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Quizzes > Science

Food Web Quiz: Test Producers, Consumers, and Decomposers

Quick, free ecosystem energy flow quiz. Instant results.

Editorial: Review CompletedCreated By: Yunche WilsonUpdated Aug 28, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for food web knowledge quiz on a golden yellow background

This quiz helps you check how food web parts connect, from producers and consumers to decomposers. See how energy flows across trophic levels and spot weak points. Keep learning with the food chain energy quiz and explore patterns in the food webs quiz, or broaden your view with the ecosystem interactions quiz.

Which of the following is an example of a primary producer in most ecosystems?
Mushroom
Grass
Rabbit
Wolf
Primary producers are autotrophic organisms that convert solar energy into chemical energy through photosynthesis; grass is a classic example. Rabbits and wolves obtain energy by consuming other organisms, and mushrooms function as decomposers. Producers form the foundational trophic level that supports all consumers in the food web. .
What do herbivores primarily eat in a food web?
Other carnivores
Decomposers
Producers
Detritus
Herbivores specialize in eating producers, which are plants and algae that generate their own energy through photosynthesis. They transfer energy from the producers up the food chain to higher trophic levels. Decomposers and detritivores recycle nutrients rather than serving as primary food sources for herbivores. .
Which term describes organisms that consume both plants and animals?
Omnivores
Herbivores
Detritivores
Carnivores
Omnivores feed on both autotrophic producers (plants) and other consumers (animals), making them dietary generalists. Carnivores consume only other animals, while herbivores feed exclusively on producers. Detritivores decompose dead organic matter rather than actively hunting live prey. .
What is the main role of decomposers in a food web?
Produce glucose through photosynthesis
Act as primary consumers
Break down dead organisms and recycle nutrients
Transfer energy to the next trophic level
Decomposers like bacteria and fungi break down dead plants and animals, returning essential nutrients to the soil and water for use by producers. They complete the nutrient cycle of ecosystems. They do not perform photosynthesis or directly transfer energy up the trophic levels. .
A hawk that eats rabbits is considered what in a simple food chain?
Decomposer
Producer
Primary consumer
Secondary consumer
A hawk preys on rabbits, which are primary consumers, so the hawk is a secondary consumer. Primary consumers feed on producers, while secondary consumers feed on primary consumers. Producers generate energy, and decomposers recycle nutrients rather than consuming live prey. .
Which of these organisms is a detritivore?
Grass
Earthworm
Rabbit
Snake
Detritivores, such as earthworms, feed on dead organic matter (detritus), breaking it down into smaller particles. Grass is a producer, snakes are predators, and rabbits are herbivores. Detritivores play a vital role in nutrient recycling and soil health. .
At the base of every food web you will find which group of organisms?
Consumers
Detritivores
Producers
Parasites
Producers, such as plants and algae, form the base of all food webs by converting inorganic energy from the sun into organic compounds. Consumers rely on producers either directly or indirectly for energy. Detritivores and parasites occupy other ecological roles beyond the food web base. .
What does the term "trophic level" refer to in an ecosystem?
A type of habitat
A feeding position within a food web
The lifespan of an organism
The size of an organism
A trophic level describes an organism's position in a food web based on its source of energy, from producers at level one to top predators at higher levels. It does not refer to lifespan, size, or habitat type. Understanding trophic levels helps ecologists track energy flow in ecosystems. .
What does a food web illustrate that a simple food chain does not?
Biomass distribution over time
Rate of nutrient cycling
Exact energy values at each level
Interconnected feeding relationships among multiple species
A food web maps the complex network of multiple feeding relationships in an ecosystem, whereas a food chain shows only a single linear sequence. It captures how many predators may feed on the same prey and vice versa. Energy values, biomass, and nutrient cycling rates require additional data beyond a basic web. .
In energy pyramids, approximately what percentage of energy is transferred from one trophic level to the next?
90%
10%
50%
100%
The 10% rule states that roughly only 10% of the energy at one trophic level is passed on to the next, with the rest lost as heat and metabolic processes. This principle explains why food chains rarely exceed four to five levels. Higher percentages do not reflect typical ecological efficiency. .
In an aquatic food web, phytoplankton is consumed directly by zooplankton. Zooplankton are considered what trophic level?
Producers
Tertiary consumers
Primary consumers
Secondary consumers
Zooplankton feed on phytoplankton, which are producers, making zooplankton primary consumers. Secondary consumers would eat primary consumers, and tertiary consumers would feed on secondary consumers. Producers synthesize their own energy rather than consuming other organisms. .
What term describes the phenomenon when predators indirectly increase plant biomass by controlling herbivore populations?
Ecological succession
Mutualism
Trophic cascade
Parasitism
A trophic cascade occurs when predators reduce herbivore numbers or activity, leading to increased plant biomass or altered vegetation structure. It highlights the indirect influence of top predators on lower trophic levels. Succession, mutualism, and parasitism describe other ecological interactions. .
Which of the following best describes a keystone species?
A species whose impact on its community is disproportionate to its abundance
The most abundant species in an ecosystem
A species that only acts as a primary producer
A top predator only found at high trophic levels
A keystone species exerts a disproportionately large influence on community structure relative to its abundance; its removal can lead to dramatic ecosystem changes. Abundance alone does not denote a keystone. Keystone species can occupy any trophic level, not just producers or top predators. .
Which of these organisms would be considered an apex predator?
Tiger
Earthworm
Grasshopper
Rabbit
An apex predator sits at the top of its food web with no natural predators; the tiger is a classic example. Rabbits and grasshoppers are herbivores or primary consumers, and earthworms are detritivores. Apex predators help regulate prey populations. .
In a food chain grass ? grasshopper ? frog ? snake, what is the frog's trophic level?
Primary consumer
Secondary consumer
Producer
Tertiary consumer
The frog eats grasshoppers, which are primary consumers, making the frog a secondary consumer. Primary consumers feed on producers, tertiary consumers feed on secondary consumers, and producers generate energy via photosynthesis. .
In some aquatic ecosystems, biomass pyramids appear inverted because:
Aquatic producers store more biomass than terrestrial plants
Phytoplankton have high turnover but low standing biomass
Consumers convert energy more efficiently underwater
Fish reproduce faster than algae
Phytoplankton reproduce and are consumed so rapidly that their standing biomass is lower than that of the populations they support, inverting the pyramid. Aquatic consumers often have higher biomass at any moment despite lower productivity. Energy efficiency and reproduction rates alone don't explain inversion. .
What is net primary productivity (NPP)?
Energy lost as heat to the environment
Total energy fixed by photosynthesis
Biomass consumed by herbivores
Gross primary productivity minus respiration by producers
NPP represents the energy that producers store after accounting for the energy they use in respiration. It is the energy available to support consumers in the ecosystem. Gross primary productivity (GPP) includes all energy fixed during photosynthesis before respiratory losses. .
How does an algal bloom most immediately affect aquatic food webs?
Lowers water temperatures
Increases biodiversity of fish species
Improves energy transfer efficiency
Reduces oxygen levels when algae decompose
When algal blooms die off, decomposers consume them rapidly, depleting dissolved oxygen and causing hypoxic conditions harmful to aquatic life. This process can lead to dead zones where few organisms survive. Blooms often result from nutrient pollution rather than beneficial ecological effects. .
Which best defines gross primary productivity (GPP)?
Energy consumed by herbivores
Net energy available to secondary consumers
Energy remaining after producer respiration
Total energy captured by producers via photosynthesis
GPP is the total amount of chemical energy produced by photosynthesis in producers before subtracting the energy used for their respiration. It represents the maximum energy input in an ecosystem. NPP is derived by subtracting respiratory losses from GPP. .
Which human activity is most likely to disrupt a terrestrial food web by removing top predators?
Overhunting of carnivorous species
Planting monoculture crops
Restricting grazing by herbivores
Applying organic compost
Overhunting top predators removes crucial control on herbivore populations, leading to trophic cascades and altered plant communities. Monocultures, composting, and grazing management affect other ecosystem aspects but do not directly eliminate apex predators. Predator loss has disproportionate ecological effects. .
What is the most likely ecological result of bioaccumulation of toxins in apex predators?
Elevated toxin concentrations leading to health issues
Uniform toxin distribution across trophic levels
Immediate toxin breakdown in predators
Reduced toxin levels over time
Bioaccumulation causes toxins to concentrate in organisms over time, and biomagnification leads to higher levels in apex predators, potentially causing reproductive and health problems. Lower trophic levels have lower toxin loads. Toxins are not uniformly distributed or immediately broken down. .
What factor primarily defines the maximum number of trophic levels in a food web?
Energy loss with each trophic transfer
Rate of photosynthesis
Total number of producer species
Number of decomposer species
Energy diminishes at each transfer due to metabolic heat loss and inefficient consumption, limiting the length of food chains. More producers or decomposers don't extend trophic levels without additional energy input. The rate of photosynthesis affects energy input but not the transfer efficiency directly. .
In a food web, bottom-up control refers to which phenomenon?
Predators regulating herbivore populations
Mutualistic interactions driving productivity
Climate factors altering species distributions
Resource availability at lower trophic levels controlling higher levels
Bottom-up control occurs when the abundance and productivity of producers and resources limit population sizes and dynamics of higher trophic levels. Top-down control involves predators regulating prey populations. Mutualism and climate are separate ecological influences. .
What is an ecological pyramid of numbers?
A chart of biomass distribution over time
A diagram of energy flow efficiency
A graphical representation of organism counts at each trophic level
A map of nutrient cycling routes
An ecological pyramid of numbers charts the number of individuals at each trophic level, showing how many organisms support higher levels. Biomass and energy pyramids depict mass and energy flow, respectively. Nutrient cycling maps are a different type of ecological diagram. .
If net primary productivity is 5,000 kJ/m²/year and ecological efficiency at each trophic transfer is 10%, what is the approximate energy available to tertiary consumers?
0.5 kJ
500 kJ
50 kJ
5 kJ
Applying the 10% rule: primary consumers receive 10% of 5,000 kJ (500 kJ), secondary consumers receive 10% of that (50 kJ), and tertiary consumers receive 10% of 50 kJ, equaling 5 kJ. This demonstrates rapid energy loss across trophic levels. .
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Study Outcomes

  1. Identify Producers, Consumers, and Decomposers -

    Readers will recognize and classify the primary roles organisms play in a food web, distinguishing between producers, consumers, and decomposers.

  2. Analyze Trophic Levels and Energy Flow -

    Readers will trace how energy moves through different trophic levels, understanding the flow from producers to apex consumers.

  3. Interpret Species Interdependencies -

    Readers will interpret the connections among organisms to answer food web questions effectively and appreciate ecosystem complexity.

  4. Apply Critical Thinking to Quiz Items -

    Readers will use logical reasoning and scientific concepts to solve questions about food webs and assess ecosystem stability.

  5. Differentiate Food Chains from Food Webs -

    Readers will distinguish between simple linear food chains and more complex, interconnected food webs in natural habitats.

  6. Evaluate Environmental Impacts on Food Webs -

    Readers will assess how factors like climate change or habitat loss can disrupt food web dynamics and species interactions.

Cheat Sheet

  1. Trophic Levels and Energy Flow -

    Producers, primary consumers, secondary consumers and decomposers define each trophic level in a food web. Use the 10% rule from classic studies (e.g., Cornell University's EFB department) which shows only about 10% of biomass energy passes up each level. A handy mnemonic is "P-H-C-D" (Producers → Herbivores → Carnivores → Decomposers) to tackle food web questions efficiently.

  2. Energy Pyramids and Ecological Efficiency -

    Energy pyramids graphically represent the distribution of energy among trophic levels, highlighting ecological efficiency often cited as 5 - 20%. Remember the formula En = E(n−1) × 0.1 (En = energy at level n) from foundational ecology texts like Odum's Ecology (USGS). Visualizing these pyramids aids recall when answering questions about food webs and biomass transfer.

  3. Species Interactions and Network Complexity -

    Food web quiz items frequently probe interaction types: predation, competition, mutualism and parasitism, as detailed in Ecology Letters research. For example, wolves predating elk demonstrates top-down control, while nitrogen”fixing bacteria and plants illustrate mutualism. Sketching small network diagrams and labeling interaction arrows helps with questions on food web complexity.

  4. Keystone Species and Ecosystem Stability -

    Keystone species exert a disproportionate influence on ecosystem dynamics; sea otters regulating urchin populations is a classic example featured in university case studies. Recognizing these species can answer advanced questions on food web resilience and tipping points, with references from marine ecology journals. Remember: "One species to rule them all" as a fun way to recall their pivotal role.

  5. Connectance and Network Metrics -

    Quantifying food web structure involves metrics like connectance (C = L/S², where L = links and S = species), as per network theory in PNAS studies. High connectance often implies greater stability, a concept tested in many food web quiz challenges. Constructing an adjacency matrix for a simple community can cement understanding for any set of questions about food webs.

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