Food Web Model Assessment

Quiz · Grade 6 · Science · ngss

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Questions

• Q1. In a food web, which organisms are responsible for capturing energy from the sun and converting it into food through photosynthesis?

  • Consumers
  • Decomposers
  • Producers
  • Predators

  Answer: Producers

  Explanation: Producers (plants, algae, and some bacteria) use sunlight to make their own food through photosynthesis. They form the base of every food web and are the entry point for energy into the ecosystem. (DCI: MS-LS2-3)

• Q2. A student draws a food web and includes arrows between organisms. What does each arrow in a food web correctly represent?

  • The direction energy flows from prey to predator
  • The direction matter flows from predator to prey
  • Which organism is larger in the ecosystem
  • Which organism lives longer in the ecosystem

  Answer: The direction energy flows from prey to predator

  Explanation: Arrows in a food web show the direction of energy and matter transfer — from the organism being eaten (prey) to the organism doing the eating (predator). This models the flow of energy through the system. (DCI: MS-LS2-3)

• Q3. A forest food web includes grass → rabbits → foxes → decomposers. If a disease kills most of the foxes, what is the most likely immediate effect on the rabbit population?

  • The rabbit population will decrease because they lose a food source
  • The rabbit population will increase because their predator is gone
  • The rabbit population will stay the same because foxes are not important
  • The rabbit population will move to a different ecosystem

  Answer: The rabbit population will increase because their predator is gone

  Explanation: Removing a predator (fox) reduces the pressure on its prey (rabbits), allowing the rabbit population to grow. This demonstrates how disrupting one part of a food web can cascade through the system. (DCI: MS-LS2-4)

• Q4. Which of the following best explains why decomposers are included in a complete food web model?

  • They produce energy from sunlight to feed other organisms
  • They break down dead matter and return nutrients to the soil, cycling matter back into the system
  • They are the top predators that control all other populations
  • They only consume living plants and animals

  Answer: They break down dead matter and return nutrients to the soil, cycling matter back into the system

  Explanation: Decomposers (fungi, bacteria) break down dead organisms and waste, returning nutrients to the soil. Without them, matter would not cycle back to producers, and the ecosystem would eventually run out of available nutrients. (DCI: MS-LS2-3)

• Q5. A student's food web model shows that a hawk eats snakes, rabbits, and mice. What does this tell us about the hawk's role in the ecosystem?

  • The hawk is a producer because it gets energy from multiple sources
  • The hawk is a decomposer because it eats many organisms
  • The hawk is an omnivore that also performs photosynthesis
  • The hawk is a consumer that helps control multiple prey populations

  Answer: The hawk is a consumer that helps control multiple prey populations

  Explanation: Because the hawk eats multiple species, it acts as a consumer that regulates the populations of snakes, rabbits, and mice. This illustrates the interdependence of species within a food web. (DCI: MS-LS2-4)

• Q6. In a food web, energy is transferred from one trophic level to the next. What happens to most of the energy at each level?

  • It is stored permanently in the organism's body
  • It is passed entirely to the next consumer
  • It is lost as heat and used for life processes, so only about 10% moves to the next level
  • It is recycled back to producers by decomposers

  Answer: It is lost as heat and used for life processes, so only about 10% moves to the next level

  Explanation: At each trophic level, organisms use most of the energy they consume for their own life processes (movement, growth, reproduction), releasing much of it as heat. Only about 10% is available to the next level, which is why food chains are short. (DCI: MS-LS2-3)

• Q7. Which statement correctly describes the difference between how matter and energy move through a food web?

  • Both matter and energy flow in one direction and are never reused
  • Matter cycles repeatedly through the ecosystem, while energy flows in one direction and is not recycled
  • Energy cycles repeatedly through the ecosystem, while matter flows in one direction
  • Both matter and energy cycle repeatedly through all parts of the ecosystem

  Answer: Matter cycles repeatedly through the ecosystem, while energy flows in one direction and is not recycled

  Explanation: Matter (like carbon and nitrogen) cycles continuously through living and nonliving parts of an ecosystem. Energy, however, flows in one direction — from the sun through producers to consumers — and is lost as heat at each step, so it must be continuously added. (DCI: MS-LS2-3)

• Q8. A scientist studying a grassland ecosystem notices that a drought has killed most of the grass. Using a food web model, which prediction is best supported by evidence?

  • Only the organisms that eat grass will be affected; all others will remain unchanged
  • The effects will be limited to producers and will not reach consumers
  • The loss of grass will cascade through the food web, affecting consumers and decomposers at multiple levels
  • Decomposers will immediately replace the grass as the new producers

  Answer: The loss of grass will cascade through the food web, affecting consumers and decomposers at multiple levels

  Explanation: Because all parts of an ecosystem are interdependent, losing the primary producer (grass) reduces food for herbivores, which then reduces food for carnivores, and so on. This cascade demonstrates how disrupting one component affects the whole system. (DCI: MS-LS2-4)

• Q9. Humans apply large amounts of fertilizer to farm fields. Some fertilizer washes into a nearby lake, causing massive algae growth that blocks sunlight and kills underwater plants. Which crosscutting concept best describes this situation?

  • Scale, Proportion, and Quantity — because the lake is larger than the farm
  • Cause and Effect — because the human action of adding fertilizer caused changes throughout the lake ecosystem
  • Structure and Function — because algae have a different structure than underwater plants
  • Stability and Change — because the lake has always had algae in it

  Answer: Cause and Effect — because the human action of adding fertilizer caused changes throughout the lake ecosystem

  Explanation: This is a clear example of cause and effect: human activity (fertilizer use) caused a chain of changes in the ecosystem (algae bloom → blocked sunlight → plant death). It also shows that humans are part of natural cycles and can disrupt them. (DCI: MS-LS2-4, MS-LS2-5)

• Q10. Two student groups propose solutions to restore a degraded forest ecosystem where decomposer populations have collapsed. Group A proposes reintroducing native fungal decomposers. Group B proposes planting more trees. Which argument is best supported by food web reasoning?

  • Group B, because more trees will automatically bring back decomposers without any other action
  • Group A, because restoring decomposers will restart nutrient cycling, which supports producers and all other organisms
  • Group B, because trees are producers and producers are always the most important part of any ecosystem
  • Group A, because decomposers are the top of the food web and control all other populations

  Answer: Group A, because restoring decomposers will restart nutrient cycling, which supports producers and all other organisms

  Explanation: Without decomposers, nutrients locked in dead matter cannot be returned to the soil, so producers cannot grow even if seeds are planted. Restoring decomposers addresses the root cause — broken nutrient cycling — making it the solution best supported by understanding of matter cycling. (DCI: MS-LS2-5)

Grade

• 6

Subject

• Science

Answer Key

• Answer: Producers
• Number: 1
• Explanation: Producers convert sunlight into chemical energy through photosynthesis, forming the base of the food web and the entry point for energy into the ecosystem.
• Answer: The direction energy flows from prey to predator
• Number: 2
• Explanation: Arrows in a food web point from the organism being eaten to the organism eating it, showing the direction of energy and matter transfer.
• Answer: The rabbit population will increase because their predator is gone
• Number: 3
• Explanation: Removing the fox (predator) reduces population control on rabbits (prey), causing the rabbit population to grow — a cascade effect from disrupting the food web.
• Answer: They break down dead matter and return nutrients to the soil, cycling matter back into the system
• Number: 4
• Explanation: Decomposers are essential recyclers. Without them, nutrients would not return to producers and matter cycling would stop, making them indispensable to all other life.
• Answer: The hawk is a consumer that helps control multiple prey populations
• Number: 5
• Explanation: A hawk that eats multiple species is a consumer regulating several prey populations, illustrating interdependence and the complexity of food web relationships.
• Answer: It is lost as heat and used for life processes, so only about 10% moves to the next level
• Number: 6
• Explanation: Most energy at each trophic level is used for the organism's life processes and released as heat. Only ~10% is stored and available to the next trophic level, explaining why food chains are short.
• Answer: Matter cycles repeatedly through the ecosystem, while energy flows in one direction and is not recycled
• Number: 7
• Explanation: Matter is conserved and cycles through living and nonliving parts. Energy flows in one direction from the sun through the food web and is lost as heat — it must be continuously supplied.
• Answer: The loss of grass will cascade through the food web, affecting consumers and decomposers at multiple levels
• Number: 8
• Explanation: Losing the primary producer disrupts the entire food web because all consumers depend directly or indirectly on producers for energy and matter.
• Answer: Cause and Effect — because the human action of adding fertilizer caused changes throughout the lake ecosystem
• Number: 9
• Explanation: The fertilizer runoff is a human-caused disruption that triggered a cascade of changes in the lake ecosystem, demonstrating both cause-and-effect relationships and that humans are part of natural cycles.
• Answer: Group A, because restoring decomposers will restart nutrient cycling, which supports producers and all other organisms
• Number: 10
• Explanation: Decomposers are critical for returning nutrients to the soil. Restoring them addresses the broken nutrient cycle, which is the root cause of the ecosystem's degradation, making it the most effective and evidence-based solution.

Difficulty

• Medium

Total Questions

• 10

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