Selena constantly thinks about climbing up the stairs to the roof of her building and jumping into the street below. selena's uncontrollable thoughts could be considered an example of

How does human environment effect the biosphere

Which event would lead to primary succession of a forest?

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