishing diversity of
intricate shapes during their 600 million year history. They take their
name from the radial symmetry, often marked by radial skeletal
spines, characteristic of many forms.
The central capsule is enclosed in a membrane. It contains not only
the nucleus but mitochondria (respiratory organelles) and Golgi
bodies (secretory organelles), as well as vacuoles, lipid droplets, and
food reserves. Reproduction, respiration, and biochemical synthesis
are functions carried out in the central capsule.
The ectoplasm extends into a complex network of pseudopodia,
called axopods. Axopods aid the in the buoyancy of these organisms.
Pseudopodia surround projecting skeletal spines, protecting them
from dissolution in sea water. The pseudopods may be quite active,
capturing prey and disposing of wastes, and reacting to external
stimuli. They are able to cling to and move the individual about
surfaces of laboratory vessels, and may thus cling to foreign objects
in nature.
• Radiolarians are mostly marine plankton.
• Reproduction of radiolarians can occur
both sexually and asexually.
• Radiolarians also participate in symbiotic
relationships with algae, especially
zooxanthellae.
• Radiolaria are also separated into two
separate lineages, polycystina, and
spasmaria.
• When radiolarians die, they become ooze
at the bottom of the sea.
• Radiolarians, like forams, are used in the
fossil record for dating.
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Slime molds are independent organisms
that mass together and move as a group
to find new nutrition sources.
Their name refers to a period in their lives
where they seem to be a mass of
gelatinous “slime.”
Slime molds reproduce with spores, they
are usually found in soil, lawns, and forest
floors.
Slime molds feed off dead plant matter.
The plasmodial slime molds form a
structure called a plasmodium, a mass of
cytoplasm that contains many nuclei but
has no cell walls or membranes to
separate individual cells. The plasmodium
is the feeding stage of the slime mold. It
moves much like an amoeba, slowly
sneaking along decaying organic material.
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Acrasiomycota are cellular slime molds that
are haploid blobs that live independently in
much the same fashion as other slime molds
until food or water becomes unavailable.
Interestingly, they then leave a chemical trail
that acts like a pheromone to attract other
cellular slime mold cells to a central location,
where they form a pseudoplasmodium.
During this stage, the individual cells, by still
unknown means, communicate and
coordinate their movements to act as one
large blob. As the pseudoplasmodium
moves, it can divide and (in unfavorable
conditions, such as high heat or excessive
dryness) form fungi-like fruiting bodies that
develop haploid spores. The haploid spores
remain dormant until favorable conditions
return, at which time they grow into
individual haploid slime molds.
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Acellular slime molds, Myxomycota, are unique in
producing structures called plasmodia, which
appear to be a mass of cells, but in reality are one
large cell that contains many nuclei free to float
unhindered by internal membrane barriers. The
plasmodium slime mold remains in this blob stage
feeding on bacteria, fungi, and other organic
nutrients, typically found on the floor of a
deciduous forest, because of its mobility. In its
blob form, it also has greater surface area to
transfer materials to and from the environment.
However, when food or water is scarce or the
environment becomes too dry, the plasmodium
transfigures into the moldlike mass and produces
the characteristic fungilike fruiting bodies. The
fruiting bodies create haploid spores via meiosis,
which then combine to become diploid and begin
growing into amoebalike blobs when conditions
again become favorable.
• Although slime molds do not cause any type
of diseases, they can be very alarming to find
in your backyard.
• Slime molds often kill gardens by consuming
their nutrients.
• Slime molds are important in labs, since they
are not difficult to grow, they are inexpensive,
and they are very complex.