Which of these is incorrect? a. most extracellular signal molecules specifically bind to a single type of receptorb. for a given signaling molecule, every cell will have the receptor for that moleculec. different cell types may respond to the same signal molecule in different waysd. cell "relay" systems for signaling can cause more than a single cell responsee. cells may respond to multiple, different signals that converge and integrate with each other.

Which of the following observation darwin shape his concept of descent with modification? a) species diversity declines farther from the equator. b) fewer species live on islands than on the nearest continents. c) birds live on islands located farther from the mainland than the bird's maximum nonstop flight distance. d) south american temperate plants are more similar to the tropical plants of south america than to the temperate plants of europe. e) earthquakes reshape life by causing mass extinctions.