Ch.24

Question 1

Progressive Hypothesis

Answer 1

proposes that viruses evolved from mobile genetic elements, which acquired the ability to exit host cells and become infectious agents through the addition of structural proteins proposes that viruses evolved from more complex, possibly free-living organisms that gradually lost genetic information as they became obligate intracellular parasites proposes that viruses or virus-like entities existed before cellular life, potentially serving as precursors to the development of cells and playing a crucial role in the evolution of early life forms

Question 2

Regressive Hypothesis

Answer 2

proposes that viruses evolved from more complex, possibly free-living organisms that gradually lost genetic information as they became obligate intracellular parasites

Question 3

Virus-First Hypothesis

Answer 3

proposes that viruses or virus-like entities existed before cellular life, potentially serving as precursors to the development of cells and playing a crucial role in the evolution of early life forms

Question 4

Viruses are not cellular, but they:

Answer 4

• Infect all cellular forms of life.
• Replicate, mutate, evolve, and interact with other organisms.
• Evolve independently of other organisms.
• Are derived from cells of other living organisms
* same forms of genetic information storage & transmission

Question 5

There are far more metabolic pathways in the __________________ than the ____________________

Answer 5

archaea & bacteria / eukaryotes

Question 6

Eukaryote energy metabolism is done

Answer 6

in mitochondria and chloroplasts that are descended from bacteria.

Question 7

Anaerobes do not

Answer 7

use oxygen as an electron acceptor in respiration.

Question 8

obligate anaerobes

Answer 8

oxygen is poisonous to them

Question 9

facultative anaerobes

Answer 9

can shift metabolism between aerobic and anaerobic modes, such as fermentation

Question 10

________________ cannot survive without oxygen

Answer 10

obligate aerobes ( NOT obligate Anaerobes )

Question 11

what anaerobes are not damaged by oxygen but do not conduct cellular respiration

Answer 11

Aerotolerant anaerobes

Question 12

photoautotrophs

Answer 12

perform photosynthesis

Question 13

Bacteriochlorophyll absorbs longer wavelengths ( infrared light ) than chlorophyll which means…

Answer 13

they can live in water underneath dense layers of algae

Question 14

Photoheterotrophs

Answer 14

use light as an energy source, but get carbon from compounds made by other organisms—carbohydrates, fatty acids, alcohols.

Sunlight provides ATP through photophosphorylation

Question 15

Chemoautotrophs

Answer 15

get energy by oxidizing inorganic compounds and use the energy to fix CO2

Some oxidize ammonia or nitrite ions to form nitrate ions; others oxidize H2, H2S, S, and others

Many prokaryotic archaea are chemoautotrophs.

Question 16

Chemoheterotrophs

Answer 16

obtain both energy and carbon from complex organic compounds that were synthesized by other organisms

Most bacteria and prokaryotic archaea are chemoheterotrophs, as are all animals, all fungi, and many protists

Question 17

lithotrophs

Answer 17

species that get energy from breakdown of inorganic molecules

Question 18

Many prokaryotes are decomposers

Answer 18

Organisms that metabolize dead organic compounds

The products, such as CO2, are returned to the environment, key steps in the cycling of elements

Question 19

Denitrifiers

Answer 19

use NO3– as an electron acceptor in anaerobic conditions, and release Nitrogen gas (N2 )

(e.g., species of Bacillus and Pseudomonas)

Question 20

Nitrogen fixers

Answer 20

convert atmospheric Nitrogen gas (N2) into ammonia (NH3)

This vital process is carried out by many archaea and bacteria, including cyanobacteria, but no other organisms.

Question 21

Nitrifiers are…

Answer 21

chemoautotrophic bacteria

Nitrosomonas and Nitrosococcus oxidize ammonia (NH3) to nitrite (NO2–) .
Nitrobacter oxidizes nitrite (NO2–) to nitrate (NO3–)

Electrons from the oxidation are passed through an electron transport chain

Question 22

Deep-sea hydrothermal vent ecosystems depend on

Answer 22

chemoautotrophic prokaryotes

These bacteria get energy by oxidizing H2S and other compounds released from the volcanic vents

Question 23

Why Virus phylogeny is still poorly known ?

Answer 23

• Viral genomes are tiny, which restricts analyses that can be done.
• Rapid mutation rate and evolution cloud evolutionary relationships.
• There are no known viral fossils.
• They are very diverse and probably evolved repeatedly.
* evolved rapidly among each of the major groups of life

Question 24

what are viruses classified on ?

Answer 24

genome structure

Question 25

Hadobacteria

Answer 25

are thermophiles (heat lovers)

Question 26

extremophiles

Answer 26

thrive under extreme conditions that Would kill most Other organisms

Question 27

Deinococcus

Answer 27

are resistant to radiation, can consume nuclear waste and other toxic materials, and survive extreme cold as well as heat

Question 28

Thermus aquaticus

Answer 28

originally isolated from a hot spring, was the source of thermally stable DNA polymerase, critical for development of PCR

Question 29

T. aquaticus

Answer 29

is found wherever hot water occurs (including hot water heaters)

Question 30

hyperthermophilic bacteria

Answer 30

Extreme thermophiles that live in hot springs, near volcanic vents, deep oil deposits, and other hot environments

Question 31

Firmicutes

Answer 31

mostly low GC gram-positive bacteria with genomes that have a low ratio of G-C to A-T nucleotide base pairs

Question 32

endospores

Answer 32

heat-resistant resting structures with tough cell walls and spore coats that can survive harsh conditions because they are dormant Closteridium and Bacillus form endospores. Some can be reactivated after 1,000 years of dormancy Bacillus anthracis (anthrax) endospores activate when they sense the presence of macrophages in mammal blood It has been used as a bioterrorism agent

Question 33

Staphylococcus ( staphylococci )

Answer 33

are abundant on skin and cause boils and other skin problems

Question 34

S. aureus

Answer 34

causes skin diseases and respiratory, wound, and intestinal infections

Question 35

S. aureus

Answer 35

causes skin diseases and respiratory, wound, and intestinal infections

Question 36

mycoplasmas

Answer 36

have no cell wall, are extremely small, and have very small genomes They have less than half as much DNA as other prokaryotes, which may represent the minimum amount of DNA needed for a living cell

Question 37

Actinobacteria (high-GC Gram-positives)

Answer 37

High ratios of G-C/A-T base pairs Form elaborately branching filaments Some reproduce by forming chains of spores at the filament tips Actinobacteria includes Mycobacterium tuberculosis Most antibiotics are derived from the actinobacteria Streptomyces produces streptomycin and hundreds of other antibiotics.

Question 38

Photosynthetic

Answer 38

uses chlorophyll alpha and release O2 gas many species fix nitrogen