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Harper College Bio114: Fundamentals of Organismal Biology Lab 3—Ecology Name: ______________________________________________

Date: ______________

Objectives:  Identify and describe the following trophic levels in a food chain or food web: primary producer, primary consumer, secondary consumer, tertiary consumer, quaternary consumer, top predators, decomposer  Be able to draw and interpret a food chain and food web  Explain what a trophic cascade is  Distinguish between direct and indirect interactions & between positive and negative interactions  Describe and use the mark-recapture method to estimate population size Introduction: Ecology is the study of organisms and their relationship to the environment. Ecology is quite a broad field, as there are many levels at which we can study these organisms and their relation to the environment. In this lab, we will examine two different levels of ecology: population ecology and community ecology. Population ecology studies factors and conditions that affect the geographic distribution and the size of a population of fungi, plants, or animals. Community ecology examines the diversity of organisms that live in a particular environment as well as the relationships between these organisms (predation, competition, mutualism, parasitism, etc.).

Exercise 1: Trophic interactions The trophic structure of a community refers to the feeding relationships that exist between different organisms in a community. Food energy transfers upwards from plants and other producers to herbivores to carnivores and eventually to decomposers. A food chain is a linear depiction showing these feeding relationships among set of organisms. Food chains are organized into different trophic levels that can be labeled as primary producers (plants and other autotrophs), primary consumers (herbivores or organisms that eat plants), secondary consumers (carnivores), tertiary consumers (carnivores), and quaternary consumers (carnivores). Decomposers are typically not presented in food chains. Arrows in a food chain point in the direction of energy flow.

Figure 1: A terrestrial food chain (Source: http://igbiologyy.blogspot.com/2014/03/107-foodchains-food-web.html) 1

A food web is used to show the complexity of feeding relationships within an entire community. There are many food chains within a food web While a food chain shows a linear path of feeding, a food web shows that these paths can interconnect by having an organism feed off several different organisms from the trophic level below them. Sometimes in a web, we can see that one organism may be placed in two different trophic levels, depending on which chain is followed.

Figure 2: A terrestrial food web (Source: https://sites.google.com/a/hdsb.ca/ms-parker-s-classwebsite/science/thefoodweb ) Note in the food web above, the buzzard serves as a secondary consumer, a tertiary consumer or a quaternary consumer depending on which chain is followed. It is a secondary consumer if you follow the chain that includes the plantain and rabbit. It is a tertiary consumer if you follow the chain that includes the berries, titmouse, and snake. It is a quaternary consumer if you follow the chain that includes the berries, butterfly, frog and snake. A. Trophic interactions in your neighborhood (OUTSIDE ACTIVITY) For this exercise, your goal is to identify 15 or more different organisms that are around where you live. You can choose a location by your house or you can go to a park or natural area nearby you to sample organisms. If you do choose to go to a public park or natural area, make sure to wear a mask and practice social distancing. Note, the best time of day to find a lot of animals is typically just after sunrise or just before sunset. 1. Explain the differences between a food chain and a food web. A food web consists of many food chains. A food chain only follows just one path as animals find food. eg: A hawk eats a snake, which has eaten a frog, which has eaten a grasshopper, which has eaten grass. A food web shows the many different paths plants and animals are connected.

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2. What do the arrows on a food chain represent? . Arrows are used to show the feeding relationship between the animals. The arrow points from the organism being eaten to the organism that eats it. For example, an arrow from a plant to a grasshopper shows that the grasshopper eats the leaves

Procedure: 

Choose a location outside and sit down with a notepad or piece of paper to collect data on (and/or maybe a tablet, laptop, phone or nature book to look up the names of what you are seeing).

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Record the names of at least 15 different species that are around you. These can include organisms you see or hear. You may see various species of plants, insects, birds, amphibians, reptiles, or mammals. Make sure that you include at least 3, but no more than 5 producers because every food chain or food web requires a producer as the base.

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Try to be as specific as possible in your identifications (ex. “bird” is too general of an identification and will not work for this exercise; “robin” would be better because it is more specific). To help you identify organisms, there are a few online resources you can use, including: o The iNaturalist app (https://www.inaturalist.org/) is free and will assist in identifying plants, animals and fungi. Make an account and your data will be saved. The great part about iNaturalist is that if you are not certain about an identification, other naturalists will assist in identification, as this app uses crowd sourcing. Not only is this a great way to learn about your local ecosystem, but in the process, you are conducting citizen science and contributing to tracking species in your area. o What birds are in my backyard: (https://www.whatbirdsareinmybackyard.com/2019/08/what-are-most-commonbackyard-birds-in-illinois.html) o Insect Identification for the casual observer: (https://www.insectidentification.org/insects-by-state.asp?thisState=Illinois)

3. After you have your list of 15 organisms, fill them into Table 1 below. 4. Next, determine what each organism in your list eats or how they obtain their food and note their trophic level (i.e. producer, primary consumer, secondary consumer, or tertiary consumer). You may need to look up information online to determine some of this information. Note: some organisms may fit into more than one trophic level

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Table 1: Feeding information and trophic levels of organisms sampled in exercise 1 Species name

What food does it eat?

Trophic level? (Can fit more than one level)

Dragonfly Frog Snake Mouse Squirrel Rabbit

5. Below, make a food chain using 3-4 of the organisms that you found. Always start with a producer and make sure that your arrows are going in the correct direction from the food to the eater showing how the energy moves through the food chain. Refer to figure 1 for help, if needed. a. To make arrows on your computer use two dashes “-“ and a chevron “>”.

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6. On a separate piece of paper, make a food web using at least 10 of the organisms that you found. Again, make sure that the arrows are pointing in the correct direction and remember to include producers in your web. This ‘web’ should look complex because the feeding patterns of an ecosystem are intertwined. Refer to Figure 2 for help if needed. a. Take a picture of this food web & make sure to submit this picture with your lab submission for this week.

7. Why was it essential to include producers in the food web that you made? Be specific.

B. Trophic Cascades Trophic interactions consist of both direct interactions and indirect interactions among the organisms in the community. Direct relationships are depicted in a food chain and food web. However, it is possible that two species that do not directly interact with one another may nevertheless have effects on one another. This activity will help you to explore these indirect interactions. 

Go to the “Exploring Trophic Cascades” activity at: https://media.hhmi.org/biointeractive/click/trophiccascades/

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Click “Introduction” and engage with the interactive activity while answering the following questions. 8. What are ecosystems comprised of?

Ecos y s t emsar ecompr i sedofacommuni t yofor gani s msandt hei rphy si c al envi r onment . 9. What do ecologists study?

Ecol ogi st sst udyt hei nt er act i onsamongt heseor gani smsandt hef act or st hat affector gani sms ’ di s t r i but i on 10. List the following trophic levels that might be represented by a pyramid from bottom to top: primary consumers, secondary consumers, producers.

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Click the grey arrow to the right of the screen to proceed. Watch the 2-minute video and answer the following questions. 11. In the North-East Pacific Ocean, what happened to the sea urchin population when sea otters were hunted to near-extinction? 5

12. What is a trophic cascade?

13. If the elimination of a top predator has an effect on producers, is this an example of a direct or indirect effect?

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Click on “Kelp Example” at the top of the page and use the grey arrows to the right of the screen to proceed. Answer the following questions. 14. Fill in the blank: When tracking changes in an ecosystem, a solid line represents _ ____________ 15. When sea otters were hunted to near-extinction along the Pacific coast of North America, what happened to kelp forests?

16. What do the plus (+) and minus (-) signs mean when tracking changes in an ecosystem?

17. What does a dashed arrow represent when tracking changes in an ecosystem?

18. What happened to the diet of Glaucous-winged Gulls when the otters disappeared?

19. What happened to the diet of bald eagles when the otters disappeared?

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Click on “Case Studies” at the top of the page and click and learn about the Arctic Tundra, Midwestern Lake, African Savanna, and Venezuelan Jungle. Use the grey arrows to the right of the screen to proceed. Answer the following questions. 20. For the Arctic Tundra: Fill out the table below to note whether each of the organisms or nutrients listed at the top has a positive (+) or negative (-) effect on the organisms or nutrients on the left. You do not need to fill anything out in boxes marked NA.

On seabirds On soil nutrients On grass

Fox -

Effect of Seabirds NA +

Soil Nutrients NA NA

-

+

+ 6

21. In the Arctic Tundra, why do fox have a negative effect on the grass?

22. In the Midwestern Lake, do bass fish have a positive or negative effect on minnows?

23. In the Midwestern Lake, why do phytoplankton have a positive effect on carbon influx into lakes? 24. Thought question: If you removed bass from a midwestern lake, how would this affect the amount of carbon dioxide that can be absorbed from the atmosphere by the lake ecosystem?

25. In the African Savannah, why does rinderpest have a negative effect on wildebeest?

26. In the African Savannah, why does vegetation have a positive effect on wildfire?

27. In the African Savannah, how does rinderpest affect the frequency and intensity of fires?

28. Highlight the answer that best fills in the blank: In the Venezuelan jungle, large predators have a ________________ effect on vegetation. a. positive direct b. positive indirect c. negative direct d. negative indirect

Exercise 2: Estimating population size Remember, a population is made of all individuals that are members of the same species that live in a specific area. In order for ecologists to understand the conditions and factors that affect populations, they must be able to determine the number of individuals in those population (or 7

population size). Unfortunately, going out and counting every single individual in population is very time consuming and can be very difficult when organisms can move and hide from investigators (for example, think about how difficult it is to conduct the US census to determine human population size in the US). As an alternative, population ecologists can use estimation techniques to estimate the population size for various organisms. One of these estimation techniques is called the mark-recapture method, which you will investigate more in this exercise. 

Go to the “Estimating Population Size” Activity at: http://www.classzone.com/books/hs/ca/sc/bio_07/virtual_labs/virtualLabs.html

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Click “Estimating Population Size.” You will be asking the question “How does a scientist count a mobile population?” Read the problem, then engage with the interactive activity while answering the following questions. You will be recording some data both in the virtual lab notebook as well as this worksheet. 29. Why do scientists and farmers want to count migratory grasshoppers?

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Click and read “background.” 30. Describe how the mark and recapture method works.

31. What is population density?

32. What are some conditions that promote the population growth of grasshoppers?

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Explore the lab. 33. What will you use to mark the grasshoppers?

34. How do scientists capture grasshoppers?

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Click “procedure” and follow the instructions of the lab while answering the following questions. You will be recording your answers and data both in the virtual lab notebook and below.

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35. List some difficulties you might encounter if you tried to determine the population of grasshoppers by simply examining the meadow.

36. What are some steps you can take to make a more accurate estimate of the population size?

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Complete to step 2-3. 37. Where did you mark the grasshopper?

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Proceed to step 4. 40. Record the number of grasshoppers counted in the first capture both in the virtual lab notebook and in Table 2 below. Table 2: Number of Grasshoppers Collected During Each Capture First Capture Date: July 19 Number of grasshoppers in first capture and marked (M) Total number of grasshoppers in second capture, including both marked and unmarked (n) Number of marked grasshoppers in second capture (R)

Second Capture Date: July 26 NA

NA

41. True or false: After counting the grasshoppers, the grasshoppers are released into a separate meadow so that they are not counted a second time.

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Complete steps 6-7. 42. Record the total number of grasshoppers in the second capturer and the number of marked and recaptured grasshoppers in the virtual lab notebook and in Table 2 above. 9

43. Why do you think so few grasshoppers were re-counted in the second capture?

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Advance to step 8.

44. The Lincoln Index is an equation used to estimate animal populations. Using the equation (P=Mn/R), how many grasshoppers did you calculate in the one acre surveyed? P=

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Answer the following questions to analyze and conclude the lab. You no longer need to interact with the online lab simulation. 45. What are some factors that might cause changes in the population of grasshoppers?

46. What are some factors that might affect the accuracy of your estimate?

47. What are the advantages and disadvantages of the capture-mark-recapture method?

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