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Biology 108 > Lecture 11 Protists > Flashcards

Lecture 11 Protists Flashcards

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1
Q

what caused the oxygen revolution?

A

photosynthetic cyanobacteria from 2.7-2.3 bya

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2
Q

what are features of eukaryotic cells? (4)

A
  • DNA in linear chr
  • membrane bound organelles, such as mt and plastids
  • cytoskeleton that allows them to change shape (ex: endo/exocytosis)
  • often larger than prok
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3
Q

what is the endosymbiont theory?

A

proposes that mt and plastids (chloroplasts and other related organelles) were formerly small prok living in a larger host

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4
Q

what is step 1 of the endosymbiont theory?

A
  1. ancestral host cell developed some structures gradually by infoldings of the cell membrane
    - endoplasmic reticulum
    - nuclear envelope
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5
Q

what is step 2 of the endosymbiont theory?

A
  1. ancestral host cell took on an endosymbiotic aerobic heterotropic prokaryote
    - probably a proteobacterium
    - uses O2 and organic matter to make energy
    - eventually became a mitochondrion
    - at this point cell is a “true” eukaryote
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6
Q

what is step 3 of the endosymbiont theory?

A

other lineages engulfed photosynthetic prokaryotes

  • most likely cyanobacteria
  • uses light and CO2 to make organic compounds
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7
Q

what is primary endosymbiosis?

A

prokaryotes being taken on by eukaryotic cells

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8
Q

what is secondary endosymbiosis?

A

engulfing of eukaryotic cells by other eukaryotic cells

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9
Q

what is serial endosymbiosis

A

supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events

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10
Q

what are the 5 pieces of evidence that supports the endosymbiotic origin of mt and plastids

A
  1. mt and ch have their own circular DNA which replicate independently of nuclear DNA
  2. division (binary fission) is similar in these organelles and some prokaryotes
  3. inner membranes are similar to plasma membranes of prok
  4. their ribosomes are more similar to prok ribosomes (70s instead of 80s euk ribosomes)
  5. resemble bacteria in size and structure
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11
Q

what is the 3 domain system?

A
  • bacteria: bacteria
  • archaea: archaea
  • eukarya: protista, plantae, fungi, animalia
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12
Q

what two domains does the tree of life suggest are more related?

A

euk and arch

- based on rRNA genes as these evolved slowly

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13
Q

what is Horizontal Gene Transfer (HGT)?

A
  • movement of genes from one genome to another
  • occurs by exchange of transposable elements and plasmids, viral infection and fusion of organisms
  • complicates efforts to build a tree of life for eukaryotes
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14
Q

which endosymbiosis produced the diversity of plastids

A
  • secondary endosymbiosis in protists
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15
Q

what are protists?

A
  • informal name of a group of mostly unicellular eukaryotes (some are colonial and multicellular)
  • excludes plants, animals, and fungi
  • taxonomically diverse group of eukaryotes
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16
Q

what kind of diversity do protists exhibit?

A
  • structural and functional diversity – more than any other eukaryotes
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17
Q

what are characteristics of protists?

A
  • single celled protists can be very complex
  • have to exist as complete organisms unto themselves
  • biological functions are carried out by organelles in each individual cell
  • can reproduce asexually or sexually
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18
Q

what are the three trophic levels of protists (most nutritionally diverse)

A
  • photoautotrophs – contain chloroplasts
  • heterotrophs – absorb organic molecules or ingest larger food particles (ex: heterotroph consumers - protozoans & heterotrophic decomposers - slime/water molds)
  • mixotrophs – combine photosynthesis and heterotrophic nutrition (ex: marine protists)
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19
Q

what did plastids bearing lineage of protists evolve into?

A

red and green algae

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20
Q

what taxa does plastid gene DNA in red and green algae closely resemble?

A

cyanobacteria DNA

21
Q

which endosymbiosis did red and green algae undergo + what were they ingested by?

A

secondary endosymbiosis– heterotrophic eukaryote

22
Q

how many supergroups are eukaryotes now?

A

five – protista is no longer a valid kingdom

23
Q

what are the five supergroups of eukaryotes?

A
  1. Excavata *
  2. Chromalveolata *
  3. Rhizaria
  4. Archaeplastida *
  5. Unikonta *
24
Q

what kind of polytomy are the five supergroups?

A

basal polytomy – relationship is unknown

25
Q

Five Supergroups:
what are excavates? (4)
what does it include?

A
  • include protists with modified mitochondria and unique flagella
  • unicellular
  • some have a feeding grove
  • might have a reduced mt – mitosomes
  • includes diplomonads, parabasalids, and euglenozoa
26
Q

what are diplomonads and and parabasalids? (3)

what is an example?

A

excavata

  • don’t have plastids
  • modified mt
  • most live in anaerobic enviro – non photosynthetic
  • ex: Giarda intestinalis – in H2O contaminated w/ feces with parasite cysts
27
Q

what are euglenozoa? (3)

what are two examples?

A

excavata

  • diverse clade
  • includes predatory heterotrophs, PS autotrophs, parasites, mixotrophs (ex: Euglenids)
  • characterized by spiral or crystalline rod structures in flagella
  • ex: trypanosoma – sleeping sickness– tstse fly – parasite crosses through blood-brain barrier
  • ex: Euglenids – 1 or 2 flagella that emerge from a pocket at one end
28
Q

Five Supergroups
what are chromalveolata? (3)
what does it include? (I: 3 II: 4)

A
  • probably monophyletic clade
  • originated by secondary endosymbiosis event (red alga?)
  • controversial as it includes alveolates and stramenopiles
  • alveolates: dinoflagellates, apicomplexans, ciliates
  • stramenopiles: diatoms, brown alga, oomycetes (golden algae)
29
Q

what is the alveolate taxa? (2)

what does it include? (3)

A

division of chromalveolata

  • have membrane bound sacs (alveoli) just under the plasma membrane
  • fxn of alveoli is unknown
  • includes: dinoflagellates, apicomplexans, ciliates
30
Q

what is the stramenopiles taxa? (2)

what does it include? (4)

A

division of chromalveolata

  • includes important phototrophs as well as several clades of heterotrophs
  • must have hairy flagellum paired with a smooth flagellum
  • includes: diatoms, brown algae, golden algae, oomycetes
31
Q

what are dinoflagellates? (4)

A

supergroup chromalveolata : alveolate

  • two flagella on each cell is reinforced by cellulose plates
  • abundant marine and freshwater phyloplankton
  • diverse group of aquatic phototrophs, mixotrophs, and heterotrophs
  • toxic red tides are caused by dinoflagellate blooms
32
Q

what are apicomplexans? (4)

give an example

A

supergroup chromalveolata: alveolate

  • parasites of animals, some cause serious human diseases
  • spread as infectious cells called sporozoites
  • apex (one end) contains a complex of organelles specialized for penetrating host cells and tissues
  • most have sexual and asexual stages that require two or more hosts
  • ex: malaria from Plasmodium spp. parasites
33
Q

what are ciliates? (3)

give an example

A

supergroup chromalveolata: alveolate

  • large, varied groups of protists, use cilia to move and feed
  • many free - living species feed on bacteria & smaller protists via phagocytosis
  • usually reproduce asexually by binary fission, but sometimes engage in conjugation
  • ex: paramecium
34
Q

what are diatoms? (4)

A

supergroup chromalveolata: stramenophyla

  • unicellular algae w/ unique two-part glass-like wall of hydrated silica
  • usually reproduce asexually, and occasionally sexually
  • diatoms are a major component of phytoplankton and are highly diverse
  • important contributors to carbon sequestration
35
Q

what are brown algae? (6)

A

supergroup chromalveolata: stramenophyla

  • larges and most complex algae
  • all are multicellular, and most are marine
  • brown algae include many species commonly called “sea weeds”
  • giant seaweeds called kelps live in deep parts of the ocean
  • the algal body is plant-like but lacks true roots, stems, leaves
  • life-cycle of some algae involves alternation of generations
36
Q

what are oomycetes? (5)

A

supergroup chromalveolata: stramenophyla

  • include water molds, white rusts and downly mildews
  • once considered fungi based on downy mildews
  • most are decomposers and parasites
  • have hyphae that facilitate nutrient uptake
  • can have great impact – potato famine bc of Phytophora infestans
37
Q

Five Supergroups

what are archaeplastida? (4)

A
  • supergroup that includes red algae, green algae, land plants
  • over a billion years ago, heterotrophic protists acquired a cyanobacterial endosymbiont
  • photosynthetic descendents of this ancient protist evoled into red algae and green algae
  • land plants and descended from green algae
38
Q

What are ‘algae’? (5)

A
  • photoautotrophic eukaryotes that are not members of kingdom plantae
  • not monophyletic – photoautotrophy evolved several times
  • many are single celled (many Diatoms of marine and freshwater Phytoplankton)
  • others are multicellular and can be large
  • fxn in global ecosystem
39
Q

what is red algae? (4)

A

archaeplastida

  • reddish due to accessory pigment phycoerythrin – masks chlorophyll
  • colour varies greenish–red in shallow water to dark red or almost black in deep water
  • usually multicellular, largest are seaweeds
  • most abundant large algae in coastal waters of the tropics
40
Q

what are green algae? (4)

what are the two sub groups?

A

archaeplastida

  • named for green pigments
  • paraphyletic group – excludes land plants
  • most live in fresh water
  • single cells to multicellular forms
  • two main groups are chlorophytes and charophytes (char are most closely related to land plants)
41
Q

what are (multicellular) chlorophytes?

A

archaeplastida – green algae

42
Q

how did the larger size and greater complexity of chlorophytes evolve? (3)
what are the sex cycles of chlorophytes like?

A
  1. formation of colonies from individual cells
  2. formation of true multicellular bodies by cell division and differentiation
  3. repeated division of nuclei with no cytoplasmic division
    - chlorophytes have complex life cycles with both sexual and asexual reproductive stages
43
Q

Five Supergroups
what are unikonts? (2)
what does it include? (I: 3 II:4)

A
  • root of eukaryotic tree remains contreversial
  • unclear whether unikonts separated from other eukaryotes relatively early or late
  • 2 clades: amoebozoans (slime molds,gymnamoebas, entamoebas) & opisthokonts (nucleariids, fungi, choanoflagellates, animals)
44
Q

what are amoebozoans? (2)

what does it include?

A

unikonts

  • amoeba that have lobe or tube shaped (rather than threadlike) pseudopodia
  • very flexible body shape that move by extending pseudopodia and feet by phagocytosis
  • includes: slime molds, gymnamoebas, entamoebas
45
Q

what are gymnamoebas? (2)

A

unikonts: amoebozoans
- common unicellular amoebozoans in soil, freshwater, marine environments
- most heterotrophic and actively seek and consume bacteria & protists

46
Q

what are entamoebas?

give an example

A

unikonts: amoebozoans
- parasites of vertabrates and some invertabrates
- Entamoeba histolytica causes amebic disentry – 3rd cause of human death via euk parasites

47
Q

what are slime molds? 3

A

unikonts: amoebozoans
- once thought to be fungi
- in this clade bc of molecular systematics
- two main groups: cellular vs plasmodial

48
Q

what are cellular slime molds? (2)

A

unikonts: amoebozoans
- spend most of lives as individual unicellular protists
- when food is depleted – cells cluster into multicellular aggregates - act as one organisms - fruiting body

49
Q

what are plasmodial slime molds?

A

unikonts: amoebozoans
- form a mass called a plasmodium
- not multicellular
- enclosed within a single membrane as one large “super cell” – essentially a bag of cytoplasm containing 1000s of individual nuclei
- extends pseudopodia through decomposing material, engulfing food by phagocytosis

Biology 108 (27 decks)

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