Which one of the following statements about lipids and biological membranes is incorrect?
a) increased temperature can change the membrane from gel phase to fluid phase.
b) membrane fluidity is affected by lipid composition but not by temperature.
c) phospholipid bilayers are fluid.
d) for lipid movement, flex is faster than lateral shift.
e) ions are not allowed to freely traverse a lipid bilayer.

The images show two species of tree frogs in a particular region. the gray tree frogs are adapted to the trees of the woodlands, while the green tree frogs can survive in woodlands or grasslands. the gray frog was abundant in the woodlands. because of climatic changes, most of the trees in the region died, and the woodlands changed to grasslands. in such a case, the . the gray tree frog is closely related to the green tree frog genetically, but they have different mating calls. this suggests that speciation occurred because of .