Have you ever seen a picture that shows a little fish about to be eaten by a big fish? Sometimes the big fish has an even bigger fish behind it. This is a simple food chain. A food chain is the path of food energy from one organism to another in an ecosystem. (An organism is any living thing.) energy: what is needed to do work or cause change Organisms get energy from the food they eat. Before the little fish gets eaten, it eats a plant for its energy. Food chains are the way energy is moved from one organism to the next. But where does the energy in the food chain start? How does energy move through the food chain? Where does the energy from a food chain start? Plants get their energy from the Sun. Plants use the light from the Sun to make their own food. This food gives plants energy to grow and survive. Plants also store food to use for energy later. What is eating what in this simplified food chain? Most of the energy on Earth comes from the Sun. So, the Sun is at the top of most food chains. The organisms that get their energy directly from the Sun are called producers. A producer uses sunlight to make its own food. The organisms that get their energy by eating producers are called consumers. We will study consumers in the next section. Sun: the star at the center of the Solar System that supplies heat and light to Earth The Sun gives energy to these corn plants. 1
How does energy flow through a food chain? Consumers may eat producers (plants) or other consumers (other animals). Consumers are called predators when they eat other animals. The organisms eaten by predators are called prey. The eagle is a predator. The fish is the eagle s prey. When an animal eats a plant, it gets the energy stored in the plant. The animal can use this energy to move and to stay healthy. One animal may also eat another animal. The predator gets the energy stored inside of the prey animal. The predator can then use this energy to move and stay healthy. The diagram above is an example of a food chain. The energy comes from the Sun. Plants use the energy to produce plant seeds. A mouse eats the plant seeds. Then, a snake eats the mouse. Finally, an eagle eats the snake. Notice that the arrows point from the Sun to the eagle. In other words, the arrows show the direction in which the energy flows. Sometimes, people draw food chains with the arrows pointing in the wrong direction. Because the eagle eats the snake, you may think it makes sense for the arrow to point from the eagle to the snake. It is important to remember that the flow of energy always goes from the Sun to producers to consumers. 2
Is the organism shown in this picture a producer or a consumer? How do you know? In this activity, you will locate consumers and producers where you live. 1. Begin by thinking about the living things in your classroom or home. Do you have any plants or pets? Identify each living thing that you see. Decide whether it is a consumer or a producer. 2. Next, take a walk outside. Identify the living things that you see. Decide whether each is a consumer 3. or a producer. Be safe. Do not touch any plants you re unsure of or approach any animals. 4. Don t forget to think about yourself. You are a living animal in a food chain. Are you a consumer or a producer? What happens to a food chain in an ecosystem if an organism is removed? Ecosystems may have many different producers and consumers. An ecosystem may contain many food chains. A balanced ecosystem has enough producers to support all the consumers. Some ecosystems contain lots of biodiversity. In other words, they contain many different kinds of living things. If one organism dies out, other organisms may take its place in a food chain. 3
In other ecosystems, however, food chains might be affected much more. If that organism dies and no other species fill that role, you can imagine how many other organisms will be affected! Whatever the organism eats might grow more quickly, and whatever predators eat the organism will have trouble finding food. Can you think of what else might happen? Let s think about frogs in a pond. In a pond ecosystem, frogs are consumers of many different organisms. They eat snails and small insects that get their energy from green algae. Green algae are the producers in the pond food chain. Large animals like herons eat the frogs. Many ponds contain only one kind of frog. If a disease kills off all the frogs, the heron and other large consumers lose a large part of their food source. They may die off as a result or have to find a new food source. On the other hand, fewer frogs mean fewer predators eating insects and snails. More insects and snails may survive. If this happens, they may eat too much of the pond s algae. As a result, the food chain may become affected or broken in several places. Without bees in an ecosystem, flowers won t be pollinated. Insects such as this caterpillar will have fewer plants to eat. Looking to the Future: Bee Colony Collapse Disorder Bees are part of the ecosystems in which they live. When they move from flower to flower they pick up pollen on their bodies. The bees then move the pollen to the next flowers they land on. By doing this, they help the flowers make fruits and seeds. Without the bees to move the pollen the plants could not reproduce. Scientists do not know why, but colonies of bees have been disappearing. This was first observed in 2006 in North America. Since then, it has been happening all over the world. This problem is called Colony Collapse Disorder (CCD). Because of CCD, many fruits and other crops have been ruined. 4
Scientists aren t sure what is causing CCD. They have several hypotheses: Poison that is sprayed on crops kills bees. Insects such as mites harm the bees. A virus harms the bees. Humans have damaged the habitats where bees live. hypothesis: a possible answer to a scientific question Scientists also think that CCD could be from all of these things. They watch bee colonies carefully and record what they see. They test dead bees to find out what caused them to die. They are also working to improve the health of living bees. What do you know? Food chains are made up of producers and consumers. Identify whether each of the following is a producer or a consumer. 5
The Food Chain in Store for You To help students learn more about food chains and to make the connection to their everyday lives, take them with you to your local grocery store. As you walk the aisles with them, point out different foods and discuss where that food comes from. From their studies in the classroom, they should be able to identify whether each food is a producer or a consumer. Then, encourage students to take it a step further and describe a possible food chain for the item. For example, point out a fruit or vegetable. They should identify this as a producer. When they think about a possible food chain, they should explain the plant gets energy from the Sun; students might also describe a small animal that eats the plant and perhaps a larger animal that eats the small animal. Here are some questions to discuss with your child: Is everything in the produce aisle of the grocery store a producer? Are there any consumers in the grocery store? Consider some packaged food, such as bread or cereal, and ask students to look at the ingredients to determine the source of the food. This may take a little more prompting; for example, students may not realize that flour comes from wheat. 6