Understanding the Energy Pyramid 8 th Grade Science

Understanding the Energy Pyramid 8 th Grade Science Spring 2015

Consider This: • How do you think ENERGY flows through a food chain? – Do you think that every organism passes on the same amount of energy to the next organism in the food chain? • Think about this question during the Brain. Pop video • Be prepared to share your understanding of the question after the video

Guided Notes Learn more about the transfer of energy through the energy pyramid here – Teachers: You will have to click “view” to begin the guided notes presentation – Students: Follow along with the presentation and fill in the blanks on your handout

A burger and corn for lunch! They’ll provide me with much of the energy my body needs this afternoon: 250 calories of energy in the burger and 75 calories in the corn!

The story begins at the Sun, which sends energy out into our solar system. We can see some of that energy as Sunlight. Only a small amount of the energy that leaves the Sun actually reaches the Earth.

Can you guess how much energy reaches Earth? Choose one: 5% (1/20) OR 0. 0000005%

About half a billionth of the Sun’s energy strikes the Earth. Lucky for you, it’s not 5 percent- you’d be vaporized!

That cornfield over there is one tiny part of the Earth that receives the Sun’s light. That’s the scene for the next part of our story: photosynthesis.

In photosynthesis, green plants capture the energy from sunlight to manufacture sugar from water and carbon dioxide.

Can you guess how much of the Sun’s energy that reaches the plant gets stored in them? Choose one: 20% OR 5% 5%

Most of the energy gets reflected back into space by the leaves or is absorbed by the plants and warms them. The chemical reactions of photosynthesis store only 5 percent of the energy, in the chemical bonds of glucose molecules.

So 5 percent of the energy that lands on the corn plant’s leaves gets absorbed into the chemical bonds made by photosynthesis. Much of this energy is bounced from molecule to molecule as the sugars provide energy for the production of proteins and other plant materials in complex sets of reactions. Some of the energy is stored in the form of Starch in corn kernels.

Can you guess what percentage of the energy the corn plant captures in photosynthesis ends up in its kernels? Choose one: 10% OR 75% 10%

People raise corn for its Ears, but most of the solar energy it captures in photosynthesis goes into building and operating the plant itself, not preparing for the next generation of plants. That’s what the kernels on an ear of corn are really all about. Each of those kernels is a seed that can grow into a new corn plant.

Now the story takes us into the body of a cow! The cow is feed some of the corn. Then in digestion and in the cow’s cells, many more chemical reactions take place, releasing energy.

The Energy is used to keep the cow warm, to produce and power its muscle cells, and to take care of other needs. Some of the energy gets stored for later use in cells containing fat. And then one day, the cow’s muscle and fat gets turned into hamburger Meat.

Can you guess what percentage of the energy stored in the ears of corn winds up in burgers? Choose one: 50% OR 10%

Most of the cow’s energy, like yours, goes into heating and operating the body, not making meat.

Only about 10 percent of the energy in an animal’s food winds up in the meat you might eat. That’s why some vegetarians say eating more plants would help the world feed itself: You lose 90 percent of the captured solar energy by passing it through animals.

Energy Flow Summary 1: Sun _10_% of energy _10_ % of energy 4: Secondary Consumers (Humans) Only half a billionth of the Sun’s energy strikes the Earth. 3: Primary Consumers (Cows) 2: Producers (Corn Plant) One-tenth of the solar energy captured is stored in corn on the cob

Thinking Questions • Discuss the following questions as a class after completing the guided notes • Students: Record your answers on your handout

Question 1 Why is a pyramid a good representation of energy moving through a food chain?

Question 2 What happens to the energy that is not available to be passed from one level to the next?

Question 3 Where in a food chain are the largest populations? How is this shown by a food pyramid?

Question 4 Where in the food chain are populations the smallest? How is this represented by a food pyramid?

Question 5 What happens to the total amount of energy in a food chain as the energy moves through the chain from producer to different levels of consumers?