Ecosystem Interactions
Which of the following best describes a symbiotic relationship where one organism benefits and the other is unaffected?
A) A tick attaching to a deer to consume blood.
B) Nitrogen-fixing bacteria living in the root nodules of legumes.
C) Epiphytes, such as bromeliads, growing on high branches of tropical trees to reach sunlight.
D) Two species of finches competing for the same size seeds on an island.
C) Epiphytes, such as bromeliads, growing on high branches of tropical trees to reach sunlight.
Which biome is characterized by a combination of low average annual precipitation and high average annual temperatures?
A) Tundra
B) Subtropical Desert
C) Boreal Forest
D) Temperate Grassland
B) Subtropical Desert
Which of the following is a major "sink" (reservoir) that stores carbon for millions of years?
A) Atmospheric CO₂
B) Terrestrial green plants
C) Marine sedimentary rock
D) Livestock and agricultural runoff
C) Marine sedimentary rock
Which of the following best defines Net Primary Productivity (NPP)?
A) Total solar energy captured by producers.
B) Energy lost by producers as heat during metabolic processes.
C) Energy available to consumers after producers have used what they need for respiration.
D) The rate at which decomposers break down organic matter.
C) Energy available to consumers after producers have used what they need for respiration.
In a food chain consisting of grass → grasshopper → sparrow → hawk, the sparrow occupies which trophic level?
A) Primary consumer (2nd level)
B) Secondary consumer (3rd level)
C) Tertiary consumer (4th level)
D) Producer (1st level)
B) Secondary consumer (3rd level)
Which of the following interactions is correctly paired with its impact on the two species involved?
A) Commensalism: (+ / +)
B) Parasitism: (+ / -)
C) Mutualism: (+ / 0)
D) Interspecific Competition: (+ / -)
B) Parasitism: (+ / -)
Which of the following best explains why the soil in a tropical rainforest is nutrient-poor despite the high amount of vegetation?
A) The high rate of evaporation prevents nutrients from forming.
B) Nutrients are rapidly taken up by plants or leached by heavy rainfall.
C) Decomposers cannot survive in the high humidity of the rainforest.
D) The soil is frozen for most of the year, preventing nutrient cycling.
B) Nutrients are rapidly taken up by plants or leached by heavy rainfall.
The process by which specialized bacteria in the soil convert nitrates (NO₃⁻) back into nitrogen gas (N₂) is known as:
A) Nitrification
B) Nitrogen Fixation
C) Assimilation
D) Denitrification
D) Denitrification
An ecosystem has a GPP of 4 kg C/m²/year and a respiration loss of 1.5 kg C/m²/year. What is the NPP?
A) 5.5 kg C/m²/year
B) 2.5 kg C/m²/year
C) 6.0 kg C/m²/year
D) 0.37 kg C/m²/year
B) 2.5 kg C/m²/year
If there are 10,000 kcal of energy at the producer level, roughly how many kcal will be available to the tertiary consumers?
A) 1,000 kcal
B) 100 kcal
C) 10 kcal
D) 1 kcal
C) 10 kcal
In a coniferous forest, two species of birds forage for insects on the same tree; however, one species stays near the top while the other stays near the bottom. This is an example of:
A) Resource partitioning to reduce competition.
B) A mutualistic relationship for protection.
C) A trophic cascade caused by a lack of predators.
D) Commensalism due to habitat sharing.
A) Resource partitioning to reduce competition.
Which aquatic zone is characterized by the highest rates of photosynthesis and is often rich in nutrients from land runoff?
A) The Abyssal zone
B) The Benthic zone
C) The Littoral zone
D) The Profundal zone
C) The Littoral zone
Which of the following best explains why phosphorus is often a limiting nutrient in many ecosystems?
A) It is easily lost to the atmosphere as a gas.
B) It cycles very slowly and originates primarily from the weathering of rocks.
C) Plants cannot absorb phosphorus through their roots.
D) It is only found in the deep ocean and is inaccessible to land plants.
B) It cycles very slowly and originates primarily from the weathering of rocks.
Which of the following ecosystems has the lowest Net Primary Productivity per unit area?
A) Open Ocean
B) Estuary
C) Tropical Rainforest
D) Salt Marsh
A) Open Ocean
A "top-down" control in an ecosystem, where the removal of a predator causes a collapse of the producer population, is known as:
A) A positive feedback loop
B) A trophic cascade
C) Successional growth
D) Competitive exclusion
B) A trophic cascade
Which of the following is an example of a biotic factor that would limit the population growth of a herd of elk?
A) An unusually cold winter with heavy snowfall.
B) A decrease in the amount of available nitrogen in the soil.
C) An increase in the population of gray wolves in the area.
D) A reduction in the annual precipitation of the ecosystem.
C) An increase in the population of gray wolves in the area.
Which of the following biomes depends on periodic fires to clear out dead vegetation and allow certain seeds to germinate?
A) Tropical Rainforest
B) Shrubland (Chaparral)
C) Tundra
D) Taiga
B) Shrubland (Chaparral)
Which of the following cycles is primarily driven by solar energy and gravity?
A) The Carbon Cycle
B) The Nitrogen Cycle
C) The Hydrologic Cycle
D) The Phosphorus Cycle
C) The Hydrologic Cycle
Most of the energy that enters a food chain is eventually:
A) Converted into biomass in top predators.
B) Recycled by producers to start the cycle again.
C) Lost to the environment as heat.
D) Stored indefinitely in the soil.
C) Lost to the environment as heat.
Which of the following is the most likely result of the extinction of a keystone predator in an ecosystem?
A) An increase in the biodiversity of the ecosystem.
B) A decrease in the population of primary producers due to an explosion of herbivores.
C) An increase in the energy efficiency of the food web.
D) The immediate extinction of all decomposers.
B) A decrease in the population of primary producers due to an explosion of herbivores.
Two species of insectivorous birds, the Bay-breasted Warbler and the Myrtle Warbler, both live in the same spruce forest. A study finds that the Bay-breasted Warbler spends 90% of its time foraging in the middle branches of the trees, while the Myrtle Warbler spends 90% of its time foraging on the very bottom branches. Which of the following best explains how these two species are able to coexist in the same ecosystem?
A) One species eventually outcompetes the other, leading to competitive exclusion and local extinction.
B) The species engage in mutualism by sharing the energy costs of finding prey in different parts of the tree.
C) The species reduce interspecific competition through resource partitioning by utilizing different niches.
D) The species have a commensal relationship where the Myrtle Warbler provides protection for the Bay-breasted Warbler.
C) The species reduce interspecific competition through resource partitioning by utilizing different niches.
An area of the ocean characterized by low salinity and high turbidity where a river meets the sea is known as:
A) A coral reef
B) The open ocean
C) The intertidal zone
D) An estuary
D) An estuary
Which of the following human activities is most likely to result in the eutrophication (excess nutrients) of a nearby body of water?
A) The burning of coal for electricity.
B) The application of synthetic fertilizers to agricultural fields.
C) The clearing of a forest for timber.
D) The construction of a hydroelectric dam.
B) The application of synthetic fertilizers to agricultural fields.
A team of biologists measures the solar energy captured by a field of corn. They are measuring:
A) Trophic efficiency
B) Net Primary Productivity
C) Gross Primary Productivity
D) Biomass accumulation
C) Gross Primary Productivity
Which of the following best explains why there are usually fewer organisms at higher trophic levels?
A) Top predators have fewer offspring.
B) There is less energy available at higher levels due to the second law of thermodynamics.
C) Higher level organisms are more susceptible to disease.
D) Higher level organisms are smaller and require less food.
B) There is less energy available at higher levels due to the second law of thermodynamics.