Which rock layer is the oldest and why?             redwall limestone because limestone is older than shale   a. tapeats sandstone because it is the bottom layer   b. hermit shale because shale is the oldest type of rock   c. kaibab limestone because it is the topmost layer   d. question resources

Texas bluebonnet plants seen in this photo are an example of which ecological unit?

Match the types of competition to their descriptions.

Next pretest: evolution select the correct answer in a laboratory population of flies, the female flies are gray and the males are yellowish gray. biologists observed that all the male flies had an equal chance for reproduction, but the male flies with the brightest colors were more likely to successfully reproduce. what phenomenon could explain such a change? a sexual selection b. disruptive selection c. stabilizing selection d. directional selection