3 Food Chains and Food Webs-High

Food Chains and Food Webs Written by Kira Freed

Introduction Ana sits down at the table for a breakfast of oatmeal, yogurt, and orange juice before going to school. The food she takes in will provide energy for learning, gym, and her other morning activities. Where did the energy in her oatmeal, yogurt, and orange juice come from? This book explores how living things get the energy and matter they need to survive. You will learn how one living thing depends on another, and that ultimately all living things depend on energy from the Sun. You will also learn what happens when a food source is taken away.

Producers and Consumers Living things are either producers or consumers. Producers make their own food. Green plants are the major producers. They produce food by using energy from the Sun to combine water with a gas from the air. This process is called photosynthesis. Without energy from the Sun and the producers that use it for photosynthesis, most living things on Earth would not survive. Consumers are living things that cannot make their own food. Instead, they depend on producers for food. For example, grass is a producer. When a cow munches on the grass, the cow is a consumer. The cow cannot make food from sunlight. Consumers eat, or consume, producers or other consumers. The cow that munched on the grass was growing and making milk. When you sit down to drink a glass of milk or eat a hamburger that comes from a cow, you are a consumer, too. Producers and consumers depend on each other in complex relationships. Let's look into some of these relationships.

Food Chains Scientists often use food chains to illustrate how one living thing depends on another living thing and how energy and matter move from producers to consumers. Food chains can be short or fairly long. Since producers make food, they are the first link in a food chain. A food chain has only one link for producers but many links for consumers. Primary consumers are organisms that eat producers. They are the next link in the food chain. Primary consumers, called herbivores, can be as small as a grasshopper or as large as an elephant. Special body parts help many herbivores break apart tough plant material so they can get the energy stored in certain plant parts. Parrots have tough beaks that can crack open the outer cases of tropical fruits and nuts. Elephants have special teeth to grind tree bark.

Even with special body parts, many herbivores must spend an enormous amount of time eating to obtain enough energy to stay alive. For example, giant pandas must eat for about sixteen hours each day to get enough nutrients and energy from their diet of bamboo leaves and stems.

To review, the first link in a food chain is the producers, or plants. The second link is the primary consumers, or herbivores. The third link in a food chain is secondary consumers— animals that feed on the herbivores. These animals are carnivores, or meat eaters. When people think of carnivores, they often think of animals such as tigers and wolves. But other animals, such as insect-eating spiders, bats, and anteaters, are also carnivores. So are penguins, bald eagles, and other fish eaters. Can you guess the next link in a food chain? After primary consumers (which eat plants) and secondary consumers (which eat herbivores), many food chains have tertiary consumers— animals that eat other carnivores. For example, let's say a mouse (primary consumer/herbivore) eats grass, and a snake (secondary consumer/ carnivore) eats the mouse. A hawk that eats the snake is a tertiary consumer— a carnivore that eats another carnivore. Word Wise Primary 1st Secondary 2nd Tertiary 3rd