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Note: To answer many of these questions, it is recommended that you also download and review the document “background_for_aoa_protist_lab.docx” from msbonaguroluoa..

Protists in Excavata

Euglena

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1. Euglena are primarily photo-autotrophs (providing their own nutrition from photosynthesis), but in fact they are opportunistic heterotrophs. From your study of euglena, however, they do not have a mouth and gullet like the paramecium. Moreover, they have a solid pellicle sourrounding their body.

So the only way they can ingest any food stuff is by phagocytosis, similar to the amoeba, which leads us to ask:

(a) What food items are they able to ingest?

(b) What must the pellicle be capable of to allow for phagocytosis?

 

Protists of Rhizaria

Diatoms

1. What structural element is unique to the diatoms among protists? Of what inorganic material is the structure composed? What is the source of the material?

2. Like other minerals and compounds, this structural material goes through natural cycles. When the material is scarce, diatoms fall to the depths of the ocean where they lie in a kind of suspended animation until currents change and bring both the structural material and the diatoms back up to the upper layers of the ocean.

(a) What feature of the deep ocean helps reduce diatom metabolism?

(b) What nutritional activity necessarily shuts down in the ocean depths?

3. Where oceans once existed on the Earth, geological layers of ocean deposits are all that are left. What is "diatomaceous earth" and what abrasive white powder makes up 90% of its composition?

Paramecium

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1. A paramecium moves very quickly, but how does it find prey?

2. In a sample of pond water there will be a multitude of protist species. Will the paramecium be predator or prey?

3. You've seen the didinium prey on a paramecium. Did the paramecium attempt to defend itself? Is there evidence that trichocysts are used by the paramecium in defense?

Stentor

1. From the video footage it appears that stentors are selective about what they feed on. Using their mouth cilia, how might potential prey be evaluated for suitability?

2. When stentors swim, they turn into a football shape:

(a) What does this say about their attached shape like a long trumpet? Which shape is the "natural" one?

(b) You may have noticed that the stentors rotated while swimming. Can you think of why this happens?

(c) What might cause a stentor to pick up and swim elsewhere?

 Dinoflagellates

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1. Many dinoflagellates are photoautotrophic, making nutrients by photosynthesis.

(a) What structure is responsible for this?

(b) In what form are the nutrient products stored?

2. Some dinoflagellates have developed a symbiotic relationship with other organisms that ingest them. For example, certain corals rely almost exclusively on their dinoflagellate symbionts for their nutrition.

(a) Symbiosis must benefit both parties. How does the dinoflagellate benefit by being ingested and living inside its partner?

(b) What feeding adaptation must the coral have undergone in order to be a symbiotic host for the dinoflagellate?

(c) The symbiont host (e.g. coral) benefits by digesting some of the starch created during photosynthesis. What adaptation must the dinoflagellate have undergone in order to make this relationship work? The dinoflagellate gets to have nutrients.

Seaweed

1. Why are seaweed not plants, even though they are multicellular?

2. Why do most seaweeds grow only in shallow water?

3. Red algae (rhodophytes) absorb blue and violet portions of the visible spectrum. How does this allow the red algae to live at greater depths in water. (Look up refraction of sunlight entering water in morning and evening hours of the day.) It is still able to get light.

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