BIO 100 Holechek ASU Exam 4 Review Questions and Answers

A fungus and an algae grow together to produce what we call a lichen. When investigators separate out the fungus from the alga and try to grow them in the same habitat but each alone, they all die. What hypothesis most logically explains this phenomenon? Ans: The fungus and the algae have a mutualistic relationship. They only survive when they are together because each organism benefits from their interaction, thus when they are separated they do not get the benefits as when they are together. Polar Bears live on the Arctic ice and are huge. They are fierce predators and hunt seals to make it through the cold winters at these high latitudes. What hypothesis most logically explains why Polar Bears are so large? Ans: Polar Bears are so large because they have a lot of fat and fur that keeps them warm while living in extremely cold environments. They have a higher volume to surface area ratio so they lose less heat. A five-degree increase in the ocean temperature off the coast of Washington caused sea stars to stop feeding on clams in the rocky intertidal. The clams quickly became the dominant species in the intertidal, and the diversity of invertebrate species in this habitat fell by half. Why? Ans: The Sea Stars were the Keystone Species. Once they were gone, the balance of life in the interval was thrown off allowing the clams, that were once kept in place by the sea stars, to become the dominant species. If the Earth's axis of rotation were perpendicular to the sun's rays and not tilted 23.5°, what would result Ans: NO SEASONS In the tropical rain forest of Borneo, six species of closely-related insectivorous birds live in the same section of forest. Investigators have been able to establish that insect food for all these species is the limiting resource that controls their population numbers and survival. These investigators have also shown that the size of the bill of each of these species determines the size and type of insect each species can eat. What hypothesis could explain how these six bird species could avoid or minimize competition for the insects? Ans: They will have different types/sizes of beaks so they can eat different foods Pioneer species in plant succession arrive at cleared areas to germinate. However, when they grow, the shade they produce makes it impossible for their own seeds to again germinate there because of their shade intolerance. Instead other more shade-tolerant species come in, grow, and force out the pioneer species. How do pioneer species ever get their seeds germinate if the parent plants always modify the habitat enough to make it inhospitable? Ans: Pioneer Species would be able to grow if they are moved to a new area by wind or other similar mechanisms