Chapter 7 Critical thinking questions

Compare the effects of isotonic, hypotonic, and hypertonic solutions on an amoeba and on a bacterial cell.

-Isotonic = concentration of solutes of solution is equal to inside the cell; ideal for both amoeba and bacterial cell -Hypotonic = concentration of solutes is higher inside cell than outside, water rushes in (cell bursts); in bacterial cell swelling occurs, in amoeba typically bursts but has contractile vacuole to pump water out -Hypertonic = concentration of solutes greater outside cell than inside, water rushes out (cell shrivels); in bacterial cell shrivels, in amoeba shrivels

Provide evidence in support of or refuting the following statement: Microbial life can exist in the complete absence of sunlight or organic nutrients

Microbial life is extremely diverse and can be found in the most uninhabitable of conditions. Even in the abcense of sunlight or organic nutrients , microbial life has been known to exist. The class of bacteria which can grow in the absence of sunlight and organic nutrients is called chemo-litho- autotrophs. These bacteria utilize chemical energy and electrons from inorganic compounds for their growth

How can you explain the fact that an unopened bottle of milk in the fridge will eventually spoil even if it has never been opened?

Psychrotrophs - even though an unopened container is treated with heat to make it last longer, it is not a stable substance and will eventually spoil.

A pathogen would be described as a a. parasite b. commensal c. symbiont d. saprobe

a

An organism that van synthesize all it's required organic components from CO2 using energy from the sum is a a. photoautotroph b. photoheterotroph c. chemoautotroph d. chemoheterotroph

a

Which of the following is true of passive transport? a. it requires a gradient b. it uses the cell wall c. it includes endocytosis d. it only moves water

a

A cell exposed to a hypertonic environment will _____________ by osmosis a. gain water b. lose water c. neither gain nor lose water d. burst

b

In a viable count, each _____________ represents a ________________ from the sample population a. CFU, colony b. colony, CFU c. hour, generation d. cell, generation

b

Which statements are true with respect to environmental factors' influence on microbes? Select all that apply a. The optimum temperature range for microbes reflects the highest temperature at which growth will occur b. Microbial cells often adapt to the temperature of their habitat, modifying their metabolic processes to allow for survival c. Certain microbes require a higher carbon dioxide concentration for growth than that found in our atmosphere d. All microbes live and/or grow within a narrow pH range of 6 to 8 e. The majority of microbes live in hypotonic and/or isotonic solutions

b, c, e

Most bacteria increase their numbers by a. sexual reproduction b. hyphen formation c. binary fission d. endocytosis

c

Which descriptors are likely to have applied to the earliest microbes on the planet a. chemoautotrophic b. thermophilic c. chemoheterotrophic d. two of the above

d (chemoauto and thermo)

A saprobe derives its energy from a. sunlight b. conversions of nutrients from other organisms c. utilizing the tissues/fluids of a living host d. metabolizing the organic matter of dead organisms

d- saprobes thrive off of dead organisms

Mineral ions used in microbial nutrition include a. sodium b. potassium c. calcium d. magnesium e. all of these

e