prokaryote Flashcards
what are the two mass extinctions that occurred on earth?
the permian extinction and the cretaceous period
95% of life went extinct from what extinction?
permian
75% of life went extinct from what event during what period?
asteroid impact in the cretaceous period
where was the first sign of life found? what is it?
stromatolites, which are rocks composed of cyanobacteria and sediment
what are prokaryotes?
small, unicellular molecules that have diverse nutritional and metabolic adaptations
are there more eukaryotes or prokaryotes in the biosphere?
prokaryotes
what are some characteristics of prokaryotes?
-no nucleus
-circular ring of DNA like a rubber band
-plasmids that are a smaller DNA ring containing extra genes
-lack membrane enclosed organelle
what is the flagellum?
a hair-like organelle composed of 42 proteins used by cells and microorganisms for movement
the flagella of eukaryotes, archaea and bacteria are what type of structure?
analogous (similar characteristics not derived from a common ancestor)
what is exaptation?
existing structures evolve to have new function through descent with modification
why are prokaryotic cells so small?
they are limited by diffusion since they do not have complex transport mechanisms
the ______ the cell, the _________ diffusion takes
bigger, longer
what does diffusion rely on?
a concentration gradient
what are the characteristics of the cell walls of prokaryotes?
-not made of cellulose
-gives the cell shape and protection
-prevents the cell from exploding when placed in a hypotonic solution
what is a hypotonic solution
outside environment is lower in solutes than the cell (explode)
bacterial cell walls contain _________? what are they made of?
peptidoglycans; made of amino acids and sugars/polypeptides
how would they determine if a peptidoglycan was pathogenic?
a gram-stain
what is the difference between gram-negative and gram-positive bacteria?
gram-negative bacteria has an extra cell wall to prevent antibiotics from penetrating the cell wall (stain washes), whereas gram-positive does not have an extra cell membrane (stain sticks)
do human cells have peptidoglycan
no!
how do prokaryotes reproduce?
asexually through binary fission
prokaryotes have a ____ mutation rate which _________ genetic diversity
high, increases
what kind of transmission do prokaryotes experience
vertical (parent to offspring)
how do prokaryotes exchange genetic information?
horizontal gene transfer
what is transformation?
‘naked’ DNA is picked up from dead prokaryotes in the environment
what is transduction?
DNA transferred by a virus (like a syringe)
what is conjunction?
transfer of DNA between cells temporarily joined by a mating bridge
what are the five steps of transduction?
- phage injects host cell with DNA
- phage DNA is replicated using cell machinery
- new phage particles assembled with some host DNA packed as well
- phages, some containing DNA from previous host, infects the new recipient cell
- recombination between donor and recipient DNA
what are the three steps of conjugation?
- one cell attaches its pilus to another
- donor cell transfers DNA to recipient cell
- transfer of genetic material is unidirectional from pilus producer to receiver
all organisms are divided into two categories based on how they receive energy. what are they, and how do they receive energy?
phototrophs receive energy from the sun and chemotrophs receive energy from chemical compounds
phototrophs and chemotrophs can be divided into two categories based on how they receive carbon. what are they, and how do they receive carbon?
autotrophs receive carbon from carbon dioxide and heterotrophs receive carbon from organic compounds
what are the two lineages of prokaryotes?
bacteria and archaea
what are the three kinds of domain archaea? what kind of habitat do they live in?
methanogens live in oxygen free habitats
halophiles live in salty habitats
thermophiles live in hot habitats
what are the three characteristics of domain bacteria?
diverse, numerous with 5 major clades, and live in almost all habitats
what kind of relationship do prokaryotes have?
symbiotic relationship
what is endosymbiont?
inside the host cell (intracellular) or extracellular in multicellular hosts
what are the three categories of ecological relationships?
mutualism (both benefit)
parasitism (symbiont steals from host; one is harmed)
commensalism (symbiont lives with host, but does not harm nor benefit host
what is proteobacteria?
a large diverse group of bacteria
what does mutualistic bacteria do?
takes inorganic nitrogen and converts it inti a useable form of ammonia through nitrogen fixation
what is a rhizobium in mutualistic bacteria?
lives on the root modules and gets carbohydrates from plants
what are characteristics of cyanobacteria? (3) what did they allow to be created?
-photoautotrophs
-evolved chloroplasts
-produced oxygen in atmosphere
-allowed for aerobic, eukaryotic cells to be created
what happened in the oxygen revolution?
photosynthetic cyanobacteria used the sun’s energy to split water into hydrogen and oxygen. mass amounts of prokaryotes died due to oxygen abundance, but some began to adapt and began respiring aerobically
