ASU BIO 100 Exam 3 Practice Questions

1. A fungus and an alga 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?

2. 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 hypotheses most logically explains why Polar

Bears are so large?

As it gets big, smaller the volume- surface aea ratio is. The easier it is to stay warm. Polar bear is dense.

If they could retain heat, then they would die.

3. 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?

The starfish is the keystone sepcies. Once they were gone there was no

more room for other species to come, making the clams the dominant

species. Because the starfish are the ones that clear out and make room for

others but no room for new babies.

because the sea stars could not keep up with the temperature change. In the

intertidal the invertebrate has to be able to survive in a wet and dry climate

and if one gets worse than the other the star fish don't eat the clams and then

there is no space for hte new clams to live on the rocks.

4. If the Earth's axis of rotation were perpendicular to the sun's rays and not tilted 23.5°, what would

change here on Earth?

5. 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?

Although their beaks are similar in size, some other parts of their bodies, such as their legs, are different

sizes and these differences permit each species to feed at a different height in the forest to partition

resources in space. Character divergence.

6. Unrelated predaceous plant species that eat insects occur in every

biome except the ocean and permanently ice-covered areas of high

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