Answer: C. Organisms interact with environment. An ecosystem includes organisms and the physical and chemical environment with which they interact.
Which is a biotic component of a forest ecosystem?
A A population of trees
B Soil minerals
C Rainfall
D Sunlight
Answer: A. A population of trees. Biotic components are living organisms, such as trees, animals, fungi, and microbes.
Which is an abiotic component of a lake ecosystem?
A Water temperature
B Algae
C Fish
D Bacteria
Answer: A. Water temperature. Water temperature is a nonliving environmental condition and is therefore abiotic.
Which organisms make organic material using sunlight?
A Primary consumer
B Producer
C Decomposer
D Secondary consumer
Answer: B. Producer. Producers use light energy to make organic compounds from inorganic materials.
What trophic role fits a plant-eating herbivore?
A Decomposer
B Primary consumer
C Producer
D Tertiary consumer
Answer: B. Primary consumer. Primary consumers feed directly on producers.
Which organisms commonly break down dead plants and animals?
A Top predators
B Pollinators only
C Herbivores only
D Fungi and bacteria
Answer: D. Fungi and bacteria. Decomposers break down dead organic matter and release nutrients back into ecosystems.
What does a trophic level show?
A Age in years
B Body size
C Geographic location only
D Feeding position in an ecosystem
Answer: D. Feeding position in an ecosystem. Trophic levels describe feeding positions, from producers to consumers at higher levels.
How does a food web differ from a food chain?
A Links feeding relationships
B Shows only one feeding path
C Shows only predators
D Excludes decomposers
Answer: A. Links feeding relationships. A food web represents the multiple feeding connections among organisms.
What is the main energy source for most ecosystems?
A Earthquakes
B Tides only
C Sunlight
D Wind alone
Answer: C. Sunlight. Most ecosystems receive energy from sunlight captured by photosynthetic organisms.
How does energy move through an ecosystem?
A One-way, with heat loss
B Creates new energy
C Cyclic with no losses
D Independent of organisms
Answer: A. One-way, with heat loss. Energy flows through ecosystems and much is lost as heat rather than recycled.
What happens to nutrients, unlike energy?
A Cycles through living and nonliving
B Are never reused
C Are created by consumers
D Move only into the atmosphere
Answer: A. Cycles through living and nonliving. Elements such as carbon, nitrogen, and phosphorus cycle between organisms and air, water, and soil.
What does biomass measure?
A Incoming solar energy
B Rate of rainfall
C Number of food chains only
D Living organic mass
Answer: D. Living organic mass. Biomass is the mass of living organic matter in a particular area or trophic group.
What is a habitat?
A A species’ genetic code
B A measure of ecosystem energy
C An organism’s living place
D A food chain position
Answer: C. An organism’s living place. Habitat describes the place or environmental setting in which an organism lives.
What does an ecological niche describe?
A Role and resource use
B Body mass only
C Age at reproduction only
D Number of cells
Answer: A. Role and resource use. A niche includes how a species uses resources and interacts with other organisms and conditions.
What characterizes a biome?
A A single mineral
B One individual organism
C One food chain only
D Climate and characteristic communities
Answer: D. Climate and characteristic communities. Biomes are broad ecological regions defined by climate and characteristic vegetation and organisms.
How does freshwater usually differ from marine water?
A Low salt content
B No dissolved minerals
C Saltier than ocean water
D No producers
Answer: A. Low salt content. Freshwater environments have much lower salinity than marine ecosystems.
What characterizes marine ecosystems?
A A lack of decomposers
B Only freshwater organisms
C Saline water
D No nutrient cycling
Answer: C. Saline water. Marine ecosystems contain salt water and include oceans, seas, and many coastal habitats.
What defines an estuary ecosystem?
A A river has no organisms
B A desert meets a forest
C Freshwater mixes with seawater
D A glacier meets a mountain
Answer: C. Freshwater mixes with seawater. Estuaries are coastal areas where river freshwater mixes with saline ocean water.
How are wetlands commonly defined?
A High mountain elevation
B Seasonally saturated soils
C Permanent absence of water
D Lack of plant life
Answer: B. Seasonally saturated soils. Wetland soils are saturated or flooded for sufficient periods to shape their conditions and communities.
What are coral reefs known for?
A No species interactions
B Biodiversity, complex habitat
C Freshwater conditions
D Always low productivity
Answer: B. Biodiversity, complex habitat. Coral reefs provide structurally complex habitat and support diverse marine communities.
Which is an example of an ecosystem service?
A A rock changing color
B An individual organism growing
C A DNA mutation
D Wetlands filter pollutants
Answer: D. Wetlands filter pollutants. Water purification is one ecosystem service provided by natural systems such as wetlands.
Food and timber are examples of which ecosystem services?
A Supporting services only
B Cultural services
C Abiotic factors
D Provisioning services
Answer: D. Provisioning services. Provisioning services are material products obtained from ecosystems, such as food, fuel, and timber.
Wetland flood regulation is an example of which service?
A Genetic mutation
B Regulating service
C Provisioning service
D Cultural service
Answer: B. Regulating service. Regulating services include ecosystem processes such as flood attenuation and water-quality regulation.
Which ecosystem services include recreation and spiritual value?
A Abiotic interactions
B Provisioning services only
C Cultural ecosystem services
D Nutrient cycles
Answer: C. Cultural ecosystem services. Cultural ecosystem services include nonmaterial benefits such as recreation, aesthetic, and spiritual values.
What does ecosystem resilience describe?
A Remain exactly unchanged forever
B Recover after disturbance
C Avoid every disturbance
D Prevent all species interactions
Answer: B. Recover after disturbance. Resilience describes the capacity to recover or reorganize after disturbance while retaining important functions.
Why can ecosystem boundaries vary by study?
A Only one habitat
B Scale follows the question
C Only large landscapes
D Only fixed geographic regions
Answer: B. Scale follows the question Ecosystem scale depends on the process or management question being examined.
What forms an ecological community?
A Individuals from one species
B Interacting populations of different species
C All organisms worldwide
D Nonliving environmental factors
Answer: B. Interacting populations of different species A community consists of populations of different species living and interacting in an area.
What is a population in ecology?
A Different species across regions
B All organisms on Earth
C Only plants in a forest
D Same species in one area
Answer: D. Same species in one area A population is a group of individuals of one species in a defined area.
Which interaction benefits both species?
A Predation
B Mutualism
C Parasitism
D Competition
Answer: B. Mutualism In mutualism, both participating species benefit from the interaction.
In commensalism, what happens?
A One kills the other
B Both species are harmed
C Both species benefit equally
D One benefits, other unaffected
Answer: D. One benefits, other unaffected Commensalism describes one species benefiting while the other is neither helped nor harmed.
How does parasitism affect its host?
A Parasite benefits, host harmed
B Both species benefit
C Host benefits, parasite harmed
D Neither species is affected
Answer: A. Parasite benefits, host harmed A parasite gains resources while harming its host.
Why do two species compete?
A One consumes the other
B Both benefit from shelter
C They occupy unrelated habitats
D Both need limited resources
Answer: D. Both need limited resources Competition occurs when organisms require the same limited resource.
What is predation?
A Organisms exchange nutrients mutually
B One species gains shelter
C One organism consumes another
D Both species share food
Answer: C. One organism consumes another Predation involves one organism capturing and consuming another.
What is an ecological limiting factor?
A Factor limiting growth or survival
B A place where organisms live
C A species’ feeding position
D An interaction benefiting both species
Answer: A. Factor limiting growth or survival A limiting factor constrains survival, growth, or population distribution.
How does carrying capacity describe a population?
A Total area of a habitat
B Rate of nutrient recycling
C Species count in a web
D Maximum sustainably supported population
Answer: D. Maximum sustainably supported population Carrying capacity refers to the population size an environment can support over time under given conditions.
What begins primary succession on bare rock?
A Colonization without existing soil
B Seasonal migration by consumers
C Rapid growth of mature forest
D Recovery after farmland abandonment
Answer: A. Colonization without existing soil Primary succession starts on surfaces where developed soil is absent.
Secondary succession often follows which condition?
A New volcanic rock without soil
B Disturbance where soil remains
C A newly formed ocean
D The creation of Earth’s crust
Answer: B. Disturbance where soil remains Secondary succession follows disturbance where soil or biological legacies remain.
How do pioneer species influence early succession?
A Prevent later species arrival
B Stop environmental change
C Alter early habitat conditions
D Remove all soil nutrients
Answer: C. Alter early habitat conditions Pioneer species colonize early and can change conditions for later organisms.
What makes a species a keystone species?
A Large effect despite low abundance
B Highest population count
C Only one web producer
D Largest body size in habitat
Answer: A. Large effect despite low abundance Keystone species can have effects on ecosystem structure disproportionate to their abundance.
When is an introduced species considered invasive?
A When it enters new habitat
B Whenever it is nonnative
C When it causes adverse impacts
D When populations are small
Answer: C. When it causes adverse impacts Non-native status alone is not enough; invasive species cause or threaten harm.
How does nitrogen fixation affect ecosystem nutrients?
A Remove all nitrogen from soil
B Convert nitrogen into usable forms
C Stop decomposition processes
D Turn oxygen into protein
Answer: B. Convert nitrogen into usable forms Nitrogen fixation converts atmospheric nitrogen into forms that organisms can use.
Which process moves carbon dioxide into plant organic matter?
A Photosynthesis
B Evaporation
C Predation
D Decomposition alone
Answer: A. Photosynthesis Photosynthesis uses carbon dioxide to build organic molecules in producers.
What does primary productivity measure?
A Speed of predator movement
B Total soil in habitat
C Rate of producer biomass creation
D Total number of consumers
Answer: C. Rate of producer biomass creation Primary productivity is the rate at which producers create organic matter.
Why is an energy pyramid usually upright?
A Nutrients disappear from ecosystems
B Consumers are always larger
C Energy decreases at each transfer
D Producers occupy the smallest area
Answer: C. Energy decreases at each transfer Energy becomes less available at successive trophic levels because transfers are inefficient.
In a food web, what does an arrow show?
A From predator to its prey
B From food to consumer
C From decomposer to dead matter
D From soil to sunlight
Answer: B. From food to consumer Food-web arrows indicate the direction of energy transfer, from resource to consumer.
How can habitat fragmentation affect wildlife?
A Removes all competition
B Increases every population equally
C Guarantees greater biodiversity
D Isolates populations and movement
Answer: D. Isolates populations and movement Fragmentation can divide habitat and restrict movement and exchange among populations.
What approach integrates management of land, water, and living resources?
A Single-species management only
B Short-term harvesting plan
C Ecosystem approach
D Urban zoning alone
Answer: C. Ecosystem approach The ecosystem approach integrates management of land, water, and living resources.
How should managers respond to ecosystem uncertainty?
A Assume systems never change
B Monitor, learn, and adapt
C Ignore new evidence
D Set one plan permanently
Answer: B. Monitor, learn, and adapt Adaptive management uses monitoring and learning to adjust decisions as conditions change.
Why are repeated ecosystem observations valuable?
A Reveal trends over time
B Replace every field study
C Show only one species
D Guarantee stable conditions
Answer: A. Reveal trends over time Repeated observations help distinguish longer-term trends from short-lived snapshots.
What role do humans have in many ecosystems?
A Always the dominant producer
B Only ecosystem consumers
C External to every ecosystem
D Integral ecosystem components
Answer: D. Integral ecosystem components The Convention on Biological Diversity notes that humans are an integral component of many ecosystems.