Concept 29.2

Question:
I. Identify three derived traits that distinguish plants from charophyceans and facilitate life on land. Explain.

Answer:
a) They have walled spores that are toughened by sporopollenin. They have multicellular, dependent embryos. And they have cuticle. All of which prevents land plants from drying out.

Question:
II. Identify each structure as either haploid or diploid:

sporophyte - diploid (2n)
spore - haploid (n)
gametophyte - haploid (n)
zygote - diploid (2n)
sperm - haploid (n)
egg - haploid (n)

Concept 29.1

Question:
I. Describe the evidence linking plants to a charophycean ancestry.

Answer:
a) They share rosette cellulose-synthesizing complexes. They both have peroxisomes which minimize loss to photorespiration. They have similar structure of flagellated sperm.

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.