Ecosystem Quiz
Questions: 16 · 10 minutes
1. An insect species disappears from a meadow, and several flowering plants then produce fewer seeds. Which interaction most likely connected the insects and plants?
The insects decomposed all dead plant material
The insects competed with the plants for soil minerals
The insects pollinated the plants while obtaining food
The insects increased the meadow's rainfall
2. Two coastal marshes have similar climates, but only salt-tolerant plants thrive in one of them. Which observation would best explain this difference?
The marsh contains more plant species
Its soil water has a higher salt concentration
Its plants experience less competition for space
Its decomposers recycle dead material more quickly
3. In a simple food chain, grass is eaten by rabbits, and rabbits are eaten by foxes. If the rabbit population drops sharply, which short-term effect is most likely?
Foxes have less prey available
Foxes gain access to more food
Grass receives less sunlight
Grass becomes a decomposer
4. A dense tree canopy is removed from part of a forest. Which abiotic change is most likely at ground level during the day?
Atmospheric nitrogen disappears from the site
Soil minerals become living components
More sunlight reaches the soil surface
Decomposition stops because consumers are absent
5. A wetland experiences a long drought. Which change is the most direct change to an abiotic factor?
The amount of available surface water decreases
Aquatic plants compete more strongly
Frogs produce fewer offspring
Predatory birds move to another habitat
6. Which statement correctly compares matter and energy in an ecosystem?
Both matter and energy are continuously recycled without loss
Energy cycles, while matter moves in one direction and leaves as heat
Neither matter nor energy passes between trophic levels
Matter is recycled, while energy flows through and is eventually dissipated as heat
7. A population grows rapidly after entering a habitat, then levels off as food and nesting sites become limited. What best explains the leveling off?
Energy has begun cycling back from consumers to the Sun
The organisms have stopped interacting with abiotic factors
The population has become a separate ecosystem
The population has approached the habitat's carrying capacity
8. Which statement best defines an ecosystem?
A community of organisms interacting with one another and with the nonliving environment
All populations of one species living within a particular area
A geographic region defined only by its climate and dominant vegetation
A feeding sequence that transfers energy between organisms
9. Which feature of a forest is an abiotic factor?
The fungi decomposing fallen leaves
The pH of the soil
The insects pollinating flowers
The trees competing for sunlight
10. What is the main ecological role of decomposers?
They convert sunlight directly into chemical energy
They break down organic matter and release nutrients for reuse
They return all energy in dead matter to producers
They prevent consumers from exhausting prey populations
11. Why does less usable energy generally reach organisms at higher trophic levels?
Producers store no chemical energy in their tissues
Organisms use much of the energy they obtain for life processes, with some dissipated as heat
Energy is recycled completely by decomposers before reaching predators
Consumers receive energy only from abiotic components
12. Fertilizer runoff adds large amounts of nitrogen and phosphorus to a pond. What is the most likely initial response?
A permanent increase in dissolved oxygen at every depth
Immediate removal of decomposers from the pond
Rapid growth of algae and other aquatic producers
Conversion of the pond into a saltwater ecosystem
13. After a lava flow cools, lichens begin growing on bare rock where no soil remains. Which process is beginning?
Secondary succession
Biological magnification
Competitive exclusion
Primary succession
14. Scientists want to test how light intensity affects algae growth. Which design best isolates light intensity as the independent variable?
Use different algae species under different temperatures and light levels
Compare one lit container with a pond containing fish and plants
Keep nutrients, temperature, and algae type constant while varying only light intensity
Vary nutrient concentration while keeping every container equally lit
15. A stream warms after shade-producing vegetation is removed from its banks. Why might some cold-water fish decline?
Warmer conditions can reduce dissolved oxygen and exceed the fish's temperature tolerance
Removing vegetation turns fish from consumers into producers
Water temperature cannot affect aquatic organisms unless salinity also changes
Warmer water always contains more dissolved oxygen for fish
16. A new predator enters an ecosystem and reduces the number of herbivores. If other conditions remain similar, which indirect effect is most plausible?
Plants immediately stop carrying out photosynthesis
Decomposers lose the ability to recycle nutrients
Sunlight becomes a biotic component of the ecosystem
Plant biomass may increase because grazing pressure decreases