Which of the following is a population?

all the animals in a prairie ecosystem.
all the mesquite trees in a desert ecosystem.
all the living organisms in a river ecosystem.
the tree where a squirrel lives in a forest ecosystem.

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