The Protists (Kingdom Protista)
The Kingdom Protista
- Found in the domain eukarya.
- Protista is likely not one kingdom, it probably consists of
many kingdoms. Scientists cannot agree. For our
study, we are going to consider protists to be in one
kingdom (The Kingdom Protista).
- Protists are generally unicellular but can be colonial like
volvox. Some protists can be relatively simple
multicellular organisms (Body is a thallus).
-Protista includes a wide variety of species.
-Protists include organisms that are fungal-like, animal-like
and/or plant-like. Eukaryotes that don’t belong in the
other eukaryote kingdoms are often put into protista.
- Protists are the most primitive eukaryotes and are the first
eukaryotes to appear in evolutionary terms.
A Cladogram Showing
Phylogenetic
Relationships Among
Some Groups of
Protists.
Protist groups shown
are Heterokonts,
Avelolates,
Euglenoids,
Amoebozoa and Early
Protists.
Note: The kingdoms
animalia (Animals),
fungi and plantae
(Land Plants) are
shown on this The term “land plants” is general and includes all
organisms in the plant kingdom. This includes aquatic
cladogram.
plants such as cattails, cypress, etc.
Physarum, a slime mold.
The kingdom
protista includes
organisms that are
fungal-like but do not
fit into the kingdom
fungi. Such a protist
example is slime
mold.
The kingdom protista includes organisms that are animal-like
but do not fit into the kingdom animalia. These animal-like
protists are called protozoans. Examples include amoeba
and paramecium. These 2 protozoans are classified by how
they move and they are found in different evolutionary
groups. Amoeba move by pseudopods. Paramecium move
by cilia.
An amoeba
The kingdom protista includes organisms that are plant-like
(they photosynthesize) but do not fit into the kingdom
plantae. Such protist example include seaweed and
euglena.
Photosynthetic protists are often called algae.
The feathery red alga Polysiphonia.
Algae (The Photosynthetic Protists)
- 20,000 to 30,000 known species.
- Mostly Aquatic.
- Single cells or clusters, filaments, sheets or
3-dimensional.
- Basis of many aquatic food chains (Algae are part of
phytoplankton).
Volvox
Phytoplankton, which is a
photosynthetic organism
(generally one-celled) that
is part of the plankton, a
body of floating cells near
the surface of fresh or
saline bodies of water.
Phytoplankton (grasses of
the sea) make ½ of all the
oxygen gas in the
atmosphere.
Algal Diversity
(a) A unicellular Micrasteria.
(b) A colonial Gonium.
(b)
(a)
(c) A colonial Volvox.
(d) Filaments of Spirogyra.
(e) Caulerpa with
differentiation into rootlike,
stemlike, and leaflike
regions. All of these are
green algae.
Seaweeds are (f) the
intertidal red alga Porphya
and (g) the brown alga
(e)
Fucus.
(d)
(c)
(f)
(g)
Euglenoids
- Usually Unicellular and Photosynthetic.
- Possess eyespot,
which is a unique
organelle that orients
individuals to light.
- No known sexual
reproduction.
- Move by 2 flagella.
- No cell wall.
- Found mainly in
polluted freshwater.
- 1/3 of all species are
photosynthetic but
the majority ingest
food.
- Example: Euglena
2 Euglena Cells.
Note the
chloroplasts
&red eyespots.
Alveolates
- Possess membranebounded sacs lying
beneath the plasma
membrane.
- Examples:
Dinoflagellates (Cause
Red Tides), formanifera,
ciliates (Paramecium)
and the apicomplexa.
Paramecium
Heterokonts
- All heterokonts all
have 2 unequally
sized flagella.
- Includes several algal
groups.
- Examples: Golden
algae, brown algae
(Fucus), diatoms and
the oomycota (water
molds, downy
mildews).
- Diatoms are typically
single-celled algae
with silica cell walls
that create vast
deposits over time.
The Giant Kelp,
a brown algae
Protista and Humans
- Protists cause some serious diseases like amoebic
dysentery and malaria. Malaria is caused by protozoan
parasites of the genus Plasmodium (phylum Apicomplexa).
- Algae serve as medicine, food and fertilizer
– Seaweed is an important food.
– Industrial Use
• Diatomite (or diatomaceous earth) is a sedimentary rock
composed of fossilized diatom cell walls. Diatomite is
used in cement, stucco, plaster and abrasives.
• Agar - a polysaccharide analogous to starch and cellulose
that is used in the microbiology laboratory to grow
bacteria.
Protista Reproduction
- Some protists carry out conjugation, a primitive form
of sexual reproduction.
- Algal life cycles include gametic, zygotic, and sporic
types (See Life Cycles Slide Show). In many cases,
however, asexual reproduction (by cell division,
fragmentation of filaments, or mitospores) is more
common than sexual reproduction.
The Kingdom Plantae (The Land Plants)
Evolved from Protists
From an evolutionary
perspective, red algae
and/or green algae
gave rise to the land
plants
(The Kingdom
Plantae).
A great wealth of molecular data support the idea that red algae, green algae,
and land plants belong in the same clade. Biologist have long suspected – on
the basis of cellular details, biochemistry, life cycles, and morphology – that
green algae gave rise to land plants. Analyses of proteins and nucleic acids
have provided overwhelming support for this suspicion and also showed that
red algae belong in this clade. So are red algae and green algae, protists or
plants? Maybe both or somewhat in between.
BIO 141 Botany with Laboratory
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