Week 07
Protists
Reading Modules in Principles of Biology:
87. Protists
• Protist Characteristics
• Five Main Groups of Eukaryotes
88. Protists in Our Environment
• Roles of Protists in Ecosystems
89. Lineages of Protists
• Lineage of Protists
Reminder: e questions you encounter embedded within the reading or after it are there to give you feedback on
your understanding of the text. Answering those questions is optional (but encouraged), and your answers to those
questions are not visible to me or recorded by me.
This Week’s Schedule
Course Related
Other
SUN
MON
TUE
†
Lecture: Week 07 Reading Quiz (8:00–8:05)
Basic Protist Phylogeny & Introduction
Begin Protist Survey
Lab: Protist Diversity
Prelab Activity due in MasteringBiology by 8 a.m.
WED
THU Lecture:
Finish Protist Survey
Protist Ecology
FRI
SAT Week 07 Homework due in MasteringBiology by 10 p.m.
†
†Indicates
an assignment due date.
Lecture art and a variety of other materials are available online. Log into Canvas, navigate to
the current week, and open the resource folder to see what is available.
Explain how historical protist phylogeny was inadequate and led to the current
five-group theory.
•
✓ ✓
e problem with the protists is that they are a paraphyletic group, meaning that
they include a common ancestor (some very ancient eukaryotic cell) but only
some of its descendants. e descendants not included in the protists are the
plants, fungi, and animals.
Describe the main characteristics of protists.
•
All protists are eukaryotic.
•
Most are unicellular, although there are common exceptions to this, such as
seaweeds.
•
Many protists have evolved unique (and sometimes downright weird) organelles
that help them function.
•
Protists are extremely diverse in their metabolism, and some can even switch
between different types of metabolism depending on the conditions.
•
Some protists can reproduce sexually. (is is a uniquely eukaryotic
phenomenon.)
Explain endosymbiotic theory as the mechanism responsible for protist
diversity, including the role of secondary symbiosis.
•
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Learning Outcomes for Week 07
✓ ✓
✓ ✓
We can trace past endosymbiotic events by looking at the numbers of membranes
surrounding certain organelles.
Describe the current five-group theory of eukaryotic phylogeny.
•
Remember: the goal is to organize organisms into monophyletic groups (clades).
•
We are in the process of reclassifying the eukaryotes into monophyletic
supergroups. is will better describe their evolutionary relationships to each
other.
✓ ✓
Explain the roles of protists in the environment or in relation to other
organisms.
✓
Summarize the connection between protist populations and climate change
issues.
✓
Describe characteristics of each of the five main groups of protists.
✓ ✓ ✓
•
is is how we’ll spend most of our class time this week.
Compare and contrast characteristics of protist diversity.
✓ ✓ ✓
Recognize current proposed phylogenic relationships between protists and
other eukaryotes.
✓ ✓
•
is is something we’ll come back to as we cover the plants, fungi, and animals as
well.
Note: is week’s lab will cover protist diversity, with emphasis on the non-algae groups. e
Week 09 lab (after Spring Break) will deal with algae and their relationship to plants.
Terms, Titles, and People You Should Know
secondary endosymbiosis
mixotroph
alga (sing.), algae (pl.)
protist
dinoflagellates
plankton
producer
supergroup
Phylogenetic Groups You Should Know (with pertinent examples)
is table is intended to serve as a study guide following what we cover in class.
Grouping
Shared Derived Characters
Representative
Members
Supergroup
Excavata
• All members are unicellular
• Possess greatly reduced mitochondria
Euglena (common
freshwater organism)
(named for their
excavated surface
groove)
• Possess a groove along cell surface, possibly used for
feeding or for flagellum attachment
Giardia (intestinal
parasite)
Supergroup
Chromalveolata
• Many scientists believe this group originated from a
secondary endosymbiosis event.
Alveolates:
Dinoflagellates
Apicomplexans
Ciliates (incl.
Paramecium)
• Contains two subgroups:
(their name is a
portmanteau* of
Chromista, an older
grouping of algae, and
Alveolata)
Supergroup
Rhizaria
(rhizo- means “root,”
referring to their
pseudopod structure)
Alveolates: Possess membrane-lined sacs
beneath plasma membrane (alveoli). All
members are unicellular.
Stramenopiles: Often have two flagella, one
“hairy” and one smooth. Contains both
unicellular and multicellular members.
• is is a diverse group of protists defined by DNA
similarities.
Stramenopiles:
Diatoms
Water molds
Brown algae
Golden algae
Forams
Radiolarians
• All members are unicellular, amoeba-like organisms
with thread-like pseudopods that emerge from hard
exoskeletons.
• Radiolarians have silica-based exoskeletons, while
foraminiferans (a.k.a. forams) have calcium
carbonate-based exoskeletons.
*A portmanteau is a word that is created by joining two other words together. Examples of portmanteaus: smog
(smoke + fog); brunch (breakfast + lunch), etc.
Supergroup
Archaeplastida
(archae– means
“ancient”; plastida
refers to presence of
plastids)
• Chloroplast-containing organisms that perform
photosynthesis.
Rhodophytes
(red algae)
• is group contains both unicellular algae,
multicellular algae, and all plants.
Chlorophytes
(green algae)
• Red algae contain slightly different pigments than
green algae and plants; this allows them to absorb
sunlight in deeper seawater.
Charophytes
(green algae)
• Green algae called charophytes are the closest
protistan relatives of plants.
Supergroup
Unikonta
• Very diverse group assembled based on similar
DNA sequences.
• Subgroups:
(uni– means “one”;
kont– refers to a
flagellum. All members
of this group possess,
at least at some point
in their lives, a single
flagellum)
Amoebozoans: “true” amoebae that have tubular
pseudopods and slime molds.
Opisthokonts: unicellular and multicellular
organisms characterized by the presence of a
single, posterior flagellum. Includes:
• Choanoflagellates: closest protistan
relatives of animals
• All animals
• All fungi
Plant Kingdom
(Weeks 09 & 10)
True amoebae
Slime molds
Fungi Kingdom
(Week 08)
Animal Kingdom
(Weeks 11 & 12)