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genetics evolution and diversity > eukaryote protists > Flashcards

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
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2
Q

great oxygenation event

A
  • O2 generating cynaobacteria increased atmospheric O2
  • aerobic prokaryotes proliferated
  • evolution of large eukaryotic cells
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3
Q

precambrian era

A
  • 1.5bya
  • eukaryotes began to diversify
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4
Q

cambrian explosion

A
  • 540mya
  • extensive diversification and radiation of eukaryotes
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5
Q

mesozoic era

A
  • 252-66mya
  • distinct terrestrial biotas evolved on each continent
  • 5 mass extinctions
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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
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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
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8
Q

origin of modern eukaryotic cell

A
  1. origin of flexible cell surface allowing for growth, movement, vesicles
  2. origin of cytoskeleton, allowing for structural integrity, transport, cell division, movement
  3. origin of nuclear envelope, enclosing genome
  4. appearance of digestive vacuoles
  5. acquisition of certain organelles by endosymbiosis
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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

genetics evolution and diversity (12 decks)

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