Part 1 Simulating Heat Loss in an Ecosystem

Ecosystem Energy Pyramids

Background: The living portion of an ecosystem is best described in terms of feeding levels known as trophic levels. Green plants make up the first trophic level and are known as producers. Plants are able to convert energy from the sun into food in a process known as photosynthesis. In the second trophic level, the primary consumers, known as herbivores, are animals and insects that obtain their energy solely by eating the green plants. The third trophic level is composed of the secondary consumers, flesh-eating or carnivorous animals that feed on herbivores. At the fourth level are the tertiary consumers, carnivores that feed on other carnivores. Finally, the fifth trophic level consists of the decomposers, organisms such as fungi and bacteria that break down dead or dying matter into nutrients that can be used again.

Some or all of these trophic levels combine to form what is known as a food web, the ecosystem’s mechanism for circulating and recycling energy and materials. In this way nutrients and the energy that green plants derive from sunlight are efficiently transferred and recycled throughout the ecosystem. In this lab, you will explore the concept of energy pyramid – the idea that an ecosystem can support more producers than consumers at higher trophic levels.

Hypothesis: We think that... (pyramids are or are not useful shapes for showing the approximate amount of energy at various trophic levels of an ecosystem.)

Procedure:

Part 1 – Simulating Heat Loss in an Ecosystem

1. The total energy passed from one level to the next is only about _____ of the energy received from the

previous level. Therefore as you move up the food chain the amount of energy available ______.

1. At each level of a food chain about _____of the energy is lost in the form of heat.
2. Complete the data table on your answer sheetshowing the total amount of energy passed on from each level of the food chain and the amount of

energy lost as heat. Keep moving the decimal point in the appropriate direction to see how the amount of energy passed on from the sun keepsgetting smaller and smaller as you progressively increase trophic levels in an energy pyramid.

1. 1 L of water is measured out in the large beaker. How many mL of water is this equal to?

1. If 10% of the total volume of water from the large beaker is transferred to a smaller beaker. How much is this? This represents the amount of the sun’s energy that can be used for photosynthesis.

1. If 10% of the energy available for photosynthesis is passed on to the next level – to the grasshopper – how much would that be in mL?

1. 10% of the energy available to the grasshopper is transferred to the frog. How much water would that be?

1. If 10% of the frog’s energy is taken in by the snake what volume of water is that equal to?

1. If 10% of the snake’s energy is taken in by the hawk what volume of water is that equal to?

Further Demo

1. Gather a beaker filled with stock solution (colored water) label this beaker as a producer.
2. Fill 3 other beakers with 30mL of water. Label the beakers as the energy pyramid. Primary, secondary, and tertiary consumers
3. From the stock solution, obtain 3mL of water in a pipette.
4. Empty the stock solution from pipette to primary consumers beaker. This is the amount of energy that is transferred to herbivores. Herbivores are primary consumers.
5. Continue taking 3mL of water from primary consumers to secondary consumers and then from secondary to tertiary.
6. What do you notice happening from the stock/ Producers level?
7. What does this represent?

Creating Food Chains, Food Webs, and Energy Pyramids

1. Color and cut out the cards of the organisms. Using the information provided, logically arrange them into a food web. You should use all twelve cards.
2. Glue the cards down on a sheet of construction paper and provide a descriptive title for your diagram.
3. Draw arrows pointing away from the organisms being eaten towards the consumers.
4. On the backside of the paper with the food web that you created, create an energy pyramid of a single food chain within your food web.
5. List the names of the organisms or draw them.
6. Label the producer, primary, secondary, tertiary… levels and again separate each trophic level with a horizontal line.
7. You do not need to include the energy content this time!

Analysis:

A. What is the main source of energy in all ecosystems?

B. Why are there more producers than higher level consumers in any given ecosystem?

C. In any given food chain, which organism is going to have to eat the greatest amount of food in order to survive – a primary, secondary, or tertiary consumer?

D. Only 10% of the energy from each trophic level is passed on to the next level. What happens to the other 90%?

E. In an aquatic ecosystem algae and aquatic plants use sunlight to produce energy in the form of carbohydrates. Primary consumers such as insects and small fish may feed on some of this plant matter and are in turn eaten by secondary consumers such as salmon. A brown bear may play the role of the tertiary consumer by catching and eating salmon. Bacteria and fungi may then feed upon and decompose the salmon carcass left behind by the bear, enabling the valuable nonliving components of the ecosystem such as chemical nutrients to leach back into the soil and water where they can be absorbed by the roots of plants.

Write the numbers of the blank circles shown in the food web below and identify the appropriate organismsfrom the passage above that should be written in each one.

F. Which organism(s) in the above ecosystem possess the greatest amount of energy that can be passed on when eaten?

G. At what feeding level is the brown bear in this food web?

H. What important role do bacteria and fungi fulfill in all ecosystems?

I. Which organism would you expect there to be the fewest of in this ecosystem? Why?

Name(s) ______

Energy Pyramids Lab Results

Give 2 Examples of a food chain

1. . ______→ ______→ ______→ ______→ ______→

______

1. . ______→ ______→ ______→ ______→ ______→

______

Energy Pyramids Lab 1