Topic 7- first life: prokaryotes Flashcards
prokaryotes have no ______________ unlike eukaryotes
membrane bound nucleus/ other organelles
Which domains are prokaryotes?
domain bacteria and domain archaea
The first unicellular organisms were ____( first life)
prokaryotes
What 3 things makes prokaryotes so adaptable/ successful ?
- small size (few needs)
- reproduce via binary fission (fast, don’t need to find a mate)
- short generation time (evolution can occur quickly, but may be inhibited by asexual reproduction)
prokaryotic cells have ____ DNA, and a nucleus that __(is/ isn’t) enclosed by a membrane
circular
is not
What does taxes mean? (singular = taxis)
give an example
movement away from or towards stimulus
eg. positive phototaxis is movement toward light
Plasmids are present in prokaryotes. Define plasmid
small rings of dna containing a few “extra” genes
prokaryotes have/ lack membrane enclosed organelles
some have ____ __ ____ ______
lack
infolding of cell membrane
despite reproducing asexually, prokaryotes have high genetic diversity. how?
- short generation time and high mutation rate compared to eukaryotes = increased diversity
how do bacteria exchange genetic info? (modify their genome)
genetic recombination via horizontal gene transfer
name and explain the 3 types of horizontal gene transfer
- transformation: ‘naked’ dna is picked up from dead bacteria in the environment (b/c when a cell dies, dna is released)
- transduction: dna transferred by virus (bacteriophage)
- conjugation: dna transferred between 2 bacteria
define autotrophs and their 2 varieties
autotroph: make their own energy from inorganic sources
- chemoautotroph: use energy obtained by oxidizing inorganic chemicals, and co2 ( doesn’t need sunlight)- many prokaryotes
- photoautotrophs: use light energy and co2 (primary producers that support food web) eg. cyanobacteria–> O2!
define heterotrophs and their 2 varieties
- don’t make their own energy! most bacteria must eat… enzymes digest organic molecules in environment absorbed through membrane
- photoheterotrophs: uses light energy; C source from organic molecules to help them process energy
- chemoautotrophs: use organic molecules for both energy and C source (eg animals, fungi, many prokaryotes, a few plants)
many prokaryotes are symbiotic. If inside the host organism it’s ____
endosymbiotic
define commensalism
A lives on/ with B, but neither harms nor benefits B
define amensalism
A harms B, but A does not gain anything from it
Studies of ___ structure revealed that there are actually __ very different lineages of prokaryotes
RNA
2
bacteria have _____ in their cell walls
peptidoglycan
archaea have more/ less variety in rna than bacteria
more
why don’t archaea respond to antibiotics?
antibiotics act on the peptidoglycan in the cell wall & cause the cell wall to break (inhibits eubacterial growth)
therefore antibiotics only work on bacteria, not archaea
most archaea live in ____ environments
extreme
archaea methanogens live in _______
they produce ___ as a waste product
oxygen-free habitats such as swamp substrates and cow guts
methane
archaea halophiles live in ____
very salty habitats
archaea thermophiles live in ____
many are
very hot environments
chemoautotrophs