Three children were racing toy cars. they held them at the top of a ramp. when one said, “go,” they all let go. the cars rolled down the ramp and across the finish line. the children timed their cars. the red car finished in four seconds, the white car finished in two seconds, and the blue car finished in six seconds. question: which car rolled the fastest? explain how you know. which car rolled the slowest? explain how you know. if a fourth car was added to the race and came in second, how would you describe its speed?

Which two molecules do green plants use to make glucose? o a. nitrogen and water o b. hydrogen and oxygen o c. carbon dioxide and water o d. methane and iron oxide

Which of the organisms listed below performs nitrogen fixation? a. legumes b. plants c. bacteria d. fungi

Female luna moths (actias luna) attract males by emitting chemical signals that spread through the air. a male hundreds of meters away can detect these molecules and fly toward their source. the sensory organs responsible for this behavior are the comblike antennae visible in the photograph shown here. each filament of an antenna is equipped with thousands of receptor cells that detect the sex attractant. based on what you learned in this chapter, propose a hypothesis to account for the ability of the male moth to detect a specific molecule in the presence of many other molecules in the air. what predictions does your hypothesis make? design an experiment to test one of these predictions.