Ch. 27 HW – Flashcards

The second and third answers are correct. *The short generation times and large population sizes in most prokaryotic species, coupled with their ability to exchange genes, helps to increase genetic variability beyond what we would expect in asexually reproducing organisms.

on plasmids *Genes for the resistance to antibiotics are usually located on plasmids.

Gram-positive bacteria -Have a thick peptidoglycan layer. - Alcohol rinse does not remove crystal violet. - appear purple after Gram staining. Image= arrow pointing purple strand.Gram- negative bacteria -have a thin peptidoglycan layer. -have an outer membrane as part of their cell wall structure. -alcohol rinse easily remove crystal violet -appear pink after Gram staining. both -have a plasma membrane *Correct Gram staining is a technique for classifying bacteria based on differences in the structure of their cell walls. Gram-negative bacteria and gram-positive bacteria both have a plasma membrane surrounded by a cell wall that contains peptidoglycan. However, the cell wall of gram-negative bacteria is composed of a thin layer of peptidoglycan and an outer membrane, whereas the cell wall of gram-positive bacteria is composed of a thick layer of peptidoglycan. Gram-negative bacteria appear red or pink because the alcohol rinse washes away the crystal violet dye. Gram-positive bacteria appear purple because the alcohol rinse does not wash away the crystal violet dye.

Nutritional Modes of Bacteria Left side: require energy only from inorganic sources (a) autotroph-- Use chemicals as energy source (c) chemoautotrophs Use light as energy source (d) photoautotrophs Right side: requiere energy from at least one organic nutrient (b) heterotrophs Use light as energy source (e) photoheterotrohs Use chemicals as energy source (f) chemoheterotrophs Center: also classified as (g) phototrophs also classified as (h) chemotrophs * Correct Some bacteria obtain energy from light (phototrophs), whereas other bacteria obtain energy from chemicals (chemotrophs). Autotrophs (literally "self-feeders") require only an inorganic substance, such as carbon dioxide, as their carbon source; heterotrophs (literally "other-feeders") require at least one organic nutrient as their carbon source.

1.They are shaped like rods. 2.They can convert atmospheric nitrogen to ammonia. 3. They use O2 for cellular respiration. 4.They have a relatively thin layer of peptidoglycan in their cell wall.*Correct Azotobacter is a genus of rod-shaped bacteria (bacilli). After Gram staining, bacteria in this genus appear pink due to the thin peptidoglycan layer in their cell wall. They require oxygen for cellular respiration and can convert atmospheric nitrogen to ammonia, which they incorporate into amino acids and other organic molecules

chemoautotrophs *Correct They use inorganic molecules (in redox reactions) for energy, and carbon dioxide for carbon.

cyanobacteria •Cyanobacteria built stromatolites.

cyanobacteria *Correct Cyanobacteria are aerobic photosynthesizers.

gram-positive bacteria *Correct S. pyogenes attracts the violet Gram stain.

chlamydias *Correct Chlamydia trachomatis causes nongonococcal urethritis.

proteobacteria *Correct Proteus vulgaris is classified with proteobacteria.

spirochetes *Correct The name of these organisms provides the answer to the question.

Euryarchaeota ... Crenarchaeota *Correct The branching pattern of the phylogenetic tree indicates that, of the pairs listed here, this is the one whose members are the most closely related.

Prokarya *Correct Prokarya was not one of the groups described in Woese's tree of life analysis.

Presence of a membrane-bound nucleus Correct Before the tree of life analysis, organisms were classified as prokaryotes if they lacked a membrane-bound nucleus or eukaryotes if they possessed a membrane-bound nucleus.

True

A paraphyletic group consists of a common ancestor and some of its descendants. *Correct This statement is true; the common characteristics of a paraphyletic group may have arisen from lateral gene transfer to some, but not all, lineages.

Ribosomal RNA *Correct Ribosomal RNA was the molecule used to produce Woese's phylogeny because it evolves slowly and is critical to the function of the ribosome, which serves the same function in all three domains in the tree of life.

Physical transfer of a gene from a species in one lineage to a species in another lineage. *Correct Lateral gene transfer is the physical transfer of a gene between distantly related lineages.

halophiles *Correct These archaea live in salty environments such as the Dead Sea.

symbiotic * Correct This is the definition of symbiosis.

The disease-suppressive properties of soils are due to the activities of soil microorganisms.

soil treatment

percentage of seedlings with fungal disease

20 pots total, 32 plants per treatment *Correct Total number of pots = 5 treatments × 4 pots each = 20 pots. 4 pots per treatment × 8 plants per pot = 32 plants per treatment. Using multiple pots per treatment and multiple plants per pot gave the researchers a larger sample size and reduced the chances that conditions in one particular pot or the condition or characteristics of one particular plant would drive the results of the experiment in a nonrepresentative way.

the amount of light the plants were exposed to

Fungal infection rate increased in seedlings grown in disease-suppressive soil that had been heated. * Correct Heating the disease-suppressive soil killed any microorganisms living in that soil. Because the infection rates for seedlings grown in heated soil were higher than the rates for seedlings grown in unheated disease-suppressive soil, the researchers concluded that microorganisms must account for the soil's disease-suppressive properties.

if seedlings had similar fungal infection rates when grown in heated and unheated disease-suppressive soil *Correct Unheated disease-suppressive soil contains living microorganisms, but heating the soil kills them. Therefore, if the researchers had found similar fungal infection rates when seedlings were grown in heated and unheated disease-suppressive soil, that would have indicated that microorganisms are not responsible for the soil's disease-suppressive properties.

Endotoxins are released only when bacteria die and their cell walls break down. *Correct Endotoxins are a component of the outer membrane of gram-negative bacteria.

the use of organisms to remove pollutants from the environment *Correct This is the general use of the term bioremediation.