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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Protists (Chapter 28)
Protists
Broken into three general categories based on ecological context:
1. More structural and functional diversity than any other
group of organisms…
2. Most are unicellular, some colonial and multicellular…
3. Most nutritionally diverse eukaryotes
1. Photosynthetic (plant-like) protists
- algae
2. Ingestive (animal-like) protists
- protozoans
3. Absorptive (fungus-like) protists
A. photoautotrophs
B. heterotrophs
C. mixotrophs – combine photosyn with hetertrophic
nutrition
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Protists
Phylogeny of protists
Fig. 28.4
How did such incredible diversity arise?
Many species resulted from two rounds of endosymbiosis…
Phylogenetic tree showing the major clades of protists.
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Phylogeny of protists
Phylogeny of protists
Fig. 28.4
Fig. 28.4
What’s a clade?
A complete branch of a phylogenetic tree. Above how many clades are highlighted?
Two, the blue and the red because these are complete branches. The green is not
complete.
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Euglenozoa
Fig. 28.8
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Euglenozoa
Fig. 28.8
Characterized by spiral or
crystalline rod within flagella in
addition to 9+2 arrangement of
microtubules.
Cyrstalline structure has unknown
function.
Phylum kinetoplastid
Ex. Genus Trypanosoma
- Causes sleeping sickness
- Spread by African tsetse fly
- Fatal if untreated
- Evade immune system by repeatedly changing the proteins on the surface of the cell
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Euglenozoa
Fig. 28.8
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Phylogeny of protists
Fig. 28.4
Phylum euglenid
Ex. Euglena
- Found in freshwater
- Photoautotroph if sunlight available otherwise heterotroph by absorbing
nutrients from environment (mixotroph)
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Alveolata
Fig. 28.8
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Alveolata
Characterized by sacs below
membrane called alveoli having
yet unknown function
Phylum dinoflagellates
- Abundant as both marine and freshwater phytoplankton
Phytoplankton – phyto = photosynthetic, plankton = “free-drifting”
- free-drifting photosynthetic organisms (cyanobacteria is also a
large part of phytoplankton)
- Bloom (explosion of growth) can cause “red tide”
- Secrete toxins that bioaccumulate in molluscs making them dangerous to eat
- Have internal “plates” of cellulose giving its characteristic shape…
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Alveolata
Kingdom Alveolata
Phylum Ciliates
Phylum Ciliates
- Obviously use cilia to move and feed
Ex) Paramecium
Two types of nuclei
- Large (macro) nucleus
- Smaller (micro) nucleus
Macronucleus
- Contains dozens of copies of genome
- Genes are not on chromosomes (they don’t have chromosome)
- Arranged in small units each having many duplicates of a single gene
- The gene products (i.e. proteins) control daily functions like feeding,
waste removal, etc…
- Can have more than one of each
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Alveolata
Kingdom Alveolata
Phylum Ciliates
Phylum Ciliates
Feeding
Reproduction
- Mainly on bacteria, which are moved through oral groove and
phagocytosed at “cell mouth” into food vacuoles.
- Food vacuoles fuse with lysosomes
- Undigestable material is egested when lysosomes fuse with cell
membrane
- Mostly asexually by “binary fission”
Conjugation
- Genetic diversity, NOT REPRODUCTION
- two organisms exchange haploid micronuclei (see fig 28.12b above and
use book for more detail)
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Phylogeny of protists
Kingdom Stramenopila
Fig. 28.4
Phylum Diatom (Bacillariophytes)
- Unicellular Algae
- glass-like silica based cell wall as shown in figure
- Protection from predators
- Withstand pressures up to 1.4 million kg/m2 (pressure applied by the leg
of a table with an elephant standing upon it)
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Stramenopila
Kingdom Stramenopila
Phylum Diatom (Bacillariophytes)
Phylum Golden Algae (chrysophytes)
Reproduction
(chrysos = golden)
Dinobryon
- Usually asexually by mitosis
- Contain yellow/brown cartenoid pigments
- Sexual reproduction is not common, but does occur
- Freshwater and marine plankton
- All obviously photosynthetic, some species mixotrophs
Diversity
- Estimated 100,000 species
- Most unicellular, but some, as shown, are colonial
- Major component of phytoplankton in oceans and lakes
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Stramenopila
Kingdom Stramenopila
Phylum Brown Algae (phaeophytes –
guess what phaeo means…)
Phylum Brown Algae
Kelp
- Largest and most complex algae (its what you call seaweed)
- All are multicellular and most are marine (salt water – ocean)
Sea palm (Postelsia)
Kelp
Thallus
- The body of the seaweed that is plant-like
- Basically, the holdfast, stipe (stem-like) and blades (leaf-like) (see above)
Holdfast
- root-like structure at base solely for anchoring, not absorption like roots
of plants
- Common along temperate costs like ours
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Stramenopila
Phylogeny of protists
Fig. 28.4
Phylum Brown Algae
Life-cycle: Alternation of Generations
This is important to understand
because as you might guess, since
plants evolved from multicellular
algae, they also do this.
Heteromorphic
- The two generations are
structurally different as opposed
to being isomorphic
Laminaria (a brown algae)
Let’s examine a handful of these clades…
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Cercozoans and Radiolarians
Kingdom Cercozoans and Radiolarians
- Amoeba with threadlike pseudopods
- Amoeba is a general term for a protist that uses pseudopodia to move and
feed. There is no one clade or kingdom that consists of amoebas
Foraminiferans (Forams)
Radiolarian
- Foramen means “little hole”
- Tests made of silica
- Named for porous shells called tests
- Pseudopodia called axopodia
- Organic molecules hardened with CaCO3
- Pseudopodia extend through pores of shell and
fx in test formation, swimming and feeding
Both of these phyla consist of
amoebas because…
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Phylogeny of protists
Kingdom Amoebozoans
Fig. 28.4
- Amoeba with lobe shaped rather than threadlike pseudopods belong to this clade:
Let’s examine a handful of these clades…
Now this amoeba belongs to the above kingdom…
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Amoebozoans
Kingdom Amoebozoans
Phyla: Gymnamoeba
Phyla: Slime Molds (mycetozoans)
Were once thought to be fungus hence the name, but molecular evidence
has revealed convergent evolution
Two major types:
1. Plasmodial Slime Molds
2. Cellular Slime Molds
Phagocytosis of a ciliate:
They in part by their life cycles…
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Amoebozoans
Kingdom Amoebozoans
Phyla: Slime Molds (mycetozoans)
Phyla: Slime Molds (mycetozoans)
Plasmodial Slime Mold Life Cycle
Cellular Slime Mold Life Cycle
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Phylogeny of protists
Kingdom Rhodophyta
Fig. 28.4
Rhodo = red
Red Algae
Red due to pigment known as phycoerythrin, which masks chlorophyll
Most large and multicellular, living in tropical waters
Alternation of Generations
Let’s examine a handful of these clades…
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Chlorophyta
Kingdom Chlorophyta
Chloro = green
Chloro = green
Green Algae
Green Algae
Much like plants, systematics has shown close relationship b/w green algae and
plants as you would expect…
Two groups - Chlorophytes and Charophyceans
1. Chlorophytes
- More than 7,000 species, most in fresh water
- Simplest are unicellular
- These are the ones that live in mutualism
with fungus to form lichen
Watermelon snow showing the
incredible diversity of chlorophytes
Larger size and complexity arose via:
1. Colony formation (ex. Volvox)
and multicellular filament
formation.
2. Repeated division of nuclei
without cytoplasmic division
(ex. Caulerpa)
3. True multicellular forms with
cell division and differentiation
(Ex. Ulva)
*Charophyceans and most related to land plants and are discussed at beginning of Ch. 29 with plants
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Chapter 28: Protists - structure, function,
diversity, evolution, impact
Chapter 28: Protists - structure, function,
diversity, evolution, impact
Kingdom Chlorophyta
Chloro = green
Syngamy = fusion of gametes, aka
fertilization/conception
Green Algae
Complicated life cycle of asexual and sexual stages:
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