IB Biology: C4.2 Transfers of Energy and Matter

What distinguishes an open system from a closed system in ecology?

• Energy and matter can enter and exit in an open system, but only energy can pass in and out of a closed system.

• Only matter can pass in and out of a closed system, while both energy and matter can move in an open system.

• Open systems allow neither energy nor matter to move in and out.

• Closed systems allow both energy and matter to pass freely.

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What is the primary source of energy for most ecosystems?

• Heat from Earth's core

• Sunlight

• Chemical energy from decomposers

• Wind energy

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In a food chain, how is chemical energy transferred?

• From decomposers to producers

• From one organism to another when it is consumed

• Directly from the sun to all organisms

• From primary consumers to producers

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What role do decomposers play in an ecosystem?

• They provide energy directly to producers.

• They break down organic matter, recycling carbon and nutrients.

• They consume primary consumers to maintain energy balance.

• They produce their own food through photosynthesis.

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Which of the following best describes a photoautotroph?

• An organism that obtains energy from oxidizing inorganic substances

• An organism that obtains energy from light and converts it into chemical energy

• An organism that relies on consuming other organisms for carbon compounds

• An organism that decomposes organic material

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Why is energy lost between trophic levels in a food chain?

• Energy is destroyed during metabolic processes.

• Organisms at higher trophic levels use all the energy they consume.

• Some energy is lost as heat due to cell respiration and metabolic activities.

• Energy moves more efficiently at higher trophic levels.

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Why are ecosystems generally limited to a few trophic levels?

• Energy loss at each trophic level limits the amount available to higher levels.

• Organisms refuse to eat at higher trophic levels.

• There is an unlimited supply of energy available at every level.

• Decomposers absorb all available energy before it reaches higher trophic levels.

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What does the Keeling Curve measure?

• The annual rate of species extinction

• The levels of carbon dioxide in the atmosphere over time

• The flow of nitrogen through ecosystems

• The rate of photosynthesis in plants

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What happens when respiration exceeds photosynthesis in an ecosystem?

• The ecosystem acts as a carbon sink.

• The ecosystem releases more oxygen than carbon dioxide.

• There is a net release of carbon dioxide into the atmosphere.

• The ecosystem stops cycling carbon.

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What is the function of decomposers in the carbon cycle?

• They absorb carbon dioxide from the atmosphere and store it in their tissues.

• They break down dead organic matter, releasing carbon back into the environment.

• They prevent carbon from being released, stabilizing ecosystems.

• They produce oxygen for aerobic respiration.

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