Lecture 11 Protists

Question 1

what caused the oxygen revolution?

Answer 1

photosynthetic cyanobacteria from 2.7-2.3 bya

Question 2

what are features of eukaryotic cells? (4)

Answer 2

• 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

Question 3

what is the endosymbiont theory?

Answer 3

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

Question 4

what is step 1 of the endosymbiont theory?

Answer 4

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

Question 5

what is step 2 of the endosymbiont theory?

Answer 5

2. 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

Question 6

what is step 3 of the endosymbiont theory?

Answer 6

other lineages engulfed photosynthetic prokaryotes

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

Question 7

what is primary endosymbiosis?

Answer 7

prokaryotes being taken on by eukaryotic cells

Question 8

what is secondary endosymbiosis?

Answer 8

engulfing of eukaryotic cells by other eukaryotic cells

Question 9

what is serial endosymbiosis

Answer 9

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

Question 10

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

Answer 10

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

Question 11

what is the 3 domain system?

Answer 11

• bacteria: bacteria
• archaea: archaea
• eukarya: protista, plantae, fungi, animalia

Question 12

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

Answer 12

euk and arch

- based on rRNA genes as these evolved slowly

Question 13

what is Horizontal Gene Transfer (HGT)?

Answer 13

• 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

Question 14

which endosymbiosis produced the diversity of plastids

Answer 14

• secondary endosymbiosis in protists

Question 15

what are protists?

Answer 15

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

Question 16

what kind of diversity do protists exhibit?

Answer 16

• structural and functional diversity – more than any other eukaryotes

Question 17

what are characteristics of protists?

Answer 17

• 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

Question 18

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

Answer 18

• 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)

Question 19

what did plastids bearing lineage of protists evolve into?

Answer 19

red and green algae

Question 20

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

Answer 20

cyanobacteria DNA

Question 21

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

Answer 21

secondary endosymbiosis– heterotrophic eukaryote

Question 22

how many supergroups are eukaryotes now?

Answer 22

five – protista is no longer a valid kingdom

Question 23

what are the five supergroups of eukaryotes?

Answer 23

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

Question 24

what kind of polytomy are the five supergroups?

Answer 24

basal polytomy – relationship is unknown

Question 25

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

Answer 25

- 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

Question 26

what are diplomonads and and parabasalids? (3) | what is an example?

Answer 26

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

Question 27

what are euglenozoa? (3) | what are two examples?

Answer 27

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

Question 28

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

Answer 28

- 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)

Question 29

what is the alveolate taxa? (2) | what does it include? (3)

Answer 29

division of chromalveolata - have membrane bound sacs (alveoli) just under the plasma membrane - fxn of alveoli is unknown - includes: dinoflagellates, apicomplexans, ciliates

Question 30

what is the stramenopiles taxa? (2) | what does it include? (4)

Answer 30

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

Question 31

what are dinoflagellates? (4)

Answer 31

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

Question 32

what are apicomplexans? (4) | give an example

Answer 32

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

Question 33

what are ciliates? (3) | give an example

Answer 33

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

Question 34

what are diatoms? (4)

Answer 34

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

Question 35

what are brown algae? (6)

Answer 35

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

Question 36

what are oomycetes? (5)

Answer 36

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

Question 37

Five Supergroups | what are archaeplastida? (4)

Answer 37

- 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

Question 38

What are 'algae'? (5)

Answer 38

- 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

Question 39

what is red algae? (4)

Answer 39

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

Question 40

what are green algae? (4) | what are the two sub groups?

Answer 40

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)

Question 41

what are (multicellular) chlorophytes?

Answer 41

archaeplastida -- green algae

Question 42

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

Answer 42

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

Question 43

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

Answer 43

- 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)

Question 44

what are amoebozoans? (2) | what does it include?

Answer 44

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

Question 45

what are gymnamoebas? (2)

Answer 45

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

Question 46

what are entamoebas? | give an example

Answer 46

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

Question 47

what are slime molds? 3

Answer 47

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

Question 48

what are cellular slime molds? (2)

Answer 48

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

Question 49

what are plasmodial slime molds?

Answer 49

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