Lesson 5: Protists Flashcards
Kingdom Protista
Eukaryotic microorganisms
have a nucleus
have membrane bound
organelles
Unicellular
some form colonies
The current theory suggests
that the first eukaryotic cell
took 2 billion years to evolve.
Evolution of Protists
Endosymbiont Hypothesis
This suggest that the more
complex eukaryotic cells arose as
complexes of prokaryotes living
together.
Chloroplasts arose from
blue-green algae
Mitochondria from aerobic
bacteria
Flagella from spirochete
bacteria
Classification of Protists
The kingdom was created to classify simple organisms that didn’t
fit anywhere else.
They can be defined by exclusion. That is, they are not plants,
animals, fungi or prokaryotes.
Protists are divided into the animal-like, plant-like and
fungus-like organisms.
Animal-like Protists
Most are free-living heterotrophs.
Examples: Paramecium,
Trichomonas
Some are motile through the use
of pseudopods or “false feet”
(projections of cytoplasm)
Example: Amoeba
Some are non-motile spore
producing parasites
Example: Plasmodium
Harmful Relationships
Plasmodium causes malaria
Trypanosoma causes African
sleeping sickness
Entamoeba causes dysentery
Helpful Relationships
Trichonympha live in the digestive
tracts of termites and allow them
to digest cellulose
Plant-like Protists
Contain chloroplasts and are
photosynthetic.
They are among the most
abundant photosynthetic
organisms in the oceans.
Commonly referred to as algae
A large group of these are
called diatoms and have silicon
(Si) in their cell walls creating a
glass like quality.
Harmful Relationships
They populate rivers and streams. Where there
is excessive nutrient runoff a bloom can occur,
resulting in eutrophication of the body of water
Some species produce a toxin that gets into food
sources
Ex. Red Tide
Helpful Relationships
Symbiosis: Dinoflagellates can live as
intracellular symbionts with coral reducing their
need for nutrients
Phytoplankton, the small photosynthetic
organisms in the surface water of the sea are the
producers in many food chains.
70% of the Earth’s O2 comes from these
organisms.
Fungus-like
Protists
Are heterotrophic
decomposers
Release digestive
enzymes to
decompose dead
organic matter
Are unicellular but
can act together as
a colony
Examples:
slime moulds
water moulds
