Introduction to the Kingdom Protista. Main characteristics, classification and different types of protists. Translation revision by Steven T. Gosch.

1. Pablo León Cruz www.biogeosfera.es
KINGDOM PROTISTA

2. Protists
Main characteristics of protists
 Eukaryotic organisms.
 Can be unicellular or multicellular.
 Very small, usually microscopic.
 Very simple structure: they have no organs or tissues.
 This kingdom includes eukaryotic living beings that, due to their
characteristics, cannot be included in the other kingdoms, since they are
not fungi, plants, or animals.
 There are two large groups: algae and protozoa.

3. Classification of the protists
Algae
 Eukaryotic organisms.
 Can be unicellular or multicellular.
 Unicellular algae are microscopic in size, whereas multicellular can be
several meters long.
 All algae live in aquatic environments.
 The vast majority float on water and are part of the plankton.
 Nutrition: Autotrophic.
 Interaction: Free-living, sometimes form colonies.
 Reproduction: Can be asexual by bipartition in unicellular organisms or
by fragmentation in multicellular organisms but can also be sexual.
 They are classified into green algae, brown algae and red algae.

4. Classification of the protists
Algae classification
 Unicellular algae: Can live freely, like Euglena, or form colonies, like
Volvox.
 Multicellular algae: Classified by the pigments they use for
photosynthesis.
 Green algae or chlorophytes: Pigment is chlorophyll. Almost all are
found in freshwater areas, although there are some marine algae.
 Brown algae or pheophytes: Pigment is fucoxanthin. Form marine
forests in the oceans of temperate and arctic areas.
 Red algae or rhodophytes : Main pigment is phycoerythrin. Inhabit
marine ecosystems located in tropical regions.

5. Classification of the protists
Green algae

6. Classification of the protists
Brown algae

7. Classification of the protists
Red algae

8. Classification of the protists
Protozoa
 Eukaryotic organisms.
 All are unicellular.
 All are microscopic.
 All protozoa live in aquatic environments.
 Move using cilia, flagella or pseudopods. Some are sessile.
 Nutrition: Heterotrophic organisms.
 Interaction: Most are free-living, though some are parasitic.
 Reproduction: Usually asexual by bipartition.
 Classified as flagellated, ciliated, rhizopods or sporozoans.

9. Classification of the protists
Classification of protozoa
 Flagellated: Have one or more flagella for movement and can be parasitic
or free-living. An example is Trypanosoma.
 Ciliated: Have cilia with which they can move and can be parasitic or free-
living. An example is Paramecium.
 Rhizopods: Move through pseudopods and can be parasitic or free-living.
An example is Amoeba.
 Sporozoans: No structures for movement and are parasitic. An example is
Plasmodium.

10. Classification of the protists
Different types of protozoa

11. Importance of protists
Protists are important for the following reasons
 Algae are part of the phytoplankton, which is the set of producer
organisms in aquatic ecosystems.
 Certain species of algae have high culinary value and are used in human
food, especially oriental cuisine.
 Agar, a substance used in microbiology, the preparation of medicines,
perfumes and certain foods such as soup and ice cream, comes from the
cell wall of some algae.
 Protozoa are part of the zooplankton, a set of microscopic organisms that
feed many small fish.
 Many protozoa have an important role in the decomposition of organic
matter in very humid soils or stagnant water.
 Parasitic protozoa can seriously damage the health of humans. This is the
case for dysentery, malaria and sleeping sickness.