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UMUC 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
What is the % concentration of oil in the
first, second, and third trophic levels in our food chain?
How did the concentration of oil change from
one trophic level to the next?
How does the change in concentration
represent biomagnification? (200-500 words)
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
82
Lab 8: Ecological Interactions
83
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
84
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.
Lab 8: Ecological Interactions
85
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
Lab 8: Ecological Interactions
86
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.
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