To see what happen when predator are remove from lower tropical level competition

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Anneth Game Tanda 2020125 Ecology lab 3

Title: Competition in tropical level Aim To see what happen when predator are remove from lower tropical level competition Introduction The impacts of predator in lower tropical level can be directly and indirectly. White acorn barnacle living on the shell of mussels were grow very fast compared to those on empty mussels shells. These two species do not have any effects on each other. Both are invertebrates and sessile filter feeder which means they can’t move out from the place they live. They catch there food from water.

Procedure/ Method section 1 1. Start virtual lab and select predator competition from the list of assignments. The lab will open on the Ecology lab bench.

2. Go to the clipboard and click on the Competition preset. You will see scenery and settings for a marine biome. In the Species tracking box, you will see listed the purple sea star, California mussel, and white acorn barnacle. Read the descriptions in the Species Selector to learn about these organisms of the intertidal zone.

3. Run the simulation for about 20 years to track the three populations under normal conditions. (Save your results to the Lab Book as Normal.)

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Results Questions 1. When the original three species interact under normal conditions, what are their growths patterns like?

Barnacle white Acorn -its graph started by decreasing, increasing and constant segment.

Mussel California- its graph begin with increasing, fluctuating slightly and basically constant Sea Star purple -its graph is increase fluctuating bit but then it is basically constant.

2. What happens when the sea stars are removed?

When the sea star removed there is a change occur in the other two species.

Barnacle White Acorn -When the sea star removed the barnacle white acorn population became decrease slightly and constant.

Mussel California-When sea star removed, the mussel population became increase.

3. Why does the removal of the sea stars cause the mussel population to change in this way?

Use the term limiting factor in your answer The removal of sea star cause the population of mussel to increase because they have the predator prey relationship between them so when sea star declined it causes the mussel to reproduce more and expanded. Sea star is the main limiting factor of mussel they open the mussel shell with their strong arm (predator /prey).

4. Why does the exploding mussel population seem to be correlated with a steep decline in the population of white acorn barnacles? If the mussels aren’t eating barnacles, how else could they be reducing the barnacle population?

The increasing of mussel population is often in correlated with declined of white acorn barnacle population because this two species live in same intertidal zone. The presences of mussels have some impact on barnacle density even though mussels not eat them.

Mussels and barnacle are not predator or prey to each other, so when sea star is declined, mussels increased while barnacle is decreased and constant, this is because nothing happened between them only the sea start can eat them since it’s are carnivorous ,its feed on both of mussels and barnacle.

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5.

How would you describe the mussel’s population growth rate after the removal of the sea stars? How would you describe the barnacle’s decline?

After removal of sea star, the mussel population is extremely high up to 683,120 from initial population of30,000 while barnacle population after 10th years is low 100,037 from initial population of 450,000 and the sea star is decline from initial 120 to 0 population but after 5th year it collapse.

6. Is there anything about your answer to Question 5 that seems odd?

The oddest thing is the collapse of sea star which completely gives chance for the mussels and barnacle to reproduce and expand more.

Part 2 Microscopy

7. Do any of the images give you any clues as to how the barnacle population could persist even though the mussel population is exploding at an exponential rate and depriving the barnacle of space on the rocks? Explain.

Barnacles is basically surviving, they attached themselves from the shells of the mussels.

Even though the mussel’s population is increasing the barnacle population is relatively constant.

8. If you were managing a marine conservation zone that saw a huge increase in California mussels after people collected a large number of sea stars, how would you try to restore balance to the intertidal community? Explain.

As a manager of marine conservation zone, firstly is to make sure that the predator /prey relationship are stable and maintain to avoid starvation in the community.

9. Would you call the purple sea star a keystone species? Why or why not?

Yes, because sea star is one of the important species in the marine environment and also known as keystone species, hence purple sea star are keystones species because they are only species that preys on animal that do not have any natural predators and once they removed from the environment, their prey will increases its number which will drive out species.

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Discussion From the above result, it shows that when the three species under normal condition there growth pattern are different .In the case of barnacle species, its graph is started from decrease, increase and constant .California Mussels shows that it started by increasing ,fluctuating slightly and basically constant. The sea star graph in normal begins with increasing, fluctuating bit and constant. When the sea star is removed, the population of the other two species is change. The barnacle population became decline slightly and constant all through, while mussel population increases. The huge increasing on mussels population is because ,sea star and mussels have the predator /prey relationship, so therefore when predator declined mussel increses.Unlike Barnacle and mussels they do not have any predator /prey among them but they live on each other, and survive by filter water for food. They sessile which means they do not go around they live in one place on the rock.

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Conclusion It is truly the competition in lower tropical level is very high. The predator is been removed and its effects to these two species is clearly shows. Population graph show s barnacle became decreases slightly while mussels are increases.

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