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Quizzes > Science

Biotic Factor Examples: Ecology Practice Test

Quick, free biotic factors quiz to check your understanding. Instant results.

Editorial: Review CompletedCreated By: Fatiya NabilaUpdated Aug 25, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration with layered leaves trees promoting free ecology practice quiz on teal background

This short quiz helps you spot biotic factor examples in real ecosystems and check your understanding. For deeper review, explore how living and nonliving parts connect with our ecosystem interactions quiz, practice contrasts with an abiotic factors quiz, and sharpen terms with an ecosystem vocabulary quiz.

Which of the following best describes an ecosystem?
A community of living organisms interacting with their nonliving environment
Only the plants in a forest
A group of the same species in one area
The total biomass of an area
An ecosystem includes both biotic (living) and abiotic (nonliving) components and their interactions. It encompasses energy flow and nutrient cycling among organisms and their environment. This holistic view is fundamental to ecology research and management.
What term describes organisms that convert sunlight into chemical energy?
Decomposers
Secondary consumers
Primary producers
Primary consumers
Primary producers, such as plants and algae, use photosynthesis to convert solar energy into organic compounds. They form the base of food chains by supplying energy to consumers. Without primary producers, ecosystems could not sustain higher trophic levels.
Which term refers to animals that eat only plants?
Herbivores
Omnivores
Carnivores
Detritivores
Herbivores consume only plant material and play key roles in transferring energy from producers to higher trophic levels. They influence vegetation structure and nutrient cycling. Understanding herbivory is essential for ecosystem management.
Which cycle describes the movement of water through the environment?
Hydrologic (water) cycle
Nitrogen cycle
Carbon cycle
Phosphorus cycle
The hydrologic cycle involves evaporation, condensation, precipitation, and runoff, circulating water through atmosphere, land, and oceans. It is crucial for climate regulation and supporting all life forms. Human activities can alter this cycle through land-use changes.
What process do plants use to convert sunlight into chemical energy?
Respiration
Photosynthesis
Transpiration
Evaporation
Photosynthesis allows plants, algae, and some bacteria to produce glucose and oxygen from carbon dioxide and water using sunlight. It is the foundation of most food webs and oxygenates the atmosphere. Photosynthesis efficiency shapes productivity in ecosystems.
Which of these is an example of an abiotic factor in an ecosystem?
Plants
Bacteria
Temperature
Fungi
Abiotic factors are nonliving components like temperature, light, water, and soil properties that influence ecosystem dynamics. They determine species distributions and ecosystem productivity. Biotic factors, by contrast, are living organisms.
What percentage of Earth's atmosphere is nitrogen?
Approximately 21%
Approximately 5%
Approximately 78%
Approximately 50%
Nitrogen makes up about 78% of Earth's atmosphere by volume, making it the most abundant gas. It is relatively inert but essential for building proteins in living organisms after fixation. Atmospheric nitrogen cycles slowly without living mediation.
What role do decomposers play in ecosystems?
Produce energy via photosynthesis
Break down dead organic matter and recycle nutrients
Prevent soil erosion
Consume living prey
Decomposers like fungi and bacteria break down dead organisms and waste, releasing nutrients back into the soil and water. They form a critical link in nutrient cycles, ensuring continued ecosystem productivity. Without decomposers, ecosystems would accumulate dead matter and nutrients would be locked away.
What is a food web?
The decomposition process
A single path of energy flow
A network of interconnected food chains in an ecosystem
All autotrophs in an area
A food web illustrates how multiple food chains overlap, showing the complex feeding relationships among organisms in an ecosystem. It demonstrates that most species consume and are consumed by several other species. Food webs help ecologists understand energy flow and stability.
Which biome is characterized by low rainfall and extreme temperatures?
Tundra
Savanna
Desert
Rainforest
Deserts receive less than 25 cm of rain per year and experience large temperature swings between day and night. They support specialized organisms adapted to conserve water. Studying deserts reveals strategies for survival in harsh conditions.
What do we call a group of individuals of the same species living in one area?
Population
Community
Biome
Ecosystem
A population consists of all individuals of a single species in a defined area at a given time. Population studies address growth, density, distribution, and demographic structure. These factors influence conservation and management decisions.
What term describes the maximum population size that an environment can sustain indefinitely?
Biotic potential
Niche capacity
Carrying capacity
Ecological limit
Carrying capacity (K) is the maximum number of individuals of a species that an environment can support long-term without degradation. It reflects resource availability, habitat conditions, and interactions. Overshooting carrying capacity can lead to population crashes.
Which species is termed a keystone species in its ecosystem?
A species whose presence has a disproportionately large effect on its environment relative to its abundance
Only apex predators
Any invasive species
The most abundant species in a habitat
Keystone species have a critical role in maintaining community structure and ecological balance. Their removal often leads to significant changes in ecosystem composition and function. Classic examples include sea otters and certain fig trees.
In which biome would you commonly find permafrost?
Temperate grassland
Tundra
Chaparral
Taiga
Permafrost is permanently frozen ground found mainly in the Arctic tundra. It influences drainage, vegetation types, and carbon storage. Climate warming threatens permafrost stability and releases greenhouse gases.
What term describes ecological succession starting on bare rock with no soil?
Ecotone development
Secondary succession
Primary succession
Climax community
Primary succession occurs on newly exposed substrates, such as lava flows or glacial retreats, where no soil exists. Pioneer species like lichens initiate soil formation through weathering. Over time, soil depth increases, allowing more complex communities.
Net primary productivity (NPP) is defined as:
Total solar energy reaching the ecosystem
The energy captured by producers minus the energy they respire
Energy stored in consumers
Energy lost as heat in trophic transfers
NPP equals gross primary productivity (GPP) minus the energy producers use for respiration. It represents the biomass available to consumers. NPP is a key indicator of ecosystem health and carbon sequestration.
Which of the following best describes an invasive species?
Any species with high reproductive rate
A native species that adapts to new habitats
A species introduced for biological control
A non-native species that causes harm to ecosystems, economies, or human health
Invasive species spread rapidly outside their native range and often outcompete or prey on native species. They can alter habitat structure, nutrient cycling, and food webs. Management of invasives is a key conservation challenge.
Genetic diversity within a species refers to:
Variation in genes among individuals of the same species
Number of species in a community
Different trophic levels in a food web
Variety of ecosystems in a region
Genetic diversity is the basis for adaptation and resilience to environmental change. Higher genetic variation reduces extinction risk and supports healthy populations. Conservation strategies often aim to maintain genetic diversity.
What does the term ecological footprint measure?
Biodiversity loss per year
The number of species endangered by human activity
The land and water area required to support a population's resource use and waste
The total carbon emissions of a country
Ecological footprint quantifies human demand on ecosystems by measuring the area needed to produce resources and absorb wastes. It highlights sustainability and overshoot when demand exceeds supply. It is used to compare impacts across populations.
Which process converts atmospheric nitrogen into forms usable by plants?
Nitrogen fixation
Denitrification
Nitrification
Ammonification
Nitrogen fixation is carried out by certain bacteria and cyanobacteria, converting N? to ammonia or related compounds. This step makes nitrogen accessible to plants and initiates the nitrogen cycle. Industrial fixation (Haber-Bosch) also provides fertilizers.
What does the law of tolerance describe in ecology?
The range of environmental conditions within which a species can survive
Thresholds for ecosystem collapse
Limits to genetic variation in populations
Maximum growth rate of a population
The law of tolerance states that an organism's success is determined by environmental factors being within a specific range. Factors beyond these limits cause stress or mortality. It explains species distributions and habitat suitability.
Which type of species interaction benefits one species and has no effect on the other?
Competition
Mutualism
Parasitism
Commensalism
Commensalism describes interactions where one organism gains benefits like food or shelter while the other is unaffected. Examples include barnacles on whales. It is one of the four major ecological interaction types.
What does biomagnification refer to?
Production of biomass by producers
Increase in toxin concentration at higher trophic levels
Decomposition of organic matter
Transfer of energy through food chains
Biomagnification occurs when persistent pollutants like mercury concentrate in organisms at each successive trophic level. Top predators accumulate the highest concentrations. This process poses health risks to wildlife and humans.
Which human activity is the largest source of greenhouse gas emissions?
Waste management
Deforestation
Industrial agriculture
Burning fossil fuels for energy
Fossil fuel combustion for electricity, heat, and transportation releases the most CO? globally. It is the primary driver of anthropogenic climate change. Mitigation focuses on transitioning to renewable energy sources.
What is the main cause of ocean acidification?
Rising sea temperatures
Increased carbon dioxide dissolving in seawater
Excess nitrogen runoff
Plastic pollution
CO? reacts with water to form carbonic acid, lowering ocean pH and altering carbonate chemistry. This affects shell-forming organisms and coral reefs. Ocean acidification is a direct consequence of elevated atmospheric CO?.
Which biome has the highest net primary productivity per unit area?
Desert
Tundra
Taiga
Tropical rainforest
Tropical rainforests have abundant sunlight, high rainfall, and warm temperatures year-round, driving exceptional plant growth. Their dense canopies and biodiversity contribute to very high productivity. They account for a disproportionate share of global carbon fixation.
The intermediate disturbance hypothesis suggests that species diversity is:
Highest at no disturbance
Lowest at moderate levels of disturbance
Unaffected by disturbance
Highest at moderate levels of disturbance
The hypothesis states that intermediate disturbance allows coexistence of both early- and late-successional species. Low disturbance leads to competitive exclusion, while high disturbance reduces species survival. It explains patterns of diversity in many ecosystems.
Which model describes oscillations in predator and prey population sizes?
Metapopulation model
Logistic growth model
Lotka-Volterra equations
Island biogeography model
The Lotka-Volterra equations mathematically model predator-prey interactions, predicting cyclic fluctuations. They assume constant environmental conditions and no time lags. Despite simplifications, they provide insight into population dynamics.
At large spatial scales, which factor is the primary determinant of biome distribution?
Climate (temperature and precipitation)
Species interactions
Soil pH
Historical land use
Climate patterns of temperature and rainfall largely dictate vegetation types and biome boundaries. Soil and biotic interactions matter at local scales but are secondary globally. Climate change thus shifts biome distributions.
Which ecosystem stores the most carbon per unit area?
Peatlands
Tropical rainforest
Coral reefs
Grasslands
Peatlands accumulate partially decayed organic matter under anaerobic conditions, storing vast amounts of carbon. Though they cover only 3% of land, they hold about one-third of soil carbon. Protecting peatlands is critical for climate mitigation.
Which type of ecological pyramid is always upright?
Energy pyramid
Inverted pyramid
Pyramid of biomass
Pyramid of numbers
Energy pyramids depict energy flow through trophic levels and must narrow at each level due to the second law of thermodynamics. Biomass and numbers pyramids can be inverted in some systems. Energy transfer efficiency is typically below 20%.
Which nutrient is most often limiting in freshwater ecosystems?
Phosphorus
Nitrogen
Carbon
Sulfur
Phosphorus inputs are typically low in freshwater, making it the key limiting nutrient for algal and plant growth. Excess phosphorus from runoff can lead to eutrophication. Management focuses on reducing phosphorus pollution.
What does an age structure diagram show for a population?
Spatial distribution of subpopulations
Trophic levels occupied by the population
Genetic diversity across generations
Distribution of individuals among age classes
Age structure diagrams display proportions of individuals in pre-reproductive, reproductive, and post-reproductive age classes. They help predict population growth trends and social needs. They are used in demography and wildlife management.
In population ecology, what does the intrinsic growth rate (r) represent?
Population growth when resources are limited
Carrying capacity of an environment
Maximum per capita rate of population increase under ideal conditions
Average lifespan of individuals
The intrinsic rate of increase (r) is the theoretical maximum growth rate per individual under perfect conditions. It influences how quickly populations can grow. It is a key parameter in the exponential and logistic growth models.
Which factor is considered density-independent in regulation of populations?
Predation
Natural disasters
Competition for resources
Disease outbreaks
Density-independent factors, like floods and fires, affect populations regardless of their size or density. They can cause sudden declines but do not regulate populations at equilibrium. Density-dependent factors vary with population density.
Which process releases phosphorus from rocks into ecosystems?
Volatilization
Leaching
Weathering
Denitrification
Physical and chemical weathering breaks down phosphate-containing rocks, releasing soluble phosphate into soils and water. This is the primary natural source of biotic phosphorus. Unlike nitrogen, atmospheric phosphorus cycling is negligible.
What defines a metapopulation?
A group of spatially separated populations connected by migration
A genetically uniform population over a large area
A population with extreme age structure
A single population at carrying capacity
Metapopulations consist of distinct local populations that exchange individuals through dispersal. They can persist even if local extinctions occur, due to recolonization. This concept aids conservation of fragmented habitats.
The paradox of the plankton refers to:
Rapid evolution of plankton species
High species diversity in seemingly uniform aquatic environments
Plankton existing without predators
Seasonal disappearance of plankton
The paradox, articulated by G. Evelyn Hutchinson, questions how numerous plankton species coexist despite limited resources and homogeneous conditions. Mechanisms like microhabitat variability and temporal fluctuations help explain this diversity. It remains a central question in community ecology.
Ecological stoichiometry studies the balance of:
Energy flow among trophic levels
Population growth rates
Species diversity in ecosystems
Chemical elements in ecological interactions and processes
Ecological stoichiometry examines the ratios of elements like carbon, nitrogen, and phosphorus in organisms and their resources. It links nutrient availability to ecological processes such as growth, decomposition, and food web dynamics. This framework informs nutrient cycling and ecosystem management.
Which equation describes the species - area relationship in ecology?
E = mc^2
G = G0e^-kt
S = cA^z
P = rN(1-N/K)
The species - area curve, S = cA^z, relates species richness (S) to area (A) with constants c and z fitted empirically. It underpins island biogeography and habitat fragmentation studies. It helps predict biodiversity loss from habitat reduction.
In ecology, hysteresis refers to:
Rapid species adaptation to new conditions
Daily fluctuations in photosynthesis rates
Genetic drift in small populations
A system's dependence on its past conditions, leading to different paths for degradation and recovery
Hysteresis describes situations where ecosystem restoration follows a different trajectory than degradation, often requiring greater effort or different conditions to revert. It highlights threshold effects and alternative stable states. Recognizing hysteresis is crucial for effective ecological restoration.
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Study Outcomes

  1. Understand Nutrient Cycles -

    Grasp the processes of carbon, nitrogen, and water cycles by answering targeted ecology practice quiz questions designed to reinforce key environmental science concepts.

  2. Analyze Food Web Dynamics -

    Interpret various trophic levels and species interactions in multiple-choice items to see how energy flows through ecosystems.

  3. Identify Biodiversity Components -

    Recognize the roles of producers, consumers, and decomposers by tackling ecosystem trivia that highlights species diversity and ecological balance.

  4. Apply Ecological Principles -

    Use real-world scenarios in this free ecology practice test to apply concepts like carrying capacity and ecological succession.

  5. Evaluate Human Impacts -

    Assess how pollution, deforestation, and climate change affect habitats through true-or-false and multiple-choice questions in an environmental science quiz format.

  6. Recall Key Ecology Terms -

    Reinforce your vocabulary in ecology quiz for students by reviewing definitions of biotic and abiotic factors, symbiosis, and more.

Cheat Sheet

  1. Nutrient Cycles: Carbon and Nitrogen -

    Understanding the carbon cycle equation (6CO2 + 6H2O → C6H12O6 + 6O2) and the steps of the nitrogen cycle (e.g., fixation, nitrification, denitrification) ensures you can trace element movement through ecosystems (NASA Earth Observatory). A handy mnemonic for nitrogen transformations is "FAN-D" (Fixation → Ammonification → Nitrification → Denitrification).

  2. Energy Flow and Trophic Levels -

    Recall the "10% rule," where only about 10% of energy at one trophic level is passed to the next, highlighting efficiency losses in energy transfer (Odum, 1971). Sketching food webs with producers, herbivores, and apex predators helps you visualize these relationships and energy pathways.

  3. Primary Productivity: GPP vs. NPP -

    Net primary productivity (NPP) equals gross primary productivity (GPP) minus plant respiration (R), summarized by the formula NPP = GPP − R (University of California, Davis). Comparing NPP rates in biomes like tropical rainforests and deserts connects climate factors to ecosystem energy budgets.

  4. Biodiversity Indices -

    Species richness (the total number of species) and evenness are key metrics for ecosystem health, while the Shannon index (H′ = - Σ pi ln pi) quantifies diversity by weighting species abundances (Journal of Ecology). Remember "Shannon = Super diversity," where higher H′ values indicate more complex communities.

  5. Ecological Succession -

    Primary succession begins on newly formed substrates (e.g., lava flows) with pioneer species like lichens, whereas secondary succession follows disturbances in established soils (Smithsonian Environmental Research Center). Use the "LIPSD" mnemonic (Lichens → Mosses → Herbs → Shrubs → Deciduous trees) to recall the typical sequence of community development.

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