lecture 17: protists

Question 1

Morphology of protists?

Answer 1

Many unicellular, some colonial, some multicellular

Question 2

Size of cells of protists?

Answer 2

Large range in size, some large and complex and some as small as prokaryotes

Question 3

Reproduction of protists?

Answer 3

Asexual or sexual: most = asexual routinely and sexual only intermittently

Question 4

Are there any unique characteristics to protists?

Answer 4

No

Question 5

Where do you find protists?

Answer 5

Common feature: tend to live in environments where they are surrounded by water

Question 6

What are protists?

Answer 6

All eukaryotes EXCEPT land plants, fungi and animals —> very diverse group

• No unique trait in found in protists
• Some are more related to plants/animals than to other protist groups
• Protists = paraphyletic: represent some, but not all of the descendants of a single common ancestor

Question 7

3 informal protist groups?

Answer 7

1. Protozoa: animal-like —> energy source, no cell wall, motile
2. Algae: plant-like —> photosynthetic cell wall, photoautotroph, not really motile
3. Slime- or Water-Molds: fungus-like —> decomposers

Question 8

Examples of protists

Answer 8

Desmids, diatoms, amoebae, ciliates (stentor and paramecium), euglenids, volvox

Question 9

2 modes of nutrition and description

Answer 9

CHEMOHETEROTROPHS: (protozoa)
1. Ingestive nutrition: organic material are taken into cell by endocytosis & digested with lysosomes (broken down in food vacuoles) —> possible in animal-like protists that lack a cell wall
2. Absorptive nutrition: absorb organic nutrients directly form environment across plasma membrane
PHOTOAUTOTROPH: (algae)
3. Photosynthesis: CO2 fixed into organic molecules using light energy

Question 10

3 modes of locomotion

Answer 10

Move to find food/light

1. Pseudopodia (amoeba) —> amoeboid motion
2. Cilia (ciliates) —> swimming
3. Flagella —> swimming

Question 11

Describe life cycles of protists

Answer 11

• Very diverse & complicated
• Asexual and sexual loops
• Can be dominated by haploid or diploid cells

Question 12

Photosynthetic pigments in photosynthetic protists

Answer 12

Very diverse —> Lead to diverse properties

Question 13

Explain possibilities of evolution of photosynthesis in algae (and some protists) + accepted hypothesis

Answer 13

Only some protists are photosynthetic
1. Photosynthesis could have evolved independently several times
2. Several groups could have lost ability to do photosynthesis
3. SECONDARY ENDOSYMBIOSIS: photosynthesis transferred to many unrelated groups by horizontal gene transfer
- Mutualism between algae and chemoheterotroph protists
—> Rise of chloroplasts in algae from primary endosymbiosis —>Secondary endosymbiosis between algae that already had chloroplast & protists —> Photosynthetic protists

Question 14

3 ecological roles of protists

Answer 14

1. Primary producers = phytoplankton: desmids, diatoms, volvox —> Algae and cynobacteria
2. Primary consumers = zooplankton & Decomposers: ciliates, amoeba —> Protozoa and smaller animals
3. Symbionts: parasites of plants and animals & mutualists

Question 15

What are algal blooms?

Answer 15

Rapid increase in abundance of algae in fresh water and marine ecosystem

• Produced by eutrophication: excessive algal growth due to increased in resources and nutrients
• Can be natural (increase of nutrients from bottom of ocean) or human-induced (phosphate in laundry detergent)
• Harmful algal blooms = red tides —> when toxin-producing dinoflagellates reach high densities and poison shellfish which can poison organisms that use these shellfish for food

Question 16

Impact of protists on humans?

Answer 16

• Cause disease in plants and animals
• Products made by protists = used for commercial products: food industry, agar, diatomaceous earth
• Research on evolution and biology of Eukarya

Question 17

Protist pathogens cause..

Answer 17

Parasitic protists

• Cause disease in animals and affect human health —> Malaria cause of parasitic protozoa
• Cause disease in plants and affect crops —> Irish potato famine caused by a protist (water mold)