How Do Matter and Energy Move in the Ecosystem

1. Why is the base of an energy pyramid larger than the top?

• Organisms at the top produce energy for organisms at the bottom.
• Energy is converted into matter to form larger organisms at the top.
• Organisms at the top use less energy than organisms at the bottom.
• Energy is lost as heat at each level so less energy is available at the top

What do all food chains have in common?

• They are all made up of the same organisms in different orders.
• They all produce and use the same amount of energy.
• They all have more consumers than producers.
• They all begin with a producer.

Since humans can eat foods from many different ecosystems, they are

• part of many food webs.
• not counted as consumers.
• part of a simple food chain.
• considered to be producers.

How are food webs related to food chains?

• Food webs consist of overlapping food chains.
• Food chains occur on land whereas food webs occur in water.
• Food chains are made up of individual food webs.
• Food chains produce energy for food webs.

The king cobra of southeast Asia is one of the longest poisonous snakes in the world. Its favorite foods are other snakes, but it will also eat mice, rats, and lizards. Based on its diet, how would you describe the king cobra’s connections to other animals in its food web

• It is a producer and so begins a food chain.
• It eats a wide variety of producers, as do other first-stage consumers.
• It eats a wide variety of consumers to meet its energy needs, but doesn’t eat producers.
• It decomposes both producers and consumers, releasing matter back into the environment as waste and heat.

Cattle farmers need almost two football fields of grassland to feed just one animal for a year. How much of the energy at the base of the pyramid shown reaches the top (humans), and why?

• All of it; unlike matter, energy cannot be consumed or destroyed.
• None of it; cows release all of the grass’s energy as heat, then create their own, new energy.
• Some of it; the grass and cattle release some energy as heat before it reaches the human consumer.
• Most of it; cattle release some energy as heat, the grass does not release energy as heat.

Sharks are the highest-level consumers in the ocean, but because humans hunt them for food, their populations are decreasing by about 100 million sharks per year. You have to choose to make a model of a food chain or a food web to show how the loss of sharks might affect this coral reef. Which is the best choice and why?

• A food web is best because it shows many foods that the shark eats.
• A food chain is best because a food chain shows only one food that the shark eats.
• A food web is best because only food webs show how humans can change ecosystems.
• A food chain is best because it only shows consumers, while food webs show producers and consumers.

Producers, consumers, and decomposers use and recycle matter in an ecosystem. Carbon is solid matter that is recycled. Carbon dioxide and oxygen are gases that are recycled. How should the gray, purple, and brown arrows be labeled to complete the model shown?

• gray: carbon dioxide; purple: oxygen; brown: carbon
• gray: carbon; purple: carbon dioxide; brown: oxygen
• gray: oxygen; purple: carbon dioxide; brown: Carbon
• gray: carbon dioxide; purple: carbon; brown: oxygen

Americans may not live in the ocean or in a tropical rainforest, but they consume food from those ecosystems. Chocolate comes from cacao beans that grow in rainforests. Tuna salad comes from tuna that live in the ocean. How do Americans fit into the food chains and food webs of these ecosystems?

• Humans are part of many food chains, but only one food web.
• Humans are only consumers in the ecosystems where they currently live.
• Humans are the highest-level consumers in many food webs because we eat food from around the world.
• Humans are both consumers and producers in many food webs, because we grow energy-plants.

Lake Michigan is one of the Great Lakes. A team of scientists wanted to investigate how animals that were accidentally brought there now affect the Lake Michigan food web. To do so, they had to learn what each of these animals eats in its new home. After investigating the animals of Lake Michigan, the scientists were able to develop a food web, like the one shown. . In some parts of the world, humans eat sea lampreys. However, sea lampreys are not usually eaten in the United States. What if people in the US began to catch Lake Michigan sea lampreys for food? How might this likely affect the other living things in food web there?

• Trout, salmon, and bass might become scarce because lampreys would not eat them.
• Lake whitefish may start to die out because they eat sea lampreys.
• They might not be affected because none of them depend on sea lampreys for food.
• There would be no effect because humans are not a part of food webs.