What does the nucleus of the cell contain? What role does it play in regulation of the cell?

For a comparative or experimental investigation, scientists often make a testable about a scientific question, and then they test it in the investigation. a.control b.hypothesis c.procedure d.system

Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosureb. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosureb.

Darwin’s hypothesis about how life changes over time is now called?