Concept 27.5

Question:
I. Contrast exotoxins and endotoxins.

Answer:
a) Exotoxins: can produce disease even if the prokaryotes that manufacture them are not present. Endotoxins: released only when the bacteria die and ther cell walls break down.
b) Exotoxins: proteins secreted by prokaryotes. Endotoxins: lipopolysaccharides released from the outer membrane of gramnegative bacteria that have died.

Question:
II. What features of prokaryotes make them a potential bioterrorism threat?

Answer:
a) Pathogenic prokaryotes pose a potential threat as weapons of bioterrorism. For example, Bacillus anthracis, the bacterium that causes anthrax, were found in envelopes mailed to members of news media and the U.S. Senate. Another candidate of prokaryote that could be used as weapons is the C. botulinum & Yersinia pestis, which causes plague.
b) Their quick reproduction can make it difficult to combat them with antibiotics, particularly as they may evolve resistance to the drugs. Some also have the ability to form endospores and withstand harsh environments, surviving until conditions become more favorable.

Question:
III. Identify at least 2 ways that prokaryotes have affected you positively today.

Answers:
a) eating fermented foods such as yogurt and cheese; having clean water and prokaryote-produced medicines

Concept 27.4

Question:
I. Although individual prokaryotes may be tiny, they are giants in their collective impact on Earth and its life. Explain.

Answer:
a) Although prokaryotes are small, mostly unicellular organisms, they play key roles in ecosystems by decomposing wastes, recycling chemicals, and providing nutrients to other organisms.

Question:
II. Explain how the relationship between humans and B. thetaiotaomicron is an example of mutualism.

Answer:
a) This bacteria, B. thetaiotaomicron, includes a large array of genes involved in synthesizing carbohydrates, vitamins, and other nutrients needed by humans. Signals form the bacterium activate human genes that build the network of intestinal blood vessels necessary to absorb food. Other signal induce human cells to produce antimicrobial compounds to which B. thetaiotaomicron is not susceptible. Keeping other competing bacteria out of the intestines benefits B. thetaiotaomicron as well as its human host.
b)Bacteroides thetaiotatomicron, which lives inside the human intestine, benefits by obtaining nutrients from the digestive system and by receiving protection from competing bacteria from host-produced antimicrobial compounds to which it is not sensitive. The human host benefits because the manufactures carbohydrates, vitamins and other nutrients.

Concept 27.3

Question:
I. Explain how molecular systematics has greatly increased our understanding of prokaryotic phylogeny.

Answers:
a) Before molecular systematics, taxonomists classified prokaryotes according to phenotypic characters that did not clarigy evolutionary relationships. Molecular comparisons indicated key divergences in prokaryotic lineages.

Question:
II. What do syphilis and Lyme disease have in common?

Answer:
a) The two pathogenic spirochetes unexpectedly share an ATP synthase. The organism that causes Lyme disease is a bacterium, Borrelia burgdorferi, which was cultured from the midgut of Ixodes ticks in the mid-1980s. One of the most infamous relatives of this bacterium, Borrelia burgdorferi, is Treponema pallidum, the bacterium that causes syphilis. In contrast to Lyme disease, syphilis is not a modern affliction; it was first recognized in the 15th century in Europe. It is similar to B. burgdorferi in that it is a spirochete with a relatively small genome and requires a host to survive; however, at the genomic level, the two organisms are not very closely related to each other at all.
b) both diseases are caused by spirochetes.

Question:
I. What characteristics enable some species of Archaea to live in extreme environments?

Answers:
a) The ability of various archaea to use hydrogen, sulfur, and other chemicals as energy sources and to survive or even thrive without oxygen enables them to live in environments where more commonly needed resources are not present.

Concept 27.2

Question:
I. A bacterium requires only the amino acid methionine as an organic nutrient and lives in lightless caves. What mode of nutrition does it employ? Explain.

Answer:
a)Chemoheterotrophic mode of nutrition - a nutritional classification where the microbe gets its energy from chemicals and its electrons and carbon from organic compounds.
b) Chemoheterotrophy; the bacterium must rely on chemical sources of energy, since it is not exposed to light, and it must be a heterotroph if it requires and organic source of carbon rather than CO2.

Question:
II. What are the sources of carbon and nitrogen for the cyanobacterium Anabaena?

Answers:
a) Anabaena is a photoautotroph that obtains its carbon from CO2. As a nitrogen-fixing prokaryote, Anabaena obtains its nitrogen from N2.

Concept 27.1

Question:
I. Identify and explain at least 2 examples of adaptations that enable prokaryotes to survive in environments too harsh for other organisms.

Answer:
a) Adaptations include the capsule, plasmids, and the formation of endospores.

Question:
II. Contrast the cellular and genomic organization of prokaryotes and eukaryotes.

Answer:
a) Prokaryotes vs Eukaryotes: prokaryotes lack a nucleus enclosed by membranes, lack other internal compartments bounded by a membrane so instead they use the infolded regions of the plasma membrane to perform many metabolic functions including cellular respiration and photosynthesis, while eukaryotes have internal compartments bounded by a membrane, have smaller and simpler genomes than eukaryotes, may also have smaller rings of DNA, plasmids, that consist of only a few genes unlike in eukaryotes; prokaryotes can survive in most environments without their plasmids because essential functions are programmed by the chromosomes.
b) Prokaryotic cells generally lack the internal compartmentalization of eukaryotic cells. Prokaryotic genomes have much less DNA than eukaryotic genomes, and most of this DNA is contained in a single ring-shaped chromosome located in a nucleoid region rather than within a true membrane-bounded nucleus. In addition, many prokaryotes also have plasmids, small ring-shaped DNA molecules, containing a few genes.

Question:
III. Explain how rapid reproduction allows prokaryotes to adapt to changing environments.

Answer:
a) Prokaryotes can adapt quickly to changes in their environment through evolution by natural selection. Because of prokaryotes' rapid reproduction, mutations that confer greater fitness can swiftly become more common in a population. Horizontal gene transfer also facilitates rapid evolution in prokaryotes.
b) Rapid reproduction enables a favorable mutation to spread quickly through a prokaryotic population by natural selection.

Concept 28.8

Question:
I. Identify 2 ways in which red algae are different from brown algae.

Answer:
a) Brown Algae: color results from the carotenoid FUCOXANTHIN; carbohydrate storage product: LAMINARIN
Red Algae: color results from PHYCOERYTHRIN; carbohydrate storage product: FLORIDEAN STARCH
b) many red algae contain an accessory pigment called phycoerythrin, which gives them a reddish color and allows them to carry out photosynthesis in relatively deep coastal water. Also unlike brown algae, red algae have no flagellated stages in their life cycle and must depend on water currents to bring gametes together for fertilization.

Question:
II. Why is it accurate to say that Ulva has true multicellularity but Caulerpa does not?

Answer:
a) Ulva's thallus contains many cells and is differentiated into leaflike blades and a rootlike holdfast. Caulerpa's thallus is composed of multinucleate filaments without cross-walls, so it is essentially one large cell.

Concept 28.7

Question:
I. Contrast the pseudopodia of amoebozoans and forams.

Answer:
a) Amoebozoans have lobe-shaped pseudopodia, whereas forams have threadlike pseudopodia.

Question:
II. In what sense is 'fungus animal' a fitting description of a slime mold? In what sense is it not a fitting description?

Answer:
a) Slime molds are fungus-like in that they produce fruiting bodies that aid in the dispersal of spores, and they are animal-like in that they are motile and ingest food. However, slime molds are more closely related to gymnamoebas and entamoebas that to fungi or animals.

Question:
III. Does cooperation between cells exist in amoebozoans? Explain.

Answer:
a) Yes, in the life cycle of a cellular slime mold, individual amoebas may congregate in response to a chemical signal, forming a slug-like aggregate from that can move. Then some of the cells from a stalk that supports an asexual fruiting body.

Concept 28.6

Question:
I. Why do forams have such a well-preserved fossil record?

Answer:
a) Because foram tests are hardened with calcium carbonate, they form long-lasting fossils in marine sediments and sedimentary rocks.

Question:
II. Compare feeding forams and radiolarians.

Answer:
a) Forams feed by extending their pseudopodia through pores in therir tests. Radiolarians ingest smaller microorganisms by phagocytosis using their pseudopodia; cytoplasmic streaming carries the engulfed prey to the main part of the cell.

Concept 28.5

Question:
I. What unique cellular feature is common to all stramenopiles?

Answer:
a) Stramenopiles have "hairy" and smooth flagella. In some stramenopile groups, the only flagellated cells are motile reproductive cells.
b) A pair of flagella, one hairy and one smooth.

Question:
II. Compare the nutrition of oomycetes with that of golden algae.

Answer:
a) Golden Algae: all are photosynthetic, some are mixotrophic, & can also absorb dissolved organic compounds or ingest food particles and prokaryotes by phagocytosis. While, Oomycetes: do not carry out photosynthesis, instead they acuire nutrients as decomposers or parasites.
b) Oomycetes acquire nutrition mainly as decomposers or parasites; golden algae are photosynthetic, but some also absob dissolved organic compounds or ingest food particles and prokaryotes by phagocytosis.


Question:
III. How is the structure of a borwn alga such as Laminaria well suited to its intertidal zone habitat?

Answer:
a) They have unique adaptations that enable them to withstand the waves & the intense heat of the sun. For example, their cell walls are composed of cellulose and gel-forming polysaccharides that help cushion the thalli from waves and reduce drying when the algae are exposed.
b) The holdfast anchors tha alga to the rocks, while the wide, flat blades provide photosynthesis surfaces. The cellulose and algin in the alga's cell walls cushion the thallus from waves and protect it from drying out.

Concept 28.4

Question:
I. What morphological feature supports molecular data that suggest dinoflagellates, apicomplexans, and ciliates are members of a single clade?

Answer:
a) Membrane-bounded sacs under the plasma membrane

Question:
II. Why is a 'red tide' a cause for concern to people who eat locally caught seafood?

Answer:
a) Red Tide is a microorganism containing a concentrated toxin and occasionally washes onshore. Though not all people are susceptible to the effects of red tide, it can be absorbed by humans directly, as well as be absorbed in shellfish. Red tide can also affect humans if they consume contaminated molluscan shellfish. During a red tide, bivalve shellfish, including clams and oysters, concentrate the toxin. This concentrated toxin can cause neurotoxic shellfish poisoning (NSP) in humans who eat bivalve shellfish. Both mild gastrointestinal and neurological symptoms occur in NSP.
b) A red tide is a bloom of dinoflagellates, some of which produce deadly toxins that accumulate in molluscs and can affect people who eat molluscs.

Question:
III. Why is it incorrect to refer to conjugation in ciliates as a form of reproduction?

Answer:
a) During conjugation, two ciliates exchange micronuclei, but no new individuals are produced.

Concept 28.3

Question:
I. How is Trypanosoma's ability to produce an array of cell-surface proteins advantageous to its survival?

Answers:
a) The surface of a trypanosome is coated with millions and millions of copies of a single protein. Before, a host's immune system could mount an attack, new generations of the parasite switch to another surface protein with a slightly different molecular structure. Frequent changes in the structure of the surface of the protein prevent the host from developing immunity, thus contributing to its (Trypanosoma) survival.
b) The proteins have slightly different structures, but only one protein at a time is expressed. Frequent changes in expression prevent the host from developing immunity.

Question:
II. Is Euglena an alga? Explain your answer.

Answer:
a) Euglena could be considered an alga because it is a photosynthetic autotroph; however, it could also be considered a fungus-like protist because it can absorb organic nutrients from its environment.

Concept 28.2

Question:
I. Why do some biologists describe the mitochondria of diplomonads and parabasalids as "highly reduced"?

Anwers:
a) Diplomonads and parabasalids are adapted to anaerobic environments. They lack plastids, and their mitochondria do not contain DNA, an electron transport chain, or citric-acid cycle enzymes.
b) Their mitochondria do not have DNA, an electron transport chain, or citric-acid cycle enzymes.

Question:
II. How is the structure of Trichomonas vaginalis well suited to its parasitic lifestyle inside its host's reproductive and urinary tracts?

Answer:
a) Diplomonads have multiple flagella and 2 nuclei. Parabasalids, include trichomonads, which move by means of flagella and an undulating part of the plasma membrane.
b) Its flagella and undulating membrane enable it to move along the mucus-coated lining of these tracts inside its host.