What respiratory structures evolved independently in several invertebrate groups as well as in vertebrates?
a. Lungs
b. Gills
c. Air lobes
d. Tracheal systems
e. Spiracles

Click an item in the list or group of pictures at the bottom of the problem and, holding the button down, drag it into the correct position in the answer box. release your mouse button when the item is place. if you change your mind, drag the item to the trashcan. click the trashcan to clear all your answers. label the following topographic map. click on a label below the map to select it, and then click on the appropriate box on the map to place the label. (increments for contour lines is 50 ft).

Did you know that a single bee would have to go to over 2 million flowers to make a single pound of honey?

What is the most appropriate method of gaining weight (muscle mass)