Hiv acts by attaching to receptors on the surfaces of t-cells that aid other lymphocytes in fighting infection. once hiv is inside a cell, its rna is reverse-transcribed and its product dna is integrated into the host cell. it then directs the production of new virus particles. as time goes on the number of t-cells a) increases. b) decreases. c) stays the same. d) is unpredictable.

Heat from earths interior and pressure from overlying rock transform the remains of marine sediments into

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.

Interactions between organisms and their environment impact the organism’s overall population. the jaguar panthera onca is the largest cat in north america. it is found in areas across the southwest, including arizona, new mexico, and texas. it is a carnivore that has powerful jaws and sharp teeth and preys on fish, turtles, tapirs, and many smaller mammals. which shows the relationship between the jaguar and turtles?