Unformatted text preview: Ecological Pyramids
How does energy flow through an ecosystem? Why?
Every organism in an ecosystem is either eating or being eaten. When cows eat grass, they obtain some of
the energy that the grass transferred from the sunlight it absorbed. If cows could carry out photosynthesis, would they have access to more energy than they get as herbivores? Which organisms in an ecosystem
require the most energy to sustain life? Model 1 – Pyramid of Energy
24 kcal Values in the pyramid are
per square meter per year.
(carnivore) 470 kcal
Blue jays (omnivore) 4,000 kcal 25,500 kcal Caterpillars (herbivore) Oak tree leaves (producer) Sunlight hitting Earth’s surface = 3,190,000 kcal 1. A unit used to measure energy is the kcal.
a. What is the source of all energy in the pyramid in Model 1? sunlight
b. How much energy does this source provide to a square meter of the Earth per year? (Be sure
your answer includes units.) 3190,000 kcal in one square meter per year 2. Label the pyramid levels in Model 1 with the following: primary producers, primary consumers,
secondary consumers, and tertiary consumers. See model 1 3. The arrows in Model 1 represent the energy available to the next level of the pyramid.
a. What percentage of the source energy from Question 1a is absorbed by the oak leaves in
Model 1? 0.8 percentage
b. By what process do the oak leaves harness this energy? Photosynthesis Ecological Pyramids 1 4. Describe how the consumers in one level of the pyramid obtain energy from the organisms at the
previous level of the pyramid. Eat the pyramid.
5. Refer to Model 1.
a. How much energy per year do the caterpillars in Model 1 obtain from eating the leaves in a
square meter of the oak tree? 4000
b. What percentage of the energy that was originally absorbed by the oak leaves is passed on to
the caterpillars? 4000/2550=16percentage
c. What percentage of the energy absorbed by the oak leaves is not passed on to the caterpillars? 84percentage d. With your group, list at least three possible uses and/or products of the energy absorbed by
the oak leaves that did not contribute to the production of biomass. It produce lot of oxygen, water inside the tree and transpiration 6. Calculate the percentage of energy that is transferred from one level of the pyramid in Model 1
to another for all of the levels.
a. Oak leaves to caterpillars (see Question 5b). 16 percentage
b. Caterpillars to blue jays. 12 percentage
c. Blue jays to hawk. 5%
7. Calculate the average percentage of energy that is transferred from one level to another using
your answers in Question 6. Note that this average percentage transfer is similar for many different types of energy pyramids in nature. 33% = 33\3= 11% 8. As a group, write a statement that describes the pattern of energy transfer among consumers
within a pyramid of energy. In this model in every state only 10 % of the energy pass on,
which mean there are almost 90% of energy that are wasted.
The pass of the energy will be seen less as you get to the top of
the pyramid 2 POGIL™ Activities for High School Biology 9. What percentage of the caterpillars’ original energy is available to the hawk? 0.6%
10. What percentage of the oak leaves’ original energy is available to the hawk? 0.09%
11. Explain why an energy pyramid in any ecosystem typically is limited to four or five levels only. leave- Caterpillars-Blue jays - Hawk 12. Propose an explanation for why populations of top carnivores, such as hawks, are always smaller
than the populations of herbivores, such as caterpillars. Becasue there is not a lot energy for a single hawk, this little energy
can support a large population of hawks. Read This!
Each level in the pyramid in Model 1 is a trophic level. The word “trophic” refers to feeding or nutrition.
Model 1 shows one example of one organism that would be included in each level, but each level in an
ecosystem includes many species of organisms.
13. List at least three other species that might be found in the trophic level with the oak trees. Grass,tree, flower. 14. List at least three other species that might be found in the trophic level with the blue jays.
Eagles, peacocks,fox Ecological Pyramids 3 Model 2 – Pyramid of Numbers
Pyramid A Pyramid B
1 hawk 1 hawk 20 blue jays 20 blue jays 1000 caterpillars 1000 caterpillars 2 oak trees 100,000 oak leaves 15. Compare and contrast the two pyramids in Model 2. List at least two similarities and two
differences. Both of them have same among of caterpillars, they also only have one hawk
Pyramid have less oak trees. Pyramid seen to be unhealthy compare
16. How does the number of organisms change as you move up the levels in Pyramid A compared to
Pyramid B? In B, the number of organisms decreases from one level to the next. In A, the firs
level has a little number of organisms and the remaining level follow the same
pattern as in A 17. Are the “producers” levels in the two pyramids in Model 2 referring to the same organisms or
different organisms? Explain. The tree is the same, the caterpillars eat only the oak tree leaves 18. Which of the two pyramids in Model 2 gives a more accurate account of what occurs in this
ecosystem? Use complete sentences to explain your reasoning. The producers in A have two oak tree, but the source on these two producers in tens of
thousands of leaves.
the number of leaves is much more relrvant tha the number of trees. 4 POGIL™ Activities for High School Biology Model 3 – Pyramid of Biomass
Pyramid X Pyramid Y Hawk (80 g/m2)
Blue jays (400 g/m2) Heron (20 g/m2)
Perch (100 g/m2) Caterpillars (800 g/m2) Zooplankton (210 g/m2) Oak trees (11,000 g/m2) Phytoplankton (40 g/m2) 19. Biomass is measured as grams of dry mass within an area. What is the mass of the oak trees in
Pyramid X of Model 3? 11000gm
20. What is the mass of the phytoplankton in Pyramid Y of Model 3? 40gm
21. Refer to Model 3.
a. Identify the trend in biomass as you move up the trophic levels in Pyramid X. The biomass decreases steadily
b. Is the trend in biomass in Pyramid X the same as seen in Pyramid Y? Explain your answer. NO,the mass of producers is smaller than the mass of primary consumers. Read This!
Phytoplankton are microscopic aquatic organisms that are quickly consumed by microscopic animals
(zooplankton). Because they are eaten so quickly there is a need for the phytoplankton to reproduce
rapidly for survival.
22. Explain why the Pyramid Y ecosystem can exist with a smaller biomass at the producer level. Phtoplankton reproduce rapidly. so they will sustain a large number of primary consummers
23. Use examples from the previous models to explain the advantage of using a pyramid of energy or
biomass rather than a pyramid of numbers to explain the relationship between different trophic
levels. Biomass varies drastically with different organisms for example” tree Vs caterpillar” Ecological Pyramids 5 Extension Questions
24. What type of organisms are missing from all of the trophic pyramids shown in Models 1–3? Decomposers is the most obvious missing organisms
25. Explain why a vegetarian diet is considered a more energy-efficient diet for humans than one
based on beef, chicken or pork. Because, beef chicken and pork are from animals, and those animals take
energy from plant and lot of energy are loss in the process of energy change. So
eat vegetarian can save more energy. 6 POGIL™ Activities for High School Biology ...
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