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Quizzes > Science > Biology

Test Your Knowledge: Energy Flow in Ecosystems Quiz

Think you can ace our ecosystem energy quiz? Challenge your understanding of energy transfer now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art layers illustrating sun energy passing from plants to herbivores to carnivores with arrows on dark blue background

This quiz helps you practice energy flow in ecosystems by tracing how energy moves from producers to consumers and on to top predators through food chains and trophic levels. Use it to spot gaps before a test. If you want a quick refresher, skim this study guide and then start.

Which organisms are primary producers in an ecosystem?
Plants and algae
Fungi
Detritivores
Herbivores
Primary producers, such as plants and algae, use sunlight to synthesize organic compounds through photosynthesis, forming the base of the ecosystem's energy pyramid. They convert inorganic carbon into biomass that supports all other trophic levels. Organisms like fungi, herbivores, and detritivores cannot produce their own food and rely on organic matter generated by producers. Without primary producers, ecosystems would lack the foundational energy source.
What is the main source of energy for most ecosystems?
Sunlight
Geothermal heat
Water currents
Soil nutrients
The sun provides the vast majority of energy that drives biological processes in terrestrial and shallow aquatic ecosystems through photosynthesis. Solar energy is captured by chlorophyll and converted into chemical energy in producers. Soil nutrients and water currents help support life but do not supply the primary energy input. Geothermal heat is significant only in select deep-sea ecosystems like hydrothermal vents.
In a simple food chain, which organisms feed directly on producers?
Carnivores
Herbivores
Omnivores
Decomposers
Herbivores are animals that consume plants and other photosynthetic organisms, directly linking producers to higher trophic levels. Carnivores feed primarily on other animals, not producers. Decomposers break down dead material, and omnivores eat both plants and animals. The role of herbivores is critical for transferring energy from producers up the food chain.
What term describes organisms that break down dead organic material?
Consumers
Autotrophs
Decomposers
Producers
Decomposers, such as bacteria and fungi, chemically break down dead organisms and organic waste, recycling nutrients back into the ecosystem. Consumers ingest living or recently killed organisms, while producers synthesize organic materials. Autotrophs are another term for producers that make their own food via photosynthesis or chemosynthesis. Decomposers complete the nutrient cycle by converting complex organic materials into simpler compounds.
Which of the following is an example of a primary consumer?
Grasshopper
Oak tree
Mushroom
Wolf
A grasshopper is an herbivore that feeds directly on plants, making it a primary consumer in the food chain. Wolves are tertiary or secondary consumers that prey on other animals. Oak trees are producers that perform photosynthesis. Mushrooms are decomposers that break down dead organic matter. Primary consumers are crucial for transferring energy from producers to higher trophic levels.
Approximately what percentage of energy is transferred from one trophic level to the next?
10%
1%
50%
90%
Ecological efficiency averages around 10%, meaning only about one-tenth of the energy at one trophic level is passed on to the next. The remaining energy is lost as heat through metabolic processes and respiration. This low efficiency explains why energy pyramids narrow at the top and why ecosystems rarely support many trophic levels. Variations can occur, but 10% is a widely used estimate in ecology.
What process do producers use to convert light energy into chemical energy?
Transpiration
Photosynthesis
Fermentation
Respiration
Photosynthesis is the process by which plants, algae, and certain bacteria convert sunlight, water, and carbon dioxide into glucose and oxygen. It captures solar energy and stores it in chemical bonds. Cellular respiration, by contrast, releases energy from glucose. Transpiration and fermentation are unrelated to the primary energy capture in ecosystems.
Which of these is a decomposer in most ecosystems?
Algae
Deer
Bacteria
Hawk
Bacteria are key decomposers that break down complex organic materials into simpler compounds, returning nutrients to the soil and water. Deer are herbivores, hawks are predators, and algae are primary producers. Decomposers play a vital role in nutrient cycling and energy flow by transforming dead matter into forms usable by producers.
What term describes the interconnected feeding relationships in an ecosystem?
Food web
Food chain
Ecological niche
Biomagnification
A food web consists of multiple interlinked food chains showing how energy and nutrients flow among organisms. Food chains represent a single linear pathway. Ecological niches describe an organism's role and habitat rather than feeding links. Biomagnification refers to the accumulation of toxins up the food chain, not the feeding relationships themselves.
What is an apex predator?
A decomposer
A primary producer
A scavenger feeding on carrion
A top-level consumer with no natural predators
An apex predator sits at the top of its food web with no natural predators, regulating prey populations and influencing ecosystem structure. Primary producers create organic matter, while scavengers consume dead animals. Decomposers break down organic waste. Apex predators often drive trophic cascades through their top-down effects.
What does biomass in an ecosystem refer to?
Number of species
Total mass of living organisms
Energy flow rate
Nutrient concentration
Biomass is the total mass of all living organisms in a given area at a given time, often measured as dry weight. It reflects the amount of organic material available at each trophic level. Species number indicates biodiversity, not mass. Energy flow rate measures energy transfer, and nutrient concentration addresses chemical availability. Biomass pyramids illustrate how mass decreases up trophic levels.
Which ecological pyramid displays energy distribution across trophic levels?
Pyramid of energy
Pyramid of numbers
Pyramid of productivity
Pyramid of biomass
The pyramid of energy illustrates the flow of energy through each trophic level over time, with a broad base of producers and a narrow apex of top consumers. The pyramid of numbers shows organism counts, and the pyramid of biomass represents mass at each level. Pyramid of productivity is another term for pyramid of energy but is less commonly used. Energy pyramids highlight inefficiencies in energy transfer.
In an energy pyramid, which level has the smallest amount of available energy?
Primary consumers
Tertiary consumers
Primary producers
Secondary consumers
Tertiary consumers occupy the highest trophic level and therefore receive the least energy due to successive losses at each lower level. Primary producers capture solar energy directly and have the most. Primary and secondary consumers occupy intermediate positions. The sharp decrease at higher levels reflects ecological efficiencies around 10%.
Which term describes organisms that feed on dead or decaying matter?
Omnivores
Herbivores
Carnivores
Detritivores
Detritivores, such as earthworms and certain insects, consume detritus, which is dead organic matter and plant debris. Herbivores feed on live plants, carnivores prey on live animals, and omnivores eat both live plant and animal material. Detritivores help recycle nutrients back into the soil for use by producers.
What happens to energy that is not used for growth or reproduction by organisms?
It is stored in biomass
It is recycled in soils
It is converted to matter
It is lost as heat
According to the second law of thermodynamics, energy transformations are not 100% efficient, and unused energy dissipates as heat. This heat is unavailable to higher trophic levels and contributes to entropy. Only a portion of consumed energy is stored in biomass for growth or reproduction. The rest fuels metabolic processes and is released.
Which term describes the rate at which producers capture energy?
Ecological efficiency
Secondary productivity
Gross primary productivity
Net primary productivity
Gross primary productivity (GPP) is the total amount of solar energy converted into chemical energy by producers per unit time. Net primary productivity (NPP) is GPP minus the energy producers use in respiration. Secondary productivity refers to energy captured by consumers. Ecological efficiency describes the transfer ratio between trophic levels, not primary capture.
According to the second law of thermodynamics, why is energy transfer between trophic levels inefficient?
Sunlight fluctuates seasonally
Organisms do not assimilate nutrients fully
Some energy is lost as heat, increasing entropy
Biomass decays instantly
The second law of thermodynamics states that energy transformations increase entropy, meaning some energy is always lost as heat during metabolic processes. This loss limits the amount of energy available to the next trophic level. Organisms do assimilate nutrients to various degrees, but the primary cause of inefficiency is heat loss. Seasonal sunlight variation does not govern the universal 10% rule, and biomass does not decay instantaneously.
Which of the following best defines net primary productivity (NPP)?
Gross primary productivity minus energy used in respiration by producers
Total solar energy reaching the atmosphere
Energy consumed by herbivores
Energy stored in decomposer biomass
Net primary productivity (NPP) represents the energy that producers store as biomass after subtracting the energy they use for respiration from the gross primary productivity (GPP). It is the energy available to consumers in the ecosystem. Total solar energy is not biologically converted, and energy consumed by herbivores is secondary productivity. Decomposers recycle nutrients but do not define NPP.
Why are there rarely more than five trophic levels in an ecosystem?
Predators avoid complex food chains
Insufficient energy is available to support higher levels
Decomposers dominate above five levels
Producers die off quickly
Because only about 10% of energy is transferred from one trophic level to the next, energy decreases rapidly at higher levels, making it difficult to sustain more than five levels. Predators do not avoid complexity; it is the energy limitation that restricts chain length. Decomposers operate across all levels, not just above five. Producers' survival is not the primary limiting factor for trophic levels.
In marine ecosystems, which transition typically exhibits higher trophic transfer efficiency than terrestrial systems?
Seaweed to herbivores
Phytoplankton to zooplankton
Phytoplankton to fish
Fish to marine mammals
Marine grazing chains from phytoplankton to zooplankton often transfer energy more efficiently than comparable terrestrial chains due to the small size and fast turnover rates of plankton. Phytoplankton-to-fish transfers involve more intermediate levels and inefficiencies. Seaweed-based food webs can be less efficient due to structural tissues. Fish-to-mammal transfers also involve significant energy loss.
Which factor most strongly limits net primary productivity in terrestrial ecosystems?
Nutrient availability, especially nitrogen and phosphorus
Atmospheric pressure
pH levels
Light intensity
In many terrestrial ecosystems, the availability of essential nutrients like nitrogen and phosphorus limits plant growth and thus net primary productivity. While light is necessary, many ecosystems receive adequate sunlight, making nutrients more limiting. Atmospheric pressure and soil pH influence growth but are secondary to the availability of key nutrients. Fertilization experiments often confirm nutrient limitation.
In a trophic pyramid, biomass decreases at higher trophic levels primarily due to what?
Energy loss as heat and metabolic processes
Enhanced photosynthesis
Faster reproduction rates
Increased predation
As energy is passed from producers up through consumers, most is lost as heat during metabolism and respiration, leaving less available to build biomass at higher levels. Predation affects population numbers but does not explain biomass trends. Faster reproduction would increase biomass. Enhanced photosynthesis applies only to producers. The metabolic energy losses dictate the shape of biomass pyramids.
Which description best characterizes ecological efficiency?
Proportion of species diversity in a trophic level
Amount of biomass consumed by decomposers
Ratio of energy transferred between trophic levels to energy available at the lower level
Rate of nutrient cycling in soils
Ecological efficiency measures the percentage of energy at one trophic level that is passed on to the next level, typically around 10%. It quantifies the energy available for growth and reproduction of consumers. Biomass consumption by decomposers and species diversity are separate ecological concepts. Nutrient cycling rate concerns chemical elements, not energy flow.
What term describes the phenomenon where removal of top predators causes shifts in energy flow across trophic levels?
Mutualism
Biomass accumulation
Competitive exclusion
Trophic cascade
A trophic cascade occurs when the presence or absence of top predators causes ripple effects through lower trophic levels, altering species abundances and energy flow. Removal of apex predators can lead to overpopulation of herbivores and subsequent reduction in primary producers. Competitive exclusion involves two species vying for the same resource, not top-down control. Mutualism refers to beneficial interactions between species.
Which concept accounts for parallel energy pathways through both grazing and detrital food chains?
Grazing loop
Detritus loop
Energy bifurcation
Combined circuit
The combined circuit concept in ecosystem ecology describes energy flow that integrates both the grazing chain (producer to herbivore to predator) and the detrital chain (dead organic matter to detritivore to decomposer). This framework emphasizes how energy and nutrients circulate through live and dead biomass simultaneously. Grazing loop and detritus loop are parts of the circuit but do not capture the integration. Energy bifurcation is not a standard ecological term.
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Study Outcomes

  1. Understand primary energy sources -

    Identify how sunlight drives producers' role in the 5.07 quiz energy flow in ecosystems and explain the foundation of energy input in food chains.

  2. Analyze trophic levels -

    Differentiate between producers, consumers, and decomposers on successive trophic levels and assess their energy requirements in an energy flow quiz context.

  3. Evaluate energy transfer efficiency -

    Calculate and interpret the percentage of energy passed between trophic levels, reinforcing concepts from the energy transfer quiz questions.

  4. Map food chain interactions -

    Construct and critique simple food chains and food webs, illustrating predator - prey relationships and energy pathways in a food chain quiz format.

  5. Apply ecological balance principles -

    Use insights from the ecosystem energy quiz to predict how changes in one trophic level impact overall ecosystem stability and energy flow.

Cheat Sheet

  1. Primary Productivity and Energy Capture -

    Gross primary productivity (GPP) is the total solar energy producers capture via photosynthesis, and net primary productivity (NPP) is what's left after respiration (NPP = GPP − R). A handy mnemonic, "Grow Plenty, No Rest," reminds you that plants store biomass only after accounting for respiration losses. Understanding primary productivity from sources like NASA Earth Observatory is key for the 5.07 quiz energy flow in ecosystems.

  2. Energy Transfer Efficiency and the 10% Rule -

    On average, only about 10% of energy at one trophic level moves up to the next, as described by Lindeman's 1942 study and supported by modern ecology texts (USGS). Remember "Only Ten Out, Every Time" to recall this rule of thumb for energy flow in ecosystems. This efficiency drop explains why energy flow quiz questions often focus on energy pyramids.

  3. Trophic Levels and Food Chain Dynamics -

    Producers occupy the first trophic level, followed by primary consumers (herbivores), secondary consumers, and tertiary consumers (University of Michigan Biology). A simple mnemonic, "Please Have Some Tea," helps you recall these four levels in order. Recognizing each level's role strengthens answers on the food chain quiz.

  4. Food Chains vs. Food Webs -

    Food chains are linear energy pathways, but most ecosystems form complex food webs where species interconnect (Encyclopedia of Life). Real-world examples, like a lake ecosystem with multiple fish predators, illustrate greater stability in webs. This concept is often tested in ecosystem energy quizzes to show biodiversity's impact on energy flow.

  5. Ecological Pyramids: Energy, Biomass, and Numbers -

    Energy pyramids always taper upwards due to decreasing energy availability, biomass pyramids can invert in aquatic systems, and pyramid of numbers varies with organism size (UC Davis). Use "Every Big Number" to remember the order: Energy, Biomass, Numbers. These pyramid concepts are frequent focal points in energy transfer quizzes.

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