Ch 28 Protists

If you were studying the evolutionary origin of cell-to-cell signaling systems in animals, from what protist phyla would you choose representative species to analyze?

Choanomonada

Protists that move around by means of cilia are the

ciliate protozoa

If you were interested in the evolutionary origin of land plant traits, what group would you choose to study?

Green algae

Imagine that someone sends you a sample of living single-celled protists labeled "mixotrophs". What could you infer about the sample?

The protists in the sample use a mixed mechanism of nutrition involving photoautotrophy and phagotrophy or osmotrophy

What are extrusomes?

spearlike defensive structures shot from cells as a response to attack

How would you distinguish a primary plastid from a secondary plastid?

A primary plastid typically has two outer envelope membranes; the plastids of green algae and those of land plants (which descended from green algae) are examples. A secondary plastid typically has more than two envelope membranes; the plastids of photosynthetic euglenoids, cryptomonads, and haptophytes are examples.

Pathogenic (disease-causing) protists may interact in complex ways with their hosts. In the case of malaria patients, what is the cause of the cycle of chills and fever that such patients experience?

The merozoite stage of the protist that causes malaria, Plasmodium, reproduces within red blood cells of infected people. New merozoites break out of red blood cells synchronously, every 48 or 72 hours, corresponding to cycles of chills and fever.

Recall that genomes are present in mitochondria and plastids, in addition to nuclei. When Endosymbiosis occurs, hosts often retain endosymbiont organelles or their genomic components. For example, algal cells possessing secondary plastids derived from red algae may possess genes from red algal mitochondria, plastids, and nuclei in addition to nuclear and mitochondrial genomes present in a non-photosynthetic host cell. In that case, genes are representing at least five genomes might be present in

At least seven

Imagine that you have been directed to compare the fine structures and gnomes present in different types of tertiary plastids. Which protist group would be the best source for different types of tertiary plastids?

Dinoflagellates

Which, if any, is a reasonable and testable hypothesis to answer the following question: in an aquatic environment, how might larger body size-conferred by larger cells in the cases of unicellular species or by multicellularlarity-be advantageous to photosynthetic protest?

Larger bodies might be able to convert more sunlight energy into organic compounds, larger bodies might be able to store larger amounts of essential mineral nutrients that are taken in from the surrounding environment, larger bodies might be less vulnerable to being eaten by small herbivores (all of the above)

How might you test the hypothesis that a fungus like protist acquired the capacity to take up and metabolize a compound (that is also food or fungi) by means of horizontal gene transfer from a fungal species?

compare the DNA sequences of relevant genes that occur in the genomes of fungi and fungus like protists, test the ability of a fungus like protist that lacks the trait to express the trait after using genetic engineering to incorporate one or more relevant fungal genes into the protist genome, compare the amino acid sequences of proteins needed for expression of the trait in fungi with those of fungus like protist (all of the above)

Consider the characteristics of modern classified in Alveolata, Stramenopila, and Rhizaria, three protist, supergroups that are more closely related to each other than to any other supergroup. If protists resemble the ancestor that gave rise to Alveolata, Stramenopila, and Rhizaria are still alive today, how might you recognize them?

Ancestor like protests would probably lack plastids and move by means of two flagella

Imagine that you are part of a marine biology team seeking to catalogue the organisms inhabiting a threatened coral reef. The team has discovered two new types of red macroalgae (seaweeds), each of which is present only during particular seasons of year that differ in temperature. You suspect that the two new types might be alternate generations of the same species that differ with respect to the optimal temperature for growth. How would you go about testing your hypothesis?

If you had access to molecular testing, you could analyze the two macroalgal types to see if the genomes were the same or different. If the genomes are very similar or identical, the two types are likely to represent alternate reproductive stages of the same species. If the genomes differ, the two types may be distinct species. You could also conduct experiments in which you grow one macroalgal type under controlled environmental conditions in the laboratory, then change the temperature to see if there is a reproductive transition to the second macroalgal type.

Protist of various types are employed by industry to make useful materials. If you were granted funds to start a biotechnology company based on an industrial application for any protist, what are some avenues you could pursue?

The fact that today's oil deposits largely arise from ancient algae suggests that modern algae of diverse types could be cultivated for extraction of lipids for transportation and biosynthesis uses. Green algal protists produce channelrhodopsins (light-activated ion channels) that have important uses as reporter molecules in neurobiology. Complex polysaccharides such as alginates, carrageenan, agar, and agarose, which are widely used in diverse applications, are extracted from brown and red macroalgae. Diverse haptophytes and foraminifera that produce coverings made of calcium carbonate could be cultivated to remove carbon dioxide from industrial waste streams to prevent this greenhouse gas from entering the atmosphere. Stramenopile diatoms could be cultivated to produce finely-structured silica for industrial uses. Armored dinoflagellates and many types of green algae that produce tougher forms of cellulose than the celluloses produced by plants, could be cultivated for extraction of useful celluloses. And many other possibilities exist.