AP Biology Flashcards: Energy Flow Through Ecosystems
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 34 cards to help you master important concepts.
List the levels of ecological organization mentioned in the content.
Ecological organization includes populations, communities, ecosystems, and biomes.
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List the levels of ecological organization mentioned in the content.
Ecological organization includes populations, communities, ecosystems, and biomes.
What is the nitrogen cycle?
The nitrogen cycle is the biogeochemical cycle that involves crucial microbial processes to move nitrogen through the ecosystem.
What is the hydrologic cycle?
The hydrologic (water) cycle describes the movement and storage of water within an ecosystem.
Name three key microbial processes in the nitrogen cycle.
Three key microbial processes are nitrogen fixation, nitrification, and denitrification.
What are the four main purposes for which organisms use energy?
Organisms use energy for organization, growth, reproduction, and homeostasis.
What happens to an organism that experiences a net loss of energy?
A net loss of energy results in the loss of mass and, ultimately, the death of an organism.
How is phosphorus returned to the soil from living organisms?
Phosphorus is returned to the soil through the decomposition of organic matter.
If a population of deer is rapidly declining due to a harsh winter, what can be inferred about their energy balance?
The deer population is experiencing a net loss in energy, which leads to decline.
Explain the relationship between energy availability and the size of trophic levels.
Changes in energy availability, like sunlight or producer biomass, can affect the number and size of all trophic levels in an ecosystem.
How does phosphorus move from producers to consumers?
Phosphorus is transferred to consumers when they eat producers that have taken up phosphate from the soil.
Why are biogeochemical cycles essential for ecosystems?
They are essential because they recycle matter and nutrients, which, unlike energy, are not continuously supplied from an external source.
A plant releases water vapor from its leaves into the atmosphere. What is this process called in the hydrologic cycle?
This process is called transpiration, a key part of the movement of water in the hydrologic cycle.
What are the two types of reservoirs found in biogeochemical cycles?
Biogeochemical cycles feature both abiotic (non-living) and biotic (living) reservoirs.
What is the phosphorus cycle?
The phosphorus cycle describes the movement of phosphate from rocks to producers, consumers, and back to the soil.
How does energy move through trophic levels?
Energy flows from lower trophic levels (producers) to higher trophic levels (consumers) as organisms are consumed.
What is the result of a net gain in energy for an organism?
A net gain in energy allows for metabolic needs to be met and supports growth and reproduction.
If a forest fire reduces the amount of producer biomass, how might this affect the ecosystem?
A change in energy availability, such as reduced producer biomass, can disrupt the ecosystem and affect the number and size of all trophic levels.
Define Heterotroph.
Heterotrophs are organisms that capture energy by consuming organic matter derived from other organisms.
How does energy availability influence an organism's reproductive strategies?
Organisms employ different reproductive strategies (e.g., timing, frequency) in response to the availability of energy.
Contrast the movement of energy with the movement of matter in an ecosystem.
Energy flows through ecosystems, typically in one direction, while matter and nutrients are cycled within them.
Which biogeochemical cycle is unique because its main reservoir is rock and not the atmosphere?
The phosphorus cycle is distinct as it primarily involves the release of phosphate from weathered rocks.
How do the activities of autotrophs and heterotrophs enable energy flow?
Autotrophs capture initial energy from the environment, and heterotrophs transfer this energy by consuming autotrophs or other heterotrophs.
Name four key processes in the carbon cycle.
Four key processes in the carbon cycle are photosynthesis, respiration, decomposition, and combustion.
Which process in the carbon cycle is performed by autotrophs to capture energy from a physical source?
Photosynthesis is the process used by autotrophs to capture energy and incorporate carbon.
A rabbit eats clover to get energy. In this scenario, what is the term for the rabbit?
The rabbit is a heterotroph because it captures energy by consuming organic matter (the clover).
What are the two primary methods autotrophs use to capture energy?
Autotrophs capture energy from physical sources through photosynthesis or from chemical sources through chemosynthesis.
What is the largest reservoir of nitrogen?
The atmosphere is the largest reservoir of nitrogen.
Name four key processes in the hydrologic cycle.
Four key processes are evaporation, condensation, precipitation, and transpiration.
What is the primary source of phosphate in the phosphorus cycle?
The phosphorus cycle involves the release of phosphate from weathered rocks.
Define Autotroph.
Autotrophs are organisms that capture energy from physical or chemical sources in the environment.
What is the direct effect of a change in energy availability on a population?
Changes in energy availability can lead to changes in population size.
Bacteria converting atmospheric N2 into ammonia (NH3) is an example of which key process?
This is an example of nitrogen fixation, a crucial microbial process in the nitrogen cycle.
What is a biogeochemical cycle?
Biogeochemical cycles are the pathways through which matter and nutrients are cycled in an ecosystem, featuring both abiotic and biotic reservoirs and processes.
What is the carbon cycle?
The carbon cycle is the process involving the recycling of carbon through various reservoirs and processes in an ecosystem.