Protists Flashcards
Chapter 23 of the Book
1
Q
What are the Characteristics of Eukaryotes (these are present in the last common ancestor)?
A
- Cells with nuclei surrounded by a nuclear envelope with nuclear pores
- Mitochondria
- Cytoskeleton of microtubules & mircofilaments
- Flagella & Cilia
- Chromosomes organized by histones
- Mitosis
- Sexual Reproduction
- Cell Walls
2
Q
What are all extant eukaryotes’ likely to be descendants of?
A
A chimera-like organism that was a composite of a host cell & the cell(s) of an alpha-proteobacterium that “took up residence” inside it.
3
Q
What is the major theme in the origin of Eukaryotes?
A
Endosymbiosis
4
Q
What is Endosymbiosis?
A
Engulfment of one cell within another such that the engulfed cell survives, & both cells benefit; the process responsible for the evolution of mitochondria & chloroplasts in eukaryotes.
5
Q
Is the process of aerobic respiration found in all major lineages of Eukaryotes? Is it localized in the mitochondria?
A
Yes, for both answers.
6
Q
Do all extant eukaryotes descend from an ancestor with an mitochondria?
A
Yes.
7
Q
What is the Endosymbiotic Theory?
A
States that eukaryotes may have been a product of one cell engulfing another, one living within another, & evolving over time until the separate cells were no longer recognizable as such & shared genetic control of mutualistic metabolic pathways to produce ATP.
8
Q
What is one major feature that distinguishes prokaryotes from eukaryotes?
A
The presence of mitochondria, OR their reduced derivatives
9
Q
Can mitochondria survive & reproduce outside the cell?
A
No
10
Q
What are Alpha-proteobacteria?
A
Are a large group of bacteria that includes species symbiotic with plant, disease organisms that can infect human via ticks, & many free-living species that use light energy.
11
Q
What is the FIRST evidence that suggests mitochondria appearing to be of alpha-proteobacterial origin (or were derived by endosymbiosis) ?
A
Mitochondria have their own genomes, with a circular chromosome stabilized by attachments to the inner membrane. Also have special ribosomes & transfer RNAs that resemble these same components in prokaryotes. When these genes are compared to other organisms, they appear to be of alpha-proteobacterial origin. Such genes can be found in the mitochondria or the nucleus. This is evidence that over evolutionary time, genes have been transferred from the Endosymbiont chromosome to those of the host genome.
12
Q
What is the SECOND evidence that supports the idea that mitochondria were derived by endosymbiosis?
A
The structure of the mitochondria itself. Most are shaped like alpha-proteobacteria & are surrounded by 2 membranes; the inner membrane (bacterial in nature) & outer membrane (eukaryotic in nature). The outer membrane was derived by the enclosing vesicle, while the inner membrane was derived from the plasma membrane of the Endosymbiont.The inner membrane is extensive &v involves substantial infoldings called cristae that resemble the textured, outer surface of alpha-proteobacteria, The matrix & inner membrane are rich with the enzymes necessary for aerobic respiration.
13
Q
What is the THIRD evidence that supports the theory that mitochondria were once free-living prokaryotes?
A
The production of new mitochondria. Mitochondria divide independently by a process that resembles binary fission in prokaryotes. They arise only from previous mitochondria; NOT formed from scratch by the eukaryotic cell. Mitochondria may fuse together; & they may be moved around inside the cell by interactions with the cytoskeleton. They reproduce within their enclosing cell & are distributed with the cytoplasm when a cell divides or 2 cells fuse. However their reproduction is synchronized with the activity & division of the cell.
14
Q
What is a plastid?
A
One of a group of related organelles in plant cells that are involved in the storage of starches, fats, proteins, & pigments.
15
Q
When photosynthetic cells carry out photosynthesis, what are their plastids rich in?
A
The pigment “Chlorophyll a” & a range of other pigments, called “accessory pigments,” which are involved in harvesting energy from light.
16
Q
What are photosynthetic plastids called?
A
Chloroplasts
17
Q
Plastids are derived from what?
A
Cyanobacteria that lived inside the cells of an ancestral, aerobic, heterotrophic eukaryote. This is called PRIMARY endosymbiosis.
18
Q
How many membranes surround plastids of primary origin?
A
2
19
Q
What are Cyanobacteria a group of?
A
Gram-negative bacteria
20
Q
Unlike most prokaryotes cyanobacteria have what?
A
Extensive, internal membrane bound sacs called thylakoids. Chlorophyll is a component of these membranes. Cyanobacteria have a peptidoglycan wall & lipopolysaccharide layer associated with the Gram-negative bacteria.
21
Q
What do Chloroplasts of primary endosymbiotic have?
A
- Thylakoids
- Circular DNA Chromosome
- Ribosomes (similar to those of cyanobacteria)
- Surrounded by 2 membranes
22
Q
Can complexity evolve in the absence of true multicellularity?
A
Yes
23
Q
What way can protists live as?
A
Colonies that behave as a group of free-living cells OR as a multicelluar organism
24
Q
Protists cells may be enveloped by what?
A
Animal-like cell membranes or plant-like cell walls
25
Protists may be encased in what?
Glassy silica-based shells or wound with pellicles of interlocking protein strips
26
What are pellicles?
Outer cell covering composed of interlocking protein strips that function like a flexible coat of armor, preventing cells from being torn or pierced without compromising their range of motion
27
Are protists aerobic or anaerobic?
They can be either.
28
What are photoautotrophs?
Store energy by photosynthesis & are characterized by the presence of chloroplasts.
29
What are heterotrophs?
Consume organic materials (such as other organisms) to obtain nutrition. May ingest particles by phagocytosis.
30
What is phagocytosis?
a process in which the cell membrane engulfs a food particle & brings it inward, pinching off an intracelluar membranous sac, or vesicle, called a food vacuole.
31
In some protists, where can food vacuoles form?
Anywhere on the body surface, whereas in others, they may be restricted to the base of a specialized feeding structure.
32
What does the vesicle containing the ingested particle, the phagosome, fuse with?
A lysosome containing hydrorolytic enzymes to produce a Phagolysosome, & the food particle is broken down into small molecules that can diffuse into the cytoplasm & be used in cellular metabolism.
33
What is Phagolysosome?
Cellular body formed by the union of a phagosome containing the ingested particle with a lysosome that contains hydrolytic enzymes.
34
What occurs to the undigested remains?
They are expelled from the cell (via exocytosis)
35
What are subtypes of heterotrophs called?
Saprobes
36
What are saprobes?
They absorb nutrients from dead orgainisms
37
What are mixotrophs?
obtain nutrition by photoautotrophic or heterotrophic routes, depending on whether sunlight or organic nutrients are available.
38
Do some protists have one or more flagella?
Yes & they rotate or whip
39
What can protists be covered in?
rows or tuffs of tiny cilia that beat in a coordinated manner to swim
40
What do other protists form?
cytoplasmic extensions called pseudupodia anywhere on the cell, anchor the pseudopodia to a substrate, & pull themselves forward.
41
Do some protists move toward or away from stimulus, a movement referred to as taxis?
Can be either
42
What is phototaxis?
Movement toward light
43
Which form of reproduction do most protists undergo?
Asexual Reproduction
44
What is one example in which protists reproduce asexually?
Binary Fission, which they produce 2 daughter cells.
45
In protists, binary fission can be divided into what?
Transverse or longitudinal, depending on the axis of orientation; sometimes paramecium exhibits this method.
46
Some protists such as the true slime molds exhibit what?
Multiple fission & simultaneously divide into many daughter cells
47
Other protists may follow what asexual reproduction?
They may produce tiny buds that go on to divide & grow to the size of the parental protists.
48
For protists, what 2 things are involved for Sexual Reproduction?
1. Meiosis
2. Fertilization
49
When is sexual Reproduction most likely to occur?
In periods when nutrients are depleted or environmental changes occur
50
What does sexual Reproduction allow?
Protists to recombine genes & produce new variations of progeny
51
What is protist sexual Reproduction often associated with?
Resistant CYSTS that are a protective, resting stage. Depending on the habitats of the species, the cysts may be particularly resistant to temp. extremes, desiccation (the removal of moisture from something), or low pH.
52
What do cysts allow protists to do?
To "wait out" stressors until their environment becomes more favorable for survival or until they are carried (such as by wind, water, or transport on a larger organism) to a different environment, because cysts exhibit virtually no cellular metabolism.
53
What can the life cycle of protists range from?
From simple to extremely elaborate. Certain parasitic protists have complicated life cycles & must infect different host species at different developmental stages to complete their life cycle. While some protists are unicellular in the haploid form & multicellular in the diploid form, a strategy employed by animals. Other protists may use the alternation of generations strategy, analogous to that used by plants.
54
What is alternation of generation?
Multicellular stages in both haploid & diploid forms. The haploid stage is called the gametophyte and the diploid stage is called the sporophyte, meaning the it switches between having single sets of chromosomes (haploid) and double sets of chromosomes (diploid) throughout its life cycle.
55
What are the common habitats of protists?
1. Some type of aquatic environment (freshwater, marine environments, damp soil, or even snow)
2. If parasitic will infect animals or plants
3. Dead organisms or their waste
56
What is one reason why protist classification is so challenging?
Convergent Evolution
57
What kingdom do protists fall into?
Kingdom Protista
58
What domain do protists fall into?
Domain Eukarya
59
What is the supergroup?
The emerging classification scheme that groups the entire domain Eukarya that contain all of the protists, animals, plants, & fungi that evolved from a common ancestor.
60
Each supergroup is believed to be what?
Monophyletic, meaning that all organisms within each supergroup are believed to have evolved from a single common ancestor.
61
What are the 6 Supergroups?
1. Excavata
2. Chromalveolata
3. Rhizaria
4. Archaeplastida
5. Amoebozoa
6. Opisthokonata
62
What are the members of the supergroup Archaeplastida?
1. Red Algae (Rhodophytes)
2. Green Algae
3. Land Plants
63
What are Glaucophytes?
A small group of Archaeplastida & their chloroplasts retain remnants of the petidoglycan cell wall of the ancestral cyanobacterial endosymbiont.
64
Do red Algae lack a flagella?
Yes
65
What size do red Algae range from?
From microscopic, unicellular protists to large, multicellualar forms grouped into the informal seaweed category (this size primarily).
66
Do red Algae have a second cell wall, if so where?
Yes, it is outside an inner cellulose cell wall. Carbohydrates in this wall are the source of agarose used for electrophoresis gels & agar for soldifying bacterial media.
67
Where does the "red" in the red algae come from?
From phycoerythrins, accessory photopigments that are red in color & obscure the green tint of chlorophyll in some species. Other protists classified as red algae lack phycoerythrins & are parasites.
68
What thing do red algae & Glaucophytes have in common?
Both store carbohydrates in the cytoplasm rather than in the plastid.
69
How is the life cycle of red algae unusual?
The alteration of generations includes 2 sporophyte phases, withe meiosis occurring only in the second sporophyte.
70
Green Algae exhibit similar features to what group?
Land Plants, particularly in terms of chloroplast structure. Both carbohydrates are stored in the plastid.
71
What is green Algae subdivided into?
1. Chlorophytes
2. Charophytes
72
Which subdivision of green Algae are the closest living relatives to land plants & resemble them in Morphology & Reproductive strategies?
The Charophytes
73
Where are Charophytes most common in?
Wet habitats, & their presence often signals a healthy ecosystem.
74
What do Chlorophytes exhibit?
Great diversity of form & function.
75
Where do Chlorophytes primarily inhabit?
Freshwater, damp soil,& are
a common component of plankton.
76
What are Chlamydomas?
A simple, unicellular chlorophyte with a pear-shaped morphology and two opposing, anterior flagella that guide the protist toward light sensed by its eyespot. More complex chlorophyte species
exhibit haploid gametes and spores that resemble Chlamydomonas.
77
What is unique about the Chlorophytes Volvox?
One of only a few examples of a colonial organism, which behaves in some ways like a collection of individual cells, but in other ways like the specialized cells of a multicellular organism. Each volvox has two flagellas, contained within a hollow, spherical matrix composed of a gelatinous glycoprotein
secretion. Individual cells in a Volvox colony move in a coordinated fashion and are interconnected by cytoplasmic bridges. Only a few of the cells reproduce to create daughter colonies, an example of basic cell specialization in this organism. Daughter colonies are produced with their flagella on the inside and have to evert as they are released.
78
Like the Archaeplastida, the Amoeboza includes what?
Species with single cells, species with large multinucleated cells, & species that have multicellular phases.
79
What do the Ameobozoan cells characteristically exhibit?
Pseudopodia that extend like tubes or flat lobes.
80
What are pseudopods?
They project outward from anywhere on the cell surface & can anchor to a substrate. The protist then transports
its cytoplasm into the pseudopod. Is used by other protists as a means of locomotion or as a method to
distribute nutrients and oxygen.
81
What kind of species are included in Amoebozoa?
Free-living & parasitic species.
82
What are the members of the supergroup Amoeboza?
1. Amoebae (Gymnamoeba or lobose)
2. Slime Molds
83
What kind of amoebae are included?
1. Naked amoebae like the familiar Amoeba proteus
2. Shelled amoebae, whose bodies protrude like snails from their protective tests.
84
What are Slime molds?
A subset of the amoebozoans
85
What occurs during times of stress for slime molds?
They may develop into spore-generating fruiting bodies
86
How are Slime molds characterized?
On the basis of their life cycles into plasmodial or cellular types.
87
What are plasmodial slime molds?
They are composed of large, multinucleate cells and move along surfaces like an amorphous blob of slime during their feeding stage.
88
What occurs during the plasmodial slime mold feeding stage?
Food particles are lifted and engulfed into the slime mold as it glides along.
89
What is a well known slime mold?
"Dog vomit" slime mold is a particularly colorful specimen and has the ability to creep about.
90
What occurs during maturation for Plasmodium in times of stress?
The plasmodium takes on a net-like appearance with the ability to form fruiting bodies, or sporangia. Haploid spores are produced by meiosis within the sporangia, & spores can be disseminated through the air or
water to potentially land in more favorable environments. If this occurs, the spores germinate to form ameboid or flagellate
haploid cells that can combine with each other and produce a diploid zygotic slime mold to complete the life cycle.
91
How do Cellular slime molds function as?
Independent amoeboid cells when nutrients are abundant.
92
What occurs to a cellular slime mold when food is depleted?
They aggregate into a mass of cells that behaves as a single unit, called a slug. Some cells in the slug contribute to a
2–3-millimeter stalk, drying up and dying in the process.
93
How do Cellular slime reproduce?
Cells on the top of the stalk form an asexual fruiting body that contains haploid spores.
94
What are the Opisthokonata supergroup named for?
Their single posterior flagellum seen in flagellated cells of the group.
95
What makes the Opisthokonata Supergroup unique compared to other cells?
The flagella of other protists
are anterior and their movement pulls the cells along, while the opisthokonts are pushed.
96
What are the members of the Supergroup Opisthokonata?
1. Choanoflagellates
2. Fungi
3. Animals
97
What are the forms of Choanoflagellates?
Unicellular and colonial forms
98
For Choanoflagellates, what surrounds their single, apical flagellum?
A contractile collar composed of microvilli.
99
What is the collar used for?
The collar is used to
filter and collect bacteria for ingestion by the protist.
100
What are the members of the Supergroup Rhizaria?
1. Cercozoans
2. Foraminiferans/Forams
3. Radiolarians
101
What does the supergroup Rhizaria include?
Many of the amoebas with thin threadlike, needle-like or root-like pseudopodia, rather than the broader lobed pseudopodia of the Amoebozoa.
102
Many Rhizaria make elaborate, beautiful what?
Tests, which are armor-like
coverings for the body of the cell composed of calcium carbonate, silicon, or strontium salts
103
What important role is Rhizaria in?
Carbon & nitrogen cycle
104
What occurs when Rhizaria die?
Their tests sink into deep water & the carbonates are out of reach of most decomposers, therefore locking carbon dioxide away from the atmosphere.
105
What is the "Carbon Pump"?
A process by which carbon is transported or "pumped" deep into the ocean where it is
inaccessible to the atmosphere as carbon dioxide.
106
Why is the "Carbon Pump" a crucial component of the carbon cycle?
It maintains lower atmospheric carbon dioxide levels.
107
Why are the Foraminiferans unusual?
They are the only eukaryotes known to participate in the nitrogen cycle by denitrification, an activity usually served only by prokaryotes.
108
What are the Foraminiferans?
They are unicellular heterotrophic protists & occasionally resemble tiny snails. Are associated with sand or other particles in marine or freshwater habitats. Are also useful as indicators of pollution and changes in global weather patterns.
109
As a group, what do the Foraminiferans exhibit?
A test
110
What is a test?
It is a porous shell of a Foram that is built from various organic materials & typically hardened with calcium carbonate. The tests may house photosynthetic algae, which the forams can harvest for nutrition.
111
112
What allows forms/ foraminiferans to move, feed, & gather additional building materials?
Foram pseudopodia by extending through the pores
113
What are Radiolarians?
They are the second subtype of Rhizaria & exhibit intricate exteriors of glassy silica with radial or bilateral symmetry.
114
What function to catch food particles for Radiolarians?
Needle-like pseudopods supported by microtubules that radiate outward from the cell bodies.
115
How are radiolarians very common fossils?
The shells of dead radiolarians sink to the ocean floor, where they may accumulate in 100 meterthick depths. Which are then preserved & sedimented.
116
What is Cercozoa?
The 3rd subtype of Rhizaria that is both morphologically & metabolically diverse. They also include both naked and shelled forms.
117
What are Chlorarachniophytes?
They are photosynthetic, having acquired chloroplasts by secondary endosymbiosis. The
chloroplast contains a remnant of the chlorophyte endosymbiont nucleus, sandwiched between the two sets of chloroplast
membranes.
118
What are the members of the Chromalveolata?
1. Brown Algae
2. Golden Brown Algae
3. Diatoms
4. Water Molds/Oomycetes
5. Ciliates
6. Dinoflagellates
7. Apicomplexians
119
The members can be subdivided into what?
1. Alveolates
2. Stramenopiles
120
What members are included in the Alveolates?
1. Dinoflagellates
2. Apicomplexians
3. Ciliates
121
Do the alveolates derive from a shared common ancestor?
Yes
122
What are the alveolates named for?
The presence of an alveolus
123
What are alveolus?
A membrane-enclosed sac, beneath the cell membrane. The exact function of the alveolus is unknown, but it may be involved in osmoregulation.
124
What are the dinoflagellates?
They are a member of the Chromalveolata & exhibit extensive morphological diversity. They can be photosynthetic, heterotrophic, or mixotrophic. These protists exist in freshwater and marine habitats, and are a component of plankton. They typically drift through the water and serve as a crucial food source for
larger aquatic organisms.
125
What are the dinoflagellates encased in?
In interlocking plates of cellulose.
126
What fits into the grooves between the cellulose plates?
Two perpendicular flagella, with one flagellum extending longitudinally and a second encircling the dinoflagellate. Together, the flagella contribute to the characteristic spinning motion of dinoflagellates.
127
The dinoflagellates have a nuclear variant called what?
A dinokaryon & their chromosomes are highly condensed throughout the cell cycle and do not have typical histones.
128
What does it mean for the mitosis in the dinoflagellates to be closed?
Meaning the spindle separates the chromosomes from outside of the nucleus without breakdown of the nuclear envelope.
129
What occurs when dinoflagellates are jarred or stressed?
They may generate light, called bioluminescence.
130
What is bioluminescence?
Generation & emission of light by an organism
131
What is the phenomenon called the red tide?
When blooms or population explosions tint the ocean with a muddy red color. This results from the abundant red pigments present in dinoflagellate plastids. In large quantities, these dinoflagellate species
secrete an asphyxiating toxin that can kill fish, birds, and marine mammals. Can be massively detrimental to
commercial fisheries, and humans who consume these protists may become poisoned.
132
What are the apicomplexians named for?
For a structure called an apical complex, which appears to be a highly modified secondary chloroplast.
133
The apicomplexians have a similar genome to what?
Dinoflagellate chloroplasts
134
What is the apical complex specialized for?
For entry and infection of host cells.
135
Are all apicomplexians parasitic?
Yes
136
Are the apicomplexians's life cycle complex?
Yes, as they involve multiple hosts and stages of sexual and asexual reproduction.
137
What are the Cililates covered in?
In rows, tufts, or spirals of tiny cilia.
138
How do the ciliates coordinate movement & ingest food particles?
By beating their cilia synchronously or in waves. Certain ciliates have fused cilia-based structures that function like paddles, funnels, or
fins.
139
What surrounds ciliates & provides protection without compromising agility?
Pellicle
140
What are oral grooves?
They are organized cilia into a plate-like primitive mouth, which are used to capture & digest bacteria.
141
Food captured in the oral groove enters what?
A food vacuole, where it combines with digestive
enzymes.
142
What is the anal pore?
Where waste particles are expelled by an exocytic vesicle that fuses at a specific region on the cell membrane.
143
What are Contractile Vacuoles?
They are osmoregulatory
vesicles that fill with water as it enters the cell by osmosis and then contract to squeeze water from the cell.
144
Why is the micronucleus essential?
It is essential for sexual
reproduction, & is in many ways a typical eukaryotic nucleus, except that its genes are NOT transcribed.
145
What is the transcribed nucleus?
The macronucleus, which directs asexual binary fission and all other biological functions
146
What is the macronucleus?
It is a multiploid nucleus constructed from the micronucleus during sexual reproduction.
147
Why is the periodic reconstruction of the macronucleus necessary?
Because the macronucleus divides amitotically, and thus becomes genetically unbalanced over a period of successive cell replications.
148
How do most ciliates reproduce sexually?
By conjugation.
149
Explain the conjugation process with Paramecium (a type of ciliate).
Look at the diagram in the Book. Helps with visualization.
This process begins when 2 different mating types of Paramecium make physical contact & join with a cytoplasmic bridge. The diploid micronucleus in each cell then undergoes meiosis to produce 4 haploid micronuclei. 3 of these degenerate in each cell, leaving 1 micronucleus that then undergoes mitosis, generating 2 haploid micronuclei. The cells each exchange 1 of these haploid nuclei and move away from each other. Fusion of the haploid micronuclei generates a completely novel diploid pre-micronucleus in each conjugative cell. This pre-micronucleus undergoes 3 rounds of mitosis to produce 8
copies, and the original macronucleus disintegrates. 4 of the 8 pre-micronuclei become full-fledged micronuclei,
whereas the other 4 perform multiple rounds of DNA replication. The copies of the micronuclear chromosomes are severely edited to form hundreds of smaller chromosomes that contain only the protein coding genes. Each of these smaller chromosomes gets new telomeres as the macronucleus differentiates. Two cycles of cell division then yield 4 new Paramecia
from each original conjugative cell.
150
What members are included in the Stramenopiles?
1. Diatoms
2. Brown Algae
3. Golden Algae
4. Oomycetes (Water Molds)
151
What do the Stramenopile subgroup include?
It includes photosynthetic marine algae & heterotrophic protists.
152
What is the identifying feature of the Stramenopile subgroup?
The identifying feature of this group is the presence of a textured, or
“hairy,” flagellum.
153
Many stramenopiles also have an additional flagellum that lacks what?
That lacks hair-like projections
154
What are the diatoms?
They are unicellular photosynthetic protists that encase themselves in intricately patterned, glassy cell walls composed of silicon dioxide in a matrix of organic particles. These protists are a component of freshwater and marine
plankton.
155
Most of the time diatoms reproduce how?
Asexually
156
What is a raphe?
A slit in the silica shell of diatoms through which the protist secretes a stream of mucopolysaccharides for
locomotion and attachment to substrates.
157
What occurs during periods of nutrient availability for diatoms?
Diatom populations bloom to numbers greater than can be consumed by aquatic
organisms. Due to that, the excess diatoms die and sink to the sea floor where they are not easily reached by saprobes that feed on dead organisms. As a result, the carbon dioxide that the diatoms had consumed and incorporated into their cells during photosynthesis is not returned to the atmosphere. Therefore, helping to maintain a
balanced carbon cycle.
158
Are most Golden Algae unicellular?
Yes
159
What results in the golden algae's gold color?
Results from their extensive use of carotenoids, a group of photosynthetic pigments that are generally yellow or orange in color.
160
Where can golden Algae be found?
In both freshwater & marine environments, where they form a major part of the plankton community
161
What is Brown Algae?
They are primarily marine, multicellular organisms that are known colloquially as seaweeds
162
Does the life cycle of brown algae include alteration of generation?
Yes
163
What are the oomycetes (water Molds) characterized by?
By a cellulose-based cell wall and an extensive network of filaments that allow for nutrient uptake
164
As diploid spores, many oomycetes have what?
They have two oppositely directed flagella (one hairy and one smooth) for locomotion.
165
What are the oomycetes (water Molds)?
The oomycetes are nonphotosynthetic and include many saprobes and
parasites
166
Many of the protist species classified into the supergroup Excavata include what?
They are asymmetrical, single-celled organisms, that include a feeding groove “excavated” from one side.
167
The supergroup Excavata includes what?
Heterotrophic predators, photosynthetic species, and parasites.
168
What are the subgroups or members of the supergroup Excavata?
1. Diplomonads
2. Parabasalids
3. Euglenozoans
169
What do the diplomonads have instead of mitochondria?
They have mitochondrial remnant organelles, called mitosomes, they are essentially nonfunctional as respiratory organelles, they do function in iron and sulfur metabolism.
170
What alternative pathway do diplomonads take to generate energy?
They use Glycolysis because they exist in anaerobic environments
171
Each diplomonad cell has two similar, but not identical what?
Haploid nuclei
172
Diplomonads have four
pairs of what?
They have four pairs of locomotor flagella that are fairly deeply rooted in basal bodies that lie between the two nuclei.
173
What are the Parabasalids named after?
Named after the parabasal apparatus, which consists of a Golgi complex associated with cytoskeletal fibers.
174
Other cytoskeletal features include what?
An axostyle, a bundle of fibers that runs the length of the
cell and may even extend beyond it
175
The Parabasalids move with what?
With a flagella & membrane rippling, and these and other cytoskeletal modifications that may assist with locomotion.
176
Do the parabasalids exhibit modified mitochondria?
Yes, and these structures function anaerobically and are called hydrogenosomes because they produce hydrogen gas as a byproduct.
177
Some of the most complex of the parabasalids are those that what?
Those that colonize the rumen of ruminant animals & the guts of termites.These organisms can digest cellulose, a metabolic talent that is unusual among eukaryotic cells. They have multiple flagella arranged in complex patterns & some additionally recruit spirochetes that attach to their surface to act as accessory locomotor structures.
178
What do the Euglenozoans include?
They include parasites, heterotrophs, autotrophs, and mixotrophs.
179
How do the Euglena
move through their aquatic habitat?
By using 2 long flagella that guide them toward light sources sensed by a primitive ocular
organ called an eyespot
180
What happens to the Euglena Chloroplasts, when it is dark?
The chloroplast will shrink up & temporarily cease functioning, & the cells instead take up organic nutrients from their environment.
181
What gives the Euglenoids its exceptional flexibility?
They have a tough pellicle composed of bands of protein attached to the cytoskeleton. Then those bands spiral around the cell and give Euglena its exceptional flexibility.
182
What are the 2 subgroups for Euglenoids?
1. Kinetoplastids (parasitic)
2. Euglenids (free-living)
183
What is the subgroup kinetoplastids named after?
They are named after the kinetoplast, which is a large modified mitochondrion carrying multiple circular DNAs.
184
Are protists essential sources of food & do they provide nutrition for many other organisms?
Yes for both.
185
What is a pathogen?
Is anything that causes diseases
186
What do parasitic organisms do?
They live in or on a host organism & harm the
organism. A small number of protists are serious pathogenic parasites that must infect other organisms to survive &
propagate.
187
Are there protist parasites for Plants?
Yes
188
Are there protist parasites for animals?
Yes
189
The fungus-like (decomposer) protist saprobes are specialized to what?
To absorb nutrients from nonliving organic matter, such as dead organisms or
their wastes.
190
The saprobic protists have the essential function of what?
Of returning inorganic nutrients to the soil and water. This process allows for new plant growth, which in turn generates
sustenance for other organisms along the food chain.
