Chapter 16

Question 1

Early Earth

Answer 1

Forma5on of earth—4.5 bya

•  Microbial life—found in fossils 3.5 billion years old

Question 2

Stromatolites

Answer 2

Microbial mats
of layers of filamentous
microbes and minerals

Question 3

Subsurface origin of life hypothesis

Answer 3

Life originated at hydrothermal springs on
ocean floor •  Stable condi5ons
•  Steady and abundant supply of energy (e.g., H2
and H2S)

Question 4

RNA world and lipid vesicles

Answer 4

RNA world theory
– RNA can bind small molecules (e.g., ATP, other nucleo5des)
– RNA has cataly5c ac5vity; may have catalyzed its own synthesis
•  Lipid vesicles
Last universal common ancestor (LUCA)

Question 5

Possible scheme for energy genera5on in primi5ve cells

Answer 5

Abundant H2 and FeS

Question 6

Endosymbio5c hypothesis

Answer 6

Mitochondria and chloroplasts of eukaryotes arose from engulfment of bacteria into other cells
•  Prokaryo5c ribosomes (70S) •  Bacterial 16S ribosomal RNA •  Ribosomes inhibited by same an5bio5cs •  Covalently closed, circular DNA

Question 7

Endosymbio5c hypothesis #2—hydrogen hypothesis

Answer 7

Accounts for •  Bacterial lipids •  Archaeal
transcrip5on and transla5on
•  Bacterial energy genera5on
•  Favored hypothesis

Question 8

Evolu5on

Answer 8

Descent with modifica5on

Question 9

Fitness

Answer 9

survival capacity or reproduc5ve ability
– Harmful muta5ons—lower fitness – Beneficial muta5ons—increase fitness – Neutral muta5ons—do not affect fitness,
accumulate in genome

Question 10

Gene duplica5on •  Gene loss

Answer 10

obligate symbionts and parasites •  Horizontal gene transfer

Question 11

  Environments select organisms that

Answer 11

survive and successfully compete and reproduce

Question 12

Evolution occurs rapidly in microbes because of

Answer 12

Large popula5ons – Fast reproduc5on

Question 13

Phylogeny

Answer 13

Inferred evolu5onary history •  Assump5ons:

– All organisms descended from LUCA – Sequence of DNA is record of organism’s ancestry

Question 14

Genes used in phylogene5c analysis

Answer 14

Small subunit rRNA (SSU rRNA)
– 16S rRNA in prokaryotes – 18S in eukaryotes
– Universally distributed – Func5onally constant – Sufficiently conserved
– Adequate length

Question 15

Genes used in phylogene5c analysis

Answer 15

EF-‐‐Tu•  Hsp60 •  tRNA synthetases

•  gyrB •  recA

Question 16

Molecular clocks

Answer 16

assumes that changes accumulate at a constant rate, are neutral, are random—combine data with geologic evidence

Question 17

Evolu5onary analysis

Answer 17

Obtain sequences through PCR

– Oligonucleo5de primers

Question 18

Microbial systema5cs

Answer 18

Iden5fica5on of new bacterial species:
– Genotypic—gene sequences – Phylogene5c—evolu5onary framework
– Phenotypic—morphological, metabolic, physiological, and chemical characteris5cs

Question 19

Biological species concept

Answer 19

Interbreeding popula5on of organisms that is reproduc5vely isolated from other interbreeding popula5ons
– Not valid for haploid organisms

Question 20

Phylogene5c species concept

Answer 20

Group of strains that cluster closely with each other and are dis5nct from other strains

Question 21

Ecotype

Answer 21

cells in a popula5on that

share a par5cular resource

Question 22

Prokaryo5c species

Answer 22

Defined as strains with
– 70% or greater DNA-‐‐DNA hybridiza5on – 97% or greater iden5ty in 16S rRNA sequence
•  Over 7,000 known species of Bacteria and Archaea
•  Possibly up to 100,000 species

Question 23

Binomial system of nomenclature

Answer 23

  Carl Linnaeus •  Genus names and species epithets •  La5n or La5nized Greek deriva5ons •  Italicized •  Staphylococcus aureus means “a bunch of
grapes”, “berry”, and “golden”
•  IJSEM approval required