Exam 2 Flashcards
Protists
Eukaryotes
* Mostly single-celled
– Protista used to be recognized as a kingdom
– Now a ‘group of convenience’ encompassing those eukaryotes that are neither plants, animals, nor fungi
- Protists, the most nutritionally diverse of all eukaryotes, include
– Photoautotrophs, contain chloroplasts
– Heterotrophs, which absorb organic molecules or ingest larger food particles
– Mixotrophs, combine photosynthesis and heterotrophic nutrition
What are not considered protists?
Archaeplastida
unikonta
Reproductive diversity protists
Asexual and sexual forms
- Some exhibit alternation of generations
Endosymbiotic origin of eukaryotes
- Mitochondria
– Endosymbiosis of aerobic prokaryote - Plastids
– Endosymbiosis of photosynthetic cyanobacterium
Cyanobacteria = first photosynthetic organism
* Acquired by eukaryotes via: Archaeplastida
- Integration of photosynthetic
metabolism!
Diagram 28.3 with heterotrophic eukaryote
Heterotropic eukaryoric sees cyabobacterium and engulfs it, now cyanobacterium has its own membrane.
-Hetero genetic makeup was transferred to cyan, maybe some of it was transferred in hetero
-cyan give hetero photosynthesis.Hetero gives cyan membrane
- mutual relationship
more then one event
Homology
They inherited their genes from a common ancestor
How does an Endosymbiont Become an Organelle?
It would have been advantageous to the host to maintain the cyanobacterial endosymbiont, as a source of sugar from photosynthesis
- Gene transfer from endosymbiont to the host
nucleus made it dependent on the host:
Five supergroups of eukaryotes
This is a hypothesis about the evolutionary relationships among the eukaryotes
- It is subject to change as more data become available
- We won’t be covering the diversity in detail
– Broad patterns
– Some highlights
What is in excavata
-Diplomonads
-Parabasalids
-Euglenozoans
What supergroup is diplomonads from?
Excavata
What supergroup is parabasalids from?
Excavata
What supergroup is euglenzoans from?
Excavata
What is in the SAR clade?
-Diatoms
-Brown algae
-oomycetes
-dinoflagellates
-apicomplexans
-ciliates
-forams
-cercozoans
-radiolarians
What is in stramenopiles?
Diatoms
brown algae
oomycetes
What is in the alveolates?
-dinoflagellates
-Apicomplexans
-Ciliates
What is in Rhizarians
-Forams
-cercozoans
-radiolarians
What super group is Diatoms from?
Sar Clade - stramenopiles
What super group is Brown algae from?
SAR clade - stramenopiles
What super group is oomycetes from?
SAR clade- stramenopiles
What super group is Dinoflagellates from?
SAR clade- alveolates
What super group is Apicomplexans from?
SAR clade- Alveolates
What super group is Ciliates from?
SAR clade- alveolates
What super group is forams from?
SAR clade- Rhizarians
What super group is cercozoans from?
SAR clade- rhizarians
What super group is Radiolarians from?
SAR clade- rhizarians
What are in the supergroup unresolved
-haptophytes
-Cryptophytes
What super group is haptophytes from?
Unresolved
What super group is cryptophytes from?
unresolved
What is in supergroup archaeplastida
Red algae
-chlorophytes
-charophytes
-land plants
What is in gree algae in super group archaeplastida
Chlorophytes and charophytes
What super group is red algae from?
Archaplastida
What super group is Chlorophytes and charophytes from?
Archaeplastida- green algae
What super group is land plants from?
archaeplastida
What is in supergroup unikonta
-slime moulds
-tubulinids
-entamoebas
-nucleariids
-fungi
-choanoflagellates
-animals
What is in phylum amoebozoans
-slime moulds
-tubulinids
-entamoebas
-nucleariids
What is in phylum opisthokonts
fungi
choanoflagellates
animals
What super group is slime moulds from?
unikonta- ameobozoans
What super group is tubulinids from?
unikonta- ameobozoans
What super group is Entamoebas from?
unikonta- amoebozoans
What super group is nucleariids from?
unikonta- amoebozoans
What super group is fungi from?
unikonta- opisthokonts
What super group is choanflagellates from?
unikonta- opisthokonts
What super group is animals from?
unikonta- opisthokonts
The clade Excavata is characterized by its-
(-monophyletic!)
-cytoskeleton
- Some members have an “excavated” feeding groove
- This group includes diplomonads, parabasalids, and euglenozoans
Diplomonads
Live in anaerobic environments
– Derive energy anaerobically
* E.g., glycolysis
- Have two equal-sized nuclei and multiple flagella
- Many are parasitic (e.g., Giardia intestinalis)
- Lack plastids
- Have modified mitochondria (mitosomes)
Why does it make sense that diplomonads have mitosomes instead of mitochondria?
they live in an anaerobic environment, so no oxygen to act as final electron acceptor
what are the 4 eukaryote supergroups?
- excavata
- SAR clade
- archaeplastida
- unikonta
Parabasalids
Have reduced mitochondria called hydrogenosomes that
generate some energy anaerobically
– Include Trichomonas vaginalis, the pathogen that causes yeast infections in human females
Euglenozoans
The main feature distinguishing them as a clade is a spiral or
crystalline rod of unknown function inside their flagella
- Clade includes kinetoplastids and euglenids
Kinetoplastids
have a single mitochondrion
with an organized mass of DNA called a kinetoplast
- They include free-living species that are consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems
Some species are parasitic:
– This group includes Trypanosoma, which causes sleeping sickness in humans
– Another pathogenic trypanosome causes Chagas’ disease
Euglenids
have one or two flagella that emerge from a pocket at one end of cell
- Some species can be both autotrophic and heterotrophic
(mixotrophs)
The SAR Clade is a Highly Diverse Group of Protists
Defined by DNA Similarities
The “SAR” clade is a diverse monophyletic supergroup named for the first letters of its
three major clades: stramenopiles, alveolates,
and rhizarians
The stramenopiles
includes some of the
most important photosynthetic organisms on Earth
- Stramenopiles include diatoms, golden algae,
and brown algae
Stramenopiles
- Most have a “hairy” flagellum paired with a “smooth” flagellum
- some are multicellular stramenopiles
Diatoms
are unicellular algae with a unique two-part, glasslike wall of silicon dioxide
CO2 ’pumps’
Golden algae
are named for their colour,
which results from yellow and brown carotenoids
- The cells of golden algae are typically biflagellated, with both flagella near one end
- All golden algae are photosynthetic, and some
are mixotrophs
Most golden algae are unicellular, but some are colonial
Brown algae
the largest and most complex
algae
- All are multicellular, and most are marine
- Brown algae include many species commonly called “seaweeds”
- Brown algae have most complex multicellular anatomy of all algae
Giant seaweeds called kelps
live in deep parts of the
ocean
- They have plantlike
structures: the rootlike
holdfast anchors the algae,
and a stemlike stipe supports
leaflike blades
– The similarities between
algae and plants are
examples of analogous
structures
The Life Cycle of the Brown Alga Laminaria: an Example of Alternation of Generations
diagram 28.12
Alveolates
Members of the Alveolata clade have membrane-enclosed sacs (alveoli) just under the plasma membrane
– The function of alveoli unknown
- The alveolates include
– Dinoflagellates
– Apicomplexans
– Ciliates
Dinoflagellates
have two flagella and each cell is reinforced by cellulose plates
They are abundant components of both marine and freshwater phytoplankton
- They are a diverse group of
aquatic phototrophs, mixotrophs, and heterotrophs - Toxic “red tides” are caused by dinoflagellate blooms
Apicomplexans
are parasites of animals, and
some cause serious human diseases
- They spread as infectious cells called sporozoites
- One end, the apex, contains a complex of organelles specialized for penetrating host cells and tissues
- Most have sexual and asexual stages that require two or more different host species for completion
Ciliates
a large varied group of protists, use cilia to move and feed
- They have large macronuclei and small micronuclei
- Genetic variation results from conjugation, in which two individuals exchange haploid
micronuclei - Conjugation a sexual process, and is separate from reproduction, which generally occurs by binary fission
Structure and Function in the Ciliate Paramecium Caudatum
diagram
Rhizarians
Many species in the rhizarian clade are amoebas
- Amoebas are protists that move and feed by pseudopodia, extensions of the cell surface
- Rhizarian amoebas differ from amoebas in other
clades by having threadlike pseudopodia - Rhizarians include radiolarians, forams, and
cercozoans
Pseudopodia of radiolarians radiate from the central body
Forams
- Foraminiferans, or forams, are named for porous, generally multichambered shells, called tests
- Pseudopodia extend through pores in the test
- Many forams have endosymbiotic algae
Foram tests in marine sediments form an extensive fossil record
- The magnesium content in fossilized forams can be used to estimate changes in ocean temperature over time
You are given an unknown organism to identify. It is unicellular and heterotrophic. It is motile, using many short extensions of the cytoplasm, each featuring the 9 + 2 filament pattern. It has welldeveloped organelles and three nuclei, one large and two small. This organism is most likely to be a member of which group?
Ciliates
Red algae and green algae are the closest relatives of land plants
Plastids arose after a heterotrophic protist acquired a cyanobacterial endosymbiont
-primary endosymbiosis?
- The photosynthetic descendants of this ancient protist evolved into red algae and green algae
- Land plants are descended from green algae
Archaeplastida
the supergroup that includes red algae, green algae, and land plants
Red algae
reddish in colour due to accessory pigment called phycoerythrin, which masks the green of chlorophyll
- The colour varies from greenish-red in shallow
water to dark red or almost black in deep water - Red algae are usually multicellular; largest are
seaweeds
- Green algae
named for their grass green chloroplasts
- Plants are descended from green algae
- Green algae are a:
- The two main groups are chlorophytes and charophyceans
- Charophytes are most closely related to land plants
Chlorophyceans
Most chlorophytes live in fresh water, although many are marine
- Other chlorophytes live in damp soil, as symbionts in lichens, or in environments exposed to intense visible and ultraviolet radiation
Unikonts includes:
includes animals, fungi, and some protists
- Amoebozoans
are amoeba that have lobe- or tube-shaped, rather than
threadlike, pseudopodia
- They include slime molds, tubulinids, and entamoebas
Slime molds
-mycetozoans,
-were once thought to be fungi
in the clade Amoebozoa
-include two lineages, plasmodial slime molds and cellular slime molds
Plasmodial slime molds
* Multi-nuleate (not multi-cellular) feeding stage called a plasmodium
* Has nothing to do with the malaria parasite, Plasmodium
- Undergo cytoplasm streaming to distribute nutrients and
oxygen
Cellular slime molds
- Feeding stage is solitary
- When food is scarce, they aggregate and form a mass of cells (superficially resembles a plasmodium) and put up fruiting bodies on stalks
form multicellular aggregates in which cells are separated by their membranes
- Cells feed individually, but can aggregate to form a fruiting body
Life cycle of a plasmodial slime mold
diagram
life cycle of dictyostelium, a cellular slime mold
DIagram
Tubulinids
a diverse group of amoebozoans with lobe- or tube-shaped pseudopodia
- They are common unicellular protists in soil as well as freshwater and marine environments
- Most tubulinids are heterotrophic and actively
seek and consume bacteria and other protists
Entamoebas
are parasites of vertebrates and some invertebrates
- Entamoeba histolytica causes amebic dysentery, thirdleading cause of human death due to eukaryotic parasites
- Opisthokonts
include animals, fungi, and several groups of protists
Ecological roles of protists
Protists are extremely important in ecosystems
* Examples
* Producers
* Symbionts
* Mutualists
* Parasites
Producers
Up to ¼ of the world’s photosynthesis is performed by diatoms, dinoflagellates, other algae, and other protists
- In this respect, they are vital for aquatic and marine food
webs
Mutualistic termites
Termites have a protist symbiont that enables them to
digest wood
-* Photosynthetic symbiotic dinoflagellates in
coral reefs
Parasitic
Plasmodium -> malaria
- Pfiesteria -> huge fish die-off
- Giardia -> ‘beaver fever’
- Phytophthora -> sudden oak death
- Karenia -> red tides and paralytic shellfish syndome
Impact: Marine Protists in a Warmer World
READ!
If sea surface temperature continues to warm due to global warming, this could have
large effects on
* Marine ecosystems
* Fishery yields
* The global carbon
cycle
