Biology 102 Lab8: Ecological Interactions

Grade: __ /27 points

Participate in the lab 8 study group before Sunday March 11 for an additional 8 points.

Your Name: _______________________

Save your document as “first_name last_name Lab 8.doc” and submit in assignment folder.

Biology 102

Lab8: Ecological Interactions

Experiment 1: Ecological Interactions (27 points)

Table 1: Volume and Concentration Totals

Trophic Level	Cylinder	Volume of H2O	Volume of Oil	Total Volume	% Oil
1st	1000 ml			1000 ml
2nd	100 ml			100 ml
3rd	10 ml			10 ml

Questions

1. What is the % concentration of oil in the first, second, and third trophic levels in our food chain?

1. How did the concentration of oil change from one trophic level to the next?

1. How does the change in concentration represent biomagnification? (200-500 words)

1. How does this also illustrate the amount of energy transferred from one trophic level to the next? (200-500 words)

Lab 8

Ecology

Ecological Interactions

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Lab 8: Ecological Interactions

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Introduction

An ecosystem is composed of communities or associations of numerous populations of living animals

and plants at a particular time. Each organism within a community has a habitat and a niche. An organism’s

habitat is the location of where he physically resides or is adapted to reside and an organism’s

niche refers his function or “occupation”. Occupation for an organism is the way in which the organism

obtains and sustains all of the elements needed for survival.

Figure 1: There is great variety in the habitats across the globe. From the driest of deserts to the wettest

swamps, creatures have learned to thrive in many environments.

The dynamics of an ecosystem and the complexity of its habitats are a variable of energy flow, nutrient

Concepts to explore:

??Habitat

??Trophic levels

Lab 8: Ecological Interactions

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cycling, and water. Organisms can either be producers or consumers in terms of energy flow.Autotrophs

(organisms that make their own food) are the critical link between solar radiation and every

other planetary consumer. Heterotrophs (consumers) are those that get their energy from obtaining

carbons made by primary producers. Organisms that share the same basic foods are said to be in the

sametrophiclevel (feeding level). From the autotrophs, energy flows through the system along a circuit

called a food chain. Energy "flows" through an ecosystem in the form of carbon?carbon bonds

when respiration occurs the carbon?carbon bonds are broken for energy consumption.

In biotic feeding operations only about 10% of the food calories make it from one trophic level to the

next. Wow! Energy transfer is in no way 100% efficient. Inefficient energy transfer is what accounts for

the classically depicted food pyramid.

Figure 2:Inefficient vs. Efficient transfer pyramid. There is a big difference in efficiency between direct and indirect

consumption. This loss of calories as you move up in the food chain is also the reason you have more prey

than predators.

Biomagnification is the accumulation of a substance as it works its way up the food chain by transfer of

the substance from lower trophic level organisms to higher trophic organisms. Biomagnification results

in higher substance concentrations for organisms higher in the food chain. Organisms at lower trophic

levels eat small amounts but organisms at higher trophic levels eat many lower trophic level organisms

thus chemicals accumulate in higher amounts.

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Experiment 1: Ecological interactions

Procedure

1. Measure out 990mL of water into your big jug using the 100mL graduated cylinder. The jug represents

the primary producers.

2. Measure 10mL of oil and add it to the jug with 990mL.

3. Clean the 10mL graduated cylinder so there is no oil residue.

4. Let the oil coalesce at the top of the container, the oil is the accumulation agent. It is insoluble because

we want it to represent the organism inability to break it down.

5. Calculate the volume of water and the volume of oil in your 1000mL container. Calculate % concentration

of oil. Record in table below.

*HINT? V (of two or more substances)= (V(of single substance)/ total V of the mixture)*100

6. Pour 100mL of the mixture into the 100ml graduated cylinder and let the mixture settle.

7. Calculate the volume of water and the volume of oil in your 100mL container. Calculate % concentration

of oil. Record in table below.

8. Now, pour 10mL of the mixture into the 10mL graduated cylinder.

9. Calculate the volume of water and the volume of oil in the 10mL graduated cylinder. Calculate %

concentration of oil.

Materials

1 100mL graduated cylinder

1 10mL graduated cylinder

Large pitcher/jug/glass?anything big enough to hold 1000mL*

Oil

*You must provide

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Table 1 Volume and Concentration Totals

Questions

1. What is the % concentration of oil in the first, second, and third trophic levels in our food chain?

2. How did the concentration of oil change from one trophic level to the next?

3. How does the change in concentration represent biomagnification?

4. How does this also illustrate the amount of energy transferred from one trophic level to the next?

If you would like to read more about issues surrounding bioaccumulation simply search for case studies

that address POP (persistent organic pollutants) and Biomagnification in ecosystems.