Food Webs and Food Pyramids

 

TECHNOLOGY LESSON (circle one)   No

 

Title of lesson:  Food Web

 

Date of lesson:  Tuesday of week 3

 

Length of lesson:  50 minutes

 

Description of the class:

                     Name of course:  Biology

                     Grade level:  9

                     Honors or regular:  Regular

 

Source of the lesson:

PBS website:

                     Scientific American Frontiers Archives  ÒBackyard Science:  How Ecosystems Work.Ó

                     ÒThe Living Edens – South Georgia Island:  Food WebsÓ

           

TEKS addressed:

¤112.43. Biology

(3)  Scientific processes. The student uses critical thinking and scientific problem solving to make informed decisions. The student is expected to:

(C)  evaluate the impact of research on scientific thought, society, and the environment;

(12)  Science concepts. The student knows that interdependence and interactions occur within an ecosystem. The student is expected to:

(B)  interpret interactions among organisms exhibiting predation, parasitism, commensalism, and mutualism;

(E)  investigate and explain the interactions in an ecosystem including food chains, food webs, and food pyramids

 

I.     Overview

This lesson will teach students the interactions involved in a food web within an ecosystem.  The students will also learn the importance of each organism in the food web, and how the food web is important to the ecosystem.

 
II.  Performance or learner outcomes

            1.  Students will be able to identify autotrophs and heterotrophs in an ecosystem.

            2.  Students will be able to develop a food web based on their findings of what organisms are predators and what are preys.

            3.  Students will be able to explain the relationships that are involved in a food web, and how changes affect all of the organisms in the food web.

               

III. Resources, materials and supplies needed

 

IV. Supplementary materials, handouts. (Also address any safety issues

      Concerning equipment used)

 

V.  Safety Considerations.  (may be N/A)

            

 

Five-E Organization

Teacher Does                    Probing Questions                                Student Does      

Engage:

Show video of an ocean habitat showing predators and prey

 

      

 

What does this video represent?

 

What are some strategies that predators and prey use to get food and avoid being eaten?    

A food web.

                                                   

Explore:

Lead a discussion about the video.  Who are the predators and who are the preys?

Make a list on the board or overhead.

In an ecosystem there are two categories of organisms – those that make their own food (autotrophs) and those that eat other organisms because they cannot make their own food (heterotrophs).

 

 

 

 

 

 

 

 

 

 

 

 

Have students develop a food web from the lists on the board.

Name some animals in the video and their relationships to the other animals in the video.

 

 

 

 

What are autotrophs and heterotrophs and what are examples?

 

 

 

 

 

What are two sources of energy for autotrophs?

 

 

 

 

 

How can heterotrophs, or consumers, be broken down further into groups.

 

What are the producers and consumers in the food web?

 

What organism would you consider to be the most important in the food web and why?

 

 

 

 

 

If you were to remove one of the organisms from this food web, how would it affect the other organisms?

 

Why would a scientist study an ecosystem and develop a food web for it?

 

 

 

     

Students will name different animals such as sharks, small fish, plankton, and others.  They will tell which are the predators and which are the preys.  They will tell which ones feed on what.

 

Autotrophs are producers in that they produce their own food.  An example is plants.  Heterotrophs are consumers in that they cannot produce their own food but get it from other sources.

 

Sun and chemicals.

 

 

 

 

 

 

They are herbivores, carnivores, omnivores, or detrivores.

 

Students will answer with the different organisms.

 

There will be various answers.  Some students might answer that the autotrophs are the most important because they provide their own food and provide food for other organisms in the food web.

 

 

 

 

 

 

To help an endangered species.

    

Explain:

Introduce food pyramid and trophic levels.

Scientists assign every organism in an ecosystem to a feeding level, or trophic level, depending on whether it is a producer or consumer and on which type of consumer it is. The producer is on the first trophic level; the primary consumer is on the second trophic level; the secondary consumer is on the third trophic level; the tertiary consumer is on the fourth trophic level; and the quaternary consumer, if present in a food chain, would occupy the fifth trophic level.

Draw a food pyramid and fill in with animals from the video.

 

Calculate the amount of biomass (organic matter) stored in each organism in the pyramid using the following rules:

Herbivores store about 15% of the previous trophic level's biomass.

Carnivores store about 10% of the previous trophic level's biomass.

 

 

                                               

Extend / Elaborate:

Have students research a specific organism in the food web that was created.

 

      

 

Choose an organism and write down what its adaptations are for hunting and eating its food.

 

How do humans affect the food web in the ocean?

 

Answers will vary depending on the animal chosen.

 

 

Humans might hunt a particular organism in the food web.  They might also introduce a new organism into the ecosystem that endangers an organism already living in the ecosystem.

   

  Evaluate:

Evaluate studentsÕ participation in discussions.

 

Evaluate studentsÕ reports on the organism they choose for the elaborate part of the lesson.