Which of the following best describes the lipid bilayer present in the plasma membrane? Phospholipids in double layer with heads of both layers meeting in middle
Phospholipids in single layer with heads facing outside the cell
Phospholipids in single layer with heads facing inside the cell
Phospholipids in double layer with tails facing each other and heads on both the inside and outside of the cell

The collared lizard is a species found in the desert southwest. male collared lizards show considerable color variation, ranging from brightly colored to a very dull pattern. your goal is to determine the function, if any, of male color patterns in collared lizards, using the scientific method. your tentative explanation is that male color plays a role in attracting females for mating purposes. you predict that females will preferentially choose brightly colored males over dull-colored ones. to test this prediction, you observed the interactions of female collared lizards with their male counterparts. you selected males that were the same age and size, and that differed only in their coloration pattern. you placed equal numbers of the two types of male lizards, bright and dull, in aquariums, along with one female lizard per aquarium. out of 350 aquariums observed, the female chose to mate with the brightly colored male 277 times, and the dull-colored male 70 times. in 3 instances, the females did not mate with either type. create a bar graph of your data, plotting the type of male (dull or brightly colored) on the x-axis. on the y-axis, plot the frequency with which each type of male was chosen by females. using this graph, answer the following question(s). is it reasonable to conclude (i.e., is it supported by the data) that female collared lizards prefer more brightly colored male lizards over dull-colored males?

African penguins, which inhabit the coasts of southern africa, were classified as an endangered species in 2010. two significant threats to their survival are ecosystem damage from oil spills and overfishing by humans. overfishing depletes the food supply of african penguins. the best method to reduce the threat of overfishing would be to . the risk of oil spills could be reduced by increasing the use of , which should oil consumption. if an oil spill does occur, could be used to remove the oil so the ecosystem may more quickly recover.

Which direction does the energy flow in this energy pyramid ?