Why must organisms of the estuary be adapted to varying levels of salinity? a. fresh river water flows into the estuary
b. saline ocean water flows into the estuary
c. ocean tides increase and decrease the amount of ocean water
d. all of the above

According to theories of how life began, how did early organic molecules begin to separate from the outside world? a: specialized enzymes were required b: chains of amino acids created a barrier c: formation of microspheres or vesicles d: rna catalyzed the formation of membranes