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