AP®︎ Biology: Topic 8.2 Practice Test
Prepare for your quiz, test, or the AP exam with focused practice questions on Topic 8.2 of AP Biology – Energy Flow Through Ecosystems.
Questions List
Topic 8.2
Question 1 Easy
This question tests the following: ENE-1.M
What is the primary source of energy for ecosystems?
What You’re Being Tested On:
Explore the learning objectives taken directly from the College Board’s AP® Biology Curriculum. Ensure you’re prepared for the exact topics covered on the AP® exam, in-class tests, and quizzes, and gain confidence in your mastery of the material.
Topic 8.2: Energy Flow Through Ecosystems
Learning Objective: 8.2.A
Describe the strategies organisms use to acquire and use energy.
Essential Knowledge: 8.2.A.1
Organisms use energy to organize, grow, reproduce, and maintain homeostasis. i. Organisms use different strategies to regulate body temperature and metabolism. Endotherms use thermal energy generated by metabolism to maintain homeostatic body temperatures. Ectotherms lack efficient internal mechanisms for maintaining body temperature, although they may regulate their temperature behaviorally by moving into the sun or shade or by aggregating with other individuals. ii. A net gain in energy results in energy storage, the growth of an organism, and increased reproductive output. iii. A net loss of energy results in loss of mass, a decrease in reproductive output, and, eventually, the death of an organism. Illustrative examples: Seasonal reproduction in animals and plants; Life-history strategy (biennial plants, reproductive diapause).
Essential Knowledge: 8.2.A.2
Different organisms use various reproductive strategies in response to energy availability. Some organisms alternate between asexual and sexual reproduction in response to energy availability.
Learning Objective: 8.2.B
Explain how energy flows and matter cycles through trophic levels.
Essential Knowledge: 8.2.B.1
Ecological levels of organization include populations, communities, ecosystems, and biomes.
Essential Knowledge: 8.2.B.2
Energy flows through ecosystems, while matter and nutrients cycle between the environment and organisms via biogeochemical cycles. The cycles are essential for life, and each cycle demonstrates the conservation of matter. The cycles are interdependent.
Essential Knowledge: 8.2.B.3
Biogeochemical cycles include abiotic and biotic reservoirs, as well as processes that cycle matter between reservoirs.
Essential Knowledge: 8.2.B.4
The hydrologic (water) cycle involves water movement and storage within the hydrosphere. Reservoirs include oceans, surface water, the atmosphere, and living organisms. Processes include evaporation, condensation, precipitation, and transpiration.
Essential Knowledge: 8.2.B.5
The carbon cycle involves recycling carbon atoms through Earth’s biosphere into organisms as carbohydrates and back into the atmosphere as carbon dioxide (CO₂). At the highest levels of organization, the carbon cycle can be simplified into four parts: photosynthesis, cellular respiration, decomposition, and combustion.
Essential Knowledge: 8.2.B.6
The nitrogen cycle involves several steps, including nitrogen fixation, assimilation, ammonification, nitrification, and denitrification. These steps are performed by microorganisms in the soil. The largest reservoir of nitrogen is the atmosphere. In nitrogen fixation, nitrogen gas (N₂) is fixed into ammonia (NH₃), which ionizes to ammonium (NH₄⁺) by acquiring hydrogen ions from the soil solution.
Essential Knowledge: 8.2.B.7
The phosphorus cycle involves weathering rocks releasing phosphate (PO₄³⁻) into soil and groundwater. Producers take in phosphate, which is incorporated into biological molecules; consumers eat producers, transferring phosphate to animals. Phosphorus returns to the soil via decomposition of biomass, or excretion. Phosphate can also be incorporated back into the environment via decomposition of decaying organic matter.
Learning Objective: 8.2.C
Explain how changes in energy availability affect populations, communities, and ecosystems.
Essential Knowledge: 8.2.C.1
Changes in energy availability can result in changes in population size. Illustrative examples: Food chains/webs; Trophic pyramids/diagrams.
Essential Knowledge: 8.2.C.2
Changes in energy availability can result in disruptions to an ecosystem. i. A change in energy resources such as sunlight can affect the number and size of the trophic levels. Trophic levels include producers; primary, secondary, tertiary, and quaternary consumers; and decomposers. ii. A change in the biomass or number of producers in a given geographic area can affect the number and size of other trophic levels.
Learning Objective: 8.2.D
Explain how the activities of autotrophs and heterotrophs enable the flow of energy within an ecosystem.
Essential Knowledge: 8.2.D.1
Autotrophs capture energy from physical or chemical sources in the environment. i. Photosynthetic organisms capture energy present in sunlight contributing to primary productivity. ii. Chemosynthetic organisms capture energy from small inorganic molecules present in their environment, which can occur in the absence of oxygen.
Essential Knowledge: 8.2.D.2
Heterotrophs, which include carnivores, herbivores, omnivores, decomposers, and scavengers, metabolize carbohydrates, lipids, and proteins as sources of energy. Heterotrophs capture the energy present in carbon compounds by consuming organic matter derived from autotrophs incorporating matter into their tissues.
