eukaryote protists Flashcards
1
Q
major earth events that affected evolution
A
- continental collisions and volcanic eruptions affected climate, atmosphere and sea levels
- meteor strikes caused sudden environmental shift
2
Q
great oxygenation event
A
- O2 generating cynaobacteria increased atmospheric O2
- aerobic prokaryotes proliferated
- evolution of large eukaryotic cells
3
Q
precambrian era
A
- 1.5bya
- eukaryotes began to diversify
4
Q
cambrian explosion
A
- 540mya
- extensive diversification and radiation of eukaryotes
5
Q
mesozoic era
A
- 252-66mya
- distinct terrestrial biotas evolved on each continent
- 5 mass extinctions
6
Q
cenozoic era
A
- 66mya to now
- divided into tertiary and quarternary periods, subdivided into epochs
- emergence of modern biota
- radiation of mammals
- dominance of flowering plants
7
Q
features of protists
A
- umbrella term of eukaryotes that are not animals, plants or fungi so not a formal taxonomic group
- therefore very diverse (body forms and nutritional lifestyles), many are not closely related
- mostly microscopic
- unicellular and multicellular, or colonies with different levels of integration
- some mobile
- photosynthetic or heterotrophs
8
Q
origin of modern eukaryotic cell
A
- origin of flexible cell surface allowing for growth, movement, vesicles
- origin of cytoskeleton, allowing for structural integrity, transport, cell division, movement
- origin of nuclear envelope, enclosing genome
- appearance of digestive vacuoles
- acquisition of certain organelles by endosymbiosis
9
Q
primary endosymbiosis of chloroplasts
A
- large eukaryotic cell engulfs one photosynthetic cyanobacterium
- does not ingest it but instead becomes photosynthetic
- gave rise to red algae, green algae and land plants
10
Q
secondary endosymbiosis of chloroplasts
A
- engulfment of unicellulae red or green algae by large heterotrophic eukaryote
- ingested in food vacuole but retains chloroplast
11
Q
tertiary endosymbiosis of chloroplasts
A
- dinoflagellate lost chloroplast through secondary simplification
- took up chloroplast from another protist that had acquired it through secondary symbiosis
12
Q
alveolates
A
- eukaryotic clade
- possess sac structures beneath cell membrane (alveoli), possible to support cell surface
- unicellular
- mostly photosynthetic, some parasitic
- diverse body forms
- include dinoflagellates, apicomplexans, cilliates
13
Q
dinoflagellates
A
- member of alveolates
- 2 flagella, one wrapped around cell in equatorial groove, one down longitudinal groove into surroundings
- mostly marine and photosynthetic with golden brown chloroplasts
- primary producers
14
Q
lifestyles of some dinoflagellate species
A
- some can cause red tide in perfect climatic conditions, releasing neurotoxins into the ocean
- some are photosynthetic endosymbionts on coral, coral bleaching is when they die
- some are parasitic in marine organisms
- some are bioluminescent
- some can take on different forms depending on environmental conditions
15
Q
pfiesteria piscida
A
- dinoflagellate (alveolate clade)
- has been observed taking on over 20 different forms in the lab
- controversial to whether these forms can also be found in the wild
- stuns and feeds on fish when in large numbers
16
Q
apicomplexans
A
- member of alveolates clade
- all parasitic
- all have an apical complex, a mass of organelles at apical end that helps with host invasion
- all have complex life cycles , with sexual reproduction occurring in definitive host and asexual in intermediate host
e.g. Plasmodium spp. (malaria), Toxomplasma gondii
17
Q
Plasmodium spp.
A
- apicomplexan
- malarial parasite
- anopheles mosquito is definitive host (sexual reproduction)
- vertebrate e.g. human is intermediate host (asexual reproduction)
- apical complex aids in invasion of erythrocytes
- unusual to have vertebrate as intermediate host and invertebrate as definitive
18
Q
Toxoplasma gondii
A
- rat = intermediate host (asexual reproduction), invades brain and increases risk taking behaviour to increase chance of predation
- cat = definitive host (sexual reproduction)
- also linked to risk taking behaviours in humans
19
Q
Ciliates
A
- member of alveolate clade
- numerous cilia (short flagellum) for directional locomotion (coordinated beating)
- more complex body forms than other unicellular eukaryotes
- mostly heterotrophs, a few are photosynthetic endosymbionts
- defining characteristic is 2 types of nuclei, a macronucleus and micronucleus
- macronucleus controls cell activity
- one or more micronuclei, important in genetic recombination
- e.g. Paramecium spp.
20
Q
Paramecium species
A
- ciliate of alveolate clade
- freshwater heterotrophs
- slipper-shaped cell covered by pellicle = outer membrane and inner layer of alveoli surrounding bases of cilia
- pellicle contains trichocysts, defensive organelles that shoot out of retractable mechanism
- contain cilia, contractile vacuole for osmoregulation, digestive vacuole for endocytosis
21
Q
stramenopiles
A
- clade of protists
- typically have 2 unequal flagella
- longer flagellum has tubular cells
- some lack flagella (secondary derived characteristic)
- include diatoms, brown algae and oomycetes
22
Q
diatoms (properties)
A
- in stramenopile clade
- unicellular, some associate into filaments
- synthesise carbohydrates and oils as photosynthetic storage products
- only male gametes have flagella
- carotenoids in chloroplasts (yellow/brown)
- almost all deposit silica in cell walls, cell wall is ‘petri dish’ shape
- morphologically diverse, bilaterally or radially symmetrical
23
Q
reproduction in diatoms
A
- undergo asexual reproduction, where the top and the bottom of the cell wall each become a new organism
- however, the organism would grow smaller over time and would not be able to grow due to the silica cell walls
- also undergo sexual reproduction, gametes fuse and zygotes grow before they are constrained by the cell wall
24
Q
diatoms (habitats)
A
- found in oceans, dominant in phytoplankton blooms
- responsible for 1/5 carbon fixation of the planet
- found in freshwater
- found on wet terrestrial surfaces such as mosses
25
Q
brown algae (properties)
A
- all multicellular
- branched filaments or leaf-like growths
- fucoxanthin (carotenoid) in chloroplasts plus chlorophyll makes brown colour
e.g. giant kelps such as Macrocystis
26
Q
brown algae (habitats)
A
almost all marine
- some float in mats in open ocean e.g. Sargassum spp.
- most attach to rocks near the shore with holdfasts made from alginic acid (sugar acid polymer ‘glue’)
- alginic acid also cements algal cells and filaments together
- humans use alginate as an emulsifier
27
Q
oomycetes
A
- absorptive heterotrophs, secrete enzymes to digest large food molecules into smaller ones able to be absorbed
- once though to be fungi, but have cellulose cell walls, not chitin
- all aquatic saprobic (feed on dead organic matter)
- aquatic water molds (filamentous and stationary)
- terrestrial species e.g. downy mildews, mostly decomposers, some parasitic on crops e.g. P.infestans (late blight)
28
Q
excavates
A
- protist clade
- began to diversity 1.5bya
- some lack mitochondria, secondary derived condition, shows that eukaryotic life is possible without mitochondria
- include diplomonads, parabasalids, heteroloboseans, euglenids and kinetoplastids
29
Q
diplomonads and parabasalids
A
- excavates
- unicellular
- lack true mitochondria
30
Q
diplomonads
A
- excavates
- e.g. Giardia lamblia
- intestinal parasite in contaminated water
- 2 nuclei
- cytoskeleton
- mutliple flagella (motile)
31
Q
parabasalids
A
- excavates
- flagella
- cytoskeleton
- undulating membranes for locomotion
- e.g. trichomonas vaginalis = STI
32
Q
heteroloboseans
A
- excavates
- amoeboid body forms
- resemble lobosoeans, but no relationship
- e.g. Naegleria spp
33
Q
Naegleria spp.
A
- heterolobosean
- 2 stage life cycle, amoeboid cells and flagellated cells
- some species can cause fatal nervous system diseases in humans
34
Q
euglenids and kinetoplastids
A
- excavates
- unicellular
- 2 flagella made from crystalline rod structures (unique)
- mitochondria with disc shaped cristae
- most reproduce asexually through binary fission
35
Q
euglenids
A
- flagella from pocket at anterior
- spiralling strips of protein control cell shape
- diverse nutritional requirements, some photosynthetic, some heterotrophs
- e.g. Euglenia spp. freshwater, longer flagella used for propulsion/ as an anchor, 2nd flagella usually rudimentary
36
Q
kinetoplastids
A
- kinetoplast houses proteins and circular DNA that codes for mitochondrial proteins and rRNA
- unicellular plastids
- singular large mitochondria
- 2 flagella
- include medically important trypanosomes
37
Q
trypanosoma brucei species
A
- kinetoplastids
- some cause cattle wasting disease
- some cause sleeping sickness (tsetse fly), crosses blood-brain barrier and interrupts sleep-wake patterns, leading to coma and eventual death
- immune evasion strategy through antigenic variation to avoid antigenic variation, leads to waves of fever due to waves of parasite in blood
38
Q
Rhizarians
A
- clade of protists
- unicellular
- mostly aquatic
- typically long thin pseudopodia all over or restricted to certain area that extend into environment
- contribute to ocean sediments
- include cercozoans, foraminiferans, radiolarians
39
Q
cercozoans
A
- rhizarian clade
- diverse, no shared characteristics
- phylogenetic reconstruction from RNA
- 1 group possesses chloroplasts from secondary endosymbiosis
- many habitats
40
Q
foraminiferans
A
- rhizarian clade
- some secrete calcium carbonate shells (makes limestone)
- long pseudopodia extend through openings of shell and interconnect to form sticky network to catch smaller plankton (and sometimes used for locomotion)
- live as plankton or on sea floor (don’t secrete normal shells v deep as low caco3)
- fossil record in sedimentary rock can be used to reconstruct ancient ocean currents
41
Q
radiolarians
A
- thin, stiff pseudopodia reinforced by microtubules increase surface area allowing for flotation
- distinctive radial symmetry
- almost all secrete glassy exoskeletons diverse in shape
- among largest unicellular eukaryotes (up to several mm in diameter)
- marine environments
42
Q
amoebozoans
A
- protist clade
- diverged 1.5bya
- lobed shaped pseudopodia for locomotion, different to slender pseudopodia in rhizarians
- include loboseans, plasmodial slime moulds and cellular slime moulds
43
Q
loboseans
A
- amoebozoan clade
- small
- feed on small organisms/particles through phagocytosis
- live at bottom of lakes/ponds
- most predatory, parasitic or scavengers
- e.g. testate amoebas, live in shells (tests) either secreted by itself or made from sand grains glued together
44
Q
plasmodial slime moulds
A
- multinuclate
- can grow almost indefinitely in favourable conditions
- feeding non-reproductive vegetative state is a network of strands called a plasmodium
- can stream over substance (cytoplasmic streaming) to move around (find prey and move away from unfavourable conditions)
- extends pseudopodia into environment and engulf prey through phagocytosis
45
Q
plasmodial slime moulds in unfavourable conditions
A
Either:
- forms hardened cell-like components to wait out conditions
- transforms into spore bearing fruiting structures (sporangia)
- spores germinate into swarm cells which either become wall resisting resting cysts to wait out conditions or fuse, forming a diploid zygote that makes a new plasmodium
46
Q
cellular slime moulds
A
- vegetative unit is amoeboid cell with a single haploid nuclei = myxamoeba
- engulfs food through endocytosis
- reproduction through mitosis and binary fission, or sexual reproduction
- sexual reproduction, 2 myxamoebas fuse, forming spherical structure that germinates, creating haploid nuclei
- swarms of independent cells can form
- persist almost indefinitely as long as food/moisture is available
47
Q
cellular slime moulds in unfavourable conditions
A
- aggregation of individual myxamoebas into a ‘slug’/pseudoplasmodium (cells retain membrane/identity)
- ‘slug’ migrates away from unfavourable conditions
- reorganises into stationary stalked fruiting structure, spores released germinate into myxamoeba (asexual)
48
Q
protist reproduction
A
- reproduce asexually and sexually
- some have sex without reproduction
- alternation of generations
49
Q
protist relationships with humans
A
- diatoms, diatomaceous earth, petroleum and natural gas
- limestone deposits from foraminiferan shells are useful in fossil records for climate and ocean current estimates
