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Biological Energy - Food Chain Practice

Remember that food chains are used to represent the flow of energy between organisms. As you learned on the last Sci-ber Text page, the arrows in a food chain show the direction of energy flow.

The organisms in a food chain can be producers, consumers, or decomposers.

Producers
are green plants capable of making their own food using energy from the sun in a process called photosynthesis.

Consumers are animals that cannot make their own food. They get their energy from other plants and animals. A food chain can have as many as three to four consumers.

There can be many levels of consumers who rely on each other as a food source.

  • First level consumers feed directly on plants; an example of this would be a mouse.
  • Second level consumers feed on first level consumers; an example of this would be a rattlesnake that eats the mouse.
  • Third level consumers feed on second level consumers; an example of this would be a hawk eating the rattlesnake.
  • Predators are often second or third level consumers. These organisms obtain their energy by eating a prey. An example of a predator would be a mountain lion.
  • Prey then refers to an organism that is eaten by another organism. An example of a prey for a mountain lion is a mule deer.

You can see that because energy is lost at each step of a food chain, it takes a lot of producers to support a few top consumers. The food pyramid below shows an example of this.

Notice that if there were 1000 units of energy at the producers level the primary consumers would receive 100 units of energy, the secondary consumers would receive 10 units of energy, and the tertiary consumer would receive 1 unit of energy. This pyramid helps to demonstrate the loss of energy from one level of the food chain to the next.

  • Decomposers are also unable to make their own food. Bacteria and fungi are decomposers. They break down waste products and dead organisms for food. These broken down materials are returned to the soil to be recycled and used by plants again. An example of this would be the mushroom in the picture at the right growing on decaying wood in the forest.

    Although decomposers are very important to ecosystems, they are usually not shown on the food chain.

Materials:

  • Magazines
  • Colored pencils
  • Large-sized paper for mounting pictures or drawing
  • Scissors
  • Glue

Procedure:
You should demonstrate your knowledge of food chains by creating some chains of your own. Draw (or clip pictures from magazines) and color three food chains with at least four organisms in each. Make your food chains for diverse ecosystems ... include food chains from at least one of the following: the desert, the forest, the plains of Africa, the ocean, and the Arctic. Be creative. Be sure to include arrows to show the direction of energy flow. Label each member of the food chain as the producer, first, second, or third level consumer.

Safety concerns: Be sure to follow all sharp safety rules that are specified by your teacher in all general laboratory experiences. Be careful with the scissors that you are not injured. As with all science lab activities, the most important safety rule is to follow all teacher directions.

Assessment:
Look closely at the following list of organisms and drag down to identify each as a producer, consumer, or decomposer.

Organisms Role in food chain

1 Human

2 Deer

3 Pine tree

4 Mushroom

5 Rabbit

6 Bacteria

7 Mouse

8 Snake

9 Wheat

10 Fly maggot

11 Bluegrass

12 Hawk

13 Millipede

14 Sparrow

15 Cat

16 Frog

17 Algae

18 Trout

Check your answers by highlighting the box below!

1. Consumer, 2. Consumer, 3. Producer, 4. Decomposer, 5. Consumer, 6. Decomposer, 7. Consumer, 8. Consumer, 9. Producer, 10. Decomposer, 11. Producer, 12. Consumer, 13. Consumer, 14. Consumer, 15. Consumer, 16. Consumer, 17. Producer, 18. Consumer
utah state board of education This Sci-ber Text was developed by the Utah State Board of Education and Utah educators.