Food Webs and Energy Flow in Ecosystems
Tracing energy through producers, consumers, and decomposers
Food Webs and Energy Flow in Ecosystems
Tracing energy through producers, consumers, and decomposers
Biology - Grade 6-8
- 1
In a grassland ecosystem, grass is eaten by a rabbit, and the rabbit is eaten by a hawk. Identify the producer, the primary consumer, and the secondary consumer.
Producers make their own food, and consumers get energy by eating other organisms.
The grass is the producer because it makes its own food. The rabbit is the primary consumer because it eats the producer. The hawk is the secondary consumer because it eats the primary consumer. - 2
Explain why the Sun is the original source of energy for most food webs.
The Sun is the original source of energy for most food webs because producers, such as plants and algae, use sunlight to make food through photosynthesis. That stored energy is then passed to consumers when they eat producers or other consumers. - 3
A pond food chain is algae -> insect larva -> fish -> heron. Describe how energy flows through this food chain.
Follow the arrows one step at a time.
Energy flows from the Sun to the algae, which make food. The insect larva gets energy by eating the algae, the fish gets energy by eating the insect larva, and the heron gets energy by eating the fish. - 4
What is the main difference between a food chain and a food web?
A food chain shows one simple path of energy flow from one organism to another. A food web shows many connected food chains and the multiple feeding relationships in an ecosystem. - 5
A fox eats rabbits, mice, and berries. What does this tell you about the fox's role in the food web?
Think about whether the fox eats only plants, only animals, or both.
This tells us that the fox is an omnivore because it eats both animals and plant material. In the food web, it can act as a consumer at more than one feeding level depending on what it eats. - 6
Decomposers such as fungi and bacteria break down dead organisms. Explain why decomposers are important in an ecosystem.
Decomposers are important because they break down dead plants, animals, and wastes. This returns nutrients to the soil or water, where producers can use them again, helping matter cycle through the ecosystem. - 7
If a large number of insects in a forest die from disease, how might this affect frogs and hawks in the same food web?
Think about what happens when one food source suddenly becomes scarce.
Frogs may have less food available if they eat insects, so their population could decrease. Hawks could also be affected if they depend on frogs or other insect-eating animals for food, because less energy would move up the food web. - 8
In an ocean ecosystem, phytoplankton are eaten by zooplankton, which are eaten by small fish. Which organism is the primary consumer, and why?
The zooplankton are the primary consumer because they eat the producer, which is the phytoplankton. Primary consumers get energy directly from producers. - 9
Why is less energy available at the top of a food pyramid than at the bottom?
Energy is lost at each step as organisms use it.
Less energy is available at the top of a food pyramid because organisms use much of the energy they take in for life processes such as movement, growth, and staying alive. Only part of the energy is passed on to the next trophic level. - 10
A student says that energy cycles through an ecosystem in the same way that matter does. Is the student correct? Explain your answer.
The student is not correct. Matter cycles through ecosystems because nutrients are reused, but energy flows in one direction through the ecosystem and is eventually lost as heat, so it does not cycle in the same way. - 11
List one example of a producer, one herbivore, one carnivore, and one decomposer in a forest ecosystem.
Choose organisms that fit each role in a forest.
One possible example is an oak tree as the producer, a deer as the herbivore, a wolf as the carnivore, and a mushroom as the decomposer. Other correct forest examples are also acceptable. - 12
How would removing all producers from an ecosystem affect the rest of the food web?
Removing all producers would cause the food web to collapse because producers are the main entry point for energy into the ecosystem. Herbivores would lose their food source first, and then higher-level consumers would also lose their sources of energy.