3. Chapter 28: Eukaryotes

Question 1

What are “protists”?

Answer 1

• so diverse, few general characteristics - mostly unicellular (colonial or multicellular) - most elaborate of all cells (single cell performs all basic function)

Question 2

What are the nutritional diversity of protists?

Answer 2

1. photoautotrophs 2. chemoheterotrophs 3. mixotrophs: combine photosynthesis and heterotrophic nutrition (i.e. euglena)

Question 3

How do most protists move?

Answer 3

flagella or cilia - eukaryotic flagella not homologous to those of prokaryotes - 9 +2 microtubule sustem - cilia are shorter and more numerous

Question 4

Where are protists found?

Answer 4

• almost anywhere there is water - damp soul and leaf litter

Question 5

What are the protists an important part of?

Answer 5

of plankton: aquatic communities that drift passively or swim weakly

Question 6

What is phytoplankton?

Answer 6

forms the base of most marine and fresh water food chains (cyanobacteria important member)

Question 7

What are zooplankton?

Answer 7

primary consumers that feed on phytoplankton (many are not ‘protists’ but rather animals in adult or larval stage)

Question 8

Many protists are symbionts. Where do that inhabit?

Answer 8

a host - mutualism to parasitism - some parasitic protist are important pathogens of animals

Question 9

What are some examples of human diseases caused by protists?

Answer 9

1. Malaria (Plasmodium) 2. African Sleeping Sickness (Trypanasoma) 3. Amoebic Dysentery (Traveler’s Diarrhea) 4. Giardia (Local Diarrhea drinking H2O)

Question 10

What was an evolutionary trend of larger, more complex cells?

Answer 10

compartmentalization of cellular functions into organelles - endomembrane system (ER, Golgi) from infolding of plasma membrane - endosymbiosis (mitochondria and chloroplasts; were independent prokaryotes that entered host cells as undigested prey or internal parasites evolved to beneficial symbiosis)

Question 11

What are the evidence that the mitochondria may have been independent prokaryotes at one point?

Answer 11

1. Appearance 2. Genomes 3. Enzymes 4. Ribsome 5. Binary fission

Question 12

Explain secondary endosymbiosis.

Answer 12

A protist engulfs an organism and retain its chloroplasts (ea. event adds a membrane)

Question 13

Why are taxonomic groups with chloroplasts scattered through the phylogenetic tree?

Answer 13

those of plants and green algae have two membranes, other groups have three or four

Question 14

The classic Darwinian view is that of linear descent through a series of ancestor but what does endosymbiosis imply?

Answer 14

• “horizontal” fusions (across the tree of life) - all three domains have DNA that has been transferred between domains - Replaces the classical ‘tree of life’ with a web-like phylogeny.

Question 15

What characteristics do all three domains share?

Answer 15

• Plasma Membrane - DNA - Ribosome - Electric Transfer Chains

Question 16

What do all bacteria share?

Answer 16

Peptidoglycan

Question 17

What do Archaea and Eukaryotes have in common?

Answer 17

Histones and Introns

Question 18

What characteristics does archaea have?

Answer 18

can live in temperatures of 100+ degrees celsius

Question 19

What characteristics do Euglenozoa clade share?

Answer 19

• crystalline rod in their flagella - function unknown

Question 20

What characteristic do Kinetoplastids share? (branch of Euglenozoa) What are the best known genus?

Answer 20

• single, large mitochondrion - kinetoplast: a DNA containing granules located within single mitochondrion - Trypanosoma (cause African sleeping sickness vectored by Tsetse Fly, changes surface proteins prevent host immunity development)

Question 21

What is another branch of Euglenozoa? What characteristics? Example?

Answer 21

Euglenids; one/two flagella from anterior pocket, often mixotrophic; Euglena

Question 22

What are characteristics of clade Diplomonadida? Genus?

Answer 22

• lacking mitochondria - two nuclei - thought to be primitive before mitochondria appeared, now known to have lost it secondarily - Giardia; causes giardiasis “beaver fever”, flagellated parasite of mammals, colonizes small intestine of human via feces contaminated water, severe diarrhea

Question 23

What are the characteristics of the Alveolata clade?

Answer 23

• united by molecular systematics, few morphological connections except alveoli under plasmid membrane.

Question 24

What are the three groups of Alveolata?

Answer 24

1. Dinoflagellates 2. Apicomplexans 3. Ciliates

Question 25

Alveolata: List some characteristics of Dinoflagellates (zooxanthellae)

Answer 25

• large component of phytoplankton, foundation marine food chain, shape by internal plates of cellulose, spinning movement by two flagella in groove, red tide, toxin produce by filter feeder, deadly to humans who eat contaminated shellfish (Paralytic shellfish poisoning) - some form mutualistic symbiosis with corals and anemones - some bioluminescent

Question 26

Alveolata: List some characteristics of Apicomplexans. Example?

Answer 26

• all are parasites of animals - intricate life cycles (often two different hosts) - Plasodium causes malaria (hides inside liver and blood)

Question 27

Alveolata: List some characteristics of Ciliates. Example?

Answer 27

• diverse group - use cilia to move and feed (some completely covered, others have clustered rows or tufts) - Paramecium (cilia draw food which is engulfed by phagocytosis and expel accumulated water from contractile vacuole)

Question 28

What are the characteristics of the Stramenopila Clade? Groups?

Answer 28

• Hairy flagellum paired with smooth flagellum (flagellated stage is often just reproductive cells) - Diatoms and brown algae

Question 29

Stramenoila: List some characteristics of Diatoms.

Answer 29

• common type of phytoplankton (freshwater and marine) - two flagella - hairy and smooth - plastids have 3 membranes - secondary endosymbiosis - unique glasslike walls of hydrated silica - fossilized can form diatomaceous soil (natural abrasive and pesticide - by cutting insects exoskeletons)

Question 30

Stramenopila: List some characteristics of Brown Algae.

Answer 30

• large, brown, commonly known as ‘seaweeds’ - inhabit intertidal and subtidal zones of coastal waters (temperate) - extreme physical conditions: wave forces and exposure at low tide - complex, multicellular resembling plants - holdfast (root-like), stipe (stem-like), and photosynthetic blades (leaf-like) - bladder floats near surface - no vascular tissue - brown colour due to accessory photosynthetic pigments - fucoxanthin - many have floats - giant ones known as kelp: important habitat for sea urchins and otters, fastest linear growth of any organism

Question 31

What are the characteristics of the Amoebozoa clade? What groups are they divided into?

Answer 31

• lobe-shaped pseudopodia - unicellular heterotrophs: consume bacteria via phagocytosis - Amoeba and Slime Molds

Question 32

Amoebozoa: List some characteristics of amoebas.

Answer 32

• 6 are parasites of human - Amoebic dysentry can be fatal, transmitted by contaminated water, “traveler’s diarrhea” or “montezuma’s revenge”

Question 33

Amoebozoa: List some characteristics of slime molds.

Answer 33

• once thought to be fungi - fruiting bodies produce spores - convergent evolution - descended from unicellular amoebas - plasmodial and cellular

Question 34

Amoebozoa: Slime Molds: Plasmodial Slime Molds. List some characteristics.

Answer 34

• brightly pigmented - form plasomdium - single mass of cytoplasm with multiple nuclei - feeding stage: extends pseudopodia through decomposing material, engulfing food via phagocytosis

Question 35

Amoebozoa: Slime Molds: Cellular Slime Molds. List some characteristics.

Answer 35

• Good conditions, exist as one-celled individuals, like typical amoebas - Tough times, crawl to central location and become fuse into slug-like stage; travels to surface leaf litter; cells reconfigure to form fruiting body; millions of spores released to become single-celled organisms

Question 36

What are the common characteristics of the Chlorophyta clade? Examples?

Answer 36

• evolved from common photoautotrophic ancestor - named for grass-green chloroplasts with chlorophyll a & b (similar to plants) - range in complexity: Unicellular (Chalmydomonas), Colonial (Volvox), Multicellular (Ulva, can qualify for seaweeds), symbiotically with fungi (lichen, a mutualistic collective)

Question 37

What are some characteristics of the Rhodophyta clade?

Answer 37

• chlorophyll a - large enough t be ‘seaweeds’ - red coloration due to pigment phycoerythrin: absorbs wavelengths (blue and green that penetrate deep water) - found in depth of over 260m (deep for photosynthetic organism to survive)