Name ___________________________ sec _____
Modeling Ecosystems
How does Energy flow in an Ecosystem?
Log in on a computer and go to the site listed below:
http://www.mhhe.com/biosci/genbio/virtual_labs/BL_02/BL_02.html
*** if the site does not work- Google: Model Ecosystems virtual lab. It is the first one that appears.
Read the information presented and fill in the blanks below. After you have completed the reading, follow the
procedure steps.
An ______________________ consists of a community of ______________ organisms
________________ with each other and the ________________. The source of ____________ that fuels
most ___________________ is the _______. ______________ use the Sun’s ___________ to produce food
in a process called _______________________. Organisms that use energy from the Sun or energy stored in
_____________ ____________ to produce their own _______________ are called _______________. They
are also called __________________ because most other organisms depend on autotrophs for
______________ and ______________. Heterotrophic organisms that _________make their own
_________ may obtain ________________ by eating other ______________. A ______________ that feeds
only on plants is called an _________________. Herbivores are also called ___________ order heterotrophs.
Carnivores that _________ on ____________ are called second order __________________. Carnivores that
feed on other carnivores are called third order _____________. A food ___________ is a simple model of how
__________ and _____________ move through an ________________.
Each level of _____________ and ________________ in a food chain is a _______________ level.
The _______________ form the _______trophic level, first order ____________________
(______________________) constitute the second trophic level, second order heterotrophs the third trophic
level, and third order _________________ are layered on top.
In the pyramid of ____________, the energy moves in only _______ _________________ and
decreases at each succeeding trophic level. The total ____________ transfer from one _________ level to the
next is, in general, only about ____ percent or _____. This is called the energy ________________ efficiency.
Organisms fail to capture and eat all the food _______________ at the trophic level _____________ them.
The food ______________- ingest is used to ________________ and build __________ _______________.
Some food is given off as __________. The energy ________ at each trophic level ___________ the
environment as __________.
A pyramid of _______________ expresses the weight of _____________ material at each trophic level.
Biomass is calculated by finding the average weight of each _________ at that __________ level and
multiplying the weight by the estimated number of ________________ in each ____________________. In
_____________________ ecosystems, biomass __________________ as the trophic level
____________________. In contrast to terrestrial _________________, freshwater and
_________________________ ecosystems have _______ primary producer ______________ than biomass
present at _____________ trophic levels, leading to an ______________ biomass ___________. This is
because algae and phytoplankton have a _________ lifespan, are more edible than terrestrial plants, and are
_____________ rapidly _____________. Their biomass does not ________________.
In this exploration, you will study and analyze _________ simplified model _______________: a
deciduous _____________, a hot _____________, a _________________ lake, __________________, and
an Antarctic ______________ shore. Many more ____________ and _______________ specie should be
involved in a ______________-____________ ecosystem. The _______________ notes for each model
__________________ present a profile of the __________________ and ______________ inventory for each
________________.
Read the procedure and read the field guide before beginning the activity.
Name ___________________________ sec _____
Then click on an ecosystem, and begin with the procedure. You will need to place all organisms in the levels before you
can get the pyramid data for numbers and energy. Complete these steps for all five ecosystems, fill in the information for
each ecosystem in the data table. Once the data table is complete, answer the journal questions.
Data Table: fill in the data table below by calculating the efficiency for each level for each ecosystem. The energy
conversion efficiency is calculated by dividing the energy at the higher trophic level by the energy at the lower trophic
level. Enter this data in the energy conversion efficiency column.
Ecosystem
Producers
Energy
number
Deciduous
Forest
Hot Desert
First Order
Heterotrophs
Energy
Energy Energy
conversion number conversion
efficiency
efficiency
(a decimal)
100
Second Order
Heterotrophs
Energy Energy
number conversion
efficiency
(a decimal)
Third Order
Heterotrophs
Energy Energy
number conversion
efficiency
(a decimal)
100
Grassland
100
Antarctic
Ocean Floor
100
Freshwater
Lake
100
Journal Questions: answer in complete sentences with supporting evidence (use the numbers in your data table!)
1. What does the energy conversion number suggest (is the number similar between ecosystems) ? Why
are big, fierce (third order heterotrophs) rare? Give evidence for your answer.
2. According to your data, how many producers are there in a grassland ecosystem? How many third
order hetertrophs are in a grassland ecosystem? What does this suggest about animal number and the
energy available? Explain your answer.
3. Compare and contrast two of the ecosystems (Deciduous Forest and Hot Desert) you studied. How is
the energy conversion efficiency (the amount of energy that goes to the next higher level) similar or
different?
4. Does the population size increase or decrease at higher trophic levels in the pyramid of numbers of an
ecosystem? Explain your answer.
5. What might happen to an ecological pyramid of numbers in a forest ecosystem if most of the deer were
killed due to hunting by people and disease?
6. Could there be a food chain without herbivores and carnivores?