Topic 7 Flashcards
What are were the first life forms (prokaryotes)?
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
What makes prokaryotes so adaptable?
- Small size (low maintenance, low energy, reproduce quickly)
- Binary Fission (no partner, faster, no search, identical copy)
- Short Generation Time (ideal organisms for laboratory study of evolution, they are adaptable)
What are prokaryotes?
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
How do bacteria exchange genetic information?
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
What are autotrophs?
some make their own energy from inorganic sources
What are chemoautotrophs?
use energy obtained by oxidizing inorganic chemicals and CO2
e.g. many prokaryotes
What are photoautotrophs?
use light energy, and CO2, primary producers that support food web
e.g. cyanobacteria –> oxygen
What are heterotrophs?
enzymes digest organic molecules in environment absorbed through membrane
What are photoheterotrophs?
uses light energy, carbon source from organic molecules
e.g. a few prokaryotes
What are chemoheterotrophs?
use organic molecules for both energy and carbon source
e.g. animals, fungi, many prokaryotes, a few plants
What is mutualism?
both A and B benefit from the other’s presence
What is competition?
both A and B suffer from each other’s presence
What is predation?
A eats B
What parsitism?
A steals nutrition from B
What is commensalism?
A lives on or with B, but neither harms nor benefits B
What is amensalism?
A harms B, B does nothing for A
What are ecological relationships?
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)
What are archaea?
lack peptidoglycan in cell wall
do not respond to antibiotics that inhibit eubacterial growth
most live in extreme habitats (extremophiles)
What is the archaea, methanogens?
live in oxygen-free habitats
swamp substrates, cow and termite guts (mutualists)
produce methane gas as a waste product
What is the archaea, halophiles?
halo = salt, where “salt” is any ionic crystalline compound, not just NaCl
What is the archaea, thermophiles?
live in very hot habitats
therm = heat
some can live in water >100 degrees
many are chemoautotrophs
some used for PCR techniques
What is the domain of bacteria?
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
What is a cell wall?
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)
What is a gram positive bacteria cell wall?
have peptidoglycan wall in contact with external medium which traps purple stain
What is a gram negative bacteria cell wall?
have lipopolysaccharide layer outside of cell wall and thus do not absorb stain readily
