Topic 7

Question 1

What are were the first life forms (prokaryotes)?

Answer 1

first fossil evidence of life on Erath ~3.5 BYA

first unicellular organisms

stromatolites: rock-like structures composed of layers of bacterial mats and sediments

only forms of life for ~1.5 BY

Question 2

What makes prokaryotes so adaptable?

Answer 2

1. Small size (low maintenance, low energy, reproduce quickly)
2. Binary Fission (no partner, faster, no search, identical copy)
3. Short Generation Time (ideal organisms for laboratory study of evolution, they are adaptable)

Question 3

What are prokaryotes?

Answer 3

still dominate biosphere

live wherever eukaryotes can and many places they cannot

no nucleus (circular ring of DNA not enclosed by membrane)

lack membrane enclosed organelles

small, unicellular

reproduce asexually –> clones

short generation time –> high mutation rate –> increases genetic diversity

Question 4

How do bacteria exchange genetic information?

Answer 4

genetic recombination via horizontal gene transfer

transformation: “naked” DNA is picked up from dead bacteria in the environment
transduction: DNA transferred by virus (bacteriophage)
conjugation: DNA transferred between two bacteria

Question 5

What are autotrophs?

Answer 5

some make their own energy from inorganic sources

Question 6

What are chemoautotrophs?

Answer 6

use energy obtained by oxidizing inorganic chemicals and CO2

e.g. many prokaryotes

Question 7

What are photoautotrophs?

Answer 7

use light energy, and CO2, primary producers that support food web

e.g. cyanobacteria –> oxygen

Question 8

What are heterotrophs?

Answer 8

enzymes digest organic molecules in environment absorbed through membrane

Question 9

What are photoheterotrophs?

Answer 9

uses light energy, carbon source from organic molecules

e.g. a few prokaryotes

Question 10

What are chemoheterotrophs?

Answer 10

use organic molecules for both energy and carbon source

e.g. animals, fungi, many prokaryotes, a few plants

Question 11

What is mutualism?

Answer 11

both A and B benefit from the other’s presence

Question 12

What is competition?

Answer 12

both A and B suffer from each other’s presence

Question 13

What is predation?

Answer 13

A eats B

Question 14

What parsitism?

Answer 14

A steals nutrition from B

Question 15

What is commensalism?

Answer 15

A lives on or with B, but neither harms nor benefits B

Question 16

What is amensalism?

Answer 16

A harms B, B does nothing for A

Question 17

What are ecological relationships?

Answer 17

symbiotic relationships occur when members of two species live in close, often obligatory, contact with each other

if one species is much larger than the other, it is called the host

a great many prokaryotes are symbiotic (if inside of host organism is endosymbiotic)

Question 18

What are archaea?

Answer 18

lack peptidoglycan in cell wall

do not respond to antibiotics that inhibit eubacterial growth

most live in extreme habitats (extremophiles)

Question 19

What is the archaea, methanogens?

Answer 19

live in oxygen-free habitats

swamp substrates, cow and termite guts (mutualists)

produce methane gas as a waste product

Question 20

What is the archaea, halophiles?

Answer 20

halo = salt, where “salt” is any ionic crystalline compound, not just NaCl

Question 21

What is the archaea, thermophiles?

Answer 21

live in very hot habitats

therm = heat

some can live in water >100 degrees

many are chemoautotrophs

some used for PCR techniques

Question 22

What is the domain of bacteria?

Answer 22

diverse: 5000 species in one gram of soil
numerous: molecular genetics allows us to see the previously hidden relationships among bacteria –> 5 major clades

live in almost all habitats

Question 23

What is a cell wall?

Answer 23

contains peptidoglycan

not cellulose, as in cell walls of plants, or chitin, as in fungi

peptidoglycan provides: cell shape, protection, prevents cell from exploding when placed in hypotonic solution (lower in solutes than cell contents)

Question 24

What is a gram positive bacteria cell wall?

Answer 24

have peptidoglycan wall in contact with external medium which traps purple stain

Question 25

What is a gram negative bacteria cell wall?

Answer 25

have lipopolysaccharide layer outside of cell wall and thus do not absorb stain readily