Unit 3 – Notes #2 Plant-Like Protists
(PHYTOPLANKTON) and Fungi-Like Protists
A) PHYTOPLANKTON- “Algae” is a generic term
that is used to categorize any aquatic
photoautotrophs that are either microscopic or
macroscopic but very primitive compared to a
true plant. Algae can include members belonging
to Kingdom Protista and Kingdom Plantae.
- Phytoplankton consists of free-floating
microscopic organisms that contain chlorophyll
giving them the ability to photosynthesize. The
majority of phytoplankton consist of unicellular
eukaryotes belonging to Kingdom Protista
- Plant-like protist characteristics:
a) Chlorophyll pigment to help trap sunlight,
b) Many possess a cell wall
c) Inhabit aquatic environments or moist soil.
1. Phylum – EUGLENOPHYTA
- Have both plant (photosynthetic) and animal
(motile and may resort to heterotrophism to
obtain nutrients) characteristics.
- Most common example : Euglena
- Lack a cell wall.
-They may photosynthesize using 10-20
chloroplasts if light is available, but may also
ingest organic matter through cystostome (a small
opening near flagellum) when necessary.
- Possess a red eyespot at anterior (front) end to
detect light, use single flagellum to move toward
light-filled environment.
- Euglenoids have a semirigid plasma membrane
called a pellicle.
2. Phylum – PYRROPHYTA (Fire Plants)
- Most commonly found in salt-water
environments.
- Many species are bioluminescent when agitated.
- Only eukaryotic organism to have plain DNA
like prokaryotic organisms rather than DNA
wrapped around proteins (histones).
- Most common examples : The Dinoflagellates
- Most have a brownish colour due to accessory
pigments and most possess two flagella.
- Dinoflagellates belonging to genus Gonyaulax
produce neurotoxins that cause paralytic shellfish
poisoning, when blooms give rise to heavy
concentrations of these dinoflagellates a condition
known as “Red Tide” occurs.
- This paralytic shellfish poisoning may pass up
the food chain causing death to the consumers.
- Store the products of photosynthesis as starch.
3. Phylum – CHRYSOPHYTA (Golden Plants)
- Include yellow-green algae, golden-brown algae
and diatoms.
- Most members store food as oil rather than as
starch.
- Diatoms produce fancy cell walls made of Silica,
which does not decompose.
- Much of the world’s petroleum was formed from
diatoms that lived 300 million years ago.
B. FUNGI-LIKE PROTISTS – Slime Molds
1. Phylum - ACRASIOMYCOTA (Cellular Slime
Molds)
- Amoeba-like cells that spend the majority of
their time as a unicellular animal-like protist.
They creep around phagocytosing other
microorganisms and bacteria.
- When conditions are unfavourable they
aggregate to form a large mass of cells that acts
like a single organism. It moves like a pulsating
slimy blob which may grow up to a diameter of 45
cm.
- This creeping cellular slime mold eventually
migrates toward light where the cells begin to
form stalks called fruiting bodies. These fruiting
body will begin to produce spores.
Spores  germination  ameba-like cell.
- Found in rotting wood, compost, and thick moist
lawns.
2. Phylum – MYXOMYCOTA (Acellular Slime
Molds)
- Found in same environments as Acrasiomycota.
- Amoeba-like cell divides for several generations,
but the cell’s nucleus is the only thing that divides.
- The cell gets very large and is called a
plasmodium (A giant cell that exists as a mass of
protoplasm with many nuclei). – A giant
multinucleated amoeba-like cell.
- When conditions become unfavourable, the
plasmodium forms fruiting bodies to produce
haploid spores which germinate into flagellated
cells that move to fuse with another such cell.  to
form diploid amoeba-like cell.
C) LIVING WITH PLANT-LIKE PROTISTS
a. Harmful Relationships: Very few are parasitic
but they may still cause a few problems.
i) Most Euglenophytes thrive in nutrient rich
water, when temperature is right they produces
“Blooms”. These blooms can block light from
reaching the bottom of the littoral (vegetative
shore) zone; killing plants.
ii) When dinoflagellates bloom they cause a
condition known as “Red Tide”. This toxin builds
up in shellfish which may result in the shut down
of certain fisheries.
b) Helpful Relationships.
i) Most phytoplankton play a crucial role in
producing food and they make up the bottom of
most aquatic food chains.
- 70% of all photosynthesis on Earth takes place
near the surface of the oceans. These
phytoplankton provide nourishment for
everything from shrimp  whales. The role
that plant-like protists play in oxygen production
is priceless!