1. Home
2. Sample Assignment
3. Assignment on Trophic Cascades

Go to the following web link- http://media.hhmi.org/biointeractive/click/trophiccascades/?_ga=2.71133017.874546303.1495559246-1279517233.1480957413

Complete the first slides of the introduction. Next, follow the first example of sea otters, and answer the following questions.

1. What does the otter eat? __sea urchins_______________ (1 point)
2. How does otter consumption affect the growth of the Kelp forest? (1 point)

The otter eats the sea urchins and the sea urchins eat the kelp where the otters and the sea urchins are attracted and for this reason there is not much kelp.

3. Is this otter consumption a direct or indirect effect? ___indirect effect______________ (1 point)
4. Is this otter consumption a positive or negative effect? _positive effect________________ (1 point)
5. What happened to the kelp forest when the otter was hunted to near extinction? (1 point)

The otters were being overhunted which means less sea urchins being consumed. Though, the more sea urchins consuming the kelp which makes the kelp forest start disappearing.

6. Removal of the sea otter, a top predator also had an impact on two other species, the gull and the Eagle. How did the gull diet change with the removal of the otter from the ecosystem? (1 point)

The gull diet change from mainly fish to mainly invertebrates due to the absence of otters.

7. How did the eagle diet change with the removal of the otter from the ecosystem? (1 point)

The eagle diet change from mainly fish and mammals to mainly birds due to the absence of otters.

Choose 1 of the case studies provided and write a summary of what happens when the top predator is present, including all direct, indirect, positive and negative effects at all levels. Discuss what happens when the top predator is removed. (8 points)

Midwestern Lake

The bass is the top predator and it prey on minnows so the minnows decreased because of the presence of the bass. The presence of the minnows also decreased zooplankton populations. Then the zooplankton has a negative effect on phytoplankton because of the presence of zooplankton and they feed on phytoplankton so amount of phytoplankton decreased. However, the phytoplankton has a positive effect on carbon influx from the atmosphere into lakes because it fixes carbon through photosynthesis to dissolve carbon dioxide and the result of the atmosphere has an influx of carbon dioxide when the carbon dioxide in water reduced. Therefore, when the bass is removed, it became an indirect control of the amount of phytoplankton. The bass can alter the balance between the atmospheric carbon dioxide and the amount of carbon dioxide dissolved in lakes.